Unbonded Pre-tensioned Bridge Columns with Rocking Detail

Abstract

A new pre-tensioned precast bridge system has been developed that provides seismic regions the means to construct high-performance bridges that can be built quickly. The columns are designed to rock as rigid bodies, and their ends are protected against damage by a steel shoe detail. The precast feature of the system will reduce traffic delays by moving construction off-site. The pretensioning feature leads to reduced residual displacements after an earthquake. The use of epoxy-coated strands and the quality control available in a precasting plant lead to enhanced durability. The seismic performance of the system was evaluated with pseudo-static tests of two column-footing sub-assemblies. In one column-footing sub-assembly, a ductile fiber-reinforced concrete (HyFRC developed by Ostertag) was used to fill the steel shoe and the region immediately above it. This column also contained a steel dowel bar that extended down from the body of the column into the footing. The other column did not possess any ductile concrete or dowel bar. During the tests, the columns had very low residual displacements and negligible damage to the concrete, even after being subjected to drift ratios of over 10%.