Numerical study on seismic performance improvement of composite wide beam-column interior joints

This study aims to improve the seismic performance of a post-tensioned precast wide U beam column interior joint system, consisting of a precast column, a precast wide U beam as permanent formwork with post-tensioned and cast-in-situ concrete in the joint region, through a numerical approach. The numerical model was verified by simulating a tested half-scale precast wide U beam-column interior joint (PWUBCIJ) system. After the methodological validation, numerical analyses were performed for full-scale and modified wide beam-column joints subjected to lateral cyclic loading. The modified joint models were developed to eradicate or delay diagonal shear cracks and concrete crushing of the tested control specimen. Since the wide precast U beam-column joint system possesses typical and unique joint details, improvement in reinforcement detailing was performed by varying reinforcement patterns. Moreover, a study to reduce the number of A-truss rows was performed to optimize the numbers of A-trusses used. Therefore, a series of FE analyses are performed to elucidate the contribution of each parameter in enhancing the joint strength and drift capacity of the structure. Enhanced load capacity, increased energy dissipation, and higher ductility are achieved using transverse reinforcement and transverse tendons. This is considered due to the formation of the strut-and-tie mechanism, which results in a better force and moment transfer path and from the overall confinement of the system due to the presence of transverse steel and prestressing tendon. As per numerical results, the modified full-scale precast wide U beam-column interior joint was proved to be able for application in the highest seismic zone of Thailand.