Mojsilovic, Nebojsa (1);
Petrovic, Milos (2);
Stojadinovic, Bozidar (1)
MASONRY WALLS WITH MULTI-LAYER BED JOINT SUBJECTED TO CYCLIC SHEAR: ANALYTICAL MODELLING
An analytical rheological model capable of describing the loading speed dependent in-plane shear behaviour of the unreinforced masonry (URM) walls with a multi-layer bed joint subjected to static-cyclic shear loading is presented in this paper. Such joints consist of a core soft layer protected by two thin extruded elastomer membranes, which in turn are placed in a bed mortar joint. The extruded elastomer membranes are employed to prevent and/or limit the deterioration of the core soft layer during the cyclic action observed in previous investigations. Joint behaviour is assumed to be linear elastic-perfectly viscoplastic and has been captured by a uniaxial model consisting of three elements: an elastic spring connected in series with the frictional slider and a dashpot (viscous damper). The rheological model is characterized by three material parameters that have been assessed from several series of monotonic and static-cyclic tests on small masonry specimens (triplets). Assuming a linear elastic behaviour of masonry, the model was able to describe the in-plane horizontal force-displacement behaviour of URM walls with such multi-layer bottom bed joints and could be validated against the experimental results. It was shown that, using the proposed model, for the given loading speed and horizontal displacement the force resistance of URM walls with a rubber granulate core soft layer in the multi-layer bed joint can be predicted well. Moreover, the in-plane horizontal force-displacement behaviour could be described with satisfactory accuracy. Although the model is developed and its parameters are determined for URM with a rubber granulate core soft layer in the multi-layer bed joint, the parameter space can be extended to the other types of core soft layer once the appropriate test data become available.
Bernardello, Rachele Angela (1);
Borin, Paolo (1);
Panarotto, Federico (1);
Valluzzi, Maria Rosa (2);
Giordano, Andrea (1)
BIM REPRESENTATION AND CLASSIFICATION OF MASONRY PATHOLOGIES USING SEMI-AUTOMATIC PROCEDURES
Both the development of national and European directives and the widespread use of BIM (Building Information Modeling) generated the demand to study specific modelling practices for the analysis and conservation of masonry buildings. In this sense, masonry buildings differ from the practices of contempo-rary production, starting from the typical equivalence between architectural and structural objects. It becomes so important to establish on one hand the geometric rules for the passage of information between the BIM model and the FEM analytical models, on the other, a valid methodology to describe building pathologies for masonry surfaces. Starting from an analysis of analogic and digital methods to classify these conditions, the study shows two different alternatives for integrating information, usually embedded within two-dimensional drawings, in a BIM environment. In the case of the Porte Contarine in Padova, a vaulted bridge and water treatment system, starting from photomodelling survey techniques, machine vision procedures allowed to obtain an accurate de-scription of some conditions, represented as mesh surfaces, such as biological colonisation and discoloration. This example demonstrates how it is possible to link the geometry with the associated BIMobject, thus reducing the error in positioning the elements as in the manual process could happen. A second case study describes the integration between a typical condition survey and the BIM model using VPL (Visual Programming Language). The method was tested in Villa Angaran San Giuseppe in Bassano del Grappa. The script allowed to derive geometric data from two-dimensional polylines, classify the entities based on ICOMOS condition, to import them into the BIM environment by means of projection on architectural elements. Both processes allowed to create three-dimensional semantic objects related to specific information of type of building conditions, that could help the conservation and restoration of construction elements in masonry.
Kurukulasuriya, Maithree Chiranthya;
Shrive, Nigel Graham
TESTS ON A FLAT ARCH CONCRETE BLOCK RETAINING WALL
Retaining walls are used in many situations, but most are not usually constructed of masonry. In this study, the potential for concrete blockwork to be used as a low-rise retaining wall (2.4 m high) is investigated. The wall is a shallow (flat) arch in plan view (rise of 0.8 m on a span of 7.6 m), held between two rigid supports for the abutments (in practice these would be vertical columns designed to resist the resultant thrust). The wall will be backfilled with soil, and a pipe placed in the soil (simulating part of a pipeline). The pipe will be subjected to different loadings with the aid of dead weights, and the response of the wall measured to assess the feasibility of using concrete blockwork as a retaining wall. The concept is that the blockwork wall will resist the lateral pressure of the earth and any dynamic effects from the pipe through arch action, avoiding “snap-through” of the wall. Surcharge loading will also be applied to the soil directly behind the wall. Furthermore, one half of the wall is fully grouted, while the other half has been left hollow to compare the behaviour of grouted and un-grouted masonry. While the study may open a new market in which masonry can compete, a masonry block wall would be aesthetically pleasing and easier to construct in many instances, thus making such a wall ideal for low-rise retaining walls in cities. It is expected that boundary conditions of the wall will have a strong influence on the behaviour of the wall. The effects of backfilling will be reported via strain profiles, displacement profiles and stresses in the wall.
Zahra, Tatheer (1);
Asad, Mohammad (1);
Dhanasekar, Remadevi (2);
Thamboo, Julian Ajith (3)
MORTAR-AUXETIC RENDERED DRYSTACK MASONRY WALLS UNDER CONCENTRIC AND ECCENTRIC COMPRESSION
Despite the existence of many historic buildings containing drystack walls, this walling system is not regarded as a legitimate masonry in many national standards. Unlike the thick historic drystack walls, the thin contemporary drystack walls require rendering to survive unavoidable eccentricities in the vertical compression loading and lateral loads. Commonly used fibre reinforced mortar composite (FRMC) render fails due to delamination and brittle splitting. Authors have developed mortar-auxetic fabric composite (MAFC) render as an alternative rendering that eliminates delamination. To illustrate the difference between the MAFC and FRMC, wallettes with these renders were analysed under compression and the numerical model results were validated through available experimental data on FRMC rendered drystack wallette. The mortar-auxetic composite (MAFC) render has shown to improve the response of the wallette under concentric compression through elimination of delamination. This render was then employed to analyse the mortar-auxetic composite rendered drystack wallettes subjected to eccentric compression. A traditional mortared masonry wallette without any render was also analysed as a benchmark case. Mortar-auxetic fabric rendered wallettes exhibited less sensitivity to eccentricity compared to the unrendered traditional mortared masonry under eccentric compression. It is shown that the drystack masonry walls rendered on both sides can resist much larger eccentricity to compression loading compared to the traditional mortared masonry walls. Considering the economic benefits of dry stack construction and based on the structural benefits illustrated in this paper, it appears sensible to recognise dry stack as a valid masonry system in the design standards.
QUANTIFICATION OF DAMAGE TO MASONRY STRUCTURES UNDER SEISMIC CONDITIONS
Solid and perforated brickwork is widely used in construction, both in structural and non-structural elements (e.g. bearing or infill walls, facades, etc.). Masonry elements (especially those unreinforced) are known to be rather brittle and, hence, expected to undergo early damage when subjected to in-plane lateral deformations originated by differential settlements and indeed by seismic actions. In the recent decades, extensive research has been performed on the seismic behaviour of masonry structures, through testing of masonry components. Although valuable relevant information is available, in terms of maximum resistance, ductility properties and hysteretic behaviour, the data on damage and cracking of masonry components is, in most cases, limited to qualitative information. However, relevant quantitative data for various levels of loading (pre- and post-peak) are of importance (a) for the estimation of repair, strengthening, and retrofitting feasibility and cost and (b) for the seismic design of attachments to masonry, such as facade walls, equipment, etc. Thus, the aim of this paper is to collect and assess available published experimental data on the cyclic behaviour of masonry elements, in order to reach, wherever possible, a quantitative assessment of the observed damage (e.g. damage patterns, crack locations and widths, etc.). Limitations of the proposed approach due to limited available data and future research needs are also identified.
Rots, Jan Gerrit;
NUMERICAL MODELLING OF TWO-WAY OUT-OF-PLANE BENDING TESTS ON URM WALLS: THE INFLUENCE OF LATERAL BOUNDARY CONDITIONS
Research has shown that lateral boundary conditions can have a large influence on the force capacity of two-way spanning unreinforced masonry (URM) walls subjected to out-of-plane (OOP) loading. Differently than laterally free one-way spanning walls, they show a higher force capacity, which however is underestimated by current analytical formulations. By means of nonlinear finite element analyses adopting a detailed 3D brick-to-brick model, the influence of lateral boundary conditions on two-way out-of-plane failure of a single wythe masonry wall is studied. Results indicate that the cracking pattern varies as lateral boundaries become stiffer, accordingly the force capacity increases. Numerical results are compared with analytical formulation proposed in the Australian Standard AS3700. These preliminary results will serve to evaluate how to consider the lateral boundary conditions, provided by the wall-to-wall connection, for two-way spanning walls in existing buildings.
VIRTUAL WORK METHOD FOR EVALUATION OF OUT-OF-PLANE LOAD/DISPLACEMENT CAPACITY OF TOPOLOGICAL SEMI-INTERLOCKING MASONRY INFILL PANEL
The Semi Interlocking Masonry (SIM) infill panels have been developed in Masonry Research Group at the University of Newcastle, Australia. The improving seismic performance is the main purpose of the SIM panels that is achieved by dissipating earthquake energy through in-plane sliding of brick courses on bed joints. The out-of-plane relative sliding of bricks in SIM panels is prevented by topological or mechanical interlocking. The SIM panels have reduced in-plane stiffness and increased displacement ductility and energy dissipation capacity compared to the traditional masonry panels. One of the problems of traditional masonry panels during earthquake excitation is their out-of-plane failure. The out-of-plane behavior of semi-interlocking masonry panel has not been extensively researched yet. The main objective of this paper is to present an analitical method for evaluation of the out-of-plane load/displacement capacity of a SIM panel. The developed method is based on the virtual work approach. Analytical predictions were compared to the experimental results for a topological SIM panel. The results show that the proposed method has good correlation with experimental results for the topological SIM panel and could be used potentially for estimation of the out-of-plane strength.
Rots, Jan G.
CONSTITUTIVE MODEL FOR THE NONLINEAR CYCLIC BEHAVIOR OF BRICK MASONRY STRUCTURES
Masonry is one of the oldest building materials in the world and, thanks to its aesthetics, low cost and simplicity in construction, it is still widely used around the world. However, the different properties of its constituents and their geometrical patterns eventually result in an anisotropic, non-linear material with complex mechanical behavior. Besides, many masonry structures are placed in high-seismicity areas, where they might undergo light or severe earthquakes or other cyclic loadings. The assessment of these structures requires the use of advanced numerical models, which in combination with the complex mechanical behavior of masonry render the modelling of these structures a challenging task.
The present work focuses on the development of a continuum constitutive model that describes the cyclic behavior of brick masonry. The model is based on a Total Strain Rotating Crack Method, that incorporates the orthotropic behavior of the material and is based on a phenomenological approach. This is achieved by varying the elastic and inelastic material properties (Young’s modulus, tensile and compressive strengths and fracture energies) with respect to an angle defined between the principal stresses and the mortar joints. Moreover, also the unloading and reloading paths depend on the angle, varying from secant to elastic unloading/reloading. The model allows for the definition of a different mechanical behavior for the principal stresses based on brick pattern and on the expected failure mechanism, i.e. low dissipative behavior is assumed for bed-joint’s tensile opening and high dissipative behavior for diagonal shear sliding.
The material model is implemented in a non-linear finite element program and is validated against quasi-static, cyclic, in-plane tests performed on single masonry walls at the laboratory of TU Delft. Improvements with respect to the traditional Total Strain Rotating Crack Method are discussed.
LOAD-BEARING CAPACITY OF SLENDER EARTH MASONRY WALLS UNDER COMPRESSION
Due to its good ecological properties and its positive influence on the indoor climate, masonry made of earth is a promising building material, especially for residential construction. However, the load-bearing capacity of earth masonry walls has not yet been sufficiently researched for its widespread application in the construction industry. In order to simplify the use of earth masonry in Europe, it would be useful if the existing standard EN 1996-3 was applicable for its design.
Previous compression tests have shown that earth masonry has a significantly lower Young's modulus than common masonry made of fired clay, calcium silicate or autoclave aerated concrete units. As this effect favours stability failure, this paper examines whether the design equation for slender masonry walls according to EN 1996‑3 can also be applied to the design of slender earth masonry walls.
For this purpose, a numerical model of earth masonry is created by using a simplified micro modelling approach and calibrated on the basis of component tests, taking into account its non-linear material behaviour under compression. In order to verify the numerical results, the slender-dependent load-bearing capacity is also approximated analytically.
Subsequently, the slender-dependent load-bearing capacity of earth masonry walls under eccentric compression is compared with the load-bearing capacity of masonry made of fired clay, calcium silicate or autoclave aerated concrete units. Furthermore, the design capacity according to EN 1996-3 is contrasted with the numerical results. Finally, the applicability of the existing normative regulations for the design of slender masonry walls to the design of earth masonry is evaluated.
BUILDING ACOUSTICS – CALCULATION OF SOUND INSULATION IN BUILDINGS WITH SINGLE LEAF CLAY UNIT MASONRY
In Germany the calculation of sound reduction indices is regulated in DIN 4109. In the past there was no calculation method for buildings with outside walls made of hollowed clay brick masonry included in this standard. In 2016 a completely revised version of DIN 4109 has been published. The rules of EN ISO 12354 were included now.
According to a German technical approval also based on EN ISO 12354 and DIN 4109 issue 2016 it is possible now to forecast the sound reduction index for apartments in buildings with outside walls of thermal insulating single leaf clay unit masonry.
To applicate this calculation method the knowledge of individual acoustic properties like sound reduction index, loss factor and the vibration reduction index of the clay brick wall is required.
To simplify the design and calculation of building acoustic performance of ceilings and separating walls in massive buildings the members of German clay brick association provide the software ‘Modul Schall 4.0’ that includes a large, permanently growing database of products of thermal insulating single leaf clay units as well as other constructions of massive components or lightweight elements. All relevant acoustic properties of each product are available in the software.
The values of the prognosis according to DIN 4109:2016 are compared with several results of measurements in residential buildings. The assessment of calculated value vs. measured result will be shown and the reliability of the calculation method for buildings with outside walls of monolithic clay brick units will be discussed.
Nougayrède, Paul (1);
Ciblac, Thierry (1);
Guéna, François (2)
AN INTERACTIVE TOOL FOR HISTORIC MASONRY BUILDINGS STABILITY STUDIES
These last decades, studies' interest about historic masonry buildings has highly increased. The use of limit analysis and more particularly, Jacques Heyman's works in the second half of the twentieth century widely contributed to this development. Considering three hypotheses based on most failure's observations (infinite compression resistance, no traction resistance and no sliding between the blocks), the static approach gives a simple and easy criterion of potential stability. The set of all the application points of the forces on each joint, as known as the line of thrust, must be contained within the geometric limits of each joint in order to insure the structure's potential stability. The aim of this research is to develop an interactive tool able to consider 2D geometries extracted from a 3D model (surveys for instance) and able to explore various hypotheses.
Using the multi-agent system principles of programming and a genetic algorithm, a computing tool which can apply this static theorem for any kind of two-dimensional geometry structure composed of blocks has been developed as a plugin for the 3D modeling software Rhinoceros.The user can set different kind of hypotheses, calculus settings and loadings : fixing chosen points of the thrust line, add forces and seismic solicitations. The tool's interactivity allows the user to move the joint's force's characteristics (point of application, direction and intensity) and see the graphic result immediately with the line of thrust and the forces' polygon. In addition, the tool provides a security friction coefficient for each joint and the possibility to find the extreme thrusts for any geometrical topologic equivalent of an arch. The tool's possibilities are evaluated with the application cases of the Sainte-Marie-Madeleine's Basilic in Vézelay and the Saint-Quentin's Basilic in Picardie.
Van Balen, Koenraad
THE COMPRESSIVE BEHAVIOUR OF MORTAR UNDER VARYING STRESS CONFINEMENT
The confinement of mortar in masonry under compression is one of the key effects influencing the compressive strength of the composite material. It is triggered by the mismatch of elastic properties between units and mortar, coupled with deformation conformity between the two material phases. When the mortar is particularly deformable compared to the units, this confinement results in a masonry compressive strength many times the uniaxial compressive strength of the mortar. Therefore, a careful examination of this effect is critical in understanding the mechanisms of masonry in compression.
Mortar under compression can be modelled in a damage mechanics context, following the establishment of a) a constitutive stress-strain relation, b) a model for the increase of the compressive strength under lateral confinement and c) a model for the change (increase) of the Poisson’s ratio of mortar under different stress levels. The first aspect is approached using established hardening-softening curves used for quasi-brittle materials, such as concrete. The second aspect is dealt with through the adoption of a suitable and sufficiently flexible failure criterion. The third aspect is addressed through fitting against experimental data.
The above aspects are expressed in a damage mechanics context, resulting in fast calculations of the compressive stress-strain curves for confined mortar. This approach allows the quantification of the development of damage in compression, the development of the apparent compressive strength and the relation between orthogonal strains in the mortar, leading to a full characterization of the stress, deformation and damage of the material. The analysis results are compared to experimental findings on different mortar types and are used for their interpretation and evaluation. The complexity of the behaviour of confined mortar is demonstrated, motivating the use of advanced numerical models for its accurate simulation and assessment
Dick, Jordan Christine
BEST PRACTICES FOR MATCHING REPLACEMENT BRICK TO HISTORIC FIRED-CLAY BRICK
Brick masonry has been used across the world as a popular building material for thousands of years. This popular and universal building material characterizes historic cities within New England, such as Boston, as well as many other cities and countries across the world.
Historic masonry buildings often require localized replacement of historic brick that are damaged. To maintain the historic character and appearance of the existing brick masonry, finding a blend of brick that matches aesthetically is key. However, this is not always easy, as historic brick were manufactured using techniques that are far less common or nonexistent today.
This paper discusses brick manufacturing and considerations for replacement brick and draws on several case studies to discuss strategies for matching the technical and aesthetic properties of localized new replacement brick to existing historic brick in repair and restoration projects for historic buildings.
Scacco, Jacopo (1);
Milani, Gabriele (1);
Lourenҫo, Paulo (2)
A SIMPLE HOMOGENIZATION APPROACH FOR MASONRY STRUCTURES: A DISCRETE APPROACH EXTENSION FROM WALLS TO CURVED STRUCTURES
Curved masonry structures as arches, domes and vaults are the most fascinating features of historical buildings. However, numerical analysis of these structural elements is still a challenge. In the last years the researchers have been proposing several approaches including non- linear analyses by means of micro-modeling or macro-modeling and kinematic limit analyses. Above all, these approaches may result too demanding or not enough accurate. A new discretized homogenized approach is here proposed with the aim to combine easy implementation, accuracy and speed. The model is conceived as an assembly of elastic units joint by non-linear interfaces. These latter are modeled as bricks elements and Concrete Damage Plasticity is used for modeling non-linear mechanical properties, obtained from consolidated. homogenization procedures. A validation on wall loaded out-of-plane and a dome is presented in order to show the capability of such approach.
Grillanda, Nicola (1);
Valente, Marco (1);
Milani, Gabriele (1);
Chiozzi, Andrea (2);
Tralli, Antonio (2)
FULLY AUTOMATIC EVALUATION OF LOCAL MECHANISMS IN MASONRY AGGREGATES THROUGH A NURBS-BASED LIMIT ANALYSIS PROCEDURE
Masonry aggregates constitute a large part of the structural typologies in historical centers worldwide. Their composition is the final result of a series of different structural units built during time in continuity to each other. Recent seismic events in Italy put in evidence the high vulnerability of these structures to horizontal actions. The peculiar characteristics of ancient aggregates (such as structural heterogeneity, uncertainties about walls connections, geometric irregularities and, usually, diffuses damage) suggest the exclusion of a global response to seismic actions. In this work, the analysis of masonry aggregates subjected to horizontal actions through local analyses is presented. A NURBS-based upper bound limit analysis is adopted. The representation of geometry through NURBS (Non-Uniform Rational B-Spline) surfaces, which are commonly adopted in commercial CAD software, allows to treat curved geometries (such as vaults) with very few elements, resulting in a lower computational effort in comparison with traditional Finite Element representations. A mesh of NURBS element is easily defined: each element is idealized as a rigid body with dissipation allowed only along interfaces. In order to find the minimum horizontal load multiplier, a procedure of mesh adaptation by genetic algorithm is applied. Since this procedure is fully automatic, it allows to evaluate local mechanisms on complex geometries in easy way. The analysis of a complex masonry aggregate is presented as meaningful example.
Ismaiel, Maysoun Magdy (1);
Chen, Yuxiang (2)
STATE OF ART: EVALUATING THERMAL RESISTANCE OF MASONRY WALLS
To reduce the energy consumption of buildings, masonry exterior walls need to be more energy-conserving. One approach is to increase the thermal resistance of the walls. Thermally efficient walls design can face different challenges. One of the challenges is thermal bridging, which occurs typically in places where highly conductive structural components penetrate insulating materials. There is a need for a quick technique of predicting the whole wall R-value for exterior envelope systems. To be able to develop a quick estimating tool for the computation of the R-value; A survey of literature will be conducted to identify all the important influencing factors on the thermal performance of masonry walls. This survey will also provide a reliable reference on performance simulations and analytical modelling for masonry walls.
This paper will summarize the state of the art on the cavity and single-wythe walls by reviewing the current and recent literature on both fields’ research and practice. The focus of this research is on methods to state the influencing factors on the masonry thermal performance as well as the methods of effective R-value’s measuring and calculations. Variables as the blocks’ shape, insulation’s type, ties type and location, materials’ density are discussed.
Sesigur, Haluk (1);
Alaboz, Murat (2)
ASSESSMENT OF THE STABILITY CONDITIONS OF THE TOWER OF SEDDÜLBAHIR FORTRESS IN TURKEY
In this study, assessment of a tower of the Seddulbahir Fortress is realized based on linear structural analysis and by dynamic identification outcomes. According to analytical results, structural intervention proposals are also developed. Seddulbahir Fortress is a unique defensive structure of Canakkale Bosphorus which was constructed in the era of Sultan the IV.Murat by his mother Hatice Turhan Sultan in 1658 and the Fortress is located in Gallipoli peninsula. The structure suffered during the Gallipoli (Canakkale) War and exposed to adverse weather conditions, deterioration due to conscious human harm by replacing the stones in use of their private purposes. Therefore, the structural integrity of the tower has lost and due to possible seismically originated forces, dome of the tower was collapsed. In order to assess the earthquake risk of the tower, finite element model (FEM) is developed by using 2D and 3D survey data. In FEM model, macro mechanical modelling technique and elastic material properties are used. Dynamic properties are defined by using acceleration data determined from ambient vibration tests. Natural frequency and modal shapes obtained by dynamic test are used to check the adequacy of the FEM model constructed with estimations and required modifications are done to match the behavior as much as possible. In addition to elastic analysis results, possible damage mechanisms are studied to estimate the acceleration of risk levels which activate damage mechanism of the tower. Moreover, various structural intervention methods are proposed by considering different assessment approaches.
ANALYSIS FRAMEWORK FOR SEISMIC ASSESSMENT OF SINGLE SPAN MASONRY ARCH BRIDGES
Around 20,000 masonry arch bridges are currently operational with the Indian Railways of which 16,000 bridges are at least 100 years old. There is a constant need to assess and if necessary, retrofit and upgrade these bridges to meet the current demands of new seismic performance requirements, increased axle speeds and loads, traffic volume, etc. The geometric dependence of failure mechanisms has made limit analysis an obvious choice for the assessment of masonry arch bridges. In this context, a simple, yet robust, first-level quantitative assessment procedure which can be applied to a large stock of masonry arch bridges with minimum input parameters is proposed. The collapse factor is calculated based on the equilibrium of internal and external work, resulting from the virtual displacement of the rigid block. For a given single-span masonry arch bridge under seismic action, the governing collapse factor is identified as the minimum of all possible failure mechanisms.
HUMIDITY CONSEQUENCES FOR THE APPLICATION OF THE CONTEMPORARY REPAIRS INTO HISTORIC WALLS
Brick fences are an indispensable element of historic buildings. They are often the only remnants of the historic buildings of cities. Due to the exposure, they are exposed to extreme environmental conditions. As a consequence, intensive biological and chemical corrosion develops. The purpose of the conservation and restoration works is to remove the damage caused during the operation of the fence, stop the corrosive processes and restore aesthetic values. This is connected with the applicaton of modern materials. The decision on the selection of solutions is made on the basis of typical tests: the composition of mortars, the volume density of mortars as well as bricks. As a consequence, solutions that can intensify damage are created. One of the main causes of degradation is the subflorescence of soluble mineral salts. It involves the flow of moisture in the wall, which is disturbed as a result of the application of contemporary materials. The article presents the results of experimental and in situ research on the mechanism of moisture flow in fencing walls. Moisture maps were made for selected objects and subflorescence areas were established. Laboratory tests of historical and contemporary materials were carried out: thermal and moisture properties, microstructure parameters. The obtained results served as the output data for the simulation analysis of heat and mass transport in the WUFI 2D computer application. The simulations covered three basic variants: filling the joints, reprofiling bricks and introducing new bricks and mortars to the wall. The result of the research is the distribution of moisture in the brick wall. A detailed analysis was made of the masonry area of the wall (range 0 to 50 mm), which is exposed to subflorescence. The obtained results clearly indicate that each of these elements has an impact on the moisture status.
Cescatti, Elvis (1);
Secco, Michele (1);
da Porto, Francesca (1);
Modena, Claudio (2);
Artioli, Gilberto (1);
Xu, Li (3)
CHARACTERIZATION OF MORTAR AND STONE MASONRY QUALITY IN AMATRICE HISTORICAL BUILDINGS HIT BY THE 2016 CENTRAL ITALY EARTHQUAKE
The 2016 Central Italy seismic swarm, and in particular the first stroke on 24th of August in Amatrice, hit a rural zone on Apennine composed by a typical masonry made of rubble stone, arranged in two leaves with weak mortar. The first weakness of rubble masonry is related to masonry disaggregation, which does not allow a macro-element activation.
The paper presents the research carried mainly in the Amatrice region to characterize the masonry quality and its properties. Firstly, physical and chemical characterization of the constituting mortars was performed analysing 33 mortar specimens. The bulk characterization was performed through X-ray powder diffraction (XRPD) coupled with scanning electron microscopy and X-ray microanalysis (SEM-EDS). Those analyses, compared with the analysis of the masonry quality looking at the arrangement of the entire panel, provided an evaluation of the quality and gave an insight of the main issues of the materials, defining three different mortar groups summarized in two masonry typologies. A case study is presented to focus on the accelerations which lead to the masonry disaggregation compared to those associated with the mechanism activation.
The paper aims at characterizing the masonry pointing out the weaknesses which led to the building collapse, with the goal to propose data and information crucial to design efficient and effective strengthening interventions that can avoid the dramatic effects observed.
CRITICAL REVIEW OF NORMATIVE FRAMEWORK FOR SEISMIC ASSESSMENT OF EXISTING MASONRY BUILDINGS
The multiple elements that receive and transfer the lateral loads and their interconnectivity form the lateral load path of a structure. When a structure is subjected to seismic loads, the transfer of forces follows the load path and hence it determines the hierarchy of failure. Thus, identification of load path forms the fundamental step in the assessment of any structure. However, for unreinforced masonry (URM) buildings, the lack of a well defined and continuous load path makes it difficult to set an assessment protocol. The fundamental load paths and the role of participating elements are not always properly understood and therefore, structural assessment of existing URM buildings has been an area of challenge. Further, the variation in construction typology and non uniformity in material properties across the world created difficulties in bringing uniformity to these assessment guidelines. Although the global scheme of assessment is similar to other structural types, the thin line of separation that exists between the onset of different mechanisms and the multiple interactions that happen between these mechanisms and associated elements alter the load paths in an existing structure. However, from time to time, observations made during earthquakes have necessitated revisiting the load paths and mechanisms in URM structures and modifying the assessment guidelines. The fundamentals of seismic assessment procedures across the world show similarities with each other but the differences observed are also substantial. Hence, a critical review of the normative assessment procedures based on the New Zealand assessment guidelines, “The Seismic Assessment of Existing Buildings (The Guidelines)” and “ASCE 41: Seismic Evaluation and Retrofit of Existing Buildings” is carried out to understand the similarities and shortcomings in code based assessment procedures and to identify the scope for refinement in existing methodologies.
Cazzani, Antonio (1);
Grillanda, Nicola (2);
Milani, Gabriele (2);
Pintus, Valentina (1);
Reccia, Emanuele (1)
NUMERICAL INSIGHTS ON THE STRUCTURAL ASSESSMENT OF TYPICAL HISTORICAL MASONRY VAULTS OF CAGLIARI
In this work, masonry vaults are investigated with the purpose of evaluating the role of bricks arrangement in their mechanical behaviour and in relation to the techniques adopted for their construction. Attention is focused on lowered sail vaults, obtained from the intersection of a spherical cap with a prism with a square base carved on its base, i.e. with four vertical planes, typically built during the nineteenth-century in the city of Cagliari, Italy. The peculiarity of these vaults is that they are built with several brick patterns. A series of rigorous laser scanner surveys has been performed on some of these vaults in the Cagliari area, in order to obtain the effective geometry both at macro-level –i.e. the vault shape – and at micro-level – i.e. brick patterns.
Several analyses at collapse of such vaults when subjected to horizontal actions are carried out through a NURBS-based upper bound limit analysis approach. The representation of a complex geometry through NURBS (Non-Uniform Rational B-Spline) surfaces, which are commonly adopted in commercial CAD software, is particularly suited to treat curved geometries, such as vaults. A mesh of NURBS element is defined: each element is idealized as a rigid body with dissipation allowed only along interfaces. In order to find the minimum live load multiplier, a procedure of mesh adaptation by a genetic algorithm is applied. A comparison with incremental nonlinear analyses carried out with detailed finite element modelling is also provided.
In the work, the sensitivity to brick arrangement is finally investigated: on one hand the aim is to evaluate if brick patterns plaid a role in the construction of the vaults, on the other the target is to assess the influence of bricks arrangement in the structural behaviour of such typology of vaults.
AN EXPERIMENTAL STUDY ON SLENDER REINFORCED MASONRY SHEAR WALLS SUBJECTED TO IN-PLANE REVERSED CYCLIC LOADING
Reinforced masonry shear walls (RMSWs) consisting of hollow concrete-block units reinforced with vertical and horizontal steel bars have demonstrated good seismic performance in recent experimental studies in terms of ductility potential and energy dissipation capability. This paper presents key results of an experimental study on eight full-scale cantilevered RMSW specimens with flexure-dominant response under reversed cyclic loading. The test matrix involved specimens of varying slenderness and aspect (height-to-length) ratios, vertical and horizontal reinforcement ratios and detailing, applied axial stress level, and presence or absence of boundary elements. The test specimens were designed according to the requirements of the Canadian masonry design code, CSA S304-14, and performed in a ductile manner, but experienced several failure mechanisms from the onset of testing until the failure, including i) ductile flexural, ii) shear-flexural, iii) toe crushing, iv) sliding shear, and v) out-of-plane instability. The paper discusses the observed behaviour, damage patterns, and the criteria for occurrence of the various failure mechanisms. The test results were compared with the capacity predictions from selected international masonry design codes. The paper may be of relevance to researchers and practicing engineers interested in seismic response of reinforced masonry block shear walls.
Lourenço, Paulo B.
IMPACT OF TYPE OF MORTAR ON SHEAR BOND STRENGTH OF BRICK MASONRY
When masonry is subjected to different loading conditions, quite often its failure occurs due to failure in bond between the unit and mortar. Among other factors such as surface roughness and porosity of the brick, the type of mortar used plays a significant role in influencing the shear bond strength of masonry. This work is aimed at understanding the impact of the type of mortar used on the shear strength of masonry triplets, tested according to EN 1052-3:2002. Clay bricks (solid and frogged) were used with three different mortars - 1:5 (Cement: Sand), 1:1:6 and 1:2:9 (Cement: Lime: Sand), by volume, all designed to have a flow value of 175±10 mm. Bond strength has been discussed as a function of presence of lime in the binder as well as the strength of the mortar, at 90 days of age.
DETERMINING THE COMPRESSIVE STRENGTH OF EXISTING BRICKWORK
The compressive strength of brickwork depends on the compressive strength of the bricks, the compressive strength of the hardened mortar and on the bond strength between mortar and units. In the case of existing masonry, the compressive strength of the mortar and the bond strength of the joints are difficult to obtain. At historically significant buildings the amount of samples is limited, following the concept of minimum intervention. Non Destructive Test methods (NDT) like flat jack measurements, sonic testing or Schmidt hammer may not be considered adequate for the assessment of the safety level of structures in service.
Approaches for the characterization of existing brickwork are discussed since the 1980s. In the field of applicable Moderately Destructive Tests (MDT) different testing procedures have been introduced, based on tensile splitting or compressive tests on drilled cylinders and compressive tests on smaller brickwork samples. To evaluate their level of significance, experimental tests series have been performed on minimized sandwich cores considering mortar and brick properties and on larger diameter cylinders. The results are compared with the compressive strength tested on a brickwork specimen. Mechanical properties of the mortar and the bricks have been assessed to evaluate the compressive strength of the brickwork following EC 6. The results are introduced and discussed.
Incerti, Andrea (1);
Tilocca, Anna Rosa (1);
Bellini, Alessandro (1);
Savoia, Marco (2)
IN-PLANE BEHAVIOUR OF FRCM-STRENGTHENED MASONRY PANELS
The evolution of seismic design regulations together with the degradation of the monumental heritage made necessary to increase the structural safety of a large variety of masonry buildings. A recent strengthening technique consists in the application of a fiber grid/unidirectional sheet with lime or cementitious mortar (FRCM), thanks to several advantages of this retrofitting system in comparison to traditional epoxy-based materials (FRPs), such as better compatibility with the masonry substrate, resistance to high temperatures and reversibility. In this paper, the results of in-plane tests performed on panels strengthened with different types of FRCM systems (that differ in layout, matrix, grid materials and spacing) are presented, after a complete mechanical characterization of FRCM materials, carried out through direct tensile tests and single-lap shear tests. In diagonal compression tests (DCT), failure modes and global behavior of the panels were also analyzed using Digital Image Correlation (DIC) technique, for a better understanding of their in-plane behaviour.
Iskander, George Sami Aziz Salama;
Shrive, Nigel Graham
3D MICRO-MODELLING OF BRICK MASONRY UNDER ECCENTRIC AXIAL LOAD USING FRICTIONAL AND COHESIVE BRICK-MORTAR INTERACTION BEHAVIOUR
Masonry is one of the oldest known building materials. Despite the complexity of designing and understanding the behaviour of masonry under many load combinations, masonry still represents a competitive choice to other building materials in many areas of the world because of masonry’s low cost, flexibility in creating good classical shapes, fire resistance and thermal properties. The complexity of predicting masonry behaviour results from the use of different materials, units and mortar, as well as the variation in the unit and mortar properties. The interaction between the units and the mortar plays an important role in defining masonry strength.
A micro-modeling technique has been developed to provide a non-linear, numerical material model for brick masonry. The model incorporates the non-linear behaviour of the masonry, initial geometric imperfections and non-linear contact properties to represent the normal, tangential and cohesive behaviour of the interaction. 12 different walls with different slenderness ratios and load eccentricities have been modelled using the proposed technique and verified against experimental test results available from literature. The model results are found to be in good agreement with the experimental results.
Muhit, Imrose Bin;
Stewart, Mark G.;
Masia, Mark J.
EXPERIMENTAL EVALUATION AND PROBABILISTIC ANALYSIS OF THE MASONRY VENEER WALL TIE CHARACTERISTICS
Wall tie strengths and stiffnesses are not constant for all ties in a masonry veneer wall system. This paper uses an Australian standard tie calibration experimental approach to delve into wall-tie probabilistic characterisation by estimating the mean, variance, and characteristic axial tensile and compressive strengths and how they influence failure behaviour. A total of 50 veneer brick-tie-timber subassemblies are tested using an Instron testing machine, 25 samples in compression and 25 samples in tension. Both cross head displacement and displacement across the cavity is recorded along with the complete load versus displacement response, which allows determination of elastic stiffness, peak strength and displacement capacity. Using the maximum likelihood method, a range of probability distributions are fitted to tie strength and corresponding displacement histogram data sets, and a best-fitted probability distribution is selected for each case. A Cumulative Distribution Function plot was also used along with the Anderson-Darling test to infer a goodness-of-fit for the probabilistic models.
Barattucci, Samuel (1,3);
Sarhosis, Vasilis (2);
Bruno, Walter (3);
D’Altri, Antonio Maria (4);
de Miranda, Stefano (5);
Castellazzi, Giovanni (6)
SHEAR RESPONSE AND FAILURE MODE OF MASONRY TRIPLETS SUBJECTED TO MONOTONIC AND CYCLIC LOADING
This paper presents the evaluation of the shear response and failure mode of masonry triplets subjected to monotonic and cyclic shear loadings. In this experimental campaign, different masonry triplets using different mortar compositions have been constructed and subjected to different levels of pre-compression. The cohesion and internal friction angle were derived assuming a Mohr-Coulomb criterion and using a linear regression equation. The influence of the strength of the mortar under monotonic and cyclic conditions was investigated. From the results analysis, it was shown that the mortar composition and pre-compression load strongly affect the shear strength of the masonry triplets. Also, triplets subjected to cyclic shear loading sustained a lower peak strength when compared to triplets subjected to monotonic loading.
ARSLAN, Onur (1,2);
MESSALI, Francesco (1);
SMYROU, Eleni (2);
BAL, Ihsan Engin (2);
ROTS, Jan Gerrit (1)
MECHANICAL MODELLING OF CAVITY WALL METAL TIES
The seismic assessment of unreinforced masonry (URM) buildings with cavity walls is of high relevance in regions such as in Central and Northern Europe, Australia, New Zealand and China because of the characteristics of the masonry building stock. A cavity wall consists of two separate parallel walls usually connected by metal ties. Cavity walls are particularly vulnerable to earthquakes, as the out-of-plane capacity of each individual leaf is significantly smaller than the one of an equivalent solid wall. This paper presents the results of an experimental campaign conducted by the authors on metal wall tie connections and proposes a mechanical model to predict the cyclic behaviour of these connections. The model has been calibrated by us- ing the experimental results in terms of observed failure modes and force-displacement responses. Results are also presented in statistical format.
THE ASSESSMENT OF CONFINED SEMI-INTERLOCKING MASONRY BUILDINGS USING MACRO-MODELLING APPROACH
Confined Semi-Interlocking Masonry (CSIM) is an innovative system which is constituted of the semi-interlocking masonry panel together with confining reinforced concrete elements. The semi-interlocking masonry (SIM) has already been studied as infill panels for framed structures and its suitable seismic performance was proven. It is claimed that CSIM building is an alternative to currently used confined masonry buildings. In a CSIM building, not only CSIM walls resist both lateral and gravity loads, but they are also supposed to be energy dissipation devices to the building. In this study, A CSIM building was assessed using a new macro-model suitable to simulate the behavior of CSIM. In this way, the resettable semi-active damper model was employed to simulate the behavior of SIM panels in CSIM walls. The responses of a CSIM building to a cyclic displacement excitation were assessed in terms of strength, displacement, and energy dissipation. The hysteresis behavior of the CSIM building could be appropriately presented by the macro-model. Besides, it was indicated that the CSIM building had considerable energy dissipation thanks to the presence of in-plane sliding joints in the body of SIM panels that led to higher ductility and displacement capacity for the whole building.
Rousakis, Theodoros (1);
Ilki, Alper (2);
Kwiecień, Arkadiusz (3);
Viskovic, Alberto (4);
Triller, Petra (5);
Ghiassi, Bahman (6);
Benedetti, Andrea (7);
Gams, Matija (8);
Rakicevic, Zoran (9);
Halici, Omer Faruk (10);
Zając, Boguslaw (3);
Rizzo, Fabio (4);
Colla, Camilla (7);
Bogdanovic, Aleksandra (9);
Hojdys, Łukasz (3);
Krajewski, Piotr (3);
Papadouli, E. (1);
Sapalidis, A. (1);
Vanian, V. (1);
Tekieli, Marcin (3);
Akyildiz, Tugrul (3);
Manojlovski, F. (9);
Soklarovski, A. (9)
FLEXIBLE JOINTS BETWEEN RC FRAMES AND MASONRY INFILL FOR IMPROVED SEISMIC PERFORMANCE – SHAKE TABLE TESTS
The paper reports the first results from seismic tests on shake table for a real scale reinforced concrete (RC) frame building with modified orthoblock brick wall infills, within INMASPOL SERA Horizon 2020 project. The building received innovative protection using polyurethane resin flexible joints (PUFJ) at the frame-infill interface, in different schemes. Further, PUs were used for bonding of glass fiber grids to the weak masonry substrate to form Fiber Reinforced PU (FRPU) as emergency repair. The tests validated the advanced in-plane and out-of-plane infill performance under suitably designed seismic excitations. The results confirmed remarkable delay of significant orthoblock infill damages at very high RC frame inter-storey drifts as a consequence of the use of PUFJ. Further, the PUFJ protection enabled the repair of the infill even after very high inter-storey drift of the structure up to 3.7%. The applied glass FRPU system efficiently protected the damaged orthoblock infills against collapse under out-of-plane excitation while they restored large part of their in-plane stiffness.
Ogden, Gary D.;
Schuller, Michael P.;
Woodham, David B.
DEVELOPMENT OF A FLATJACK FOR TESTING HIGH STRENGTH MASONRY
Flatjack methods are commonly used for in situ evaluation of masonry compression behaviour, determination of compressive stress present within masonry assemblages, and for loading units during tests to evaluate mortar bed joint shear strength. The original adaptation of flatjack methods considered applications for evaluating historic masonry construction with typical compressive strength in the range of 2.1 to 6.9 MPa (300 to 1000 psi), and current flatjack designs have been optimized for these applications. Some stone masonry construction and most modern masonry has a compressive strength well in excess of 6.9 MPa (1000 psi ) and in these cases masonry compressive strength is estimated based on relationships between compression modulus and compressive strength. It would be beneficial to have equipment capable of applying high stress to capture non-linear response and determine peak compressive strength directly.
A new flatjack design has been developed for evaluating compression deformability of high-strength solid-unit masonry. Laboratory calibration and proof testing shows the new flatjack design is capable of applying stress of 31 MPa (4400 psi) or greater, and the design has been used in the field for compression and shear testing with good results. With high-pressure flatjacks it is possible to exceed masonry compressive strength and special care must be taken to avoid damaging surrounding masonry. Masonry strain is monitored during load application and testing is halted at the onset of significant nonlinear deformation. Development of this flatjack follows complementary research conducted at the Department of Civil Engineering, Federal University of Sao Carlos, Brazil, where researchers have developed flatjacks for evaluating high-strength hollow-unit masonry construction.
Shrestha, Kshitij C.;
IN-PLANE SHEAR STRENGTH CHARACTERISTICS OF MASONRY WALLS WITH VARYING MORTAR TYPES AND ASPECT RATIOS
This paper presents an experimental campaign to understand the in-plane shear characteristics of clay-unit masonry walls subjected to quasi-static horizontal cyclic loading. The test matrix involves a total of 9 full-scale masonry walls with two major parameters studied, first three different mortar types and second three different aspect ratios. The adopted mortar types comprise: (i) cement mortar (CM) with cement and sand at 1:3, (ii) lime/cement mortar (LCM) with lime, cement and sand at 2:1:5, and (iii) lime mortar (LM) with lime and sand at 1:5. Here, LM (with no cement) and LCM mortars represent the mortar mix proportions of historical masonry structures in Japan constructed until the early 20th century. CM represents the mortar used in modern masonry construction. Further, the specimens cover aspect ratios of 0.63, 0.94 and 1.9. A displacement controlled horizontal quasi-static cyclic loading was applied keeping a constant vertical compressive stress.
The general observations during the tests showed strong rocking behavior in case of CM and LCM masonry wall with opening of mortar bed-joint at the bottom of the specimen. The relatively weaker LM specimen, on the other hand, showed diagonal shear cracking (X-shaped) with cracks in both head and bed joints of the mortar. The modes of failure observed were irrespective of the different aspect ratios and were primarily governed by the mortar type. Understandably, the CM and LCM walls showed higher load-carrying capacity compared to the LM counterpart. The peak horizontal shear loads recorded for CM and LCM walls were relatively close to each other with about 5% variance. The peak horizontal shear load for LM wall was about 42%, 47% and 56% of the CM and LCM walls for the aspect ratio of 0.63, 0.94 and 1.9 respectively.
Masia, Mark John;
Page, Adrian W.
EXPERIMENTAL TESTING OF UNREINFORCED LATTICE MASONRY WALLS SUBJECTED TO OUT-OF-PLANE PRESSURE LOADING
In lattice masonry (also known as hit and miss brickwork) the mortar perpend joints are left unfilled and the masonry units are spaced along the courses to leave a gap between adjacent units, allowing the passage of light and air through the wall. Regardless of whether this masonry is used in a loadbearing or nonloadbearing application, it must still be capable of spanning between supports to resist out-of-plane lateral loading to satisfy robustness requirements and to resist wind and/or earthquake actions and hence requires structural design. The Australian Standard AS3700: Masonry Structures (Standards Australia 2018) provisions for one way vertical bending can be applied in the case of lattice masonry by using a section modulus based on the net bedded area. However, the provisions for horizontal bending and two way bending require that the masonry be constructed with all perpends completely filled and therefore lattice masonry falls outside the scope of AS3700 for horizontal and two way bending. Internationally, there also exists a lack of guidance for the structural design of this form of masonry.
The paper describes an experimental study to assess the behaviour of unreinforced lattice masonry walls subjected to lateral out-of-plane pressure loading. Twenty one single leaf lattice masonry walls, of varying aspect (height : length) ratios, were constructed using extruded clay bricks (230 mm long x 110 mm wide x 76 mm high) and 1:1:6 (cement : lime : sand) mortar. Three walls were tested in one way vertical bending. Twelve walls, with varying overlap between units in adjacent courses, were tested in one way horizontal bending. Six walls, with two different aspect ratios, were tested in two way bending. The load versus deformation behaviour and the observed failure modes are reported.
López López, David;
EXPERIMENTAL TESTING OF TILE VAULTS
Tile vaults (sometimes also referred to as thin-tile, timbrel, Catalan or Guastavino vaults) are masonry structures made with thin bricks (tiles), mortar and fast-setting cement or gypsum. This traditional construction technique has produced a large quantity of built heritage examples with an important historical value. Moreover, in the last few years, its combination with new tools for the design and analysis of masonry structures has led to a rediscovery of the technique resulting in interesting architectural pieces with a new formal language.
This paper presents experimental research on tile vaults aiming at the understanding of their structural behaviour for the analysis of both built examples and new architecture. Four full-scale specimens are load-tested until failure at the laboratory, namely, two barrel vaults and two sail domes. The vaults were tested under vertical loading up to failure. Samples of the materials composing the tile vault are also tested for their characterization.
The experiments supplied valuable data about the stiffness, peak loads, post-peak behaviour, damage and collapse mechanism of the tested structures.
Rizaee, Samira (1);
Hagel, Mark Daniel (2);
Shrive, Nigel Graham (3)
SHEAR BOND STRENGTH OF MANUFACTURED THIN STONES CONSIDERING VARIOUS ADHESION METHODS
The strength of the shear bond between manufactured thin stone units and Type S mortar substrates with various surface textures was investigated to assess how and if the type of substrate texture affects the bond strength. Three different types of substrate were considered: mortar block and scratch coat, mortar block with metal lath and scratch coat, and wood block with metal lath and mortar scratch coat. The scratch coat surface was either smoothed, left unfinished, brush scratched, or scratched with a V-Notch trowel. Pre-blended Type S (1:0.5:4.5) and polymer modified mortar were used as the setting-bed. Analysis of the results demonstrated that the mortar block with encased metal lath and mortar scratch coat achieved the highest strength especially when combined with polymer modified mortar. The substrate surface texture did not affect the strength very much. Finally, the polymer modified mortar achieved higher bond strengths than Type S mortar.
Dadras Eslamlou, Soheil (1);
Masia, Mark (2);
Totoev, Yuri (3)
THE SEISMIC PERFORMANCE OF HERITAGE URM BUILDINGS: A PARAMETRIC STUDY
A project is performed in The University of Newcastle, Australia regarding assessment of the seismic performance of the culturally significant unreinforced masonry (URM) buildings. The first part of the project has been contemplated by performing a series of finite element analyses followed by the equivalent experimental tests on two leaves thick perforated URM walls which vary in the spandrel depths and the level of pre-compression stresses. The shape of the walls and their openings are representative of heritage masonry facades used in prevalent Australian URM structures. The current paper presents a parametric study on small scale one storey URM buildings using the characteristics of the mentioned URM walls to determine the performance of the hypothetical small heritage structure under seismic actions. The various parameters used in the current study are the stiffness of floor diaphragms, the opening aspect ratio which results in shallow or deep spandrels, considering one or two-sided openings in the structure which helps study the torsion effect and the pushover loading direction. The results are provided through comparison of the related structural factors and the equivalent capacity curves.
Wilczyńska, Izabela (1);
Brzozowska-Jawornicka, Aleksandra (2);
Ćmielewski, Bartłomiej (2);
Michiewicz, Mieczysław (3)
DOCUMENTATION AND ANALYSIS OF DEFORMATIONS IN A HISTORIC CHURCH A FEW YEARS AFTER ITS CONSERVATION AND REINFORCEMENT
The history of the church dedicated to the Exaltation of the Holy Cross in Ząbkowice Śląskie dates back to the 13th century, but the first document certifying its existence dates to 1302. Over the next centuries, the object was expanded, destroyed, and experienced many fires caused by storms, which is a result of not homogeneous structure. Numerous reconstructions, neglect and the passage of time caused the growing dangerous destruction of the object caused by cracks on the brick in external walls, which induce that the vaults began to threaten a construction disaster. For this reason, in 2011-2014, the church structure was strengthened, with interior renovation. The protective work consisted of implementation in the structure construction the steel braces fixed crosswise over the vaults and in the longitudinal and transverse axes of the naves.
Despite the performed protections, the deformation process of the wall and vault progressed caused cracks, so in 2017 at the request of sisters of Poor Clares of Perpetual Adoration (PCPA) research begin to carried out to determine the scale and speed of the deformations. For this purpose, authors use a classic geodetic measurement technique, such as precision leveling, inclinometers as well as modern remote sensing techniques as terrestrial laser scanning and own prototype sensors measuring the deformation of the building structures.
Based on the geotechnical documentation provided by the Sisters of the PCPA, the geotechnical conditions prevailing around the facility were known, which made it possible to carry out calculations of the bearing capacity of the ground and its impact on the movement of the construction. The research conducted by the authors also allows us to determine to a certain extent, the causes of deformations and pre-indicate the methods of further rescue operations.
Donà, Marco (1);
Carpanese, Pietro (2);
Follador, Veronica (2);
da Porto, Francesca (2);
Sbrogiò, Luca (3);
Xu, Li (1)
SEISMIC FRAGILITY AND RISK OF ITALIAN RESIDENTIAL MASONRY HERITAGE
Seismic risk mitigation at national scale requires the vulnerability assessment of the built stock, along with seismic hazard and exposure evaluation. In particular, vulnerability can be evaluated with empirical approaches, which calibrate fragility curves from observed damage, as well as through mechanical methods that aim to describe structural behaviour. In this paper, the fragilities associated with an intermediate damage state DS (between severe and moderate) of more than 500 Italian unreinforced masonry (URM) residential buildings were calculated based on a mechanical approach, by using the Vulnus_4.0 software (developed at the University of Padova). These buildings were sampled based on national representativeness criteria, allowing to derive a representative mechanics-based fragility model for Italian residential URM buildings. This model is based on the classification of the building stock in macro-typologies, defined by age of construction and number of storeys, which being information available at national level, allow simulating damage scenarios and carrying out risk analyses on a territorial scale. The model was also extended based on a reference model available in the literature – which provides generic fragilities for the EMS98 vulnerability classes – in order to obtain a fragility model distributed on the five DSs of the EMS98 scale. The model was then validated using the damage observations of the 2009 L’Aquila earthquake, contained in DaDO (Database of Observed Damage) and, lastly, it was used to derive seismic damage maps and expected annual loss estimates on a national scale, by means of the I.R.MA (Italian Risk MAps) software. I.R.MA collects, organizes and combines data of exposure (i.e., building stock information, provided by the National Institute of Statistics), seismic hazard (provided by the National Institute of Geophysics and Volcanology) and fragility (by customized fragility models), to perform seismic risk analyses from municipal to national level.
Zarrin, Orod (1);
Ramezanshirazi, Mohsen (2)
INTELLIGENCE PREDICTION SYSTEM OF SEMI-INTERLOCKING MASONRY PANELS BEHAVIOR
The new method of masonry construction inspired from dry stack system has been developed in Masonry Research Group at the University of Newcastle, Australia and named Semi-Interlocking Masonry (SIM). This system can be used as a structural element due to the ability of dissipation earthquake energy. The SIM panels dissipate energy through the sliding friction on bed joints between courses of SIM units during earthquake excitation. The main objective of this study is to investigate experimentally the out-of-plane load-displacement capacity of the SIM panel and predict its behavior by Artificial Neural Network (ANN). Attempting to introduce several ANNs to predict the maximum displacement of the SIM panels lead to find the best network capable with SIM panels. The results show that the ANNs prove a significant ability of accurate prediction. In addition, the outcomes of feature selection algorithm help to arrange the most effective factors on maximum displacement to optimize time, safety and cost of projects.
Damiani, Nicolò (1);
Miglietta, Marco (1);
Guerrini, Gabriele (2,3);
Graziotti, Francesco (2,3)
AN INNOVATIVE TIMBER SYSTEM FOR THE SEISMIC RETROFIT OF UNREINFORCED BRICK MASONRY BUILDINGS
A new timber-based seismic retrofit technique was investigated at the EUCENTRE laboratories (Pavia, Italy) within an extensive experimental campaign on the vulnerability of existing Dutch unreinforced masonry (URM) cavity-wall terraced houses. These structures typically consist of a single-wythe, calcium-silicate-brick inner leaf with load-bearing function, and an external clay-brick veneer with no structural purposes, connected to each other by steel ties. The first floor is usually built with precast reinforced concrete slabs, while the second floor and roof often consist of timber joists and planks. The main objective of the retrofit was to improve the seismic capacity of Dutch URM terraced houses with a light, cost-effective and low-invasive intervention. The proposed retrofit system included timber frames fastened to the internal surface of masonry piers and to the building floors, on which oriented-strands boards (OSB) are nailed. The retrofit was designed to increase both in-plane and out-of-plane capacities of masonry piers as well as to improve the overall connections between masonry elements and floor diaphragms. After performing quasi-static in-plane cyclic tests on two calcium-silicate URM piers, two identical full-scale two-storey buildings were tested dy-namically on the shake-table, one in bare and the other one in retrofitted configuration. This paper focuses on the experimental performance of these buildings, with emphasis on the improved seismic response of the specimens, and proposes simple design equations.
Isfeld, Andrea C.;
Stewart, Mark G.;
Masia, Mark J.
STOCHASTIC FINITE ELEMENT MODEL ERROR FOR UNREINFORCED MASONRY WALLS SUBJECTED TO ONE WAY VERTICAL BENDING UNDER OUT-OF-PLANE LOADING
The strength of unreinforced masonry (URM) walls subjected to one way bending under out-of-plane loading (no pre-compression) is known to be affected by the masonry unit tensile bond strength. Factors such as batching, workmanship, and environmental exposure alter the strength of this bond, resulting in spatial variability for any URM assembly. This paper focuses on a preliminary stochastic assessment of clay brick URM walls with spatially variable tensile bond strength subjected to uniformly distributed out-of-plane loads in one-way vertical bending. Stochastic computational modelling combining Finite Element Analysis (FEA) and Monte Carlo Simulation (MCS) is used to account for bond strength variability when estimating the walls ultimate failure loads. Previously, this approach has been used to study the effect of material variability on cracking loads, failure loads, and failure modes of URM walls in one and two-way bending. For this preliminary assessment FEA MCS has been applied to a subset of existing test data for walls with consistent properties constructed by ten different masons. For these walls a 3D non-linear FEA model was developed, followed by a stochastic analysis for which the unit tensile bond strength is spatially varied according to the measured flexural tensile bond strength and its coefficient of variation. For a set of simulations the peak load and load-displacement data was extracted and analysed, showing good agreement with the results of wall test data.
Lignola, Gian Piero;
NONLINEAR FLEXURAL CAPACITY MODEL FOR FRCM-STRENGTHENED MASONRY WALLS UNDER IN-PLANE LOADING
Recent strong earthquakes produced heavy structural damages to existing unreinforced masonry (URM) buildings, particularly in the case of historic urban centres such as L’Aquila (2009) and Amatrice (2016). Spatially-distributed damages at urban-to-regional scale, as well as the need to speed up the recovery process, have motivated an extensive use of fabric-reinforced cementitious matrix (FRCM) systems for external retrofitting of URM buildings. This has significantly motivated the development of ad-hoc guidelines for a mechanics-based design of FRCM retrofitting systems. In this paper, the authors present a novel flexural capacity model for incremental static analysis of URM walls subjected to in-plane lateral loading. The formulation makes use of a fibre-based approach that explicitly accounts for geometric and mechanical nonlinearity sources at sectional level. Capacity modelling was carried out using data sets available in the 2019 Italian building code commentary and experimental review studies. The output of this study is focused on moment–curvature diagrams remarking a number of performance limit states. This study attempts to move beyond the classical strength-based verification formats implemented in current guidelines for the ultimate limit state. The proposed capacity model allows evaluating the evolution of flexural behaviour as cracking and crushing propagate throughout the URM-FRCM cross section.
Matysek, Piotr (1);
Seręga, Szymon (2)
ASSESSMENT OF BRICK MASONRY STRENGTH USING TESTS ON CORE SAMPLES CUT FROM STRUCTURES
A common diagnostic task for masonry structures is to assess compressive strength of existing brickwork. This article presents method of assessing masonry compressive strength using tests on core samples extracted from masonry walls and pillars. This method can be classified as minor-destructive one (MDT) and is especially useful for historical buildings. In the research samples with diameters of 150 mm and 100 mm were tested. The core samples were cut from brick masonry made at the laboratory and from historical structures erected in the 19th and 20th century. The component materials were ceramic solid bricks and lime or cement - lime mortars. The size effect on compressive behaviour of core samples was analysed for different types of masonry. A similar ratio between the compressive strength measured on two geometries of samples was found. Based on test results and numerical simulations practical recommendations have been proposed.
Benittez, Lívia Regueira Fortunato (1);
Parsekian, Guilherme Aris (1);
Neves Junior, Alex (2)
REVIEW ON CO2 CAPTURE, STORAGE AND SEQUESTRATION IN NON STEEL REINFORCED PRECAST CONCRETE
Climate changes has been a cause of concern to the population, governments and scientists around the world. Such changes are caused by the growing increase in greenhouse gas emissions as a result of human activities. The construction sector stands out as responsible for the emission of one-third of the total greenhouse gases emitted. The process of extracting and manufacturing the raw materials needed to obtain concrete emits large amounts of CO2 into the environment. However, recent research has shown that Portland cement based materials have the ability to store CO2 in the form of stable carbonates, especially in the early ages, through the accelerated carbonation process. This technology can be applied to structural elements without reinforcing steel. This paper presents a review on state-of-the-art studies in this emerging technology and provides methods for quantifying CO2 sequestration in cement matrices, as well as technical information on CO2 capture from stationary emissions, transport, storage, costs and incentives financial resources. Keywords: CO2 capture, cure, accelerated carbonation, concrete.
Valluzzi, Maria Rosa
LOCAL MECHANISM ANALYSIS IN UNREINFORCED MASONRY BUILDINGS ACCORDING TO A NEW PROCEDURE BASED ON FLOOR SPECTRA EVALUATION
Local rather than global seismic behaviour is a well-known feature in both masonry aggregates and monumental buildings with large internal spans, such as churches or palaces. In such cases safety assessment through local mechanisms kinematic analysis is generally considered a viable solution. The definition of a) the correct scheme for calculations and b) the seismic forces worsens when secondary architectural elements (pinnacles, upper portions of facades, turrets, etc.) or masonry macroblocks, which may interact dynamically with the main structure, are considered, may be sometimes challenging.
Therefore, the recent update of Italian seismic code stresses the role of a building’s global dynamic response and floors’ stiffness in the evaluation of seismic actions on the macroblocks in which it can be subdivided. The main novelties concern: a) introduction of friction between macroblocks; b) horizontal seismic forces which may vary according to the floor’s deformability; c) seismic input due to a new formulation of for floor spectra; d) greater importance given to dynamic parameters (damping, frequencies) of both, the building and the local mechanism.
The paper aims at the implementation of the new procedures in an existing unreinforced masonry building (Palazzo Carraro in Noale – Venice) with flexible horizontal diaphragms. In absence of a relevant crack pattern, modal analysis is used to detect the parts of the building where local mechanism may develop. These observations are then compared to the possible local mechanism resulting from the visual inspection of vulnerability factors showing some correspondence. Safety evaluations, in linear and non-linear field, according to the previous and the current Italian seismic codes are carried out and compared. For the case study, the new procedure is much more pejorative, since acceleration and displacement demands are more than twice the ones obtained in the old one.
FORMULATION AND EXPERIMENTAL VALIDATION OF DISTRIBUTED PLASTICITY MACRO-ELEMENT FOR UNREINFORCED MASONRY WALLS
The equivalent frame modelling (EFM) approach allows the assessment of unreinforced masonry (URM) buildings with a trade-off between realistic damage simulation and computational efficiency. EFM is based on the use of macro-elements by which flexural and shear behavioural modes are simulated through nonlinear force-deformation relationships combined with axial load-shear interaction domains. In this study, a novel macro-element is presented for nonlinear static analysis of URM buildings. The macro-element relies upon force-based fibre modelling approach accounting for geometric and mechanical nonlinearities, the latter through nonlinear constitutive models for masonry in tension and compression. Shear-flexure interaction is taken into account and strain softening is considered according to a smeared crack approach. Numerical results are compared with experimental data, highlighting a good accuracy of the model and its capability of reproducing both shear and flexural behavioural modes under varying aspect ratio of the URM wall and axial load level.
Comodini, Fabrizio (1);
Mezzi, Marco (2)
VERTICAL COLLAPSE MECHANISMS IN MASONRY BUILDINGS DUE TO SEISMIC VERTICAL COMPONENT
The accelerometric recordings made in the epicentral areas during the recent earthquake in Central Italy (2016-17) show vertical components of high intensity. During the post-earthquake damage assessment operations in the epicentral areas, damage types different from those encoded in the literature have been observed, with a macro-element collapse method attributable to the earthquake vertical component. This paper presents some of these buildings characterized by the presence of horizontal lesions, by the displacement of the highest levels, by vertical lesions in the sub-windows. The masonry walls are intact without the typical shear or flexion lesions and the lower levels do not show any damage. The crack pattern and the associated collapse mechanisms are not among the classic mechanisms in the plane and orthogonal to the plane. The definition of mechanisms characterized by the loss of vertical connection of entire structural bodies is therefore hypothesized. The activation of this type of mechanism would seem to exclude the formation of the classic collapse mechanisms on which the seismic capacity checks of the masonry structures reported in the technical codes are based. The aim of the study is to reproduce the behaviour through simplified linear kinematic analyses on calculation models corresponding to the case study and to introduce criteria for the identification and verification of the mechanisms introduced, with indications for codes and design methods.
Shah, Kushi (1);
Landi, Angelo Giuseppe (2);
Tognon, Alisia (2)
EARTHEN MORTAR IN THE WALLED CITY OF AHMEDABAD (INDIA). ANALYSIS OF CONSTRUCTION TECHNIQUES AND DAMAGES OF TWO PORTION OF MASONRY
Carefully constructed brick masonry walls, built using earthen mortar are common in vast areas of India (where they coexist with the most widespread lime mortar masonry) at least until the middle of the nineteenth century. Studies on earthen mortar masonry, though in an embryonic state, already show significant differences compared to the more studied raw earth buildings. This kind of masonry was spread in India, particularly in the Gujarat region, however the use of local materials and the technological refinement achieved by craftsmen produced heterogeneous applications, also depending on the period. In particular, in Ahmedabad, the mixture of earth, sand and quicklime is well documented and a first catalogue has implemented a basic knowledge of the different types of construction and damages, which currently is largely missing.
Ferretti, Francesca (1);
Incerti, Andrea (2);
Mazzotti, Claudio (1)
EXPERIMENTAL AND NUMERICAL STUDIES ON THE SHEAR-SLIDING BEHAVIOR OF CLAY BRICK MASONRIES
The identification of the shear strength parameters of masonry can be carried out through different experimental techniques, aimed at reproducing typical failure modes of masonry structural elements. The objective of this work is to characterize the shear-sliding behavior of brick masonry through the execution of triplet tests on three different masonry typologies. Series of triplet tests (EN 1052-3) were performed in displacement control on standard samples, constituted of clay bricks and lime-based mortar, arranged in a stacked bond. The experimental results were analyzed and compared among the different masonry typologies trying to correlate the shear strength parameters to the mechanical properties of the materials. Numerical simulations of the experimental tests were also carried out, adopting a simplified micro-modeling approach. The nonlinear numerical analyses allowed to properly interpret the experimental outcomes and they were compared with them in terms of failure load, post-peak behavior and specimen deformability, obtaining a good agreement.
Baietti, Giulia (1);
Focacci, Francesco (2);
Gentilini, Cristina (3);
Carloni, Christian (4)
STUDY OF THE EFFECTIVENESS OF ANCHORAGES APPLIED TO SRG STRIPS BONDED TO MASONRY BLOCKS
Steel reinforced grout (SRG) is considered part of the broader family of fiber-reinforced cementitious matrix (FRCM) composites, which are an alternative to fiber-reinforced polymer (FRP) composites to strengthen and retrofit concrete and masonry structures. The main advantages of SRG are the low cost of the fibers, excellent resistance to high temperatures and fire, compatibility with different types of support, and vapor permeability that could be crucial when SRG is applied to historical masonry structures. Despite these advantages, there are still some open issues related to the need of anchorage systems to improve the effectiveness of the system in situations where debonding occurs, or when the lack of development length could compromise the response of the strengthened element.
This paper presents the results of an experimental work carried out to study the effectiveness of the anchorage system and its interaction with an SRG strip externally bonded to masonry. Single-lap shear tests are performed to investigate the debonding phenomenon. The SRG strip is bonded to a masonry block and features an anchorage system either at the free end or loaded end of the bonded area. Two types of anchorage are considered: 1) a separate spike that interacts with the bonded strip and 2) an extension of the SRG fibers into the masonry block obtained by bending the fibers and inserting them into a hole filled with the same SRG matrix mortar. Test results demonstrate that effectiveness of the SRG strip is positively affected by both types of anchorage systems.
Casprini, Elena (1);
Passoni, Chiara (1);
Marini, Alessandra (1);
Belleri, Andrea (1);
Giuriani, Ezio (2)
IN-PLANE CAPACITY OF BEAM AND BLOCK FLOOR SYSTEMS: AN IN-FIELD EXPERIMENTAL STUDY
This paper investigates the in-plane structural response of RC beam and clay block floor systems. Such a floor typology is quite widespread in southern Europe and characterizes constructions built after the 1960s. Seismic vulnerability of these constructions is widely acknowledged, and their retrofit is now considered a priority to increase the resilience of the built environment.
In case of earthquakes, regardless whether the building is in the as-is condition or has been retrofitted, the floor should act as an in-plane diaphragm. The diaphragm collects the inertia forces from floors and walls loaded out-of-plane and conveys them to the lateral load resisting system. The floor in-plane capacity is usually not critical in existing buildings in their as-is condition, but it may become an issue after the retrofit. This is particularly critical when high-stiffness interventions substantially increase the seismic actions on the building, and when the introduction of new seismic resistant elements lengthen the span of the diaphragm.
The evaluation of the in-plane capacity of existing floors is of fundamental importance both in the seismic vulnerability assessment and in the retrofit design, especially when retrofit interventions are carried out from the outside of the buildings. Such interventions are particularly appreciated nowadays as they overcome the major problem of the relocation of the inhabitants, but they may be hindered by the need to strengthen the floors.
In this paper, the outcomes of an in-field experimental study are discussed, which is aimed at investigating the in-plane capacity of two floor systems, consisting in RC beam and clay block floor systems either with or without additional extrados RC slab. The conceptual design of the testing bench and the main results of the experimental study are discussed. Based on the experimental results, a simplified model is proposed to estimate the ultimate capacity of existing floors.
Dalalbashi, Ali (1);
Ghiassi, Bahman (2);
Oliveira, Daniel V. (1)
FREEZE-THAW DURABILITY OF GLASS TEXTILE-REINFORCED MORTAR COMPOSITES
Application of textile-reinforced mortars (TRMs) for externally bonded reinforcement of existing masonry structures has received a considerable recent attention. The mechanical behaviour of these composites, which are composed of continuous fibers embedded in an organic matrix, and their effectiveness in improving the performance of strengthened structures are highly dependent on the fiber-to-mortar bond behaviour as well as the bond between TRM system and substrate.
Understanding the long-term performance of these mechanisms is therefore of critical importance for design of durable TRM composites and ensuring the safety of strengthened structures. To address this aspect, the effect of freeze-thaw cycles on the textile-to-mortar bond behaviour is experimentally investigated and discussed in this paper. The results illustrate a significant deterioration of the textile-to-mortar bond performance in the studied composites.
Pradhan, Bharat (1);
Zizzo, Maria (1);
Anic, Filip (2);
Penava, Davorin (2);
Sarhosis, Vasilis (3);
Cavaleri, Liborio (1);
Sucato, Vincenzo (1)
A MACRO-ELEMENT MODELLING TECHNIQUE TO ACCOUNT FOR THE IP AND OOP INTERACTIONS IN URM INFILLED RC OR STEEL BUILDINGS
RC or steel buildings with unreinforced masonry (URM) infills is a common construction practice in all over the world. To correctly assess the seismic performance of infilled frame structures, the analysis of the behaviour of masonry infills under in-plane (IP) and out-of-plane (OOP) loading, as well as their interaction, is of paramount importance. The aim of this paper is to present a new macro-element modelling technique able to simulate the IP and OOP response of URM infilled RC or steel frames subjected to earthquake actions. The model consists of a horizontal, a vertical and two diagonal struts which are represented by fiber section beam-column elements and their compressive behavior is defined by empirical strength and strain parameters. The paper also discusses on derivation of the empirical parameters based on the actual properties of infill wall. The proposed model has been calibrated with experimental results available in the literature. From the analysis, a good agreement between the experimental and numerical results is obtained. In particular, the numerical model proposed herein is capable to simulate the arching mechanism in the infill wall during the OOP loading as well as to capture the interaction between the IP and OOP actions during seismic events.
Falkjar, Kristian (1);
Erochko, Jeffrey (1);
Santana, Mario (1);
Lacroix, Daniel (1,2)
BENEFITS OF CASEIN ADDITIVES IN HISTORIC MORTAR MIXES
Casein, an organic milk protein, was used extensively in masonry mortars from medieval times until the 18th century. It was understood to improve workability of the mortar, resulting in a pourable consistency, however, little information is available on its effects on material strength. Casein is non-toxic, has minimal environmental impacts, and has no reported health hazards beyond the lime powder of the mortar itself. Recent mortar conservation projects have proposed its use, notably on the buildings of Parliament of Canada, however, a debate exists on the value of this additive.
Mortar cubes were cast for compressive and tensile tests, while square prisms were cast for flexural and shear tests. Brick-to-mortar bond strength tests were conducted in flexure and in shear. Clay bricks intended for an historic retrofit application were used. It was found that adding 0.5% casein by mass resulted in a flowable mortar, however, a 75% reduction in strength resulted. Contrarily, brick-to-mortar bond strength substantially improved.
Further tests were conducted reducing the water content while maintaining 0.5% casein by mass. It was found that reducing the water content by up to 18% resulted in a corresponding increase in material strength while maintaining the increased bond strength.
With masonry mortar repair techniques, it has been deemed critically important to appropriately specify the replacement mortar with a material strength compatible with both the brick and the original mortar. Casein protein acted as a superplasticizer, creating a liquid-like mortar if 0.5% casein by mass was added. A casein mortar would not be suitable for new construction or a complete re-build of an historic wall. However, the application of casein mortar is plausible for repointing existing mortar joints, as it has favourable flow properties. It may also be injected between mortar wythes as a means of stabilizing a multiple wythe masonry wall.
Moreno-Herrera, Joel Alberto;
Varela-Rivera, Jorge Luis;
Fernandez-Baqueiro, Luis Enrique
IN-PLANE FLEXURAL BEHAVIOR OF AUTOCLAVED AERATED CONCRETE CONFINED MASONRY WALLS
Confined masonry walls are widely used in some countries of Latin America (Mexico, Chile, Peru, Colombia, Argentina and Venezuela), Asia (Iran, China and Indonesia), Europe (Italy, Slovenia, Romania and Serbia) and Africa (Algeria and Morocco). Confined masonry is a structural system composed of flexible reinforced concrete confining elements cast around an unreinforced masonry wall panel. The shear behavior of confined walls has been widely studied. Variables studied have been the unit type, types and quantities of steel reinforcement in confining elements, wall aspect ratio, openings and wall axial compressive stress, among others. In contrast, the flexural behavior of confined walls has been barely studied. In this work, experimental results of a study on the flexural behavior of autoclaved aerated concrete (AAC) confined masonry walls are presented. Three full-scale walls were tested in the laboratory under constant axial compressive stress and incremental reverse cyclic loads until failure. The variable studied was the wall axial compressive stress. Class AAC-4 masonry-type units were considered. Cracking patterns and lateral load-drift ratio curves are presented. The behavior of walls was characterized by horizontal flexural cracks, followed by yielding of the longitudinal steel reinforcement of vertical confining elements. Then flexure-shear and diagonal cracks were observed. As expected, the wall flexural strength increased as the axial compressive stress increased. By the contrary, the displacements ductility increased as the axial compressive stress decreased. Finally, flexural strength of walls was well predicted using flexural theory (kinematics, constitutive models and equilibrium). The ratio between analytical and experimental strengths of walls varied from 0.95 to 1.05.
INVESTIGATION OF THE STRUCTURAL RESPONSE THROUGH SIMPLE NUMERICAL MODELS DERIVED AUTOMATICALLY FROM LIDAR SCANNING: THE CASE OF MASONRY VAULTS IN HISTORICAL BUILDINGS
LiDAR measurements have created a new perspective for the fast survey of historic buildings, bringing particular benefit in the case of complex systems as the masonry vaults. For this category of structures, the survey is of significant interest since the structural response is closely connected with the real vault shape and its components. Beside the accuracy and the complexity of the registered data with LiDAR technology, it is possible to create in an automatic way an approximated surface of the registered point cloud, which can be used to develop a simplified geometric model of the scanned case study.
The aim of this paper is to investigate the use of the approximated surface to develop a structural model for the fast analysis of masonry vaults. The methodology integrates scanning with LiDAR sensor, classification of point cloud with machine learning algorithms, approximation and reconstruction process based on approximation functions and structural analysis with the finite element technique.
The proposed methodology is tested in the case of masonry vaults of the Church of Santa Marta, located in the town of Arona, in the shores of Lake Maggiore in Italy. The accuracy of the simplified FEM model is compared with an accurate model 3D FEM model of the same vault, allowing to draw important conclusions on the link between the level of simplification and accuracy of structural simulation.
The results highlight that the simplified models created in a short time, allow to give important results on the structural response of the masonry vaults, including the magnitude of forces in the system, the force flow, or possible effects of settlements in the masonry vaults. These results improve significantly the quality of the structural survey, as they can guide further inspections directly during the first visit, as well as improve the decision-making process.
Aşıkoğlu, Abide (1);
Vasconcelos, Graça (1);
Lourenço, Paulo B. (1);
Del Re, Alessandro (2)
SEISMIC RESPONSE OF AN UNREINFORCED MASONRY BUILDING WITH STRUCTURAL IRREGULARITY; BLIND PREDICTION BY MEANS OF PUSHOVER ANALYSIS
Structural masonry has been widely used in construction since early civilizations and constitute a large part of the building stock in both developed and developing countries. Important developments of new structural systems, such as reinforced concrete and steel structures, resulted in a considerable reduction in new unreinforced masonry (URM) constructions. Still, owing to its simplicity and sustainable characteristics of ma-sonry, i.e. acoustic and thermal insulation, and fire protection, new URM is a promising structural typology. However, past seismic events confirmed that further developments are required to improve the seismic behavior of masonry buildings since there is a lack of seismic design rules on these structural systems. Although masonry structures have a high seismic vulnerability, it is not reasonable to assume that its construction would not be applicable in regions with low to moderate seismic hazard. Proper precautions and improved design rules would contribute to the construction of low- and medium-rise masonry buildings in seismic prone zones. Within this framework, the present study aims to develop experimental and numerical analysis on quasi-static cyclic testing on URM building with geometrical complexity. An experimental building is planned as a half-scale two-story building with structural irregularities in plan and elevation, such as having set back in one corner and irregular opening distributions, respectively. While the seismic codes cover designing rules mainly based on regular structures and impose certain penalties on structural irregularities, regular configurations are not representative ones due to architectural and functional concerns. This study focuses on understanding and assessing the global seismic behavior of a masonry building imposed to torsional effects. Thus, the numerical pushover analysis is based on blind prediction by means of finite element method to obtain capacity curves and decide a reasonable loading protocol for the experimental campaign.
Uros, Mario (1);
Atalic, Josip (1);
Savor Novak, Marta (1);
Kuk, Krešimir (2)
SEISMIC PERFORMANCE ASSESSMENT OF EXISTING STONE MASONRY SCHOOL BUILDING IN CROATIA USING NONLINEAR STATIC PROCEDURE
Seismic performance assessment of a stone masonry school building in Croatia is presented in this paper. The building is located in the seismically active southern part of the country, with the reference peak ground acceleration on the bedrock for the return period of 475 years of 0.214g. Measurements of the soil fundamental frequency were conducted. The lateral load-resisting system of the structure comprises stone masonry walls typical for this region. Seismic analyses with nonlinear static methods were performed including material non-linearities of structural elements. Criteria for evaluation and performance requirements were accounted and relevant engineering demand parameters were compared in relation to design criteria. The seismic performance assessment was made based on the obtained results, including the building collapse mechanisms and the identification of critical structural elements. It is shown that main failure mode of stone masonry walls in the building is shear diagonal cracking.
EFFICIENCY AND ACCURACY OF A MULTISCALE DOMAIN ACTIVATION APPROACH FOR MODELING MASONRY FAILURE
Masonry is a composite consisting of two very different materials, which results in complex structural behavior. There exist accurate models in which both constituents are modeled explicitly, such as microscale and mesoscale models, but they require a great amount of computational resources. A faster, alternative, strategy to model masonry structures is the use of macroscale models, where homogenized elements are used which condense constituent behavior into one composite material. This approach also removes the upper bound on finite element sizes, which can lead to a reduction in element numbers. However, using one single material type makes it hard to capture the inherent nonlinear behavior when simulating masonry failure.
In order to find a compromise between accuracy and computational efficiency one can use a scale embedding multiscale model where both macro- and microscale elements come into play, combining the advantages both have to offer. In this work a modeling framework that formulates an adaptive scale embedding multiscale technique is presented, with the goal of both accurately and efficiently simulating large masonry structures. This theory is tested and compared to show its accuracy to rival a fully microscale model, while at the same time comparatively having a higher computational efficiency. In this work, the developed multiscale model is compared to its underlying microscale model using a couple example structures, ranging from small to large scale 2D unreinforced masonry walls with openings, including an application related to failure due to soil settlement, showing a potential for the application of this type of modeling.
EXPERIMENTAL ASSESSMENT OF AN INNOVATIVE ISOLATION TECHNIQUE FOR THE SEISMIC DOWNGRADE OF EXISTING MASONRY INFILLS
The seismic vulnerability of infilled reinforced concrete (RC) frames built in the Mediterranean earthquake prone regions before the 70’s has been assessed by many post-earthquake surveys and several experimental studies. Beyond the lack of seismic-resistant detailing in the frame elements, a relevant source of vulnerability for these structural typology is represented by the in-plane interaction between the frame and the infills. Infills are typically made of masonry, selected for its good thermal and acoustic insulation performance and characterized by high stiffness and strength, but coupled with a brittle post-peak behavior. During an earthquake, the different stiffness and deformation capacity characterizing the infill and the frame can lead to severe damage, including widespread cracking and crushing in the former, and brittle shear failures in the latter. When dealing with the seismic retrofit of an existing infilled RC building, this local interaction cannot be ignored, as it could jeopardize the efficiency of the seismic retrofit intervention by triggering unexpected early collapses in the existing frame. In order to mitigate this issue, in the present paper an infill isolation technique is presented, conceived to reduce the infill-frame in-plane interaction (downgrade). The downgrade is obtained by isolating the infill from the surrounding frame with a cut on a portion of the infill perimeter. A specific innovative wall-to-frame beam connection is implemented, which promotes the masonry arching mechanism against out-of-plane actions, while ensuring in-plane relative sliding. In the paper, the experimental cyclic in-plane and out-of-plane response of a real scale specimen downgraded with the proposed technique are presented and some issues about the conceptual design of the intervention and its invasiveness are discussed.
SHEAR BEHAVIOR OF MASONRY TRIPLETS WITH A DAMP PROOF COURSE AND A THERMAL INSULATING LAYER
The energy efficiency of structures has become an important aspect in today’s society. In Belgium, the first layer placed directly on the floor is commonly executed using masonry units with higher insulating properties to serve as a thermal break layer. It, therefore, prevents the occurrence of thermal bridges between the ground and the rest of the wall. Moreover, a damp proof course (DPC) is often placed between the first two layers with two main functions. Firstly, to direct water which passes the outside wall out of the cavity through weep holes and secondly, to prevent moisture from rising into the building.
The thermal break layer and the DPC are two non-structural measures. Thermal conditions are improved with the thermal break and DPC-layers keep your inner walls dry. However, both interventions have an impact on the structural behavior. As of yet, hardly any research has been performed on the shear strength of a masonry wall where both layers are included.
In this contribution, an experimental campaign, conducted on a small- and meso-scale, is presented. Within this campaign, shear tests are performed on masonry triplets and wallets with varying combinations of bricks and with or without the application of a DPC. Normally different standards are to be applied for triplet tests with and without a DPC layer (EN 1052-4 and EN1052-3 respectively). However, to achieve more comparable results, all triplet tests are performed in accordance with EN 1052-3. The meso-scale masonry wallets are furthermore tested to observe the shear bond strength and failure behavior. In conclusion, this paper discusses the shear behavior of varying masonry types with and without the presence of a damp proof course.
Jafarzad Eslami, Babak (1);
Darban, Hossein (2);
Del Grosso, Andrea (3)
EFFECT OF MORTAR-BRICK COHESIVE INTERFACE ON SEISMIC RESPONSE OF MASONRY WALLS
Masonry is one of the oldest and most widespread structural materials with many applications in various constructions such bridges, traditional buildings and historical monument. Masonry structures are heterogeneous and composed of bricks joined by mortar with each of them having their own mechanical properties. The overall behaviour and load bearing capacity of such structures are highly affected by the mechanical and geometrical properties of bricks and mortar and their cohesive interface.
The geomorphology of Iranian territory is responsible for the occurrence of several earthquakes which induce medium to high seismic hazard levels (such as Manjil, Bam and Kermanshah). In addition, most of the historical buildings lying in this region are made of masonry, and are characterized by significant seismic vulnerability.
In this work, a cohesive fracture model is implemented in finite element code to simulate the damage occurs at the mortar-brick interface in a representative masonry wall element under seismic loadings, which are derived from some real case earthquakes occurred in Iran. Different cohesive laws are assumed and their effects on the failure load and collapse behavior of the masonry wall is investigated. Comparative results will be presented in the meeting together with discussions on different failure scenarios.
Bracchi, Stefano (1);
Mandirola, Martina (2);
Rota, Maria (2);
Penna, Andrea (1)
A NEW MACROELEMENT-BASED STRATEGY FOR MODELLING REINFORCED MASONRY PIERS
Macroelement models are widely used to study the behaviour of unreinforced masonry buildings subjected to horizontal actions, due to their proven efficiency and simplicity of use. However, in some areas reinforced masonry buildings are present; in these cases, it can be necessary to study the performance of these buildings when subjected to horizontal actions, such as earthquakes. In the present work, a new macroelement-based strategy to model the in-plane nonlinear behaviour of reinforced masonry piers is proposed, starting from a macroelement model widely adopted for unreinforced masonry and implemented in the TREMURI software. The strategy consists in coupling macroelements representative of masonry and horizontal (shear) reinforcement to nonlinear elements representative of the vertical reinforcement. To test the efficiency of this model, quasi-static in-plane cyclic experimental tests performed on reinforced masonry piers made of clay blocks were simulated. The tests were characterized by different geometries, axial loads and reinforcement ratios and allowed to study the possibility of capturing both the flexural and shear failure modes. The comparison of experimental and numerical results was performed in terms of both hysteresis curves and damage patterns. The model can be finally used to perform nonlinear analyses of entire buildings.
Triller, Petra (1);
Gams, Matija (2);
Tomaževič, Miha (1)
EXPERIMENTAL TESTING OF SEISMIC RESPONSE OF BRICK MASONRY WALLS UNDER DIFFERENT BOUNDARY CONDITIONS
In order to reproduce the seismic response of masonry piers by laboratory cyclic shear tests, the boundary conditions need to be similar to those in actual buildings. If the similarity is not adequate, tests may predict unrealistic behaviour, and in the worst case, even unrealistic failure mechanisms. To study the effect of different boundary conditions, eight walls built with group 2 hollow clay units (29x19x19 cm) and general purpose mortar (compressive strength 2.1 MPa) were tested.
In all tests the walls were fully fixed to the floor and the simulation of different boundary conditions was achieved by changing the conditions at the top of the wall. In total, four different types of boundary conditions were used in the tests (two walls per type of boundary conditions were tested). The first type of boundary conditions was of cantilever type with free vertical displacement and rotations at the top and constant vertical load. The second type had fixed rotation at the top and constant vertical load (so called fixed-fixed rotations conditions). In order to achieve zero rotation at the top, the vertical load at both sides of the wall were continuously changing, but their sum was constant. The rotation was measured using a precise inclinometer. The third type had constrained vertical displacements and rotations at the top. In this case, total vertical load changed during the test. In the fourth type, the moment at the top was applied in such a way that the zero moment was exactly at the mid height of the wall through the entire test. The vertical force was constant, but the rotations were not.
The results show that different boundary conditions have a strong influence on the force and displacement capacity of the walls, and can cause different failure mechanisms.
BEHAVIOUR OF STITCHING BARS IN THE MASONRY WALL
Stitching of cracked masonry elements with the
reinforcement is a quite popular method of repairing damaged walls. Scientific
publications often describe the effect of repair in the form of crack stitching
on models tested under compression, bending or shearing. However, it is
difficult to find a paper, whose authors made an attempt to estimate the impact
of different types of reinforcement on strengthening issues. This paper
presents results for tensile tests performed on different types of bars with a
diameter of 6, mm, pull-out
tests for twisted and ribbed bars in a masonry wall, and tests for flexural
strength of mortar beams reinforced with a stitching bar. Obtained results were
the basis for an attempt to evaluate the effectiveness of the interaction
between the stitching reinforcement and the masonry wall. The tested reinforcement
was composed of smooth bars made of common or stainless steel, ribbed bars, and
twisted bars. The most effective reinforcement proved to be the twisted bar
because it showed better deformability and adhesion to the mortar. Test results
indicated that the anchorage length of stitching bars should be greater than
Shahreza, Seyedmohammad Kahangi (1);
Molnár, Miklós (1);
Niklewski, Jonas (1);
Gustavsson, Tomas (2);
Björnsson, Ivar (1)
MAKING DECISION ON REPOINTING OF CLAY BRICK FACADES ON THE BASIS OF MOISTURE CONTENT AND WATER ABSORPTION TESTS RESULTS – A REVIEW OF ASSESSMENT METHODS
Use of clay brick masonry in façades is often motivated by its aesthetic values and durability. Yet, mortar joints exposed to climate agents erode over time, expected to cause elevated moisture content and water absorption. Thus, it is often recommended that 40- to 50-year-old facades should be repointed – a measure which is intrusive and costly. Decision is in many cases taken without a clear evidence that repointing will diminish water absorption and moisture content in the renovated walls. This paper presents the results of a state-of-the-art study on field and laboratory methods to measure moisture content and water absorption in clay brick masonry. For common buildings, use of low cost and time efficient measurement methods is feasible. However, prior to measurements, analysis of technical and climate data combined with a visual inspection might give a rational basis for decision on repointing or other alternative maintenance measures.
STRENGTHENED CLAY BRICK AND LIGHTWEIGHT AGGREGATE CONCRETE BLOCK WALLS TESTED UNDER ECCENTRIC AXIAL LOADING – A FEASIBILITY STUDY ON DIFFERENT STRENGTHENING TECHNIQUES
Strengthening of masonry walls is a means to improve the energy performance of modern external masonry walls without further increasing their total thickness. The present paper evaluates the feasibility - here referring to ease-of-application and structural performance - of several techniques aimed at strengthening masonry walls subjected to eccentric axial loading. Four full scale walls made of solid clay bricks and lightweight aggregate concrete blocks were strengthened using externally bonded reinforcement of conventional steel mesh, high-strength steel wire, masonry reinforcement and mechanically fastened strips of steel sheet. Each of the studied strengthening techniques is feasible from a structural perspective. Mechanically fastened steel strips require the least work, and no render is required since the steel is not exposed to fire. Steel mesh can be applied directly on the wall surface, which lowers the thickness of the render layer. Continued research with more replicates will confirm the presented conclusions.
Senaldi, Ilaria (1);
Guerrini, Gabriele (1);
Bruggi, Andrea (1);
Penna, Andrea (1);
Quaini, Marco (2)
EXPERIMENTAL CHARACTERIZATION OF PBO-FRCM COMPOSITES FOR MASONRY STRUCTURES RETROFIT
Over the past few decades, application of composite materials has emerged as an effective strengthening technique for existing buildings. In particular, the so-called Fabric Reinforced Cementitious Matrices (FRCM) or Textile Reinforced Mortars (TRM) have demonstrated to be suitable for the seismic retrofit of unreinforced masonry structures. Such composites incorporate fibers obtained from a variety of materials, for example glass, carbon, aramid, or basalt, and matrices consisting mainly of inorganic cement- or lime-based mortar.
The possibility of combining different materials within FRCMs, and the intrinsic variability associated with each constituent, result in a wide range of composite properties. Consequently, the performance of the retrofitted masonry structure may vary significantly depending on the applied composite. Guidelines developed by the Italian Ministry of Infrastructures and Transportation and by the European Organization for Technical Assessment define standard tensile and debonding tests, which need to be performed on FRCMs to evaluate specific mechanical properties for qualification and acceptance purposes.
This paper focuses on the experimental qualification process of PBO-FRCM composites, investigating the variability of the tensile and bond behavior depending on the textile characteristics. Direct tension test were carried out on two types of PBO meshes and composite specimens. Single-lap tests allowed determining the bond properties of the FRCM on tuff block and clay brick masonry supports. The stability of the tensile properties with respect to degradation induced by environmental actions was evaluated by performing tensile tests also on specimens conditioned by freeze-thaw cycles and artificial aging.
Di Trapani, Fabio (1);
Malavisi, Marzia (1);
Shing, Pui-Shum Benson (2);
Cavaleri, Liborio (3)
DEFINITION OF OUT-OF-PLANE FRAGILITY CURVES FOR MASONRY INFILLS SUBJECT TO COMBINED IN-PLANE AND OUT-OF-PLANE DAMAGE
The paper presents the outcomes of a probabilistic assessment framework aimed at defining out-of-plane fragility curves of unreinforced masonry infills walls which have been subjected (or not) prior in-plane damage. A recently developed in-plane (IP)/out-of-plane (OOP) four-strut macro-element model is used to model masonry infills within frames. Out-of-plane incremental dynamic analyses are performed, for a reference infilled frame, based on a suite of 26 ground motion record selection. Peak ground acceleration (PGA) and OOP relative displacement of the midspan node of the infill, are used as intensity measure and damage measure. The outcomes show fragility curves representing the probability of exceeding out-of-plane collapse at a given earthquake intensity as a function of a different combination of geometrical and mechanical parameters, in-plane damage level and supporting conditions. Results are finally summarized by curves relating in-plane interstorey drifts and out-of-plane average collapse PGA.
CHUN, QING (1);
JIN, HUI (2);
ZHANG, SHIQI (3)
STRUCTURAL PERFORMANCE AND SEISMIC RESPONSE FOR CHINESE ANCIENT STONE ARCH BRIDGE – A CASE STUDY OF THE PUTANG BRIDGE
In order to study the structural performance and seismic response of Chinese ancient stone arch bridge, a typical Chinese ancient stone arch bridge, the Putang Bridge, was taken as a study case in this study. Firstly, the finite element model of this bridge was built up by the software of ANSYS according to the on-site survey and test, the structural performance of this bridge under the vertical static loads was studied, resulting in the weak parts of the whole structure under static loads. Then, the seismic response of this bridge under different seismic wave excitations were studied, and the weak parts of this bridge under the seismic waves were obtained. The results of this study can provide the basis for the scientific conservation for the similar types of stone arch bridges.
MODELLING OF HISTORIC BRICKWORK WALLS STRENGTHENED WITH GFRP STRIPS
In recent years, the strengthening of masonry structures with external bonded (EB) fiber reinforced polymers (FRPs) has been increased to improve the strength and ductility of walls under seismic actions. The presence of FRP elements strongly affects the structural response through complex interaction mechanisms between masonry and strengthening elements. Many aspects of this strengthening method are not yet completely known; in particular, the debonding mechanisms of FRP strips need to be analyzed through more investigation.
In this paper, an iterative, incremental non linear three dimensional Finite Element (FE) model is developed to analyze the response of historic masonry wall, with and without strengthening by Glass-FRP strips, under in-plane cyclic loading, addressing particular regard to the delamination phenomenon. A numerical macroscopic model obtained from the combination of constitutive laws is adopted to simulate the behaviour of the unreinforced and reinforced masonry. Both progressive local failure and nonlinear stress-strain relationship of masonry are taken into account. For the GFRP strips, a model that considers the reinforcement perfectly glued to the masonry support has been used.
Finally, the developed analytical model is calibrated and validated by comparison with experimental results and interesting aspects are remarked.
D'Ambra, Claudio (2);
Lignola, Gian Piero (1);
Prota, Andrea (1);
Sacco, Elio (1)
EFFECT OF FRCM ON SLIDING SHEAR FAILURE OF MASONRY
Fiber Reinforced Cementitious Matrix (FRCM) has been already successfully adopted for strengthening masonry elements. In the scientific literature, most of the investigation and studies were focused on strengthening against flexural failure by means of bending tests and against shear, diagonal cracking by means of diagonal compression tests. Results confirmed the great potential of such FRCM systems; however, few results are available in terms of bed-joints sliding shear failure. This lack of knowledge jeopardizes a sound and safe design of strengthening interventions as sliding shear failure could occur as a premature failure compared to the others. In particular, squatter walls (quite common in practice) may run into this type of failure when the vertical compression stress is low. The main focus of this study concerns the experimental determination of the capacity of clay brick masonry triplets under bed-joints sliding shear loads, at different normal stress levels. A Mohr-Coulomb type failure theory has been adopted for evaluating the shear capacity as function of the applied normal load, considering the angle of internal friction and the cohesion detected for unstrengthened masonry. The FRCM consisted of a basalt fiber grid with NHL mortar matrix applied on the sides of the triplet specimens. To perform the tests, the well-known UNI EN 1052-3 has been adapted to strengthened masonry triplets, for a wider range of normal loads to account for the strengthening. Experimental tests have been performed on unstrenghtened and strengthened specimens, comparing the obtained results, demonstrating that FRCM is able to significantly increase the performance of masonry against bed-joints sliding shear failure.
Medeiros, Wallison Angelim (1);
Parsekian, Guilherme Aris (1);
Moreno Jr., Armando Lopes (2)
THE EFFECT OF FIRE TEMPERATURES ON THE MECHANICAL PERFORMANCE OF CONCRETE BLOCKS MADE OF GNEISS AGGREGATES
In Brazil, one of the most used aggregates in the concrete blocks production is the gneiss. There is few information in literature about the behavior of concrete blocks with this type of aggregate at high temperatures. Besides that, the test procedures to determine the concrete stress-strain curve is generally prescribed for cylindrical cast specimens. The concrete's properties in this type samples are different from those produced in concrete block industries that use large vibrating presses with strong compaction energy and low cement consumption. This paper describes the effects of temperature on the mechanical properties of concrete blocks made with gneiss aggregate. For this, the CMUs were heated to 800°C and their residual compression strength and deformability was determined. The test method was adapted from the RILEM TC 200-HTC recommendations. In conclusion, the aggregate was thermally stable, and the residual compressive strength of the concrete block was basically unchanged below 400°C.
Meyer, Udo (1);
van der Pluijm, Rob (2);
Andreini, Marco (3);
Pettit, Gerry (4);
Miccoli, Lorenzo (5)
DESIGN OF MASONRY PANELS SUBJECTED TO FIRE IN EUROPE: AN OVERVIEW ON THE NEW DRAFT OF EN 1996-1-2
This paper gives an overview on the new draft of EN1996-1-2 (Eurocode 6 part 1-2) being prepared by Project Team SC6.T2 of CEN/TC250. The prescriptive and performance-based approach for the design of masonry panels subjected to fire is described. An improvement to the tabulated data for the determination of the fire rating of non-loadbearing masonry panels is described. The problems associated with the calculation methods in the current version of EN1996-1-2 for the assessment of loadbearing walls are explained. A proposal is made for the improvement of the input parameters for mechanical models based on experimental tests. Finally, the results of an experimental programme carried out on some common masonry materials (units and mortar) are presented.
DE SANTIS, STEFANO;
DE FELICE, GIANMARCO
DURABILITY OF STEEL REINFORCED GROUT COMPOSITES
Mortar-based composites have proved effective for the external strengthening of existing structures and have already been widely applied in the field. To date, however, their long-term performances have not been sufficiently investigated, even if they are of the utmost importance for mitigating the risks and the costs associated to damage and repair/substitution. This is crucial for the sustainability of the building stock and of the rehabilitation measures developed for its lasting safeguarding. This paper collects the studies performed on the durability of Steel Reinforced Grout (SRG) systems, comprising ultra-high tensile strength steel textiles and inorganic matrices. Brass and zinc coated steel cords have been tested after accelerated artificial aging in saltwater solutions, salt mist, acid solutions and freeze-thaw cycles. Laboratory investigations include tensile and bond tests. Available results are discussed to make the point on current state-of-knowledge, contribute to the improvement of artificial aging protocols and test procedures, and promote future research and standardization activities.
A SIMPLE DEFORMATION-BASED DAMAGE INDEX FOR SHAKE TABLE TESTING OF HISTORIC MASONRY PROTOTYPES
The present works illustrates a simple deformation-based damage index that exploits the potentialities of advanced 3D optical systems for markers displacements measurements in shaking table testing of historic masonry mock-ups. The application of passive 3D motion capture systems to shaking table testing proved very efficient in recording a large number of measurement points, which provide accurate and complete description of the field of displacements of the studied structure. The proposed index was built as a function of the global residual deformation obtained from the measured distances between each couple of adjacent markers located on the tested structure. The results were validated by correlation with a consolidated stiffness-based index calculated through modal analysis of the structure. The proposed index considers only the mock-up deformations, while neglecting the effects of energy absorption and of different collapse mechanisms on the assessment of damage. Nonetheless, its simplicity of computation directly from the markers measurements represents a big advantage with respect to other more used damage indices that were mainly developed for numerical analysis and need to estimate structural capacity parameters. Besides, the stiffness-based indices might sometimes provide controversial results in shake table tests, as mock-ups dynamic behaviour is dependent on the boundary conditions, i.e. the observed stiffness reduction might be caused by fixing loosening and/or changes in the mock-up constraints to the table. In order to avoid misleading conclusions, the crack pattern and the deformations arisen in the tested specimen should always be considered of utmost importance for assessing the actual state of structural damage. After application with several historic masonry mock-ups, encouraging results were obtained in terms of good correlation (R2>0.9) with the consolidated index.
Cascardi, Alessio (1);
Funari, Marco (2);
Micelli, Francesco (3);
Aiello, Maria Antonietta (3)
A STRUCTURAL ANALYSIS OF A MASONRY CHURCH WITH VARIABLE CROSS-SECTION DOME
The structural capacity of masonry churches is generally hard to be investigated due to the complex geometry that characterize this relevant Heritage. Vaults, series of arches, flying buttresses, spiers, apse, dome, are often found in the field. Significant time efforts and costs are commonly expended in the ge- ometrical survey. Traditional measuring results poorly accurate (randomly made within the construction), es- pecially in case of huge buildings. On the other hand, modern technology, such as laser scanner, may result time consuming because of the data acquisition and elaboration. Moreover, the variation of thickness within the masonry members is often averaged and regularized since large endoscopy survey is forbitten for cultural Heritage restrictions. For this reason, in those cases in which the structure is affected, or even dominated, by stability issues, the accuracy of the analysis can be compromised without an adequate survey.
In this scenario, the present study provides a case study concerning the analysis of a masonry church in which a main dome (>15 m diameter) is placed on top. Both the base masonry walls and the dome have variable cross-sections. In order to achieve an accurate geometrical model, a drone was used for photogrammetry rec- ognizing both outside and within the church. Then, the digital photos were computer elaborated according to their relative GPS-metadata. As a result, an accurate 3D-solid object was obtained. Finally, FEM analysis was performed in order to quantify the displacement capacity by pushover method.
Marinković, Marko (1);
Butenweg, Christoph (2)
SEISMIC BEHAVIOUR OF RC FRAMES WITH UNCOUPLED MASONRY INFILLS HAVING TWO STOREYS OR TWO BAYS
Reinforced concrete (RC) structures with masonry infills are widely used for several types of buildings all over the world. However, it is well known that traditional masonry infills constructed with rigid contact to the surrounding RC frame performed rather poor in past earthquakes. Masonry infills showed severe in-plane damages and failed in many cases under out-of-plane seismic loading. As the undesired interactions between frames and infills changes the load transfer on building level, complete collapses of buildings were observed. A possible solution is uncoupling of masonry infills to the frame to reduce the infill contribution activated by the frame deformation under horizontal loading.
The paper presents numerical simulations on RC frames equipped with the innovative decoupling system INODIS. The system was developed within the European project INSYSME and allows an effective uncoupling of frame and infill. The simulations are carried out with a micro-modelling approach, which is able to predict the complex nonlinear behaviour resulting from the different materials and their interaction. Each brick is modeled individually and connected taking into account nonlinearity of a brick mortar interface. The calibration of the model is based on small specimen tests and experimental results for one bay one storey frame are used for the validation. The validated model is further used for parametric studies on two storey and two bay infilled frames. The response and change of the structural stiffness are analysed and compared to the traditionally infilled frame. The results confirm the effectiveness of the INODIS system with less damage and relatively low contribution of the infill at high drift levels for the investigated systems. In contrast to the uncoupled system configurations, traditionally infilled frames experienced brittle failure at rather low drift levels.
Calderón, Sebastián (1,2);
Sandoval, Cristián (1);
Inzunza-Araya, Ernesto (1);
Araya-Letelier, Gerardo (1);
Vargas, Laura (1)
INFLUENCE OF HORIZONTAL REINFORCEMENT LAYOUT ON SHEAR BEHAVIOR OF HOLLOW CONCRETE BLOCK REINFORCED MASONRY SHEAR WALLS
Partially grouted reinforced masonry (PG-RM) shear walls are used as a structural system in several countries. As a result of this, horizontal reinforcement schema varies depending on local construction practices. In some places, horizontal reinforcement bars are placed in the inner center of blocks to form the so-called bond-beams. In other locations, horizontal reinforcement is embedded in bed-joints. Recent studies have proposed to combine both types of reinforcement layouts in order to improve the seismic performance of PG-RM walls, although available experimental evidence is still limited. Considering this, the experimental results of three in-plane cyclic load tests of PG-RM walls with different arrangements of horizontal reinforcement are compared. One wall was only provided with bed-joint reinforcement type, one only with bond-beam reinforcement type, and one with both types of reinforcement layouts. Results indicate that the combination of both reinforcement types is the most suitable option, in terms of maximum lateral resistance and crack distribution.
Manos, George C.;
THE SEISMIC PERFORMANCE OF PARTIALLY GROUTED REINFORCED MASONRY
The main features of a study dealing with partially grouted reinforced clay brick masonry wall specimens are summarized here. The experimental campaign studied the in-plane behavior of such partially grouted wall specimens, built using clay bricks with vertical holes manufactured by a local industry. All wall specimens were partially grouted at specific locations hosting vertical steel reinforcement. Horizontal (shear) steel reinforcement was also included at the mortar bed joints. These specimens were rigidly attached at a reaction frame and were subjected at their top to a constant vertical load together with a horizontal seismic-type cyclic load. The mechanical properties of all used materials were measured through laboratory tests. For the tested walls, with a height over length ratio equal to 1 and for horizontal reinforcing ratio values larger than 0.085%, the flexural response together with the rather ductile plastic rotation response at their bottom appeared to dominate the observed behavior when the maximum horizontal load was reached. Furthermore, a micro-modeling numerical simulation was performed in order to simulate the observed behaviour of the tested specimens by simulating separately the clay brick units, the mortar joints and the employed longitudinal (vertical) reinforcement. It is shown that the observed mainly flexural behavior was successfully reproduced by this micro-modeling numerical simulation featuring all the geometric and construction detailing together with the measured non-linear mechanical characteristics of the mortar joints and the vertical reinforcement of the tested specimens. A critical factor of the observed performance was the behaviour of the employed clay brick unit which developed local compressive-type modes of failure, which influence the overall seismic response. Therefore, an additional objective was to produce an alternative clay brick unit in order to avoid such local compressive-type modes of failure. The various steps employed up to now to achieve this objective are presented and discussed.
Manos, George C. (1);
Melidis, Lazaros (1);
Soulis, Vassilios (1);
Katakalos, Kostas (1);
Anastasiadis, Anthimos (2)
THE IN-PLANE AND OUT-OF-PLANE BEHAVIOUR OF MASONRY PANELS WITH THERMO-INSULATING ATTACHMENT
Multi-story buildings are composed of multi-bay steel or R/C frames having unreinforced masonry panels considered as non-structural elements not included in the structural design. Such structures are subjected to strong earthquake motions, leading to potentially damaging conditions for the masonry in the form of in-plane damage or/and its dislocation and partial collapse. Several seismic design code revisions include provisions attempting to take into account such problems of unreinforced masonry– frame structure interaction in an indirect way. It was shown in the past that the contact boundary between the masonry infill and the surrounding frame, is of importance. It was also shown that introducing thermal insulation, without due consideration, can increase the vulnerability of such masonry panels. This work presents results from an on-going investigation on the behaviour of thermo-insulating masonry panels. This is done by studying through testing the influence of thermo-insulation on the in-plane and out-of-plane behaviour masonry panels built with hollow clay bricks having horizontal holes. The relevant measured response is presented and discussed. It was observed, through the limited testing executed up to now, that the out-of-plane flexural bearing capacity of the specimens including thermo-insulating panels, is larger than the corresponding bearing capacity of similar specimens without the used thermo-insulating attachments. The observed limit state for the specimens with thermo-insulation was partial debonding of the insulating panel. The used plastic anchors prevent, up to a point, the complete debonding of such thermo-insulating panels. The same effect was also observed when these panels were subjected to in-plane diagonal compression. The numerical investigation adopted here includes numerical models with non-linear interfaces in an effort to numerically simulate the observed behaviour. This methodology will be further validated with additional experimental results and parametric investigation in a variety of specimen geometry and materials used.
Bonati, Antonio (1);
Franco, Annalisa (1);
Schiavi, Luca (1);
Occhiuzzi, Antonio (1,2)
EXPERIMENTAL INVESTIGATION OF THE LONG-TERM BEHAVIOUR OF FABRIC REINFORCED MATRIX SYSTEMS
The considerable increment in use of Fabric Reinforced Matrix (FRM) strengthening systems in recent years has led to the need of investigating the durability of such kind of composites, especially when exposed to long-term actions. Single lap shear tests were performed on specimens constituted by masonry and concrete blocks reinforced with different types of fabrics embedded in an inorganic matrix. A new test setup has been developed with the aim of applying a sustained load for up to six months simultaneously to considerable amounts of specimens under the same controlled temperature and relative humidity conditions.
The paper will aim at describing the proposed creep setup and the instrumentation, as well as the results in terms of measured displacements for two different types of masonry (clay and natural stone) and concrete reinforced with fabrics made of different materials (Ultra High Tensile Strength Galvanized Steel - UHTSS, AR-glass and aramid, basalt and stainless steel).
The experimental campaign is part of an ongoing large assessment plan for the analysis of the behaviour of fabric reinforced inorganic matrix composites.
Vargas, Laura (1);
Sandoval, Cristián (1);
Calderón, Sebastián (1,2);
Ramírez, Pablo (1);
Araya-Letelier, Gerardo (1)
SHEAR STRENGTH PREDICTION OF PARTIALLY-GROUTED CONCRETE MASONRY WALLS WITH OPENINGS
As part of an ongoing research, this paper deals with the prediction of the shear strength of partially grouted reinforced masonry (PG-RM) shear wall with openings. For this purpose, one perforated wall was built and tested under cyclic lateral loading, and its resistance has been estimated trough different approaches. Three existing prediction equations were used to estimate the shear strength of the wall through the sum of the contributions of its piers. Additionally, the overlap of envelopes of hysteresis curves of previously tested isolated walls with similar characteristics of piers was also used. Lastly, the shear strength was predicted by means of fragility curves. Results show that there is considerable dispersion among the applied methods, when estimating the shear capacity of PG-RM walls with openings as the sum of the capacity of the forming piers. Horizontal displacement field suggest the forming piers should be defined according to their boundary conditions.
Bellini, Alessandro (1);
Tilocca, Anna Rosa (1);
Frana, Irene (1);
Savoia, Marco (2);
Mazzotti, Claudio (1,2)
ENVIRONMENTAL DURABILITY OF FRCM STRENGTHENING SYSTEMS AND COMPARISON WITH DRY FABRICS
Fiber Reinforced Cementitious Matrix (FRCM) composites have been recently introduced for repairing and strengthening masonry structures. Even if they proved to be an effective solution for structural applications, their durability is still an open issue, which is fundamental to guarantee the long-term effectiveness of the strengthening intervention. In fact, FRCMs may be subjected to a combination of different environmental conditions that may affect their performances: humidity, rainfall, freeze/thaw cycles, exposure to saline and alkaline environments are some of the conditions that may promote deterioration over time. In order to investigate FRCMs durability, an extensive experimental campaign has been carried out on different FRCM systems (basalt, glass and steel fibers) through tensile tests on conditioned and unconditioned samples. Tests have been performed both on FRCM coupons and on dry fabrics, with the aim of analyzing the effect of the matrix in terms of mechanical behavior and external protection of the fabric under aggressive environments. The creation of an experimental database on the effects of environmental conditions is a first step to analyze long-term properties of these composite materials and to suggest appropriate strength reduction factors to be taken into account for the design of durable retrofitting interventions.
Martins, Martins (1);
Vasconcelos, Graça (2);
Campos-Costa, Alfredo (3)
EXPERIMENTAL ANALYSIS OF BRICK MASONRY VENEERS WALLS UNDER OUT-OF-PLANE LOADING
Horizontal loads induced by earthquakes can cause severe in-plane and out-of-plane damages on masonry walls in buildings. Normally, masonry walls present particular vulnerability if pushed horizontally in a direction perpendicular to its plane (out-of-plane loading), but offers higher resistance if pushed along its length (in-plane loading). This is not only valid for loadbearing walls but also for non-structural walls that are forced to behave in a structural way in case of seismic actions. Among the non-structural walls, masonry infills and masonry veneers are well known to be used in more modern construction, where reinforced concrete frames as a structural system predominate.
Therefore, detailed investigation on the seismic behaviour of masonry veneer walls becomes necessary, specially taking into account the connection of the masonry veneers to the backing infill masonry walls. The primary gap identified through literature review was the lack of experimental research that addressed the response of masonry veneer walls, whose backing is composed by masonry infill wall inserted in a concrete frame. This represented the major motivation for conducting this research based on experimental characterization of the mechanical behavior of brick veneer walls attached to brick masonry infills with different types of steel ties and different arrangement for the ties under in-plane and out-of-plane loading.
Thus, the main objectives of the experimental work are: (1) obtainment of the static cyclic in-plane behaviour of masonry veneer walls and (2) assessment of the static cyclic out-of-plane behaviour of masonry veneer system in different walls configurations.
The main results of the experimental campaign intended to be obtained are: (1) hysteretic force-displacement diagrams under in-plane and out-of-plane loading; (2) deformation features of the walls and (3) damage patterns and failure mechanism of the masonry veneers and connections under in-plane and out-of-plane loading.
Padalu, Pravin Kumar Venkat Rao (1);
Singh, Yogendra (1);
Das, Sreekanta (2)
EXPERIMENTAL STUDY OF COMPARATIVE EFFICACY OF OUT-OF-PLANE STRENGTHENING OF MASONRY WALLS USING FRP AND WIRE/TEXTILE REINFORCED MORTAR
Unreinforced masonry (URM) walls are most vulnerable in out-of-plane failure mode due to very low tensile strength of masonry. To improve the seismic out-of-plane performance of URM specimens, three different types of strengthening techniques using welded wire mesh (WWM), a low cost material prevalent in India, basalt fibre mesh (BFM) and basalt fibre reinforced polymer (BFRP), sustainable composites comprising of natural fibres, are considered in the present study. The experimental study includes mechanical characterization of masonry and retrofit materials. In the present study, the material properties and the stress-strain relationship of brick, mortar as well as masonry are obtained from the uniaxial compression tests. The uniaxial tension tests are performed on reinforcement and composite materials to obtain mechanical properties. This has been done following ASTM and ACI standards. One-way out-of-plane flexural behaviour of URM and strengthened masonry is studied by testing a large number of masonry wallettes perpendicular and parallel to bed-joints under two-point (line) loading. The study also includes testing of full-size H-shape masonry walls simulating real boundary conditions, in two-way reversed cyclic bending under airbag loading. The experimental results for flexural strength, deformation, and energy absorption capacity are compared. The present study also identifies appropriate non-dimensional parameters to quantify the relative amount of reinforcement in different specimens for direct comparison of test results.
Minotto, Massimiliano (1,2);
Verlato, Nicolò (1);
Donà, Marco (1);
da Porto, Francesca (3)
SHEAR-COMPRESSION EXPERIMENTATION OF FULL-SCALE WOOD-CEMENT SHUTTERING BLOCK WALLS
The shuttering block construction system is used for the construction of loadbearing walls and consists of special blocks with cavities suitable for hosting vertical and horizontal reinforcements and the cast-in-situ concrete. These walls present a resistant concrete grid made of vertical columns joined together by horizontal squat beams with regular spacing. The present paper discusses the results of the experimental activity conducted at the University of Padua on 6 full-scale wall specimens of diverse aspect ratio (1:1 or 3:4) and openings (i.e. doors and windows). The blocks used in the current research activity are made of petrified wood chips and cement and have the dual function of being a disposable form-work for the cast-in-situ concrete and being a thermal-acoustic surface insulation device of the wall. Cyclic In-Plane displacements of increasing amplitude until failure were imposed (with constant vertical load) to characterize the shear-compression behaviour of the specimens.
Milanesi, Riccardo R (1);
Morandi, Paolo (2);
Hak, Sanja (3);
Magenes, Guido (1,2)
THE INTERACTION BETWEEN IN-PLANE AND OUT-OF-PLANE SEISMIC RESPONSE OF MODERN STRONG MASONRY INFILLS
Although during recent post events surveys it has been observed that several masonry infills have been collapsed or severly damaged due the interaction of the in-plane and out-of-plane seismic actions, the standard prescriptions on the in-plane/out-of-plane interaction of traditional rigidly attached masonry infills are often limited or even missing. Many studies have been accomplished on this topic, being often focused on infills made of bricks, or “weak” masonry infills with high slenderness. However, the researches and the experimental campaigns related to the out-of-plane behaviour of “strong”/“robust” clay masonry infills, for example made by vertically perforated blocks with thickness larger than 20-25 cm, are very limited. The importance of the topic is also related to the wide adoption of this typology of masonry infill in many countries also due to its thermal and acoustic performance. This paper presents a study on the out-of-plane response of a relatively “strong” infill constructed using tongue and groove clay block masonry units with a thickness of 35 cm. The work is based on the results of an experimental campaign conducted at the University of Pavia and Eucentre on real scale one-storey, one-bay r.c. infilled specimens. A series of cyclic static in-plane and out-of-plane tests has been carried out; the out-of-plane experiments have been executed on an undamaged specimen and on infills previously damaged in-plane, reaching levels of maximum drift equal to 1.00, 1.50 or 2.50%, representing the attainment of different performance levels, in order to evaluate the related out-of-plane resistance reduction. The aim of the study is to define a criterion to compute the out-of-plane resistance of strong masonry infills, through the developmenet of an in-plane/out-of-plane experimental interaction curve, where a reduction coefficient of the out-of-plane resistance of the undamaged panel is function of the in-plane drift of the infilled frame.
Akyildiz, Tugrul (1);
Kwiecień, Arkadiusz (1);
Zając, Bogusław (1);
Triller, Petra (2);
Bohinc, Uros (2);
Rousakis, Theodoros (3);
Viskovic, Alberto (4)
PRELIMINARY IN-PLAIN SHEAR TEST OF INFILLS PROTECTED BY PUFJ INTERFACES
This paper presents results of in-plain shear tests carried out in ZAG laboratory in Ljubljana (Slovenia) on a RC frame with masonry infill made of clay blocks (KEBE OrthoBlock). The frame fixed at the bottom and loaded vertically at columns’ tops was excited by horizontal cyclic loads at the top beam level. These loads forced various and gradually increasing drift levels (positive and negative) of the frame, with 3 repetitions at each level. Acquired forces and measured displacements allowed drawing hysteresis loops for determination of dissipation energy. Additionally, Digital Image Correlation (DIC) system was used for visualization of the behavior of the frame and the infill.
There were tested 3 infill specimens of different configurations at interfaces between rc frame and infills. Type A (reference) was made of the infill bonded classically to the rc frame by mineral mortar. In type B, spaces at sides and top interfaces of 2 cm thickness were cut by saw and filled by polyurethane injection making PUlyurethane Flexible Joints (PUFJ). In type C, all interfaces were constructed from prefabricated PUFJ laminates and then the infill was erected. The specimen A was forced up to 1.6% of the frame horizontal drift when crushing at the corners and complete detachment at the frame-infill interface occurred. The infill A would be destroyed even with small out-of-plane forces. The specimen B and C were forced up to 3.6% and 4.4% of the frame horizontal drift, respectively. In these both infills crushing at the corners was observed but the PUFJ interfeace protected the damaged infills against out-of-plain failure.
EVALUATION OF THE OUT-OF-PLANE PERFORMANCES OF MASONRY WALLS STRENGTHENED WITH COMPOSITE REINFORCED MORTAR
In historical masonry structures subjected to earthquake excitation frequently occurs the out-of-plane overturning or bending collapse of some walls, due to their very limited flexural resistance. Effective connections between the walls and between the walls and the floors can considerably reduce these failures. However, the out-of-plane shortcomings remain relevant in case of buildings with large interstorey (>4 m) and large distances between orthogonal walls, especially in upper storeys, where the axial load is lower and the cross section thinner.
The authors already performed experimental tests to investigate the out-of-plane performances of a CRM strengthening strategy based on fiberglass meshes, proving its effectiveness. It clearly emerged that the reinforcement is able to provide a significant increase to the out-of-plane resistance and the displacement capacity of the wall. Moreover, the authors already developed a detailed, numerical 2D finite element model for CRM strengthened masonry, whose reliability was proved by comparison with the simplified laboratory bending tests.
In this paper, the extension of the detailed 2D model to a simplified 3D one is presented, with the aim to investigate the behavior of entire walls and more articulated configurations subjected to the common actual conditions. The influence of different parameters, such as the geometry, the boundary conditions, the presence of openings, the axial load and the material properties, is investigated. The results are compared in terms of capacity curves, representing the trend of the horizontal seismic load at the varying of the wall out-of-plane deflection. Moreover, to facilitate the practice design, an evaluation in terms of resisting peak ground acceleration, based on the Capacity Spectrum Method with reference to the Floor Spectrum, is also carried out for CRM strengthened walls, so to allow also the comparison with the seismic demand.
Tamborrino, Ottavio (1);
Passerino, Carlos Roberto (2);
Aiello, Maria Antonietta (1)
PULTRUDED-FRP FOR RETROFITTING PURPOSES: MECHANICAL CHARACTERIZATION
The seismic events always evidenced the dramatic vulnerability of the masonry structures. Therefore, provisional or permanent interventions are often achieved in post-seismic scenarios. In response to this request, a large interest has been given to fiber-reinforced polymers (FRPs) composites in the recent past. These materials offer the advantages of high strength, low self-weight and durability. An innovation is noticeable in the pultruded FRPs; which are now considered as a structural material for civil engineering applications. In fact, they guarantee relevant structural reliability and efficiency under different loading conditions: dead loads, live loads, wind and seismic actions.
As a consequence, the issue related to the mechanical characterization of pultruded is a key-aspect for the proper design of pultruded FRPs utilized to retrofit existing structures. At this scope, the present paper aims to report the testing procedure for the determination of the main proprieties of glass pultruded specimens. The investigated variables were: shear, flexural, pin-bearing and tensile strength, as well as, the tensile Young’s Modulus. The characterization was conducted in accordance with available UNI-standards. In addition, full-scale flexural tests were conducted on FRP-pultruded simply supported beams (I-section). The herein contribution reports the investigation carried out in the field of pultruded material characterization and discusses the relevance of the investigated properties in relation to the design requirements and the available standards and codes.
DURABILITY OF HEMP CORDS EXPOSED TO ALKALINE ENVIRONMENT OF LIME MORTAR
ABSTRACT: The use of Textile Reinforced Mortar composites (TRM) for the reinforcement of structural elements is one of the most innovative and effective techniques in the framework of historical masonry rehabilitation. In order to propose an eco-sustainable rehabilitation, this paper focuses on a TRM made of hemp fibers imbedded in a lime mortar. The aim of this study is to identify the effectiveness and the durability of hemp fibers used in TRM characterized by lime mortar to reinforce masonry structures. Tensile tests on hemp fibers were carried out. The accelerated aging effects of the lime mortar on hemp fiber were studied by tensile tests after 7, 14 and 28 days. The aging of fibers was performed by immersing them in a solution that reproduces the same pH of lime mortar, at 23°C.The experimental results show that, in the aging condition analyzed, the hemp fibers don’t lose their strength.
Korswagen, Paul A;
Rots, Jan G
OLDER CLAY MASONRY CAN BE MORE EARTHQUAKE-RESISTANT THAN CALCIUM-SILICATE MASONRY FOR LIGHT DAMAGE
Seismic events in the northern part of the Netherlands over the past few decades have led to an intense study on the seismic performance of unreinforced masonry structures, ubiquitous in the region. Studies have focused on the safety aspect characterised by the near collapse behaviour of the structures, but also on the aesthetic and functional aspect denoted serviceability or light damage state. The latter, triggered by multiple small seismic events until now, has lead to economical losses and societal unrest.
Experimental studies, detailed in this paper, have looked at the initiation and propagation of visible cracks in clay and calcium-silicate unreinforced masonry specimens. Both materials, replicating samples from existing structures, were surveyed with high-resolution Digital Image Correlation while being subjected to repetitive loading causing horizontal, vertical and diagonal stair-case cracks. Small and full-scale experiments evidenced a difference in behaviour between clay and calcium-silicate masonry: where the former only developed cracks along the mortar joints, the latter also exhibited brick-splitting cracks. This mechanism proved extremely brittle and led to a reduced capacity of energy release for the calcium-silicate specimens during cyclic loading, and to their sudden failure.
The higher bond-strength between the silicate brick and mortar coupled with the lower strength of the bricks themselves and the overall higher stiffness of the calcium-silicate masonry, in the case of the replicated masonry specific to this study, are suspected of being responsible for the brick-splitting failures. These brittle failures, occurring at low drift levels, set calcium-silicate masonry as more vulnerable than comparable clay-brick masonry in regards to light damage, leading to wider and larger cracks.
Castellazzi, Giovanni (1);
D'Altri, Antonio Maria (1);
de Miranda, Stefano (1);
Emami, Hossein (2);
Molari, Luisa (1);
Ubertini, Francesco (1)
ON THE EFFECT OF TORTUOSITY ON THE SPALLING PREDICTION IN MASONRY THROUGH A MULTIPHASE NUMERICAL MODEL
Historical masonry structures are often subjected to degradation processes due to the damp rising, salt transport, and salt crystallization. Pores of building materials, such as natural stones or fired bricks, are filled with gaseous and liquid phases. The liquid phase could then consist of water and dissolved salts, that is then forced to migrate within the pores when external temperature and relative humidity vary. These changes could cause the precipitation of solid phase so called salt crystallization on the masonry surface (efflorescence) or within the material (subflorescence). The first is purely an aesthetic issue, the second can lead to structural damage called spalling: the flaking or peeling of superficial material. In this framework, the present paper aims at highlighting the role of the porous material properties, such as porosity and tortuosity on the whole phenomenon by a multiphase numerical model. Numerical results on benchmark simulations are presented and discussed.
CHARACTERIZATION OF FACTORS DETERMINING THE DURABILITY OF BRICK MASONRY
The paper provides characteristic of the factors affecting the durability of brick masonry, such as changing the texture of mineral material, frost destruction, salinity and the development of microorganisms. Their destructive effect occurs as a result of physical, chemical and biological processes. In actual conditions, these impacts usually have a synergistic effect. The range of influence of the factors can be described as superficial, limited to deterioration of the aesthetic appearance of the building, as well as volumetric, more dangerous as it concerns processes resulting in change to entire volume of the material, and thus also affecting the mechanical properties. The condition of all processes related to the reduced durability of materials is the presence of water. Water is a factor that is a threat in itself, because under its influence the texture of the material changes, which may result in deterioration of mechanical properties. In addition, its presence is a necessary condition in the process of chemical corrosion, resulting in efflorescence and subflorescence salting, resulting in a deterioration in the aesthetics and strength of the material, respectively. Water is also a priority for biological corrosion. The development of both organisms and microorganisms is only possible in a humid environment.
Thamboo, Julian Ajith (1);
Dhanasekar, Manicka (2)
RESPONSE OF BRICKWORK WALLETTES OF VARIOUS BONDING PATTERNS UNDER MONOTONIC AND CYCLIC COMPRESSION
Brick masonry walls of varying architectural patterns are commonly seen in many colonial period structures around the world. Subsequently with a view to understanding the monotonic and cyclic compressive characteristics of such brickwork, an experimental programme was carried out in this research. Fourteen brickwork wallettes with the geometry depicting the colonial buildings were built with two types of clay bricks and a lime mortar to simulate the strength characteristics close to the masonry found in those buildings. The failure modes, strengths and deformation characteristics of the masonry are described. It is shown that the monotonic compressive strength of masonry is consistently higher than the cyclic compressive strength. Further the monotonic and cyclic compressive stress-strain characteristics of the brickwork wallettes of varying bond patterns are discussed and their similarities and differences between single-leaf brickwork reported in the literature are examined. An analytical expression for the cyclic compressive stress-strain characteristics of the brickwork with lime mortared wallettes is also presented.
Roberts, John James
THE REVISION OF EN 1996-2
ABSTRACT: This paper looks at the revision of EN 1996-2:2006 (Eurocode 6: Design of masonry structures – Part 2: Design considerations, selection of materials and execution of masonry) by Project Team 3 of CEN TC 250/SC6. Some of the key areas identified in the review of the document by National Standards Bodies in 2014 are noted. The Project Team has reviewed twenty-four National Annexes to EN 1996-2 as part of its work and used the results to inform the proposed revisions to the code. The current draft reduces the number of Nationally Determined Parameters from two to one and recommends the retention of the three annexes as Informative.
Borbon-Almada, Ana Cecilia;
PERIDYNAMIC MODELLING OF MASONRY STRUCTURES
In many cases, masonry structures are subjected to loads that form cracks. Elasticity and damage in quasibrittle structures such as plain and reinforced concrete structures can be modeled with the peridynamic theory, proposed by Stewart Silling in 2000 and 2007. To model these structures, lattice hybrid models with brittle beam elements where used to model concrete, where cracks were expected to appear. One of the problems with lattice models is that they fail to adequately describe compressive behavior of quasibrittle materials. Another shortcoming of lattice and particle models is that they are highly demanding of computational power. Molecular dynamics may be, in some cases an appropriate tool for analyzing microcracks in quasibrittle materials in compression, but molecular dynamics becomes infeasible at scales larger than a few million atoms. In most cases, cracks form in the brick mortar joints, and concrete blocks or bricks can be assumed to have a uniform displacement field. This allows us to use the peridynamic finite element model, which is an improvement over discrete lattice models. This model assumes a continuous displacement field within each finite element, with displacement discontinuities allowed to develop between finite elements. The objective of this work is to model cracks in masonry walls with the peridynamic model. The peridynamic finite element model is shown to be much more computer time- and memory-efficient than the similar discrete particle-based models. Results show that this implementation appears to be more computationally efficient than particle or lattice models.
EVOLUTION IN THE PROTECTION OF CLAY-BASED MORTARS
Earthen structures have been part of human history and civilization ever since the first formation of agricultural human societies. Clay has been the oldest, most used building material, both as a binder and as the basic constituent of adobes and bricks. Numerous examples of such clayey constructions of monumental character can be found worldwide, especially around the Mediterranean basin. The use of clay in construction, however, never ceased. During medieval ages, earth was used all over Central Europe, while nowadays, one third of the world’s population, mostly in less developed countries, dwell in earthen structures. Due to the beneficial role of earthen materials in social, financial and environmental terms, clay has been reconsidered as a building material in modern structures.
In the present paper the physical and mechanical characteristics of old clay mortars have been analysed through different research works. The aim was to understand their behaviour as to proceed to the production of new compatible repair ones. Moving on a step further, the vulnerability of clay mortars to humidity was approached by using new materials based on nanotechnology. The behaviour of the new produced mortars was tested through different durability tests. The results are encouraging for the improvement of genuine weakness of clay mortars.
FLEMISH BOND BRICKWORK: MACROSCOPIC ELASTIC PROPERTIES AND NONLINEAR BEHAVIOUR
Assuming Flemish bond brickwork to be periodic, a finite element model of a Representative Volume Element (RVE) is developed to predict its macroscopic behavior using a homogenization approach. In linear elasticity, the numerical results are used to assess the reliability of recently proposed closed-form expressions for the macroscopic elastic properties (Taliercio, 2018). Assuming that both mortar and units experience plastic strains and damage effects, the macroscopic strength domain under in-plane principal stresses parallel to the joints is identified and compared with that predicted by Drougkas et al. (2016). Eventually, the model is applied to predict the homogenized strength of Flemish bond brickwork under elementary macroscopic in-plane stresses and transverse shear. The effect of the collar joint on the macroscopic response is pointed out by comparing the numerical results with those obtained on header bond brickwork. This effect is shown to be particularly significant under horizontal, transverse shear.
Mohamad, Gihad (1);
Fonseca, Fernando S. (2);
Roman, Humberto R. (3);
Ottoni, Tobias (1);
Lubeck, André (1)
DETERMINATION OF RITTER CONSTANT FOR HOLLOW CLAY PRISMS UNDER COMPRESSION
The main goal of this work was to determine the Ritter constant to predict the modulus of elasticity of two different hollow clay prisms under compression. For this reason, an experimental program with prisms was done to evaluate the Ritter constant. Two types of hollow clay blocks with net and gross area relationships of 0.39 and 0.49 and fmortar/fblock relationships of 0.3 and 0.7 were used. Strain measurements were done at the front and back of the prisms, using a normalized stress/strength (σ/fprism) level of 0.3. To estimate the Ritter constant for the masonry, Knutson (1993) equations for stress/strength level below 0.75 was adopted. The conclusion of this work is that the modulus of elasticity of masonry can be estimated using the Ritter constant with reasonable accuracy, but it depends of the block type and mortar compressive strength.
Perez Gavilan, Juan Jose (1);
Flores, Leonardo E. (2)
THREE STORY CM BUILDINGS WITH JOINT REINFORCEMENT: SHAKING TABLE TESTS
Two three story confined masonry buildings scaled 1:2 were tested in the shaking table. The structures represent one axis of a typical building for housing. The walls of the structures were built with concrete multi-perforated units confined with tie-columns and tie-beams. The scaled units were obtained by sawing the ones of the prototype; although they did not have the same perforation pattern they preserved the net area. The floor system was a solid concrete slab. The first building tested did not include joint reinforcement while the second included a high strength wire every three courses. Live load was included with lead ingots and the walls were posttensioned to achieve the required axial stress. The structures were subjected to a several motions based on a synthetic accelerogram with amplitudes progressively scaled up until failure. Preliminary results in terms of displacement capacity and strength are given.
Shrive, Nigel Graham
THE INFLUENCE OF EFFECTIVE FLEXURAL STIFFNESS ON SLENDER MASONRY WALL CAPACITY
Procedures regarding slender masonry wall strength capacity design in the Canadian Standard for Design of Masonry Structures (2014) are overly conservative. In the determination of secondary moment the calculated effective stiffness term, EIeff, is believed to be a significant source of error. The lateral deflections of concrete block walls tested by Hatzinikolas et al. (1978a) are compared to deflections calculated following the Standard to predict the error of EIeff. It is found that EIeff is quite inaccurate at low vertical axial load eccentricities. Using data provided by Hatzinikolas et al. (1978a), the relationship between EIeff and axial load (P/Pcr) is plotted, with some plots suggesting several slender walls with low load eccentricities are failing in compression rather than by buckling. It is proposed that the vertical axial load eccentricity be considered in addition to the slenderness ratio (kh/t) in defining walls for which buckling must be considered in design.
Purkert, Benjamin Stephan
IMPROVEMENTS IN EN 1996-3 – EXPLANATIONS AND BACKGROUND INFORMATION
In 2017, Phase 2 of mandate M515 has started, in which Project Team 2 (PT2) dealt with the systematic review of EN 1996-3. In this paper, the main improvements in prEN 1996-3 are presented. First, the new equations for determination of the capacity reduction factor are addressed, which now also applies to walls bearing partially supported slabs. Other improved design equations, e.g. for basement walls, for walls subjected to mainly lateral loading, and for concentrated load resistance as well as the improved method for simplified verification of overall stability are explained. In closing, the paper takes a look at the number of national choices.
SEISMIC FRAGILITY ASSESSMENT OF MASONRY AGGREGATES WITH IDENTICAL STRUCTURAL UNITS IN ROW
The masonry aggregates can include inhomogeneous structural units interacting together under seismic action; it is a common simplification in civil engineering field to consider a structural unit as isolated, even if it belongs to an aggregation of structural units. The first part of this work is focused on the fragility analysis of masonry structural units, considered as a part of a row aggregate and analysed at first as isolated. Some variabilities and uncertainties involved in the problem are considered through the Response Surface (RS) statistical procedure. The RS model allows to express a response parameter (in this work represented by the spectral acceleration corresponding to the attainment of the Life Safety Limit Sate) through a polynomial function of chosen variables. The calibration of the RS model is carried out through numerical data representing the structural capacity of the isolated structural units, whose selected properties are varied in prescribed ranges, and obtained performing non-linear static analyses. Finally, the data obtained from the simulations were used to plot the fragility curves, by applying full Monte Carlo simulations. Afterwards, the masonry structural units analysed have been aggregated in row in order to compare the seismic fragility of the isolated structural units with the one referred to the aggregations of identical structural units in row. The results showed relevant differences in terms of seismic fragility if different directions of the seismic action are considered, due to the geometrical properties of the walls in the two directions and to the torsional effects deriving from the aggregation. Furthermore, comparing the seismic behaviour of the isolated structural unit and its seismic behaviour when it belongs to the row aggregate, different levels of vulnerability are obtained, depending on the different position of the structural unit along the aggregate.
Simonsen, Cathrine Planck;
QUANTIFYING SURFACE DETERIORATION:EXEMPLIFIED ON FIRED CLAY BRICKS
For durability examinations of new materials, various resistance tests exists. The present work examines the resistance towards two accelerated salt crystallization methods (European Standard EN 12370 and RILEM test MS-A.2) on four types of fired clay bricks. In line with previous work, different deterioration patterns came into existence with each of these standards followed by an evaluation based on the evaluation criteria´s in the respective standards: weight changes, number of exposure cycles and photo documentation. However, a precise and true evaluation based on these existing evaluation criteria was found challenging to perform. This present work suggest a new method for quantifying initial surface deterioration, by coloring the exposed surface in a contrast color to ease distinction between non-deteriorated and deteriorated areas, followed by quantification with the point count method (best method out of three examined). This simple methodology seems to offer quantification of the surface deterioration.
Macharia, Stella (1);
Walker, Pete (2);
Peter, Ulrike (3)
COMPARATIVE CREEP CHARACTERISTICS OF LIME MORTARS AND BRICKWORK
Lime mortars can be based on air-lime, pure calcium hydroxide, or hydraulic lime being a mixture of air-lime and hydraulic components. Air-lime has traditionally been used both as a binder and as an additive to improve the workability and water retention properties of masonry mortars. The ability to accommodate movements without significant cracking, requiring fewer movement joints, is a commonly cited benefit of mortars containing lime. This paper presents findings from an experimental study into the long-term movement characteristics of air-lime mortared masonry. The creep of cement-lime based (“blended”) mortars, containing varying quantities of air-lime, have been compared in an experimental study. Axial movements on mortar specimens and masonry wall panels have been recorded at regular intervals for up to 6 months. The long-term mortar movements are related to the strength and measured creep movement of masonry wall tests.
MONTE CARLO SIMULATION OF MASONRY WALLS IN COMPRESSION CONSIDERING SPATIALLY VARIABLE MATERIAL PROPERTIES
The safety concept for the design of masonry walls in EN 1996 and in particular the National Annexes are mostly based on tradition. This is seen as an opportunity to rethink the concept and validate the historical values with studies, taking reliability theoretical approaches into account. The spatial variability of material properties can have a significant influence on the reliability of load-bearing capacity of masonry walls. This influence is highly dependent on parameters that determine the geometry and the material behavior of the wall. The conducted investigations are based on a finite element model, which is set up following the simplified micro modelling approach. The spatial variability is implemented as a unit-to-unit variability for the compressive strength and the Young´s modulus. Those two material properties determine the stress-strain behavior of the different masonry types. Nevertheless, other material properties like the fracture energy must be taken into account in order to generate numerically solid results. With the purpose of producing a series of results, a Monte-Carlo simulation is conducted. In each run of the simulation random values for the material properties are generated. The wall is then loaded until failure and a load capacity factor can be calculated. Within the study the influence of the spatial variability on the load-bearing capacity is investigated by modifying several parameters like the wall slenderness or length. On the assumption of a certain distribution function it is possible to calculate statistical values and as a result of this partial safety factors in order to interpret the influence on reliability of structural resistance.
Donà, Marco (1);
Morandi, Paolo (2);
Manzini, Carlo Filippo (2);
Minotto, Massimiliano (3);
da Porto, Francesca (4);
Magenes, Guido (5)
SECOND-ORDER EFFECTS IN URM WALLS SUBJECTED TO COMBINED VERTICAL AND LATERAL LOADING
The ongoing revision of the Eurocode 6 (EC6) on the design of masonry structures is an occasion to reconsider the current criteria for verifying the second-order effects in URM walls subjected to combined vertical and out-of-plane loading. Indeed, although the load-bearing capacity of URM walls received research attention since the 1950s, the correct methodology to evaluate its reduction due to second-order effects is still an important subject of scientific debate. The current design procedure proposed in the EC6 is based on an axial load capacity reduction factor (ϕm), which allows to evaluate the influence of wall slenderness, load eccentricity and boundary conditions on the buckling behaviour of the URM walls. However, the proposed ϕm model is based on an outdated Gaussian bell-shaped approximation to represents both the material and stability failures, and seems conservative for a wall stiffness range significant for design purposes (i.e., for E/fk<700, having been calibrated for E/fk=1000, with E the elasticity modulus and fk the characteristic compressive strength of masonry). Moreover, the fact that the safety verification of walls subjected to combined vertical and significant lateral loading (e.g. seismic action) should be carried out rationally in terms of lateral flexural capacity has not yet been fully acknowledged and the current version of the EC6 is silent in this regard. For this verification, a moment capacity reduction factor (ϕM) can be defined to evaluate second-order effects in a simplified way. Therefore, this paper offers a refined numerical evaluation of ϕm and ϕM (removing almost all simplifying hypotheses compared to previous proposals), demonstrates the one-to-one correspondence between these ϕ factors, proposes new prediction models as well as a recalibration of a model recently proposed for inclusion in the next version of EC6 and, finally, compares the results obtained with the experimental and numerical ones available from the literature.
Meyer, Udo Joachim (1);
Schermer, Detleff (2);
Schmalz, Jonathan (2);
Gams, Matija (3);
Lutman, Marjana (4);
Triller, Petra (4)
IN-PLANE SHEAR RESISTANCE OF THERMAL INSULATING MONOLITHIC CLAY UNI MASONRY
Thermal insulating single leaf clay unit masonry is a common type of construction in central Europe, a region with very low to moderate seismic exposure. The in-plane shear resistance is the most relevant parameter to describe seismic performance of that type of masonry. A shear test set-up for full-scale storey-high masonry walls was developed within the European-Commission-sponsored research project ESECMaSE. 35 tests with that ESECMaSE-test method were carried out in laboratories in Ljubljana (Slovenia) and Kassel (Germany) to identify the shear capacity for 5 typical perforation patterns of that type of masonry. The tests comprised different wall geometries, different load levels and different types of units, as well as different support lengths of the slab on top of the shear walls. The results are presented and discussed.
Franzoni, Elisa (1);
Gentilini, Cristina (2)
PULL-OFF CHARACTERIZATION OF FRCM COMPOSITES APPLIED TO STONES AND BRICKS IN ON-SITE CONDITIONS
Fiber reinforced cementitious matrix (FRCM) composites represent an alternative for the reinforcement of masonry structures with respect to fiber reinforced polymer (FRP) composites, due to their better compatibility with the substrate and resistance to ageing. Over last years, the behavior of FRCM composites applied over masonry has been studied in detail, but the problem of the adhesion of these composites to masonry substrate in conditions that can be found on-site has not been fully investigated. In fact, real historic masonry can be affected by several problems, such as rising damp and salt deterioration. In this paper, several pull-off tests were conducted, to assess the pull-off behaviour of FRCM composites on different brick and stone substrates, affected by the presence of salts. Composites made of different fibers such as glass and basalt embedded in lime-based or cement-based matrices were tested. Results show that the presence of salts in the substrate influences the bond capacity of the reinforcement.
EXPERIMENTAL TESTS OF WALL JOINTS
The paper presents the results of experimental tests of joints of walls made of autoclaved aerated concrete (AAC). Different joint types were used to connect two walls: trusses, standards profiles and profiles with widened cross-section at the joint as well as polyurethane glue (foam) commonly used for bricklaying of masonry walls. 18 models were tested altogether in five series. The tests were performed on an original test stand in which shearing of wall joints can be realized with minimized bending. Morphology of cracking and mode of failure were analyzed; the load–deflection relationships of tested models and reference models with traditional masonry bonds were also compared. The tests showed differences in cracking and failure mechanisms as well as in load-bearing capacity of different joint types.
Leone, Marianovella (1);
Cascardi, Alessio (2);
Micelli, Francesco (1);
Aiello, Maria Antonietta (1)
MASONRY ELEMENTS REINFORCED WITH FRCM: BOND BEHAVIOUR
Externally bonded reinforcements, made of fibrous meshes, embedded in a cementitious/hydraulic lime mortar, are now getting a great deal of attention, mostly for strengthening, retrofitting and repair of existing structures. When applied on masonry structures, these innovative materials have shown better behaviour than FRP (Fiber Reinforced Polymer), in terms of compatibility with the substrate, sustainability and reversibility. Moreover, these features are indispensable criteria that need to be fulfilled when the intervention is intended in the field of cultural Heritage, which largely consisting of masonry structures. As well known, the effectiveness of the strengthening is strongly related to the bond behaviour between the reinforcement system and the substrate. With this aim, the present work reports the results of experimental study on GFRCM (Glass Fabric Reinforcement Cementitious Matrix); i.e. a glass open-grid embedded in inorganic matrix, applied on two different masonry substrates. First, the mechanical properties of GFRCM reinforcements were obtained through tensile tests; then, the experimental investigation on bond behaviour was carried out by direct shear bond test. The test results were collected and processed to evaluate both the bond strength and the failure modes.
He, Huan (1);
Meijers, Sander J.H. (1);
Vonk, Rene. A. (2);
Middelkoop, F.H. (1)
NUMERICAL STUDY ON THE SEISMIC OUT-OF-PLANE PERFORMANCE OF URM WALLS
Groningen area of the Netherlands is now under the increasing induced seismic risk. Unreinforced masonry (URM) wall is one of the most vulnerable structural elements for the buildings in that area. The out-of-plane (OOP) performance of URM walls is critical for the safety of such buildings and also for the non-linear time-history analysis (NLTHA). A comprehensive masonry material model (EMM) has been developed and applied in the NLTHA of URM buildings in Groningen using a finite element DIANA. It can consider the orthotropic mechanical properties (all in tension, compression and shear) and hysteresis damping effects. The model has been validated by the comparison studies with numbers of quasi-static in-plane and out-of-plane laboratory tests. However, the performance of EMM in a dynamic OOP bending test has not yet been fully verified due to the lack of experimental references. Fortunately, recent shaking table tests performed in EUCENTRE (in Italy) provide the valuable references of dynamic one-way OOP bending performance of URM walls. Therefore, a numerical comparison study on the OOP tests of URM walls using a dynamic non-linear analysis method was realized in this study. The dynamic relative OOP responses in the whole testing process were compared, especially in the near-collapse situation. The influences of various material and model parameters were assessed in the comparison. Results and conclusions drawn in this study have been used for model validation and parameter refinements in NLTHA of URM buildings in Groningen area of the Netherlands.
THERMAL INERTIA IMPROVEMENT AND ACOUSTIC IMPACT OF WALLS WITH PROJECTING FACING BRICKS
The study consists in determining the impact of projecting facing brickwork on thermal inertia and Sound Transmission Loss (STL) of walls. Specific 3D thermal and acoustic calculation methods have been developed to be able to determine the areal heat capacities and STL of walls with non-coplanar faces. An optimization process was carried out to determine the arrangements of projecting bricks allowing a maximum areal heat capacity to be obtained. This approach led to the definition of a wall, called S for which the areal heat capacity is significantly increased compared to the reference wall with coplanar faces, with an almost constant areal mass. The structural modification of the wall is no longer consistent with the acoustic mass law. This change improves significantly the STL at low frequencies, however it degrades at medium and high frequencies compared to the 22 cm thick reference wall.
Ortega, Erika Gabriela;
Jiménez-Pacheco, Juan Carlos;
Garcia, Hernan Alfredo;
Quinde, John Alejandro
MACROELEMENT MODEL FOR NONLINEAR STATIC PUSHOVER ANALYSIS OF CONFINED MASONRY WALLS WITH OPENINGS
Seismic analysis of confined masonry buildings is complex due to the interaction between the masonry panel and the surrounding reinforced concrete frame. This complexity increases when the confined masonry wall has openings, due to the instability of the failure modes. In this context, the main objective of this work is based in the implementation of a Equivalent Strut Model for nonlinear static pushover analysis of confined masonry walls with openings.
CHANGE IN STIFFNESS OF DAMAGED RC FRAME WITH MASONRY INFILLS CONNECTED WITH STIFF AND FLEXIBLE INTERFACES
This study investigates the dynamic behaviors of RC frames with masonry infills which are constructed by different connection methods along the frame – wall boundaries. Two different connection types are considered namely, stiff connection to represent the traditional construction technique and flexible connection provided by Polyurethane PM as an innovative method. PolyUrethane Flexible Joints (PUFJ) are intended to use on both old (existing) and new (to-be-built) structures. Therefore, three single-bay and single-story frames are numerically created; Frame A has stiff, Frame B has PUFJ around the three sides of wall except the bottom one and Frame C has entire perimeter of the wall PUFJ connections, respectively. Among the frames of PUFJ implemented ones, Frame B is for representing the usage of PUFJ on existing structures whereas Frame C shows the implementation of method in new buildings. All of the frames were exposed to constant vertical loads affecting on beams. Various horizontal loads caused by seismic excitations were also used to understand the behavior of frames under different lateral load stages. Frames stiffness values were changed by means of arranging artificial column hinges that are located either only on the bottom or on both the bottom and top of columns. Thus, different damage scenarios were able to be investigated. The results are presented in terms of natural mode frequencies and maximum displacement values.
Bednarz, Lukasz (1);
Bajno, Dariusz (2)
CRITICAL OVERVIEW OF PROBLEMS WITH EXISTING BUILDINGS MADE IN THE BIG BLOCK TECHNOLOGY WITH INSULATION FROM AAC BLOCKS. MONITORING AND REPAIR POSSIBILITIES
The masonry structures have been evaluated during several thousand years of their use. From traditional (historical) wall structures, pillars, arches, ceilings, domes and vaults to, sometimes very sophisti-cated, but also impractical, solutions used in the 20th century. The article concerns untypical masonry con-structions such as fillings of residential buildings made in the big block technology, as well as external insu-lation layers from AAC wall blocks. Structures of this type were used in residential buildings for many years. Nowadays, these technologies are being abandoned but the existing buildings remain. The article presents the experience gained during the research and analysis of residential buildings made in the above described tech-nology. It also proposes ways of monitoring technical condition and technologies of repair of this type of buildings.
THE INFLUENCE OF FRCM SYSTEM WITH A BASALT MESH ON THE SHEAR PROPERTIES OF AAC MASONRY WALLS
Effective damage prevention of structural elements is a basic maintenance activities. In particular, this applies to masonry structures sensitive to various types of ground deformations. The application of FRCM strengthening systems, which are based on the materials compatible with masonry substrate is a very good solution here. The paper presents an analysis of the impact of selected FRCM system on the behavior of walls made of AAC blocks. The strengthening in the form of basalt mesh was applied on the masonry surface - in two configurations - using pozzolanic reaction cementitious mortar. Test results showed a significant increase in shear capacity of the walls strengthened on both sides, as well as a desirable mode of failure with a safety margin after obtaining the load-bearing capacity. One-sided application of the system allowed for only a slight improvement in shear properties in comparison with unstrengthened walls.
PERFORMANCE OF PERSIAN OPEN SPANDREL BRICK MASONRY BARREL VAULTS UNDER UNIFORM AND LINEAR LOADS
In this paper, the structural behaviour of Persian brick masonry barrel vaults with open spandrels under uniformly distributed load over the entire structure, linear load at the centre of the middle pier, and linear load at the apex of one of the vaults is studied using non-linear finite element analysis. Seven different shapes have been considered for the cross-section of the vaults. Results indicate that the best position for the spandrel vaults to achieve the maximum load carrying capacity is the same level as the main vaults. The semi-circular vault has the best performance under uniform load and the pointed vault has the best behaviour under linear load.