Risk assessment of a long span unsymmetrical extroversion arch bridge

Abstract

<p>Nanning Bridge is the first long span unsymmetrical extroversion arch bridge with a curve steel gird in the world. The main span of the bridge is 300m, and the incline angles of two main arch ribs are 69.7°and 66.5°. Construction technology, nature hazards and some accidents which may happen during the construction process have to be considered. A two stages risk assessment method is proposed. At the first stage, an expert investigation which is based on analytical hierarchy process (AHP) is carried out, cable supported construction scheme and hybrid supported construction scheme are compared, and cable supported schemes is recommended due to its low risks. At the second stage, 21 main risk events which may occur in the cable supported construction scheme are assessed in detail, based on a qualitative and quantitative combined assessment method, and appropriate countermeasures for those risk factors are also recommended. The risk assessment method proposed in the paper can be applied in similar bridges.</p>