Seismic fragility analysis of concrete bridge piers reinforced by steel fibers

Abstract

Seismic fragility analyses of eight bridge piers, made of steel fiber–reinforced concrete or conventional reinforced concrete, were conducted to reasonably analyze the seismic performance of concrete piers reinforced by steel fibers. The pier specimens were constructed with different steel fiber contents, stirrup ratios, and lengths of the steel fiber–reinforced concrete region. The cyclic load tests on the specimens were carried out to obtain the characteristic values of structural capacity for five damage states. The nonlinear time history analyses of the piers under a suite of selected ground motions were performed to obtain the probabilistic characteristics of structural demand. Using the data related to structural capacity and seismic demand, the fragility curves of these piers were constructed based on an assumed lognormal distribution. The fragility results indicate that (1) the seismic vulnerability of the concrete piers is reduced with the increase in steel fiber content in a certain range, (2) the reinforced concrete pier with a higher stirrup ratio is found to be more vulnerable than the steel fiber–reinforced concrete pier with a relatively lower stirrup ratio, and (3) the fragility of piers adopting steel fiber–reinforced concrete locally and suitably is similar to that of the piers adopting steel fiber–reinforced concrete wholly.