Seismic Behavior of Precast Concrete Column–Foundation Connection with PBCs

A new precast concrete column–foundation connection using pentagon bolted couplers (PBCs) was developed for rapid assembly and reliable force transmission. In the PBCs, the upper steel bar was plug-welded to the steel shoe, and the lower bolt was fastened with nuts. Quasistatic tests on one monolithic and three precast connections evaluated their seismic behavior. Results indicated that PCB1 had superior flexural capacity and ductility compared to the monolithic connection, while PCB2’s performance deteriorated with a thinner lower plate. Grouting the steel shoe in PCB3 improved initial stiffness but did not affect lateral capacity. Numerical models of PBCs, validated by tensile tests, derived formulas for end plate or weld failure to calculate tensile capacity. Strong correlations between predictions and test results guide the design of steel shoes to exceed the tensile capacity of connected bars. By applying the principle of equal bending stiffness, the column section with pentagonal steel shoes was simplified to one with square steel shoes. Using plastic theory, a method for predicting flexural capacity was developed, with calculated values closely matching test measurements, confirming its use as a reference for future research.