Effect of Debonding of Rebars on the Seismic Response of Boundary Elements of Lightly Reinforced Shear Walls

Abstract

Rebar fracture in boundary elements of lightly reinforced shear walls in recent earthquakes motivated research on the minimum longitudinal reinforcement of shear walls. These researches lead to change in the ACI 318-19 requirement for minimum longitudinal reinforcement of boundary elements. New ACI 318 requirement increases minimum longitudinal reinforcement ratio for boundary elements of shear walls with low demand, that could have economic burden. This study experimentally investigates is it possible to avoid this increase in minimum rebar by debonding rebars in critical region of boundary elements in lightly reinforced shear walls. Tests includes specimens with bonded and debonded rebars, which are tested under monotonic and cyclic loading. Load protocol to account for failure types of low reinforcement shear walls is asymmetric. Test results show that out of plane buckling of specimens with debonded rebars initiates at lower axial strains that could be attributed to reduction in element lateral stiffness due to use of debonding. On the other hand debonding resulted in reduction of local strain demand on rebar. It could be concluded that larger minimum dimension for boundary elements will be required when debonding is employed.