Evaluation and Design of a Footing Hybrid Connection for Innovative Hollow-Core Fiber-Reinforced Polymer–Concrete–Steel Composite Columns

To support the advancement of accelerated bridge construction in high-seismic regions, this study investigates a novel prefabricated column-to-footing connection designed for improved resiliency, constructability, and cost efficiency. The socket connection utilizes hollow-core fiber-reinforced polymer–concrete–steel (HC-FCS) columns with embedded corrugated steel pipes (CSPs). The composite HC-FCS column consists of a concrete shell sandwiched between an outer fiber-reinforced polymer tube and an inner steel tube. The inner steel tube is embedded into the footing connection of the HC-FCS column. The same authors tested the innovative socket connection on a large HC-FCS column under seismic loads, showing high ductility, strong moment and drift capacities, and promising potential for future design use. Building on previous experimental findings that demonstrated excellent seismic performance, this study employs finite element (FE) modeling in LS-DYNA software to conduct a parametric analysis of 50 large-scale column-to-footing connections. The FE models were used to critically assess the effect of seven parameters on the seismic behavior of such a novel column-to-footing connection. Consequently, design equations based on mechanical analysis of a simplified strut-and-tie model were proposed to determine the essential characteristics of the CSP in HC-FCS column-to-footing connections for practical implementation.