Seismic Fragility Assessment and Resilience of Reinforced Masonry Shear Wall Systems

Reinforced Masonry Shear Walls (RMSWs) are commonly used in low- to high-rise buildings as the lateral load resisting system. There have been several experimental and analytical studies that evaluated the seismic response of RMSW either as a single element (i.e., planar rectangular walls) or as a building consisting of planar walls. However, research on Reinforced Masonry Shear Walls (RMSWs) with end-confined Boundary Elements and flanged shear walls are scarce, especially considering the effects of design parameters on the system’s seismic inelastic response. The end confined RMSWs proved to have a higher level of ductility since they can postpone the reinforcement buckling in compression while increasing the compressive strength of the shear walls’ component at the same time.
\nThe objectives of the current study are to: (i) assess the seismic performance and collapse capacity of the RMSW with end confined Boundary Elements and Flanged shear walls at both structural element, and entire building level, (ii) evaluate the seismic resilience and functionality of the RMSW system when subjected to severe earthquake events, (iii) to quantify and assess the resilience index versus the uncertainty of the studied parameters. 
\nTo achieve the first goal, at the structural element level, the RM shear walls were designed with different heights to investigate the effect of the wall’s height on its seismic performance. The impact of utilizing flanged walls was assessed and characterized through new seismic performance standards and assessment approaches. In this respect, a modified macro-modelling approach has been proposed to numerically model and capture the inelastic behaviour of the RM shear walls. The proposed model can capture both flexural and shear deformations. The nonlinear model was first validated against experimental data of RM rectangular and flanged shear walls and walls with masonry boundary elements (MBEs); afterwards, the model has been utilized in simulating RM flanged wall archetypes. Collapse risk evaluation has been conducted by subjecting the wall’s numerical model to various ground motions scaled at different intensity levels. Nonlinear static pushover analysis and incremental dynamic analysis (IDA) has been conducted on numerical models. Quantification of the seismic parameters of the flanged wall system, including period-based ductility, overstrength, and collapse margin ratios, has been conducted to help better understanding the seismic response and collapse capacity of the component. Lastly, the seismic resilience of the archetypes against the expected collapse risk was evaluated, before and after adding flanges and boundary elements to the walls, in terms of functionality curves. Damage levels were considered as performance level functions correlated to the earthquake intensity and were used to estimate total loss and recovery time of the archetypes.
\nTo reach the second objective, the study is extended to investigate the impact of using end-confined masonry boundary elements at the building level by the adoption of such elements for multi-storey RMSW buildings. In this respect, the developed macro-model was updated to take the impact of out-of-plane walls’ shear flexibility into account, after adding an out-of-plane shear spring. The outcome of the test results of a one-third scale two-storey building was used to validate the modelling approach at the system level. Subsequently, the archetype buildings were subjected to multiple ground motion records using Incremental Dynamic Analysis to identify the collapse initiation and derive fragility curves. The results indicate a significant enhancement of the resilience index by using end-confined Masonry Boundary Elements (MBEs).
\n To accomplish the third objective, a probabilistic approach was utilized to quantify the seismic resilience index of the RMSW building with MBEs located in a high seismic zone of Canada. The uncertainties associated with the losses and expected recovery time and sensitivity of each parameter were studied and depicted using the resilience index threshold and the Monte Carlo simulation method. The storey shear contribution of in-plane and out-of-plane walls were also quantified for all archetype buildings. The results indicate sufficient seismic resilience of ductile RMSW buildings with MBEs when subjected to the Maximum Credible Earthquake (MCE). The findings of this part are crucial for earthquake mitigation practice and disaster risk reduction plans.

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