Seismic behavior of thin-walled stirrup-confined circular concrete-filled steel tube piers: Experimental, numerical, and restoring force model analysis

An investigation was conducted using pseudo-static testing to analyze the seismic behavior of thin-walled stirrupconfined circular concrete-filled steel tube (TSCCFT) piers. In addition, a finite element model (FEM) was developed, incorporating concrete cracks and steel ductile damage. Moreover, based on the FEM and test outcomes, a refined restoring force model (RFM) for these piers was proposed, considering pinching effect coefficients and inflection points. The research results demonstrate that TSCCFT piers outperform counterparts lacking stirrup confinement regarding seismic performance. This enhancement is evident in significant increases of 30.3 % and 31.4 % for yield and horizontal peak load, respectively, along with notable increases of 9.1 % and 5.3 % concerning cumulative energy dissipation and elastic stiffness. Furthermore, the refined RFM demonstrates excellent precision, closely aligning with test and FEM results. This refined RFM holds the potential to serve as a reference for the seismic design of TSCCFT piers, streamlining the design process.