Damage Mitigation for Precast Concrete Column-to-Pile Shaft Member Socket Connections

Designing precast concrete substructure connections, which adjoin a column to its foundation/cap beam, for satisfactory seismic performance is a daunting challenge to deploy Accelerated Bridge Construction in seismic regions. Among various connection types, member sockets feature the ease of construction due to their ability to provide large installation tolerances. However, their seismic application is limited, because resisting earthquake-induced loading often requires the column adjoining member sizes that exceed those in cast-in-situ construction. The member socket connection provides flexural load resistance mainly through prying action. Ultra-high-performance concrete (UHPC), a fiber-reinforced cementitious material with exceptional tensile properties, offers substantial potential in mitigating the prying action-induced damage to the pile shaft. This research aims to analytically investigate if and to what extent the pile shaft size can be reduced due to the excellent damage control ability of UHPC. To this end, a nonlinear finite element approach is first developed to simulate the behavior of precast concrete column-to-pile shaft member socket connections under a combination of axial and reversed cyclic loads. The modeling approaches are validated by comparing the predicted behavior with the prior laboratory test results. The verified finite element model is then used to evaluate the behavior of member sockets with different UHPC shaft diameters. Analysis results show that UHPC plays an effective role in reducing prying action-induced damage. Using UHPC for casting the shaft within the connection region presents a feasible solution to reduce the pile shaft size without compromising the connection’s ability to sustain prying-induced inelastic action.