Influence of shape memory alloy in seismic response of coupled shear wall of concrete structures

Super-elastic Shape Memory Alloys (SMAs) can undergo reversible phase transitions, experience considerable inelastic deformation, and restore their original shape after heating or stress reduction. These features of SMAs make them suitable candidates as the reinforcement of concrete shear walls particularly in seismic events. A ten-story reinforced concrete building with a SMA reinforced coupled shear wall in a high seismic zone of Bangladesh is investigated using to better understand the dynamic response of SMAs in the walls. The performance of wall-to-coupling beam joints is then modeled separately using finite element program where SMAs are used at the plastic hinge zones of the joints only to minimize the construction costs. Using the model, pushover analyses are conducted for five different SMAs to compare the performances among them and also to that of conventional steel rebars. The comparisons are made in terms of different damage states of the coupled walls such as rebar yielding, concrete cracking, core crushing, etc. Afterward, non-linear time history analyses (NLTHA) on all six coupled shear walls were performed for three renowned ground motions. The outcomes of NLTHA are presented in terms of performance-based damage states, hysteretic response, and base shear to story drift responses. The pushover analysis shows that the base shear demand is higher for RC-steel joints than that of the SMA-reinforced coupled beam joints i.e., SMA shows higher deformability, and lower base shear demand for all damage states. Time history analysis reveals that all SMA-RC shear wall-coupled beam joints produce flag-shaped hysteretic responses that result in nearly zero residual deformation. The outcome of this study demonstrates the effective application of SMAs as reinforcement of concrete wall-beam at the plastic hinge regions of coupling beam joints to enable them to undergo large deformations without permanent damage during an earthquake. Therefore, the arrangement may help the buildings to recover their original form and functional after a seismic event.