Impact of pile-to-cap fixity on the design and behavior of sensitive structures

This paper presents the results of analytical studies on the connection between piles and pile caps or footings. Two nonlinear finite element analysis software packages were used to investigate the behavior of the connection itself and the impact of connection assumptions on the overall behavior of different sensitive structures such as simple spans with uneven span lengths, segmental box girders with fixed pier tables, and straddle bents with temperature loading. Results show that the behavior of the connection is affected by variables such as pile size, pile embedment length, pile cap concrete strength, interface reinforcement, and distance between the edge of the pile and the edge of the pile cap. The study also demonstrated that significant moment can develop even with shallow pile embedment lengths. The assumed level of fixity between the pile and pile cap was found to significantly influence the behavior of some of the bridges investigated in this study.