Laterally Loaded Pile Cap Connections: Fid-Bau Portal

Laterally Loaded Pile Cap Connections

K. M. Rollins / T. E. Stenlund

This study investigated the moment capacity and load-displacement response of the pile-to-cap connection details. Lateral load tests were conducted on four pile caps (3 ft H x 3 ft W x 6.5 ft L) with two 40 foot-long steel pipe piles (12.75 inch OD) with different connection details. Two caps included a reinforced connection detail with six or 12 inch pile embedment while the other two relied exclusively on their respective embedment lengths of 12 and 24 inches. 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 cap and bending moments were computed from strain measurements in the piles. The pile cap with piles embedded two diameters (24 inches) 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. The two pile caps with shallow embedment (0.5 to 1.0 diameter) and a reinforcing cage connection still developed at least 40 to 60% of the moment capacity of the pile which was much greater than predicted by PCI design equations based only on embedment. The load-displacement curves and bending moments computed using the computer program GROUP were in very good agreement with measured values when the pile connections were considered to be fixed-head. However, assuming a free-head or pinned connection significantly overestimated displacement even for the connection with only 6 inches of embedment. These results suggest that it is relatively difficult to create a truly pinned connection detail and that some connections which are assumed to be pinned may actually behave more like fixed connections.