Experimental investigation on a non-seismic precast RC beam-column exterior joint under quasi-static lateral cyclic loading

Abstract

Beam-column joints were detected as the weakest link in existing RC momentresisting frames. The failure of beam-column joints, especially the exterior joint in a precast RC building commenced the collapse of the whole structure. Precast RC beam-column joints which were not designed in accordance with the seismic Code of Practice worsen the damage when subjected to seismic loading. This paper presents experimental work on a full-scale precast RC beam-column exterior joint with corbels when subjected to quasi-static lateral cyclic loading. The specimen was tested under reversible lateral cyclic loading up to a ±1.0% drift. Two numbers of cycles were applied for each drift level. Cracks, gap opening and closing, and spalling of concrete were monitored in successive twocycle intervals of drift. The experimental observation showed that the cracks start to occur at +0.3% drifts and no damage was observed at the corbels. At ±1.0% drift, the specimen experienced major damage at the column above the joint and also at the monolithic cast-in-place area. The specimen exhibits a captive column damaged because of the weak column-strong beam condition of the specimen. Poor detailing of reinforcement and link spacing led to unconfined concrete inside the column. The wide link spacing measured as 190 mm centre-to-centre was unable to cater for a larger load, especially lateral loading from an earthquake. In this study, it can be concluded that a precast beam-column exterior joint experienced severe damage if not designed in accordance with the seismic Code of Practice. The stiffness degradation, displacement ductility and equivalent viscous damping for the tested specimen are also discussed in this paper. © 2013 WIT Press.