Integral Abutment Bridges (IABs) have become a popular solution for reducing maintenance costs associated with conventional bridges in the United States and neighboring countries. However, the absence of standardized design procedures and a comprehensive understanding of abutment-pile behavior under combined axial and lateral loads pose significant challenges to their widespread implementation. This research addresses these challenges by conducting full-scale experimental testing and numerical simulations to evaluate the performance of steel H-piles and concrete-filled tube (CFT) piles in IABs. The study investigates the low-cycle fatigue behavior, lateral displacement capacity, and pile-structure interaction under various loading conditions. Two distinct pile configurations will be tested: individual and group piles, focusing on parameters such as pile ductility, connection details, and orientation. The experimental program requires a special testing setup for full-scale testing to test the integral abutments by applying axial load and cyclic lateral loads to the steel piles. Results from the experimental program will allow the development of an analytical approach that predicts the lateral capacity of the piles and validates used assumptions. In addition, the research will provide information on the behavior of IABs and conclude with recommendations and design requirements for safer and more efficient design and construction.