Lessons Learned from Fabrication and Experimental Testing of Prestressed UHPC H-Piles скачать в хорошем качестве

Lessons Learned from Fabrication and Experimental Testing of Prestressed UHPC H-Piles

Presented By: Gabrielle Willis, University of Alabama Ultrahigh-performance concrete (UHPC) is a high strength, resilient material well-suited for a variety of structural applications. One such application is for driven piles as a replacement for standard steel HP sections. As part of an ongoing research project, two UHPC I-shaped cross-sections (12 in. and 14 in. deep) were designed to have comparable weight and performance as standard steel H-piles. These UHPC pile sections will require less mild steel, sustain less damage during the driving process, and eliminate long-term steel pile corrosion issues. The 12-inch and 14-inch depth UHPC pile sections consisted of 8 and 10 – 0.6 in. diameter prestressing strands respectively, were designed using first principles while considering the tensile capacity of UHPC. Additionally, some details, such as concrete cover to the prestressing strand, were modified from ACI code based on previous UHPC research. A total of 10 full-scale piles from 6’-6” to 20’ in length were cast at a precast facility, with a UHPC mix design provided by an industry partner. Pile specimens were instrumented with several internal strain gauges and monitored during the curing, detensioning process and periodically after detensioning to capture transfer lengths and short-term losses. These losses are compared to current ACI and AASHTO code recommendations. The pile sections were later tested to failure under combined flexural and shear loading to characterize their structural performance. This presentation will provide the results from the fabrication, material characterization studies of the UHPC mix, and the large-scale structural testing of the pile specimens.