Splice length of prestressing strands in field-cast UHPC connections

The development length of reinforcement 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 strands can allow for a redesign of some structural systems, including spliced girder and continuous-for-live-load bridges. UHPC, when used in field-cast connections between prefabricated elements, can create robust connections which 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 PVA fiber reinforced UHPC. The volumetric fiber content was 2 %. A novel tension test method allowed for replication of the stress state that occurs 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. Applying UHPC to create lap splice connections of prestressing strands may allow for increased structural efficiency and increased structural redundancy through the use of simple, non-congested, non-post-tensioned connection details.