Cyclic performance of severely earthquake-damaged RC bridge columns repaired using grouted UHPC jacket

The bridges constructed in high seismic zones may suffer one or more earthquake shocks of certain scales during their service life. Some of them could be severely damaged during a catastrophic earthquake event. How to quickly and economically restore bridge service functions and traffic lifelines has always been the concern of bridge owners and engineers. In this study, a method for repairing seismically damaged reinforcement concrete (RC) bridge columns using ultrahigh performance concrete (UHPC) materials was developed. Seven down-scale RC bridge column specimens with three different reinforcement ratios and two different heights were designed according to the seismic design code for RC bridges. For three of the specimens, the reinforcement around the plastic hinge area were artificially corroded through chloride ion penetration method to simulate the strength degradation effect of reinforcement erosion that could occur in many aging bridge columns. All seven specimens were tested by applying cyclic loads until their plastic hinge became severely damaged, which were then repaired following the proposed procedure and with different jacket thicknesses. The cyclic tests were re-conducted for these repaired specimens. The testing results were analyzed by comparing to those from the test for the nonseismic-damaging specimens one by one with respect to their seismic performance in order to validate the seismic rehabilitation effect using UHPC materials. Additionally, an ABAQUS software based finite element model was developed for numerically simulating the hysteretic behaviors of the columns repaired using UHPC jacket. The resulting hysteretic curves for the repaired columns with different reinforcement ratios and heights well matched those from the corresponding cyclic tests. This model can be further used for seismic performance prediction and UHPC jacket design for the repaired bridge columns that have different dimensions and reinforcement configurations. All of these experimental and analytical results show that the seismic performance of the repaired bridge columns can be effectively restored in a relatively fast and low-cost manner.