Experimental and numerical investigation of self-centering L-shaped post-tensioned precast RC columns with free-uplift bases

To mitigate the construction complexity and high costs associated with conventional self-centering systems, this study proposes a novel post-tensioned (PT) precast L-shaped concrete column system, in which only unbonded PT bars traverse the column-base interface with low initial prestressing force, while the column-base joint is intentionally designed to uplift freely, thus activating a rocking mechanism. Four full-scale quasi-static cyclic tests were conducted to evaluate and compare the seismic performance of the proposed system against conventional cast-in-place columns. The results demonstrate that the novel self-centering system exhibits enhanced ductility and higher ultimate drift ratios, with minimal damage to the column itself. At failure, the system maintained a residual drift ratio of approximately 1/200(0.5%)—about 40% of that observed in cast-in-place specimen, demonstrating robust self-centering. This study further develops an analytical capacity model for the column-base interface from fundamental kinematics and section equilibrium. Closed-form computational procedures were systematically derived to identify key feature points such as the decompression, interface-opening, yielding and peak points, and to predict the force–deformation envelope. The analytical predictions matched the experimental backbone with high fidelity, indicating that the proposed analytical approach provides accurate predictions and can serve as a reliable design basis. Moreover, a set of performance-based design indices—lateral force, inter-story drift ratio, damage extent, and residual drift ratio—is established specifically for the system, providing a direct and implementable basis for performance-based seismic design. An experimentally validated finite element model was then developed to simulate the seismic response, accurately capturing the key characteristics of the self-centering behavior, including rocking-induced re-centering and damage localization, thereby demonstrating the feasibility of the proposed simplified PT-only connection for repairable L-shaped precast columns with enhanced seismic resilience. These findings indicate a constructible, cost-effective, and repairable solution and provide an analytical and numerical basis for performance-based seismic design of resilient precast concrete structures.