Laterally Loaded Pile Cap Connections Laterally Loaded Pile Cap Connections

by Stenlund, Tony Eugene

There is presently considerable uncertainty regarding appropriate connection details between driven piles and pile caps. Prior research on the subject suggests that given a proper embedment length, a specialized reinforced connection may not be necessary. Eliminating these costly connection details could save thousands of dollars on both labor and materials. This research study focuses on the importance of the pile-to-cap connection detail with respect to the reinforcement connection and pile embedment length.

Four pile caps were constructed, each with two 40 foot-long steel pipe piles, and were tested with different connection details. Two caps included a reinforced connection detail while the other two relied on their respective embedment lengths. A hydraulic ram was used to apply a cyclic lateral force to each of these pile caps until failure occurred. Load-displacement curves were developed for each pile cap and strain gauge measurements were used to evaluate tension and bending moments in the pile caps. Comparisons are presented regarding the effect of the connection on pile cap response. An analysis has been conducted to best understand possible failure modes; two computer modeling programs were used and their respective results have been presented and compared to the observed readings.

This thesis provides test data supporting the theory that a proper embedment length acts as an adequate connection in place of a specialized reinforced detail. A pile cap with piles embedded two diameters into the cap performed successfully. In contrast, a cap with piles embedded only one diameter failed after developing a large crack through the entire cap. For the two pile caps with a reinforcing cage connection; the performance was essentially the same for the piles embedded either six inches (.5 diameter) or twelve inches (one diameter) into the cap. The data produced was found to be very similar to what was estimated by the two programs used for analysis (GROUP 4.0 and LPILE 4.0).