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.

The experimental work on two full-scale precast concrete beam-column corner joints with corbels was carried out and their seismic performance was examined. The first specimen was constructed without steel fiber, while second specimen was constructed by mixed up steel fiber with concrete and placed it at the corbels area. The specimen were tested under reversible lateral cyclic loading up to ±1.5% drift. The experimental results showed that for the first specimen, the cracks start to occur at +0.5% drifts with spalling of concrete and major cracks were observed at corbel while for the second specimen, the initial cracks were observed at +0.75% with no damage at corbel. In this study, it can be concluded that precast beam-column joint without steel fiber has better ductility and stiffness than precast beam-column joint with steel fiber. However, precast beam-column joint with steel fiber has better energy dissipation and fewer cracks at corbel as compared to precast beam-column joint without steel fiber.

Corrosion of rebars in reinforced concrete structure is a big universal problem created by saline water ingress causing rebar and other metal structural member to corrode. The deterioration of concrete structures due to the harsh environment conditions leads to the deterioration of the reinforced concrete performance structure, and the premature deterioration of the structure before completing due to carbonation or the chloride content of the future services is expected to be the primary concern for engineers and researchers. Progress of corrosion location cannot be visually evaluated until the point when crack or a delamination is appearing. Therefore, in the study, the Ground Penetrating Radar (GPR) is used to investigate the artificial rebar corrosion damage on steel rebars. The methods showed the artificial rebar corrosion damage can be detected and quantified without damaging the surrounding concrete material. GPR showed the potential on detecting rebar corrosion damage on large areas and in a rapid manner.

The seismic performance of two geometrically similar precast concrete hollow core walls are investigated experimentally under biaxial lateral cyclic loading. Two wall specimens are detailed with steel-armouring at their base-to-foundation interfaces including supplementary unbonded post-tensioned prestress, fuse-bars and mechanical energy dissipators. Wall 1, with a fixed location of bonded fusebars and unbonded tendons, is tested under various biaxial load paths including "4-leaf clover" and "double 4-leaf clover" patterns. Wall 2 is similarly tested with two different configurations of unbonded tendons, unbonded fuse-bars and steel mechanical energy dissipators. A shaking table is used in slow motion to perform the reversed cyclic in-plane and out-of-plane bi-lateral quasi-static experiments. Test results show that both walls perform very well under various load paths without any discernible structural damage up to 2.0% wall drifts. It is concluded that for initial design equivalent viscous damping of 10% may be adopted to accommodate the effects of hysteretic behaviour.

No abstract