A parametric study of the inelastic seismic response of precast, prestressed concrete piles was conducted to determine whether piles with only light transverse reinforcement could act as ductile structural elements.A nonlinear, inelastic finite-element program written specifically for this project was used to validate results for both laboratory and in-place testing. The study examined single piles using several types of pile-cap connections, the addition of mild-steel reinforcement, varying levels of axial load, and a range of soil stiffness. The piles were modeled with 1% transverse reinforcement, which is less than 1/3 of that required by ACI 318. The results indicated that modest levels of transverse reinforcement will allow for ductile response. Assuming that the pile-cap connection is detailed to allow and support the formation of a plastic hinge, with subsequent redistribution of moment down the shaft to form a secondary subgrade hinge in the pile shaft, the pile configurations analyzed provided a minimum displacement ductility of 2. The addition of mild-steel longitudinal reinforcement did not enhance ductility, though it did increase flexural strength. The optimum pile-cap connection to maximize ductility is embedment of the pile head into the cap. Rotation capacity is maximized by embedment of the prestressing tendons and any mild-steel longitudinal reinforcement present into the pile cap.
