Use of UHPC piles in integral abutment bridges

摘要

In order to make the Ultra High Performance Concrete (UHPC) pile, developed in Phase I of the UHPC Pile Project at Iowa State University (ISU), a viable option in practice, laboratory testing, field testing and installation of a production pile in the field were undertaken during Phase II of this project. A detailed understanding of the section behavior and lateral loading behavior was determined and compared to that of a steal HP 10 x 57 pile through lateral load analyses of a UHPC pile section. The analysis found that UHPC piles were suitable for integral abutments of bridges.To make the field installation of UHPC piles possible, the overall performance of a common pile-to-abutment connection was verified in the laboratory by defining the UHPC pile-to-abutment connection, which is similar to the currently used connection for steel HP 10 x 57 piles. Both piles performances were verified by testing their connection when subjected to weak-axis bending. The test piles met performance criteria during the laboratory displacements of 0.28 and 0.42 inches which correspond to 1.0 and 1.55 inches in the field.Next, the field testing began to ensure that the production pile would achieve the desired behavior and capacities required by integral abutment bridges. A vertical load test on a 46-ft UHPC test pile was completed one week after being driven into the ground at the same site where the UHPC production pile was implemented into a 223-ft long integral bridge with a 24¢ª skew. Before failure, the test pile resisted 1.5 times the predicted capacity based on the Iowa Bluebook method of design for concrete piles, verifying appropriateness of reducing the UHPC production pile by 16% in length compared to the specified length of 65-ft for the HP 10 x 57 piles on the integral bridge.Additionally, a lateral load test was conducted between the second test pile with a newly designed splice detail and the vertical load test pile, which confirmed the adequacy of the splice detail and the lateral load resistance of the pile. The 46-ft test pile was also tested during the lateral load test. The results of the laboratory and field studies indicated that the UHPC pile in the field is a viable option.