Research On Force Analysis And Construction Control Of Continuous Beam-basket Arch Combination Bridge

The continuous beam-basket arch combination bridge has the characteristics of various structural forms.It is widely used for its reasonable mechanical property,graceful shape and economic cost.Approach Channel Main Bridge,the traffic bridge under the dam of Datengxia Water Complex in Guangxi,is a continuous beam-basket arch combination bridge with span of 55m+230m+55m,and the method of constructing the main girder first and then the arch rib is adopted.The main girder as tie bar bears the horizontal force of arch rib,so the number and batch of prestress are large;meanwhile,the span of basket arch is large,so it is difficult to install and locate;and the contact state of full framing is complex,so there are many sources of error,which increase the difficulty of construction control.Taking Approach Channel Main Bridge as the engineering background,the research on force analysis and construction control of continuous beam-basket arch combination bridge can provide some reference for the design and construction of the same type of bridge in the future.The main research work is as follows:(1)Building Midas civil finite element model of Approach Channel Main Bridge,and using the minimum bending energy method to get the ideal bridge state.Through the analysis of the static effect under the dead load and moving load during the operation period,as well as the linear elastic stability,natural vibration characteristics and dynamic response of moving load,the static and dynamic characteristics and corresponding laws of the large-span continuous beam-basket arch combination bridge with small width span ratio are explored.(2)Finite element models of each construction stage are established separately to determine the reasonable construction state and to optimize its construction procedure.According to the three-point principle of judging the reasonable construction state,the order of longitudinal and transverse prestress tension,the order of arch rib falling and the order of hanger tension are adjusted.Meanwhile,the feasibility of tensioning between pre-stress and boom is analyzed,which finally ensures the optimum working procedure,safety and design compliance during construction.(3)Construction monitoring system for continuous beam-basket arch combination bridge is constructed,which provides long-term,reliable and accurate test data for construction control of Approach Channel Main Bridge.A set of MATLAB program for solving unstress linear three-dimensional coordinates of basket arch is developed and compared with the three-dimensional model partition method.The verification shows that the program is accurate,and can solve the three-dimensional coordinates of any point on the basket arch,which greatly reduces the difficulty of construction control of basket arch.(4)Sensitivity analysis of design parameters of Approach Channel Main Bridge is carried out,and sensitivity factors and sensitivity percentage of each parameter are obtained.Based on the least square iteration method and BP neural network method,the parameter identification of the beam weight and the effective prestress under the nonlinear boundary condition of the full framing is completed according to the measured error of the elevation of the main girder after the boom is tensioned The results show that both methods meet the accuracy requirements,but each method has its own advantages and disadvantages.Therefore,the combination of least square iteration method and BP neural network method can accelerate the convergence speed,improve the calculation accuracy,and have a wider range of application.In order to adjust the target state with the identified parameters,the unstressed length control method is used to calculate the secondary cable adjustment.The corresponding cable force increment is quickly obtained through the k-value iteration method,and the cable adjustment construction is controlled jointly with the target anchor cup pull-out amount.Finally,the completion state of Approach Channel Main Bridge meets the requirements of design and construction,which proves the correctness and accuracy of the method.