2019 CSCE Annual Conference - Laval (Greater Montreal) Conference
Mr. Wilmar Leonardo Cortes Puentes, University of Ottawa
Dr. Dan Palermo, York University
A study is currently in progress to investigate the seismic performance of hybrid SMA-steel shear walls containing NiTi superelastic shape memory alloy (SMA) as an alternative reinforcement in the plastic hinge zone. This type of wall system provides self-centering with high levels of energy dissipation due to the hysteretic response characteristic of cyclically loaded SMA bars. The main benefit is the significant reduction of permanent deformations due to the shape recovery of the SMA. The introduction of NiTi bars in the plastic hinge region of the shear wall, where large inelastic deformation demand is concentrated, optimizes the seismic performance of reinforced concrete buildings, controlling residual deformations and thereby reducing the damage to non-structural and structural elements. This study considers two design earthquake scenarios for a prototype 10-storey office building: a moderate seismic zone in eastern Canada and a high seismic zone in western Canada. Traditional deformed steel-reinforced shear walls were designed for each seismic zone, corresponding to ductile and moderately ductile shear walls for western and eastern Canada, respectively. The resulting cross-sections were used to define the reinforcement layout of the hybrid SMA-steel shear walls. Thereby, the walls are comparable in terms of geometry and reinforcement ratio, and a reliable comparison of the post-earthquake condition (i.e. residual displacements, drifts, dissipated energy, displacement capacity) is therefore possible. To determine important features of the seismic response, full-scale 2-D finite element models of both types of walls were developed and subjected to pushover and reverse cyclic analyses. The use of a detailed finite element analysis permitted an explicit evaluation of damage, including cracking of concrete, strain and deformation of reinforcing steel and SMA. The paper presents results of the analyses and the assessment of the seismic response of the hybrid SMA-steel wall compared to the steel-reinforced wall. Expected results include similar capacity due to the use of equivalent reinforcement, slightly lower energy dissipation given the flag-shaped hysteretic response of SMA and superior restoring capacity of the hybrid-SMA wall. This study will culminate with nonlinear time-history analyses performed with a suite of earthquake records. The selection of the earthquake records will consider the magnitude, epicentral distance and frequency content characteristics of each seismic zone. Therefore, the influence of earthquakes in moderate and severe seismicity on the seismic response of the walls and the potential improvements in self-centering capacity of hybrid SMA-steel walls will also be assessed.