Stability safety assessment of long-span continuous girder bridges in cantilever construction

摘要

The overturning stability issue of continuous girder bridges is critical so that it is necessary to obtain the true overturning stability performance. At present, the parameters uncertainties in the structure were neglected in the stability evaluation method of the long-span continuous girder bridges, which leads to the unknown safety level of the continuous girder bridges during the cantilever construction. Therefore, a calculating method for overturning stability safety factors of long-span continuous girder bridges in cantilever construction based on inverse reliability theory is presented in this paper. The proposed method is extended from the traditional deterministic form of safety factor, which considered influence of uncertainty factors among structure parameters was used to obtain safety factors through target reliability index based on inverse reliability theory. Overturning stability safety factor of long-span continuous girder bridges in cantilever construction and parameter sensitivity were assessed using the proposed method, as well as the reasonableness of longitudinal overturning stability safety factors was discussed. The results show that parameter uncertainties have a major effect on overturning stability safety factors of long-span continuous girder bridges in cantilever construction, ignoring parameter uncertainties will result in overestimation of overturning stability safety factors of long-span continuous girder bridges in cantilever construction, reasonable safety factor should be obtained based on target performance. The sum of the self-weight of the travelling form and the pouring segment has the most significant effect on the safety factor. It's critical to ensure a reasonable situation of the travelling form during the construction stage in case of falling. The resistant moment of the temporary support and the eccentric distance of the support also need to be handled carefully because of the remarkable effect. The proposed method is stable and reliable, which will be convergent to the same result from different initial value in spite of different iteration progress.