Responses of self-anchored suspension bridge to sudden breakage of hangers

The girder of self-anchored suspension bridge is subjected to large compression force applied by main cables. So, serious damage of the girder due to breakage of hangers may cause collapse of the whole bridge. With the time increasing, the hangers may break suddenly for their resistance capacities decrease due to corrosion. Using nonlinear static and dynamic analysis methods and adopting 3D finite element model, the responses of a concrete self-anchored suspension bridge to sudden breakage of hangers are studied in this paper. The results show that the sudden breakage of a hanger has significant effects on tensions of the hangers next to the broken hanger, bending and torsion moments of the girder, moments of the towers and reaction forces of the bearings. The results obtained from dynamic analysis method are very different from those obtained from static analysis method. The maximum tension of hanger produced by breakage of a hanger exceeds 2.2 times of its initial value, the maximum dynamic amplification factor reaches 2.54, which is larger than the value of 2.0 recommended for cable-stayed bridge in PTI codes. If two adjacent hangers on the same side of bridge break one after another, the maximum tension of other hangers exceeds 3.0 times of its initial value. If the safety factor adopted to design hanger is too small, or the hangers have been exposed to corrosion, the bridge may collapse due to breakage of two adjacent hangers.