Seismic Behavior of Hybrid Post-Tensioned Cast in Place Concrete Shear Walls

Abstract

A hybrid concrete shear wall system is created by combining the conventional reinforced concrete construction with post-tensioning technology. Such hybrid shear wall with continuous mild steel combined with post-tensioned (PT) steel provides superior restoring, energy dissipation, and ductile behavior over larger lateral displacements. Hence, both mild steel and high-strength post-tensioning steel contribute to the flexural strength. This leads to a reduction in the total area of steel when compared to the conventional reinforced concrete shear wall. When using a hybrid system, the lateral load response varies based on the ratio of post-tensioning steel to the mild steel reinforcement. In this research, the seismic behavior of hybrid unbonded PT concrete shear walls is investigated. Finite element analysis using ABAQUS for multi-hybrid shear walls of different ratios of post-tensioning steel area to mild steel area is performed. Results show that the large nonlinear displacements in PT shear wall may be reduced by using more mild steel reinforcement in the hybrid unbonded PT system. The post-tensioning steel provides a restoring force that eliminates the permanent deformation after cyclic load and reduces the displacement peaks during a cycle. However, PT walls incorporating only post-tensioning bars do not provide a sufficient amount of energy dissipation to limit seismic displacement adequately. By increasing the mild steel reinforcement area concerning the post-tensioning steel area, seismic energy can be dissipated by the yielding of mild steel.