The severe traffic delays caused by traditional cast-in-place bridge construction can be reduced by precasting components off site and assembling them rapidly on site. In seismic regions, connecting precast concrete columns and beams creates difficulties because the connections often occur at the locations of large, inelastic moment reversals. Previous researchers have addressed this challenge through the development of a “Large-Bar, Large Duct” [Pang et al. 2008] and a “Socket” connection [Haraldsson et al. 2011]. Both connections are easy to construct and robust under simulated seismic loading.
A new system is proposed that combines the existing connections with unbonded pre-tensioning in the columns, with the goal of improving seismic performance by re-centering the column following an earthquake. Both a socket column-to-footing subassembly (PreT-SF) and a grouted-bar column-to-cap beam subassembly (PreT-CB) were subjected to combined axial and lateral loads. The test results for these subassemblies were compared with the results of tests of subassemblies without prestressing.
The pre-tensioned specimens achieved the expected moment capacity and returned to within approximately 1% of vertical even after excursions to 10% drift. However, the columns experienced spalling, bar buckling, and bar fracture at lower drift ratios, and dissipated less energy, than their reinforced concrete counterparts.
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