Performance of precast concrete beam-column joint with a hidden corbel under progressive collapse scenarios

Collapse incidents of structures caused by extreme loads have attracted the attention of academia and building regulatory bodies worldwide. Due to inherent structural discontinuity, precast concrete (PC) structures are more vulnerable to progressive collapse than cast-in-situ reinforced concrete (RC) buildings. Therefore, studies on resisting collapse performance of PC beam-column joints for PC buildings are needed. In this paper, four 1/2scaled PC beam-column joints with an in-built L-shaped corbel at each beam end were tested for progressive collapse under column removal scenario. These four joint specimens with identical non-seismic PC details were extracted from adjacent bays of the removed column, and the main parameters were the variations in the boundary and loading conditions. The deformation capacity, load-carrying capacity, catenary action (CA) and failure mode were evaluated and discussed. Parametric studies were also conducted by a proposed componentbased mechanical joint model, to investigate the effects of PC interface location, mid-height reinforcement ratio and span-to-height ratio on the collapse resistance of the 2-span substructures. The experimental results show that this type of PC joint could achieve excellent hogging moment resistance but relatively lower sagging resistance. However, both PC joints under downward and upward applied loads could achieve a subsequent increase in resistance due to catenary action at large deformation stage. Numerical parametric studies indicated that shifting the precast interface inwards towards 1/3 point of single beam span and increasing mid-height reinforcement ratio could remarkably improve load-carrying capacity at the compressive arch action (CAA) stage. These detailing features could offset the negative effect caused by the discontinuous bottom longitudinal reinforcement, which is typical for gravity-dominant design in non-seismic countries, such as Singapore.