Seismic performance of pile-cap connections of prestressed high-strength concrete pile with different details

This study investigated analytically and experimentally the pile-cap connection of a full-scale prestressed high-strength concrete pile considering three different connection details: The common connection (specimen CT-1), a strengthened connection (specimen CT-2) and an internal T-shape steel connection (specimen CT-3). Specifically, the failure modes, hysteretic performance, ductility and bearing capacity were studied. The test results show that the three connections experience different failure patterns. Specimen CT-1 was severely damaged primarily at the pile-cap connection due to the rupture of anchor plates and the formation of a plastic hinge, but no damage to the pile was observed. This connection consists of a relatively large node angle and behaves like a hinge, resulting in poor energy dissipation due to small moment resistance. Specimens CT-2 and CT-3 were damaged at lesser degree and in more sparse areas. These two types of connections have smaller node angles and behave as a rigid joint with greater moment resistance, leading to a higher energy dissipation. Bond slippage failure of anchor bars was not observed in the cap, and the anchor bar length was found to meet the design requirements. A non-linear finite element model (FEM) was established to analyse the mechanical properties of the three connections using ABAQUS. The moment- displacement curves obtained from the numerical analyses compare well with the experimental results. The degree of effects of influencing parameters on the behaviour of the connections was evaluated using the FEM.