Behavior of prestressed concrete piles subjected to slowly applied lateral loads

The Tennessee Department of Transportation uses prestressed, precast, concrete piles to support many of the jointless bridges across Tennessee. Due to the wide range of thermal changes experienced in Tennessee, these prestressed concrete piles may be subjected to deflections of 1.0 inch or more at the ground level. Concerns about the ability of prestressed concrete piles to withstand deflections of 1.0 inch or more and maintain their structural integrity led to field research conducted by The University of Tennessee Knoxville under contract with the Tennessee Department of Transportation and sub-contract with the University of Memphis. Three prestressed concrete piles were subjected to a series of slowly applied lateral load tests. Testing conducted with two piles included long term load tests and cyclic load tests. The third pile was subjected to a long term load test, a cyclic test, and a test to ultimate. The results of the tests conducted showed that prestressed concrete piles are capable of withstanding deflections of 1.0 inch or more and still maintain their structural integrity. The test results also led to the conclusion that piles subjected to a slower rate of loading led to behavior that was less stiff. The test to ultimate showed the extremely ductile behavior of a prestressed pile, in that it was capable of withstanding very large deflections before the structural integrity of the pile was compromised.