Effects of fling step on the seismic response of reinforced concrete arch bridges

Many arch bridges have been built in near-fault regions around the world and may be affected by fling step, which is the permanent ground displacement caused by the long-period pulse within the frequency content of the earthquake. This study investigates the effect of fling step on reinforced concrete deck-type arch bridges with short to medium spans. Three-dimensional nonlinear models of three existing reinforced concrete arch bridges in Iran, with span lengths of 23, 35, and 60 meters were developed. The structures were subjected to seven near-fault earthquakes in longitudinal and transverse directions, once with the fling step pulse included and once with the pulse removed. The results showed that fling step has a noticeable effect on the seismic response indicators investigated but may increase or decrease the seismic demand. The maximum curvature in the presence of fling step to that without fling step ranged between 0.54 and 2.06. Unseating in the longitudinal direction was the most sensitive to the fling step, which showed more than 200-percent increase in some cases. The effects of the fling step were correlated with the ratio of the period of the fundamental mode of vibration of the structure to that of the fling step pulse.