Masonry Shear Walls Research Articles

Numerical modeling of reinforced masonry walls under lateral loading at the component level response as opposed to system level response

Many experimental and analytical investigations were carried out on fully-grouted reinforced masonry shear walls types (rectangular, flanged or end-confined) to investigate their behavior under lateral loads. These studies mainly focused on evaluating the seismic response parameters for reinforced masonry shear walls (RMSW) such as ductility capacity, energy dissipation, stiffness degradation and strength. Yet, most of the research was conducted on studying each wall individually (component level response) and quite few investigations were carried out considering the system level response when different wall types are combined in a single building/system. In this paper, a simple numerical macro finite element model for walls is verified and used to simulate the in-plane response of a structure composed of ten RMSW having different ductility capacities but designed to have the same ultimate strength. The model was initially verified against available experimental data in the literature, then a parametric study was introduced to represent the effect of reinforcement ratio and axial compression on wall behavior prior to modeling structures composed of several walls. The current investigation intended to introduce how the structure ductility is affected when walls, having different ductility capacity, are interacting within one lateral load resisting system in the structure. Three methods were proposed to measure the yield displacement of the entire system to determine the value of displacement ductility for the structure and compared it to that of the individual walls within the system. Finally, a set of fragility curves were represented to illustrate the enhancement of seismic performance of masonry structures through adding end confined and flanged walls inside the structure. The results of this study showed that the displacement ductility of a structure could be significantly improved when flanged and end-confined boundary walls are included in the system as opposed to that constructed using only rectangular walls. The effect of adding end-confined masonry walls in improving structure displacement ductility is found to be more significant compared to adding flanged ones. Using fragility curves, the effect of end confined and flanged wall in the enhancement of the structure performance and delaying the damage state appears clearly in third and fourth damage states but did not have any contribution in enhancement of the first and second damage states.

New Constitutive Model for Interface Elements in Finite-Element Modeling of Masonry

A new interface element constitutive model is proposed in this study for analyzing masonry using the simplified micromodeling (SMM) approach, in which mortar and two unit–mortar interfaces are lumped into a zero-thickness joint (modeled using an interface element) between expanded masonry units. The new model is capable of simulating tension cracking, shear slipping, and compression failure, and is defined by a convex composite failure surface consisting of a tension-shear and a compression cap failure criterion. It removes the singularity in the tension-shear region but not in the compression-shear region. In addition, the proposed model is based on the hypothesis of strain hardening. The robustness and computational cost of the proposed model were compared with different constitutive models (which are based on three, two, and one failure criteria) that have been widely used in the literature to describe masonry behavior through a series of one-element tests and through the comparison of finite-element (FE) response simulation of an unreinforced masonry shear wall. The FE response results indicate that the proposed constitutive model is more efficient than and at least as accurate as the other constitutive models for analyzing masonry using the SMM approach.

Research of Influence of the Shape of Unreinforced Masonry Shear Walls Made of Calcium Silicate Masonry Units

We performed tests on 6 calcium silicate masonry units which were laid in thin layer mortar with uneven head joints. Walls were divided into two series and denoted by convention as HOS (Jasiński 2016) and HOS-H. Those two series differed in overall dimensions of test elements. Three walls from HOS series had identical external dimensions: l = 4.50 m, h = 2.45 m (h/l = 2.45m/4.50m), and thickness t = 180 mm. The walls were tested at different values of initial compressive stress σc = 0; 0.1; 1.0 and 1.5 N/mm2. The HOS-H elements were prepared as unreinforced test elements with the length l = 2.25 m height h = 2.45 m (h/l = 2.45m/2.25 m) and thickness t=0.18 m, and tested at initial compressive stress equal to σc = 0.1; 0.75; 1.5 N/mm2. The tests showed that the wall shape had a negligible effect on the morphology of cracks and the failure mechanism. An increase in wall length caused a roughly proportional increase in values of cracking and failure stresses. Shorter walls were under considerably greater cracking and failure stresses. An increase in wall length led to a significant decrease in values of shear strain angle regardless of initial compressive stress. The reverse situation occurred at the moment of destruction. Values of shear strain then increased with an increasing length of the wall.

Bestimmung eines Modellteilsicherheitsbeiwertes für unbewehrte Mauerwerkswände unter Knickbeanspruchung

AbstractThe design/verification method in the Eurocodes is based on the partial safety concept. Eurocode 6 suggests a constant partial safety factor for the material γM for all design/verification problems, without consideration of model uncertainty in the design/verification formula. In the following, a model partial safety factor is determined for the problem of unreinforced masonry walls mainly subjected to vertical loading. For that purpose, the newly proposed formula for EC 6, annex G will be considered [1–3]. In order to cover all aspects in tests and to use the results for design purposes, several methods have been included in EN 1990 Annex D for design based on test data. In this study, the recommended methods in Annex D of EN 1990 for resistance of the material are used to extract the partial safety factors. A database including more than 119 experimental tests on unreinforced masonry shear walls is used to compare the model prediction and the test results and to determine the model partial safety factor.

Stress-strain model for C-shape confined concrete masonry boundary elements of RM shear walls

Reinforced masonry (RM) shear walls with boundary elements have been recently presented as a more ductile alternative to RM rectangular shear walls. Evaluating the complete (i.e. including the post-peak branch) compression stress-strain behavior of the confined and unconfined masonry is essential for predicting the seismic response of the RM walls with boundary elements. Recently, the authors investigated the effect of various volumetric ratios of transverse reinforcement, vertical reinforcement ratios, and grout strength on the axial stress-strain behavior of reinforced masonry boundary elements (RMBEs). However, all the specimens had a specific height to thickness ratio (i.e., AR = 5). This study presents the observed stress-strain relationship of seventeen half-scale fully grouted unreinforced and RMBE specimens, built using C-shape blocks, tested under concentric compression loading up to failure. Thus, quantifying the effect of various aspect (height to thickness) and confinement ratios on the RMBEs peak stress, strain corresponding to peak, and post-peak behavior. The results indicate that, as the hoop spacings and/or aspect ratio decreases, the peak stress and post-peak strains increase. Moreover, this study presents a stress-strain empirical model capable of predicting the RMBE stress-strain response by computing the confined and unconfined masonry stress-strain behavior. The model is calibrated using the experimental data of thirty-three RMBE specimens, tested in this study and literature. The proposed model presents an efficient tool that can be implemented in different analytical/numerical packages.

Proposition of stiffness reduction in analysis of clay brick masonry under cyclic/seismic loads

Analysis of masonry buildings situated on seismic or mining activity terrains as well as subjected to dynamic human-induced vibrations and influences should base on the appropriated mechanical properties of masonry. There main parameters describing bending and shear stiffness’s of masonry shear walls are modulus of elasticity as well as shear modulus. Values of these parameters under seismic or cyclic loading are rapidly coming down due to the inelastic behaviour of the masonry. The problem of degradation of modulus of elasticity E as well as shear modulus G is presented and discussed based on the tests results of three types of clay brick masonry wall specimens subjected to compressive cyclic loads and some specimens under cyclic horizontally and vertical shearing (in one cycle) carried out at the Department of Structural Engineering of the Silesian University of Technology in Gliwice as well as results obtained by other researchers and available at the technical publications. As result there is proposed to determine the value of modulus of elasticity as 40 % of calculated with accordance with Eurocode 6 [1]. In case of shear modulus it is suggested to determine the G values as 20 % of initial values of modulus of elasticity, that is mean 50 % less than recommended in current version of Eurocode 6 [1] and perfectly correct with requirements given in Eurocode 8 [2].

An experimental study on cyclic behavior of aerated concrete block masonry walls retrofitted with different methods

Due to the insufficiency of the ductility, stability and low tensile stress capacity of the masonry shear walls responsible for carrying lateral loads, traditional brickwork masonry structures considered to be designed only under vertical service loads have been badly affected by the past severe earthquakes. The vulnerability of the existing masonry buildings can be decreased considerably by employing efficient retrofitting methods. This research work primarily aims to investigate experimentally cyclic behavior of aerated concrete block masonry walls before and after application of a special fiber retrofitting system. The investigated retrofitting system consists of multi-axial hybrid fabric made of alkali resistant glass polypropylene fibers for earthquake protection and white cement based plaster mortar with natural hydraulic lime. Another type of mortar with different material content was also tested to assess the adherence effect to the seismic retrofitting textile. The experimental results of this study were given with respect to force-displacement curves comparatively for all considered test specimens. It is concluded that the strength and the ductility capacity increased considerably by applying of the seismic textile, especially for two-sided retrofitting application with expanded glass granular made plastering.

Numerical modeling of a two story third-scale reinforced masonry shear wall building subjected to quasi-static lateral loading

This paper presents numerical modeling of a two-story third-scale reinforced concrete masonry building composed of walls in orthogonal directions and subjected to quasi-static cyclic lateral loading up to failure. OpenSees and Response-2000 were used to capture the behavior at the section level as well as that at the element and system levels. The results of ten experimentally tested individual walls were used to verify the modeling approach that was used to generate the building model. The models were able to accurately capture the response of individual walls and that of the tested building. Force based elements were used to represent the walls and values for the factors controlling the cyclic behavior of masonry and steel material models used were recommended. The maximum error obtained for the strength of all wall models and for the building model was 4% and 12% respectively. Numerical results showed that overall ductility of the building was higher than that of its constituent walls especially under eccentric load which was consistent with experimental results. The torsional response of flanged walls was found to be essential for the accurate representation of the building behavior under eccentric lateral loading.

Behavior of post-tensioned dry-stack interlocking masonry shear walls under cyclic in-plane loading

Dry-stacked interlocking masonry (DSIM) systems were developed worldwide to minimize the disadvantages of traditional masonry systems such as shrinkage, weak joints, and the need of skilled labors. Nevertheless, dry-stacked walls are recommended to be designed as reinforced and fully grouted. In this paper an experimental study conducted to evaluate the in-plane behavior of full-scale DSIM shear walls under cyclic in-plane loading and to explore the effectiveness of using post-tensioning (PT) instead of grout and reinforcement. A sliding control system to enhance the ductility of the DSIM system was developed. The test program consists of nine masonry shear walls constructed with three different types of locally available concrete masonry blocks (Conventional, Azar and Sparlock). The specimens were tested under reversed cyclic lateral load up to failure. The test results, including load displacement response, failure mode, modes of deformation, residual drift ratio, displacement ductility, wall stiffness, stiffness degradation, and energy dissipation are presented and discussed. The results showed that a similar behavior of Azar and conventional masonry systems in both reinforced and PT specimens. The utilization of PT with excluding the grout in DSIM shear walls improved the displacement ductility, effective stiffness and energy dissipation. Finally, the developed sliding control system in DSIM PT specimens increased the sliding contribution to 35% of total deformation, hence improved the displacement ductility.

Experimental and Numerical Study on the Seismic Performance of Prefabricated Reinforced Masonry Shear Walls

The seismic performance of prefabricated reinforced concrete block masonry shear walls (PRMSWs) was studied. Five PRMSWs were tested under cyclic loading to evaluate the effect of the axial compression ratio and the distribution of the vertical rebar on the inelastic behavior. Based on the experimental results, the lateral load capacity, failure mode, lateral drift, ductility, stiffness degradation, energy dissipation, and the seismic performance stability of the specimens were analyzed. The finite element analysis of the specimens was conducted with ABAQUS, which agreed quite well with the laboratory findings. Relevant results showed that PRMSW exhibited favorable ductility and energy dissipation. The increase of the compression ratio led to stiffer, but more brittle, inelastic behavior of the specimens that had higher flexural strength. The shear walls that had concentrated vertical rebar at the sides exhibited relatively higher load capacity and less ductility compared to the walls that had evenly distributed rebar. The inelastic lateral drift limit of the PRMSW could be assigned 1/120. The equivalent viscous damping ratio of the PRMSW was 9–13% at ultimate load. These results provide a technical basis for the design and application of the PRMSW structures.

Comparisons of confined and different types of reinforcement on the behavior of masonry shear walls

AbstractThis paper presents a comparison of results for shear walls: unreinforced (three walls), confined (six walls), and reinforced with two different types of reinforcements (four walls). Masonry walls made of autoclaved aerated concrete (AAC) had a thickness t = 0.18. Four series of different walls of the same length equal to l = 4.43 m and the height of h = 2.43 m were made and tested. Compressive strength of material masonry units and mortar for thin joints was equal to fb = 4.0 N/mm2 and fm = 6.1 N/mm2. Compressive strength of walls (according to EN 1052‐1:2000) was fc,mv = 2.97 N/mm2 and (fk = 2.48 N/mm2) and elastic modulus was Ecm = 2.040 N/mm2. Walls were tested at the same initial compressive stresses perpendicular to the plane of bed joints σc = 0.1, 0.75, and 1.0 N/mm2. In confined models, two external vertical cores and two horizontal beams were made and reinforced in accordance with the requirements of the European Standard EN‐1996‐1‐1. Steel truss‐type reinforcement and plastic grid placed in each bed joint were used in walls. The obtained values of stresses were compared at the time of cracking and destruction. The morphology of cracking and the mechanism of destruction were analyzed.

Experimental Investigation on the Seismic Behavior of Newly-Developed Precast Reinforced Concrete Block Masonry Shear Walls

Typically, a special type of concrete block with cleaning holes is used in the bottom layer of traditional reinforced masonry shear walls (RMSWs) for mortar cleaning and vertical rebar connection, which results in reduced integrity and weakened structural behavior. In this paper, a precast construction technology was introduced to overcome these shortcomings. The cleaning-hole blocks were eliminated in the newly-developed precast RMSWs. Quasi-static tests on two traditional and two precast fully grouted RMSWs were conducted. The results showed that the flexural capacity of precast walls exhibited about a 10% increase when compared to traditional RMSWs under the same axial compression. Precast RMSWs that failed in flexural mode showed favorable deformation capacity and the displacement ductility value corresponding to 15% strength degradation reached 4.9. The wall stiffness degraded rapidly to 50% of the initial stiffness, K0, at 0.2% drift and, at 0.5% drift, the corresponding stiffness decreased to about 21% K0 at a more gradual rate. Furthermore, precast RMSWs exhibited significant energy dissipation capacity. The experiment suggests that precast RMSWs have a satisfactory seismic performance.

“SEISMIC RESPONSE OF INFILL FRAME G+20 BUILDING WITH SHEAR WALL FOR LIFT USING SAP 2000 SOFTWARE”

This paper presents an analysis on performance-based seismic evaluation of G+20 RC frame Building with masonry infill (MI) and shear wall (SW) for lift using Non-linear Static Pushover Analysis with SAP2000v14 software for two different models i.e., Model-1: RC bare frame and Model-2: RC frame with MI wall and SW for lift (Soft storey). Result indicates, maximum Displacement for Model-1 i.e., 0.3346m, Model-2 gave displacement of 0.0718m respectively. These results clearly show, the stiffening in Model-2 is increased to 78.54% compared to Bare Frame. 

Stress-Strain Behavior of C-Shaped Confined Concrete Masonry Boundary Elements of Reinforced Masonry Shear Walls

Reliable material stress-strain relationship is the cornerstone of any analysis process. Unlike reinforced concrete, limited studies focused on the stress-strain behavior of confined reinforced masonry. Reinforced masonry boundary elements (RMBEs) added at the masonry shear wall ends allow placing of at least four longitudinal reinforcement bars restrained by transverse hoops and thus introducing confinement to the wall’s most stressed zone. This study presents the observed stress-strain relationship of 30 C-shaped half-scale fully grouted unreinforced and reinforced masonry boundary element specimens tested under concentric compression loading. The effect of changing hoop spacing, longitudinal reinforcement ratio, and the strength of grout on the axial stress-strain behavior of RMBE is investigated. This study quantifies and correlates the effect of these parameters on the RMBE peak stress, strain corresponding to peak, and postpeak behavior. Finally, this study investigates the capability of three existing stress-strain models in predicting the RMBE stress-strain relationship. Enhancement in both peak and postpeak stress-strain behavior were observed by decreasing the hoop spacing, increasing the longitudinal reinforcement ratio, and increasing the grout strength. The studied models overestimated the enhancement in the RMBE strength, significantly overestimated the enhancement in the RMBE strain capacity, and did not capture the postpeak stress drop. This study emphasizes the need for a new stress-strain model that can predict the RMBE response considering various confinement effects.

System-Level Seismic Damage Assessment Methodology for Reinforced Masonry Shear Wall Buildings

AbstractDamage state (DS) assessment of reinforced masonry shear wall (RMSW) building systems is key for developing simulation tools for pre- and post-earthquake risk-assessment frameworks. However...

Masonry-like material with bounded shear stress

Abstract The constitutive equation of masonry-like materials has been generalized in order to account for a limit to the tangential component of the stress, that is proportional to the normal component. This result has been achieved by suitably modifying the convex set made up of all the admissible stresses. The constitutive equation obtained in this manner retains all the properties of normal elastic materials. The model developed has been implemented in the FEM computer code MADY, and applied to the study of masonry shear-walls and arches under monotonic in-plane loads. The reliability of the proposed model is checked through comparisons with some experimental results.

Development of Fragility Curves for Reinforced-Masonry Structural Walls with Boundary Elements

Performance-based seismic design requires accurate damage/loss models for different seismic force resisting systems. Fragility functions are considered one of the most common damage/loss models that link specific demand parameter to the probability of exceedance of different damage states. Recently, reinforced masonry shear walls with boundary elements (RMSW+BEs) showed enhanced lateral performance and curvature ductility compared to that of rectangular walls. However, few experimental studies are available to date focusing on the seismic response of RMSW+BEs. FEMA guidelines provide fragility curves for reinforced masonry shear walls having only a rectangular cross section. Moreover, limited data are available to generate fragility curves for RMSW+BEs. In this paper, a numerical study is presented using the macromodeling approach embedded in the SeismoStruct software to simulate the in-plane lateral response of flexural dominated RMSW+BEs. The numerical model is validated against three RMSW+BEs walls tested under quasi-static cyclic loading reported in the literature. Subsequently, a parametric study is performed on 36 RMSW+BEs to evaluate the influence of varying the axial stress, wall aspect ratio, and vertical reinforcement ratio on the lateral response of the RMSW+BEs. It was observed that RMSW+BEs strength increases as the aspect ratio decreases, vertical reinforcement ratio increases, and level of axial stress increases. On the other hand, decreasing the wall aspect ratio, vertical reinforcement ratio, and level of axial stress enhances the RMSW+BEs displacement ductility. The drift ratios corresponding to three damage states (i.e., slight, moderate, and severe) were computed according to FEMA guidelines. Finally, fragility curves were generated for RMSW+BEs utilizing the computed numerical data of the studied walls, which can be adopted in performance-based seismic design frameworks.

Determination of partial factor for model uncertainty for unreinforced masonry shear walls

AbstractExperiments in structural engineering can play an important role in the prediction and characterization of the material properties and behaviour of structural components. In order to cover all aspects in tests and use the results for design purposes, several methods have been included in EN 1990 Annex D for design based on test data. The calculation of characteristic values and design values for material resistance are the main aspects. In this study, the recommended methods in Annex D of EN 1990 for resistance of the material will be used to extract the partial safety factors for masonry structures based on the formulation of design and characteristic values. A database including more than 100 tests on unreinforced masonry shear walls will be used to evaluate the results. The resistance model for shear walls based on the recommendation in the Eurocode will be compared with the test results. The main aim will be to compare the model prediction and the test results. Deviation of the prediction from the test is caused by model error or model uncertainty. The test database includes results for three types of masonry units – fired clay, calcium silicate and autoclaved aerated concrete. The evaluation of partial factors for masonry shear models will be undertaken based on the scatter and the model bias for the whole database. Further analysis will also be performed for each type of masonry unit for classification of the outcome.

Out-of-Plane Behavior of Slender Reinforced Masonry Shear Walls under In-Plane Loading: Experimental Investigation

AbstractThis paper presents the results of a multiphase research program aimed at investigating the out-of-plane stability of slender reinforced masonry shear walls (RMSWs) under in-plane reversed-...

Evaluation of seismic displacement demand for unreinforced masonry shear walls

Unreinforced, non-engineered low-strength brick masonry structures comprise a large percentage of buildings in the Himalayan region and have been extensively damaged in recent earthquakes. Due to t...