Reinforced Masonry Shear Walls Research Articles

Numerical assessment of TMS 402/602-22 and CSA S304-14 seismic design provisions for partially grouted reinforced masonry shear walls failing in flexure

Despite the economic benefits of using partially grouted reinforced masonry shear walls (PG-RMSWs) as a seismic force resisting system (SFRS) in low-rise buildings, using such a system in mid- and high-rise buildings is still questionable. This is because the literature lacks comprehensive studies investigating different seismic design provisions adopted for rectangular and flanged PG-RMSWs of aspect ratios greater than 2.0 and failing in flexure. Therefore, this study aims to conduct a comprehensive numerical assessment of the seismic design provisions of the North American masonry standards (i.e., TMS 402/602–22 and CSA S304–14) for designing different categories of rectangular and flanged PG-RMSWs failing in flexure. In this regard, 108 PG-RMSWs were designed and modeled using the Extreme Loading for Structures (ELS) software. Afterward, some changes were proposed to the current seismic design provisions in CSA S304–14 and TMS 402/602–22 for rectangular and flanged PG-RMSWs. In addition, a comparison was made between the seismic design provisions for PG-RMSWs and FG-RMSWs, designed according to each RMSW category, to investigate the expected differences in the behavior based on the applied seismic design provisions. Accordingly, additional 36 FG-RMSWs were designed according to CSA S304–14 and TMS 402/602–22. These additional walls were then modeled on the ELS and compared with their PG counterparts. The results show that both standards can be safely used to design rectangular and flanged PG-RMSWs only when using the two proposed provisions for each standard. For CSA S304–14, the possibility of updating clause 16.8.5.2 is concluded, allowing the use of PG-RMSWs without limitations. New seismic force modification factors were also proposed for TMS 402/602–22 for the design of rectangular and flanged PG-RMSWs. Finally, the comparison between rectangular PG and FG-RMSWs failing in flexure and designed according to CSA S304–14 and TMS 402/602–22 shows that the behavior of PG-RMSWs failing in flexure is comparable to FG-RMSWs under certain circumstances. This study is considered a significant step to prove the potential for more economical and safe usage of PG-RMSWs in mid- and high-rise buildings.

Effect of boundary element detailing on the seismic performance of reinforced concrete masonry shear walls

Laboratory tests demonstrated that reinforced masonry shear walls (RMSWs) can provide sufficient strength and ductility to be considered an efficient seismic force resisting system (SFRS) for mid-rise buildings. The ductility and overall seismic performance of shear walls were increased by providing confinement to the end zones of the walls to form boundary elements (BEs)., which enhanced the ultimate masonry compressive strain and curvature ductility of the walls. Regular stretcher blocks are commonly used in the construction of masonry boundary elements; however, they impose some constraints due to their geometrical characteristics. This study investigated the construction and testing of three half scale specimens of reinforced masonry shear walls with boundary elements (RMSWs+BEs) that were characterized by flexural dominance under reversed cyclic moment and lateral loading. In the lower story panel of a 12-story RMSW building, these walls constitute the plastic hinge zone, which is represented by a plastic hinge wall. In this study, C-shaped masonry units were used instead of stretcher units to construct BEs with different sizes and vertical reinforcement ratios. The findings of this work revealed that employing C-shaped masonry units to construct the BEs was effective in overcoming the construction limits imposed by stretcher units. Additionally, the results of this study demonstrated that when RMSWs+BEs are subjected to quasi-static reversed cyclic loading, they are capable of providing a high level of ductility with minimal loss of strength.

Comparative analyses of reinforced masonry and reinforced concrete shear walls with different end configurations: Seismic performance and economic assessment

Recent research has been demonstrating that fully-grouted reinforced masonry (RM) shear walls possess high ductile capacity levels that resulted in excellent performance under seismic loading. Considering the results of these studies, the current ductility modification factors assigned to such shear walls in relevant building codes and design standards are excessively conservative compared to the corresponding higher values assigned to their reinforced concrete (RC) counterparts. These conservative factors are mainly attributed to the lack of research studies that have been conducted to present direct comparisons between the performance of the two seismic force-resisting systems. To address this current knowledge gap and guide future editions of their relevant design standards based on experimental and analytical evidence, the objective of the current study is to show detailed comparative analyses between the performance of several RC and RM shear walls with different end configurations when both wall systems are subjected to similar seismic demands. These analyses also include a comprehensive economic assessment to equip practicing engineers and other relevant stakeholders with detailed comparisons between the two wall systems in terms of their construction costs. In this respect, six half-scaled RC shear walls were compared to three half-scaled RM shear walls, where all nine walls were tested under a quasi-static cyclic fully-reversed loading. The six RC shear walls were tested in two phases, where each phase consisted of three different wall types (i.e., rectangular, flanged, and boundary element walls) that had identical dimensions to their RM counterparts. To allow for direct comparison between the walls, Phase I RC walls with low vertical reinforcement ratios had similar lateral strength capacities as the RM walls, whereas Phase II RC walls with high vertical reinforcement ratios had similar ultimate curvature values as the RM walls. The comparison results are presented in the current study in terms of the crack patterns, load–displacement envelopes, curvature profiles, and wall displacements. Displacement ductility values, normalized periods, and equivalent viscous damping ratios are also presented for the nine walls. Finally, an economic assessment is performed to compare the walls in terms of their total rebar weights and approximate construction costs. The results demonstrate that RM shear walls can achieve an enhanced seismic performance similar to that of RC shear walls if the former walls are well-detailed (e.g., adequate confinement). Such an enhanced performance of RM shear walls is also coupled with low construction costs when compared to their RC counterparts. The current study enlarges the database of results that will facilitate assigning effective seismic performance metrics (e.g., ductility-related force modification factors) for RM shear wall buildings in future editions of building codes and design standards.

Numerical study of the seismic performance of fully grouted reinforced masonry shear walls with boundary elements subjected to dynamic loading

Reinforced masonry shear walls with boundary elements (RMSW + BEs) have enhanced curvature and displacement ductility and more energy dissipation than their rectangular counterparts when subjected to quasistatic cyclic loading. However, the behavior of walls tested under quasistatic cyclic loading is different from that under dynamic loading. Although there are many studies in the literature regarding the seismic response of RMSW + BEs, there is a gap in understanding the seismic performance parameters of RMSW + BEs when subjected to dynamic loading. Therefore, in this study, a numerical investigation of the seismic behavior of twelve previously tested half-scaled fully grouted RMSW + BEs was performed to quantify the seismic performance parameters of the walls under quasistatic cyclic loading and incremental dynamic loading. The studied walls have different design parameters that cover different aspect ratios, applied axial stress, horizontal and vertical reinforcement ratios, confinement type in boundary elements (BEs), discontinuity in BEs at upper floors and the presence of interstory slabs. A 2D numerical macromodel was developed using the Extreme Loading for Structures (ELS) software to validate and simulate the nonlinear lateral cyclic response of the studied walls. A nonlinear time-history analysis (NLTHA) was carried out using seven pairs of simulated ground motion records developed by Atkinson to represent Eastern Canada earthquake regions (i.e., Montreal, Quebec). The results showed good agreement between the walls’ results among the two loading protocols to better estimate and correlate the walls’ dynamic performance from quasistatic cyclic testing. The quasistatic loading results showed conservative lateral performance compared to dynamic loading in terms of stiffnesses, lateral capacity and energy dissipation. Moreover, the effect of different design parameters has been inspected on the dynamic performance of RMSW + BEs. Increasing the wall aspect ratio led to lower wall stiffnesses and lateral capacities at different loading stages. More energy dissipation and lateral capacity levels were observed when utilizing higher axial stresses on the walls. This study's findings will help better predict and estimate the lateral behavior of RMSW + BEs to help develop subsequent editions of the North American design standards for masonry structures.

Seismic response analysis of reinforced masonry core walls with boundary elements

The seismic design of mid- and high-rise reinforced masonry (RM) structures necessitates a reliable seismic force resisting system (SFRS) that provides adequate capacity and ductility. Core walls are commonly used as the SFRS for counterpart reinforced concrete buildings due to the convenience of locating the elevators and staircases inside it. This study introduces reinforced masonry core walls with boundary elements (RMCW+BEs) as a potential SFRS alternative to rectangular reinforced masonry shear walls (RMSWs) with and without boundary elements given their enhanced structural and architectural characteristics in typical RM buildings. A macroscale nonlinear numerical model was developed using the Extreme Loading for Structures software (ELS) to evaluate the seismic performance of RMCW+BEs. A nonlinear time history analysis (NLTHA) was carried out for three archetype RM buildings with 10-, 15-, and 20-story heights designed according to the CSA S304-14 and located in a North American moderate seismic zone. The results showed that utilizing RMCW+BEs as the main SFRS system adequately controlled the seismic demands on RM buildings subjected to typical North American ground motions. However, the 20-story building showed a shear demand exceeding the nominal flexural resistance of the core wall at the plastic hinge region at the base, which was attributed to the adverse effect of the higher modes of vibration effects on the seismic demand parameters. Therefore, the three buildings were redesigned using a dual plastic hinge (DPH) design approach. The numerical results demonstrated that using the DPH reduced the shear demand and mitigated the effect of the higher modes of vibration on the seismic response of the core walls. The findings of this study highlight the need to integrate a new shear demand magnification factor to account for the higher mode effects in estimating the seismic demand of ductile RMSWs in the next generation of the North American design standards for masonry structures.

Mann–Kendall-Based Concrete Failure Trend Analysis and Its Implementation for Dynamic Building Monitoring

Analyzing monitoring data efficiently is a classic problem in structural health monitoring. A nonparametric test method, the Mann–Kendall (MK) method, was implemented in this study, which is commonly used to detect monotonic trends in a series of environmental data. Using the MK method, three types of time series were studied: the stress time series measured in the concrete prism compression test, the resultant force time series obtained from the pseudostatic test of a reinforced masonry shear wall, and the translation velocity time series detected in a high-rise building. The statistics calculated, as well as the intersections of curves, indicate the trend change in the time series. The results demonstrated that the MK method could efficiently analyze the trend in the engineering time series.

Practical Nonlinear Analysis Methods for Flexure-Dominated Reinforced Masonry Shear Walls

Practical Nonlinear Analysis Methods for Flexure-Dominated Reinforced Masonry Shear Walls

A beam‐column element for modeling nonlinear flexural and shear behaviors of reinforced masonry walls

AbstractThis paper presents a computationally efficient beam‐column element to simulate the nonlinear flexural and shear behaviors of reinforced masonry shear walls subjected to bilateral seismic forces. A three‐field mixed formulation based on the Hu‐Washizu variational principle is adopted. This mixed element is free of shear locking, and allows a wall to be modeled with one element. The axial and flexural responses are evaluated with a fiber‐section model at each integration point along the element, while the shear response in each loading direction is represented by a phenomenological model. The element accounts for the influence of the axial load, wall aspect ratio, and wall flange, if any, on the shear response of a wall. To consider axial‐flexure‐shear interaction, the shear model takes into account the axial stress resultant from the fiber‐section model, and the compressive strength of masonry in the fiber‐section model decreases when severe shear damage developed. The model has been calibrated and validated with experiment data. It has been demonstrated that it is able to reproduce experimental results from quasi‐static cyclic loading tests of single walls as well as shake‐table tests of wall systems with good accuracy. Furthermore, the ability of the proposed model to simulate the response of reinforced masonry shear wall systems subjected to bilateral seismic forces has been examined by comparing with results from a detailed finite element model.

Sensitivity of the seismic response of reinforced concrete masonry walls with boundary elements to design parameters

The seismic design of concrete masonry structures with reinforced masonry shear walls with boundary elements (RMSW+BEs) depends on the wall design parameters. This paper aims to investigate the sensitivity of the nonlinear seismic response of RMSW+BEs to critical design parameters such as the wall geometry and the material properties to optimize the seismic design of RMSW+BEs. In this study, the influence of eight design parameters on the seismic performance of RMSW+BEs was investigated. The studied parameters were wall aspect ratio, axial compressive stress, masonry boundary element (MBE) size, wall length, masonry compressive strength, masonry compressive strain at peak stress, masonry modulus of elasticity, and vertical reinforcement ratio of the boundary elements. These combinations yielded valuable data accumulated from the nonlinear behavior of one hundred thirty-five (135) RMSW+BEs. The results showed that as the wall aspect ratio and axial compressive stress increased, the displacement ductility decreased significantly. In addition, increasing the boundary element size and wall length increased the wall lateral ultimate capacity and displacement ductility. The lateral yield capacity, ultimate capacity, and effective stiffness of the walls were found to be highly sensitive to changes in the vertical reinforcement ratio of the boundary elements. The displacement ductility was highly sensitive to uncertainties in the masonry compressive strain at peak stress. This study elucidates some of the most critical design parameters influencing the seismic response of RMSW+BEs.

Shear design equation and updated fragility functions for partially grouted reinforced masonry shear walls

This paper proposes specific ultimate shear strength expressions for partially-grouted reinforced masonry (PG-RM) shear walls that are bed-joint reinforced (BJR) and made with either multi-perforated clay bricks (MPCLBs) or hollow concrete blocks (HCBs). For each unit type, a set of constant coefficients of an arbitrary mathematical expression is optimized to minimize the error against experimental databases of walls made with the same unit types. Additionally, the assembled databases are employed to calculate lognormal empirical fragility functions, following performance-based earthquake engineering (PBEE) methodologies. For this, two different engineering demand parameters (EDPs) (story drift ratio, SDR, and normalized diagonal shear demand, NDSD) are proposed, and two damage states (DS) (named DS4 for moderate damage and DS5 for severe damage) are investigated. The proposed shear formulae are used in the normalization of calculated NDSD values. Moreover, databases are sorted by a selected design parameter (aspect ratio) to calculate design parameter-sensitive fragility functions.Overall, the results indicate that the proposed expressions are more accurate than the corresponding expressions proposed by the American and Canadian codes when assessing BJR-PG-RM shear walls in terms of the average error and dispersion of relative prediction error. All the fragility curves adjusted to the whole database pass the Lilliefors goodness of fit test (α=5%). Comparing SDR-based curves of walls of a different unit type, DS4 curves present a smaller difference in the median value (θ) than DS5 curves. Additionally, the variations in the θ of NDSD-based curves of walls of different units are smaller than those observed in SDR-based fragility functions, indicating that NDSD represents a less variant EDP to describe the probability of shear damage at DS5 when a proper expression is employed for the normalization. Regarding design parameter-sensitive fragility functions, sorting databases reduces the number of data points used to calculate the functions, which produced two SDR-based and one NDSD-based function to fail the Lilliefors test (α=5%). In general, the θ value of SDR-based curves increases in proportion to the aspect ratio. Additionally, classifying the databases by a design parameter (aspect ratio) corroborated that the proposed expression has acceptable accuracy based on the adjusted NDSD-based DS5 fragility functions. It is highlighted that calculating design parameter-sensitive functions might increase the accuracy of PBEE assessments (e.g., loss estimations) when an EDP insensitive to design parameters normalization (e.g., SDR) is employed.

Simplified analytical models for partially grouted reinforced masonry shear walls

Partially grouted (PG) masonry shear walls have commonly been used for construction in seismic regions. However, predicting their behaviour is quite complicated due to the non-uniformity presented by the materials’ variety. In this paper, an extensive analytical study was carried out to establish simplified backbone models referred here as “analytical models” as a first attempt in the literature to simulate PG masonry walls’ behaviour. A nonlinear finite element model was developed and validated against several experimental specimens from the literature. The numerical model was then utilized to compensate for the lack of experimental data by generating a comprehensive matrix of 196 numerical models covering a wide range of design and detailing parameters. These parameters include the aspect ratio, the spacing between vertical and horizontal grouted cells, the axial load, the ratio of vertical and horizontal reinforcement, and the compressive strength of grouted and ungrouted masonry units. Subsequently, three penta-linear load–displacement backbone models were proposed using linear regression analysis. Five secant stiffness expressions, namely: cracking, yielding, ultimate, 20% strength reduction, and 40% strength reduction, were derived to define the backbone curve of each wall category. Consequently, the proposed analytical models were examined against samples from the numerical matrix and the experimental specimens, which were not considered in the calibration of the analytical models. The results showed that the proposed analytical models provide good predictions of the response of PG masonry walls. Finally, the stiffness reduction factor provided by CSA S304-14 for masonry, α, was updated by developing three new coefficients for the PG walls’ categories based on regression analyses between the numerical stiffnesses at yielding and their corresponding values calculated using α.

Monotonic and cyclic stress-strain models for confined concrete-masonry shear wall boundary elements

Simulation of the seismic response of fully grouted reinforced masonry shear walls (RMSWs) built with reinforced masonry boundary elements (RMBEs) necessitates reliable nonlinear models of their RMBEs. The axial monotonic and cyclic full stress-strain curves of RMBEs are essential for predicting the lateral cyclic response of RMSWs with boundary elements. Therefore, a reliable stress-strain constitutive model for the axial monotonic and cyclic behavior of RMBEs is required. The authors recently investigated the axial monotonic compressive behavior of unconfined and confined RMBEs built with different section configurations, vertical reinforcement arrangements, transverse confinement ratios, and different construction procedures. In the current study, the authors investigated the cyclic behavior of some RMBEs whose counterparts were previously tested under axial monotonic compression. In addition, more specimens with different confinement configurations and different grout strengths were tested. Comparisons of the test results showed that increasing the vertical reinforcement ratio increased the axial load carrying capacity of the tested RMBEs but decreased their strain ductility. In addition, using a low compressive strength grout significantly reduced the strain ductility of the RMBEs. Moreover, monotonic and cyclic stress-strain models for confined and unconfined concrete-masonry boundary elements subjected to axial compression loading were developed. The proposed models showed good-to-excellent agreement with the experimental results, predicting the stress-strain rising curve, stress drop, and postpeak behavior. Furthermore, unloading and reloading curves, strength degradations, and softening of reversal and reloading branches due to cyclic degradations were well captured by the proposed model.

Experimental investigation of reinforced concrete masonry shear walls with C-shaped masonry units boundary elements

There is a global drive to promote and optimize the design of high performance buildings at low cost and minimum environmental impact. Although reinforced masonry construction is known for its better fire protection, structural durability, and construction cost reduction, its use is hindered by a lack of understanding of its resistance to earthquake loads. This research aims to quantify the effect of influential parameters on the seismic performance of Reinforced Masonry Shear Walls (RMSW) with masonry boundary elements (MBEs). A new system/configuration for RMSW with C-shaped masonry units has been proposed. A new experimental test setup was designed and built to capture the response of the lower panel of RMSW in a 12-storey building subjected to quasi-static loading protocol. Test results showed that the proposed system could provide the lateral strength and ductility required to resist earthquake events and that the average measured compressive strain was almost four times the limit specified in CSA S304-14. The results also showed that single out-of-plane support at the loading beam level was inadequate, leading to out-of-plane failure. When additional out-of-supports were provided, the failure mode changed to web crushing and buckling of vertical web reinforcement.

Probabilistic seismic resilience quantification of a reinforced masonry shear wall system with boundary elements under bi-directional horizontal excitations

The concept of resilience is gaining increased attention in disaster management due to the recent awareness of the need to reduce the detrimental post-event effects of natural disasters, e.g., earthquakes. Resilience is a practical concept that includes pre-event (preparedness and mitigation) and post-event (response and recovery) activities. Quantitative resilience assessment approaches are needed to compare the available mitigation strategies to decide on the most suitable strategy and provide better support for decision-making procedures. In this study, a methodology for quantifying the seismic resilience of reinforced masonry shear wall (RMSW) buildings with end-confined masonry boundary elements is implemented. The uncertainties associated with structural and non-structural losses and estimated recovery time uncertainties are considered while quantifying the resilience index of RMSW buildings. The archetype buildings studied have 8-, 10-, and 12-storey heights and are located in Vancouver, representing a high seismic zone in Canada. First, a numerical model was developed using OpenSees to derive the fragility surface for the studied archetypes subjected to bi-directional horizontal excitation. Second, a Monte Carlo simulation was performed to quantify the resilience index of each archetype considering the above-mentioned uncertainties. The results prove the robustness of ductile RMSW buildings having end-confined MBEs in mitigating the losses associated with disaster events. Additionally, the findings provide comprehensive and valuable information for earthquake mitigation measures and disaster risk reduction programmes.

The Hysteretic Failure Features of Reinforced Masonry Shear Walls Revealed by Modeling Experimental Residual Strain Data

ABSTRACT The hysteretic working capacity of reinforced masonry shear (RMS) walls has been estimated empirically and statistically referring to the structural ultimate state with considerable uncertainty. This investigation is to try to break this puzzlement of the uncertainty by revealing the hysteretic working features of RMS walls applying structural state-of-stress theory. The experimental residual strains are firstly modeled as generalized strain energy density (GSED) values (state variables) to describe structural state-of-stress mode and its characteristic parameter (GSED sum). Then, the slope increment criterion is proposed to detect the state-of-stress mutation point in the GSED sum-load curve. Accordingly, it is verified that the evolution of the state-of-stress mode presents the mutation feature. Thus, the starting point of the RMS wall’s failure process is revealed as the embodiment of the natural law from quantitative change to qualitative change of a system. And the hysteretic failure load of the RMS wall is defined at the state-of-stress mutation point with the attribute of certainty and generality. Furthermore, the GSED-based analysis reveals the working features between the state-of-stress submodes of structural components. This investigation explores a new way to analyze the hysteretic working behavior of RMS walls, which provides the rational reference to the accurate estimation of the failure loads of RMS walls for designs.

Sensitivity analysis of the numerical simulations of partially grouted reinforced masonry shear walls

A simplified finite element (FE) model is proposed using VecTor2 software to simulate the cyclic behavior of partially grouted reinforced masonry shear walls (PG-RMSWs) constructed with concrete-masonry blocks and having reinforced bond beams. The proposed model is validated against different experimentally tested walls available in the literature and is found to be capable of simulating the experimental behavior. Following the development of the validated model, a sensitivity analysis is conducted to study the relative effect of different grouted and ungrouted masonry modeling input parameters on the seismic response of the modeled walls. In this regard, six reference walls with different aspect ratios and different vertical reinforcement spacings are modeled. Afterward, reference values of masonry modeling input parameters are changed within ±30% from the reference values yielding 126 modeled walls. A numerical study is also conducted to compare the response of fully grouted reinforced masonry shear walls (FG-RMSWs) and PG-RMSWs to investigate the differences in their behaviors. In this regard, four walls with different aspect ratios and spacings between vertical grouted cells are considered. For the sensitivity analysis, it is concluded that the parameters of the ungrouted masonry are the most influential ones, where the walls' behavior is primarily sensitive to the input value of the angle of internal friction between blocks and mortar. However, this effect diminishes as the aspect ratio of the wall increases and spacing between grouted cells decreases. Accordingly, for shorter walls and walls with larger spacing between grouted cells, more attention shall be given to the estimation of the parameters representing the material properties of ungrouted masonry, especially the angle of internal friction. This concludes that a better seismic response of PG-RMSWs can be achieved by improving the properties of the block-mortar interface in the ungrouted portions of the walls. Comparisons of the seismic response of FG-RMSWs with PG-RMSWs show that FG walls with a lower aspect ratio have a higher ultimate load and a lower corresponding displacement compared to their PG counterparts. For walls with a higher aspect ratio, both the ultimate load and the corresponding displacement are larger for FG walls.

Effective stiffness and period-dependent seismic response modification factors for flexure-dominated fully-grouted reinforced masonry rectangular shear walls

The wall effective elastic stiffness, displacement ductility, and seismic force modification factors are important force-based seismic design (FBD) parameters for reinforced masonry (RM) shear walls. The effective stiffness, ke of reinforced masonry shear walls (RMSW) is crucial in computing the natural period and thus the elastic forces, and essential also in computing the displacements corresponding to the design seismic forces. This study analyzes previously reported test results of forty-three flexure-dominated fully-grouted rectangular RMSWs subjected to quasi-static cyclic load to evaluate the FBD parameters adopted by Canadian and American standards. In this study, based on the experimental results of 43 tested walls, a new stiffness reduction factor is proposed considering the effect of axial stress, vertical reinforcement ratio, and horizontal reinforcement ratio. Moreover, the seismic force modification factors are compared to the Canadian and US codes. The results showed that ductility related reduction factors should be dependent on the wall natural frequency and there is a room to relax the current proposed code values. In addition, incremental dynamic analysis was performed using a simplified numerical model to study the effect of dynamic loading on response modification factors and stiffness characteristics of the walls.

Detailed micro-modeling of partially grouted reinforced masonry shear walls: extended validation and parametric study

Partially grouted reinforced masonry (PG-RM) shear walls have been widely used as structural elements in low- and medium-rise earthquake-resistant buildings. Nonetheless, assessing its shear strength represents a complex task mainly because the partial grouting provides a non-constant cross section, which results in heterogeneous stress–strain patterns. Consequently, refined modeling techniques are needed to reproduce local failure mechanisms taking place in these walls, which significantly influence the global response. In response to this issue, a detailed micro-modeling approach based on the finite element method was proposed in previous studies by the authors. Although the numerical strategy provided accurate results, further validation is required. Therefore, in this study, the experimental results of seven PG-RM shear walls of multi-perforated clay bricks with bed-joint reinforcement are employed as validation cases. These seven walls presented variations in five design parameters. The validated numerical model was then employed to perform a parametric study to assess the influence of the wall aspect ratio, axial pre-compression stress, and horizontal reinforcement ratio on the in-plane lateral behavior of PG-RM shear walls. The obtained results show that the three studied design parameters modified the crack patterns of the walls. Besides, increasing the axial pre-compression stress or reducing the aspect ratio resulted in higher walls’ shear strength. Additionally, decreasing the horizontal reinforcement ratio or increasing the aspect ratio generated a higher story-drift ratio at maximum lateral force. Finally, it was corroborated that the positive effect of the axial pre-compression stress on the walls’ shear strength decreases inversely proportional to the aspect ratio.

Experimental Investigation into the Seismic Performance of Prefabricated Reinforced Masonry Shear Walls with Vertical Joint Connections

In this study, four single-story reinforced masonry shear walls (RMSWs) (two prefabricated and two cast-in-place) under reversed cyclic loading were tested to evaluate their seismic performance. The aim of the study was to evaluate the shear behavior of RMSWs with flanges at the wall ends as well as the effect of construction method. The test results showed that all specimens had a similar failure mode with diagonal cracking. However, the crack distribution was strongly influenced by the construction method. The lateral capacity of the prefabricated walls was 12% and 27% higher than that of the corresponding cast-in-place walls with respect to the rectangular and T-shaped cross sections. The prefabricated walls showed better post-cracking performance than did the cast-in-place wall. The secant stiffness of all the walls decreased rapidly to approximately 63% of the initial stiffness when the first major diagonal crack was observed. The idealized equivalent elastic-plastic system showed that the prefabricated walls had a greater displacement ductility of 3.2–4.8 than that of the cast-in-place walls with a displacement ductility value of 2.3–2.7. This proved that the vertical joints in prefabricated RMSWs enhanced the seismic performance of walls in shear capacity and ductility. In addition, the equivalent viscous damping of the specimens ranged from 0.13 to 0.26 for prefabricated and cast-in-place walls, respectively.

Reinforced masonry shear wall blast response limits for ASCE 59 and CSA S850

The current blast response limits for reinforced masonry (RM) walls in North American blast standards are based on parameters that neither account for the wall ductility capacities nor the influence of different design configurations on the wall damage tolerance levels. Specifically, ASCE (2011) and CSA (2012) currently assign a support chord rotation limit for each damage state (i.e., Superficial, Moderate, Heavy, and Hazardous) regardless of the different ductility capacities that structural components may possess when different design configurations are adopted. However, recent relevant studies demonstrated that wall configurations and their different design parameters significantly influence the out-of-plane performance of RM walls. For example, RM shear walls with boundary elements are considered a promising blast-resisting system due to their enhanced out-of-plane characteristics (e.g., strength and ductility) compared to those with typical cross-sections (i.e., rectangular). Nonetheless, the aforementioned standards do not assign separate design requirements or response limits for this new system due to the limited number of relevant studies available when such standards were being developed. To address this knowledge gap, the current study evaluates the blast behavior of such walls with different configurations and subsequently proposes new related blast response limits for ASCE 59 and CSA S850. An OpenSees model was developed and then validated through the results of several previous test programs under quasi-static and blast loads. Subsequently, the new response limits were generated using the model and compared to those currently available (i.e., ASCE 59–11/CSA S850-12) using pressure-impulse diagrams. Finally, the blast response of several RM walls with different configurations was evaluated when such walls were subjected to different blast demands. The results highlight the blast-resistance enhancements that boundary elements can provide to RM shear walls at different damage states and the need to develop category-specific blast response limit within blast design standards.