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The occurred damages during the past significant earthquakes have proved that vertical seismic excitation has tremendous effect on bridges. Three-component earthquake excitations are preferred to resemble the earthquakes. In this article, a cable-stayed arch bridge, a new type of bridge with the hybrid system of half-through arch and stay-cables, was analyzed under a set of different earthquake excitations (more than 21 ground motion records). Both vertical and horizontal components of the ground motions were considered to act simultaneously at the bridge supports. By using different three-component earthquake excitations, the dynamic responses of the bridge, including the displacements and accelerations of the main parts of the bridge, were obtained. The effects of various parameters such as soil type, epicentral distance, spatial variation of the ground motions, and dimensional variation of the structure were investigated. The results of the numerical study indicate that the cable-stayed arch bridge subjected to both horizontal and vertical components of earthquakes are more vulnerable than those subjected to horizontal ground motion only.

Vertical or inclined cables which are placed in bridges as a hanger system affect the dynamic performance of bridges. Inclined hangers can be used instead of vertical hangers to improve the stability of the bridge aerodynamically. However, inclined hangers are susceptible to fatigue more than vertical ones. Considerable signs of distress or slackness might be shown by some inclined hangers because of their location on the bridge. In this study, a cable-stayed arch bridge with vertical and inclined hangers has been compared to investigate the effect of hangers on the dynamic performance of the bridge. To reduce the internal cable forces and the probability of fatigue or force fluctuation in hangers, additional horizontal cables are applied on inclined hangers that transfer the tensile load from overstressed hangers to adjacent ones with lower forces. By modification, the results demonstrate the higher stiffness and human comfort level for the bridge that improve the dynamic behavior and control the responses of the bridge.

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