Modelling of mid-rise concrete shear walls reinforced with superelastic shape memory alloys: Nonlinear analysis

摘要

The response of hybrid Shape Memory Alloy (SMA)-steel reinforced concrete shear walls containing NickelTitanium superelastic SMA as alternative reinforcement in the plastic hinge region was investigated using nonlinear finite element modelling. The hybrid wall system promotes self-centering and significant reduction of permanent deformations. Two types of conventional steel-reinforced concrete shear walls were designed for a prototype 10-storey office building according to the current Canadian concrete design standard, assuming two distinct seismic design scenarios. A moderately ductile shear wall was designed for a moderate seismic zone in eastern Canada, whereas a ductile shear wall was designed for a high seismic zone in western Canada. Equivalent, hybrid SMA-steel reinforced concrete shear walls were defined following the design of the two conventional shear walls, in terms of geometry and reinforcement layout. Full-scale, two-dimensional finite element models were developed to assess the pushover and hysteretic responses of the walls. Similarities in wall crosssection and yield force capacity of the steel and SMA reinforcement permitted a comparison between the walls, including strength, stiffness, self-centering, and energy dissipation capacities. The results indicate similar lateral strength and displacement capacities, and superior restoring capacity of the SMA-reinforced walls in comparison to the steel-reinforced walls. Furthermore, a preliminary study was conducted to investigate the effect of the SMA-bar length in the ductile wall due to concentration of damage near the base of the wall. Lengths corresponding to approximately 50% and 20% of the original SMA length were considered. Based on the analyses, a satisfactory response could be achieved with shorter SMA reinforcing bars, which reduces the quantity of SMA reinforcement without significant loss in self-centering capacity.