Design of column footings supported by a grid of piles or drilled shafts

Pile foundation is one of the common practices for bridges. Pile cap serves the purpose of load transfer from the superstructure to the group of piles or drilled shafts. Despite of being a critical structural element, it does not have a unique procedure to design them. As a result, designers tend to use either sectional approach or strut-and-tie method as required by the code. Further, this results in lack of uniformity in the pile caps.

The primary objective of this study is to recommend an appropriate design method for pile caps. This study discusses the load transfer mechanism involved in pile caps and considers the strut and tie method to be most appropriate procedure to design them.

This study reports a modified strut-and-tie model based on ACI 318-08. Modifications in the reinforcement layout, placement and anchorage were developed from the research data already available. A series of pile caps were designed and were analyzed to determine the maximum capacity in ABAQUS. Simulated results were compared against the experimental results that are already available.