Theoretical Modeling and Lateral Load Testing of Driven Steel Pile Bridge Bents

Abstract

In this thesis, multiple lateral load tests on bridge bents were modeled and performed. FB Multipier models were created for eight load tests: four load tests conducted on a bridge bent under construction in an Alabama Macon County Road 9 bridge, two load tests on an in-service bridge on US Highway 331, and two load tests on battered and vertical pile bents constructed at the AUNGES site in Opelika, Alabama. These models were used to predict pile bent behavior under lateral loading conditions. The initial models predicted deflection amounts under load conditions selected to prevent in-service bridges from failing, and to ensure that failure could be reached for standalone bridge bents constructed for the project. After modeling was completed, full scale load tests were conducted on the bridge bents. The Macon County Road 9 bridge was subjected to four separate load tests: without the deck, with the deck and no load truck, with the deck and a load truck centered on the bent, and with the deck and a load truck centered over the edge girder. During each load test, the bent was loaded to approximately 75 kips. The US 331 bridge was tested with no load truck and with a load truck centered over the edge girder to approximately 90 kips. Two load tests were conducted at the AUNGES site, one on a battered pile bent and one on a vertical pile bent. Both bents were tested to failure at loads approaching 140 kip. Failure was seen in both cases at the pile to cap connection where the battered pile bent experienced rotation inducing a tensile pull out failure at the cap and the vertical pile bent drifted laterally until yielding occurred in the pile flanges. Models were then calibrated to match the observed pile behavior. Results show that vertical pile bents perform comparably to battered pile bents under lateral loads though they are less stiff. Vertical pile bents, however, do not experience the significant increases in axial load to the interior piles. Vertical pile bents should be the preferred ALDOT bridge bent design due to their constructability and performance under lateral load.