Seismic performance of a foundation shoe connection for precast columns combining starter bolts and grouted corrugated ducts

The use of dry-assembly systems to connect precast concrete columns to foundations has become a common method for constructing commercial and industrial buildings. In such structures, the column base is a critical section, as the design typically follows a cantilever frame arrangement where columns are fixed to the foundation and hinged to beams supporting the floors. Consequently, column-to-foundation connection systems must resist both static and seismic forces, allowing the columns to develop the plasticity and energy dissipation capacity required to meet seismic demands. This study introduces a novel precast column-to-foundation connection system adopting steel bolted shoes and intermediate rebars grouted into the foundation during on-site installation. Unlike existing systems, the proposed design employs only four steel shoes welded to the longitudinal corner rebars of the column. The research involved two reverse cyclic tests on precast columns constructed with the proposed connection system. Two different connection configurations were investigated: the former adopted only the four bolted steel shoes; the latter combined the four bolted shoes with intermediate rebars grouted into corrugated ducts embedded in the foundation. The tests evaluated resistance, energy dissipation capacity, displacement and curvature ductility as well as the failure mechanisms governing the behavior of entire column-foundation assembly subjected to simultaneous combination of axial and bending actions. Additionally, an analytical approach to determine the plastic hinge length suitable for columns provided with the adopted precast connection was proposed. Finally, a beam model with lumped plasticity was developed to simulate the monotonic response of precast columns using the proposed connection system.