Assessment Of Risk In Main Girder Cantilever Construction Processes Of Continuous Rigid Frame Bridge In Mountain Highway

In recent years,with the improvement of road traffic network in the middle and eastern developed areas,the focus of basic transportation facilities construction in China has been shifted to the western mountainous area on a large proportion,where the continuous rigid frame bridge constructed by the cantilever construction method is widely used to cross the deep valleys and rivers.However,the long construction cycle,complicated construction processes of continuous rigid frame bridge and complex natural environment lead to frequent accidents during the construction phase,on which this thesis is based to conduct risk assessment research.Combining the structural features of the continuous rigid frame bridge and the special natural environment of the mountain area,the thesis studied the construction risk in the processes of the cantilever construction of this kind of bridge from the aspects of risk factors identification and risk evaluation.Based on the method of Work Breakdown Structure,this thesis divides the processes into four stages,they are,0# block construction,main girder cantilever construction,side-span construction in-situ and final closure of main girder and a construction risk factors table was established from five perspectives: construction management,construction personnel,materials and equipment,design and construction technology,and natural environment.Then,in order to solve the shortcomings that the large dispersion caused by inconsistent experts’ judgements will lead to unreasonable evaluation results existing in the traditional Analytic Hierarchy Process(AHP),the AHP optimized by the method of Principal Component Analysis(PCA)was proposed;On this basis,a series of key risk factors considering actual situation of the project were selected to establish a cantilever construction risk evaluation index system and AHP-PCA was used to calculated the overall weights of all risk factors.Lastly,based on fuzzy comprehensive evaluation method,a dynamic fuzzy comprehensive risk evaluation model for cantilever construction was proposed,which could realize dynamic assessment by selecting appropriate measurement indicators for each risk factor and constructing its corresponding membership function according to relevant specifications.Taking a bridge on the expressway from Wushan to Fengjie as the engineering background,the method proposed in this thesis was used to conduct risk assessments for the stage of the main girder cantilever construction.In general,The innovation of this thesis is embodied in: the improved AHP-PCA method is proposed to make up for the deficiency of the traditional Analytic Hierarchy Process when dealing with the large dispersion cases;the dynamic fuzzy comprehensive evaluation model for cantilever construction is established,which has more practical significance and application value compared with previous static evaluation.