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Splice Length of Prestressing Strand in Field-Cast Ultra-High Performance Concrete Connections

Project Information

Project ID: 
FHWA-PROJ-12-0106
Project Abstract: 

The development length of reinforcements embedded into ultra-high performance concrete (UHPC) can be significantly shorter than the lengths normally associated with conventional concrete. Shortening the development length of prestressing strand can allow for a redesign of some structural systems, including spliced girder and continuous-for-live-load bridges. Ultra-high performance concrete, when used in field-cast connections between prefabricated elements, can create robust connections that emulate monolithic components. This study investigated the development length of 12.7 and 15.2 mm diameter untensioned prestressing strands embedded in steel fiber and polyvinyl alcohol (PVA) fiber reinforced UHPC. The volumetric fiber content was 2 percent. A novel tension test method allowed for replication of the tension-tension stress state that could occur when strands are lap spliced within a connection between two linear elements. The results suggest that, for the steel fiber reinforced UHPC, the 12.7 mm diameter strands can be fully developed within 51 cm and the 15.2 mm diameter strands can be fully developed in approximately 61 cm. The 12.7 mm diameter strands can be fully developed in the PVA fiber reinforced UHPC in approximately 91 cm. Engaging UHPC to create lap splice connections of prestressing strands may allow for increased structural efficiency and increased structural redundancy through the use of simple, noncongested, nonpost-tensioned connection details.

Goals

The objective of this research study is to evaluate the lap splice length of untensioned prestressing strands embedded in field-cast ultra-high performance concrete (UHPC) connections. This research result is critical to the broader use of UHPC-class materials as field-cast grouts in connections between Prefabricated Bridge Elements and Systems (PBES) components. The research may allow for new connection designs and new structural configurations that enhance robustness and efficiency.

Project Status: 
Completed
Project Funding Amount (Contract Award Amount): 
$25,000
Start Date: 
Wednesday, February 1, 2012
End Date: 
Friday, January 31, 2014
Public Access Plan: 
No
Laboratory: 
Concrete Laboratory, Structures Laboratory
FHWA AMRP Program: 
Infrastructure
FHWA AMRP Activity: 
Structures
FHWA Activity: 
Ultra-High Performance Concrete (UHPC)