Iowa Department of Transportation
Justin Dahlbergdahlberg@iastate.edu email >
Brent Pharesbphares@iastate.edu email >
Bridge Research Engineer, BEC
Zhengyu Liuzhengyu@iastate.edu email >
Research Engineer, BEC
About the research
With slide-in bridge construction (SIBC), the bridge superstructure is constructed off the final alignment and then slid laterally from the temporary worksite onto the in-place substructure. Once the sliding is complete, closure joints between the bridge super- and sub-structure are cast to establish continuity. The cementitious materials and reinforcement design used to complete the closure joints affect when the bridge can be opened to traffic or construction loading.
The goal of this research was to investigate the performance of closure joints using ultra-high performance concrete (UHPC) and noncontact lap-spliced reinforcing steel bar, with a specific focus on determining when a noncontact lap-splice has sufficient strength to either open a bridge or expose it to additional construction loading.
The research was also conducted to explore an alternative material to UHPC—hybrid composite synthetic concrete (HCSC)—which may be able to provide sufficient early-age capacity when used in the same way.
A series of laboratory tests were performed on 96 samples including four noncontact lap-splice connection designs with different rebar development lengths and joint filling materials. A time-dependent pull-out test was performed on each design with a focus on the performance at the material early age. Each sample was loaded with a pull-out force until failure. The ultimate capacity of each sample was captured and analyzed.
Based on the test results, recommendations for the selection of UHPC/HCSC closure joints reinforced with lap-spliced rebars were developed.