Poly-lactic acid and carbon fibers 3D printed bars for seismic retrofitting RC beam-to-column joints subjected to elevated temperature

Abstract

This research proposes novel three-dimensional (3D) printed bars for seismic repairing RC beam-to-column joints subjected to elevated temperatures. A total of eight joint specimens were subjected to a high temperature of 900˚C for 3 h and then exposed to cyclic loading. An experimental program was conducted to retrofit the joints using near-surface mounted (NSM) 3D printed bars adopting several strengthening configurations. Finite element models were then developed using a commercially available code, and a comparison was made between the experimental, analytical, and numerical results. Test results showed that NSM 3D printed bars are highly recommended for retrofitting RC members subjected to cyclic loading. The 3D printed bars made using poly-lactic acid (PLA) and 20% of carbon fibers considerably increased the ductility and drift ratio of the heat-damaged RC joints up to 206% and 216%, respectively. They also increased the load capacity of the joints up to 51%. The load-carrying capacity of the retrofitted joints was then predicted based on the ACI formulations with a proposed empirical factor for calculating the effective strain values of the 3D printed bars.