Research On Construction Control And Risk Assessment Method Of Asymmetric Two-Side Cantilever Construction For A Hybrid Girder Cable-stayed

The construction of hybrid girder cable-stayed bridge is mainly based on cast-in-place or assembly of side span concrete girder bracket and suspension assembly of middle span steel girder.There are also hybrid girder cable-stayed bridge girder using the "asymmetric double cantilever" construction scheme,that is,the side span concrete beam using the cable hanging basket cantilever construction,the mid span steel-concrete composite beam using the crane cantilever assembly construction.For the hybrid girder cable-stayed bridge with this kind of double cantilever construction method,the current construction experience and research data are less.What problems need to be paid attention to in the construction control process are worth studying.In addition,the cable-stayed bridge constructed by this method is faced with a variety of risks during the construction period.In order to reduce the structural risk of the cablestayed bridge during the construction period and prevent the occurrence of engineering accidents,it is very important to carry out risk assessment.Taking a cable-stayed bridge with a main span of 530m as the research object,a series of studies are carried out the key issues of construction control of asymmetric double cantilever hybrid girder cable-stayed bridge,including stress characteristics,demonstration and optimization of key processes,sensitivity analysis of construction parameters,determination of construction control accuracy,and on the risk assessment method of cable-stayed bridge.The main work and results are as follows:(1)A simulation calculation model for the entire construction process of the cable-stayed bridge was established by using finite element software.The comparison of the calculation results of the two sets of software showed the accuracy of the finite element calculation results,and the structural stress characteristics of asymmetric double cantilever hybrid girder cablestayed bridge in construction and operation stages are obtained.(2)The important construction procedures of the cable-stayed bridge were demonstrated and optimized,and the degree of influence of the changes in the procedures on the stress and alignment of the main structure was analyzed.The installation form of the Z1 beam section of the mid-span can be changed from large-scale floating crane hoisting to bridge deck crane hoisting;the cable tensioning plan is optimized based on the cable force adjustment idea of the difference iteration method,and the original plan has three side spans.The cable force and the mid-span withdrawal tension cable force are adjusted to reduce the number of adjustments to the full bridge cable force after the construction of the bridge deck system and auxiliary works.(3)Taking the cable-stayed bridge as the engineering background,from the perspective of construction control,based on the finite element modeling calculation and analysis,this paper discusses the sensitivity of cable force,main beam weight,construction temporary load and other parameters of hybrid girder cable-stayed bridge under asymmetric double cantilever construction to the structure and the construction control accuracy requirements,and demonstrates the maximum cantilever length of hanging basket passing through temporary and permanent Auxiliary Pier.The study shows that in the construction control process of the bridge,the linear control should be given priority to,and the cable force control should be supplemented.(4)In order to make up for the subjectivity of analytic hierarchy process(AHP)in the construction risk assessment of cable-stayed bridge,a construction risk assessment method of cable-stayed bridge based on the combination of AHP entropy weight method and fuzzy comprehensive evaluation method is proposed.By using the advantages of AHP method and entropy weight method,the distance function is introduced to optimize the subjective weight and objective weight,and a more objective and reasonable comprehensive weight is obtained.A fuzzy comprehensive evaluation model is established to analyze the construction risk of the superstructure of a hybrid girder cable-stayed bridge with asymmetric double cantilever construction.The evaluation results show that the construction risk level of the superstructure of the bridge is grade III,which belongs to the high risk level and it is consistent with the actual situation of the project,so we should pay attention to and take measures to reduce the construction safety risk.It is concluded that AHP entropy weight method can give full play to the subjectivity of researchers’ professional knowledge and experience and the objectivity of evaluation data,make the weight of risk index more scientific and reasonable,and improve the accuracy and reliability of cable-stayed bridge construction risk assessment results.