Pile Cap Interaction with Bridge Pile Foundations under Lateral Loads

Abstract

The paper presents an analytical pile–cap soil model to determine the lateral resistance of a pile cap in sandy soils and its contribution to the lateral resistance of the bridge pile group–cap foundation system of pinned or fixed pile head connections with the pile cap. The strain wedge (SW) model approach was adopted to incorporate the pile cap in an interactive pile group–cap foundation system. The proposed model allows the calculation of the mobilized passive and side shear cap–soil resistance based on soil, cap, and pile properties. The study demonstrated the contribution of the pile cap in sandy soils to the total pile group–cap bridge foundation system (i.e., the bridge foundation lateral stiffness), which could approach 50% of the total pile group–cap lateral resistance. Such relative contribution varied with lateral deflection and the soil around the cap and pile group as well as the rotational restraint of the pile head–cap connection. The proposed technique was validated through comparisons with full-scale load tests.