Research On Asymmetric Tension Construction Control Method Of Long Span Steel Concrete Composite Girder Cable Stayed Bridge

To ensure the safety and rationality of the construction process and completed state of a steel-concrete composite beam cable-stayed bridge,as well as to improve controllability and accuracy of the construction and reduce the difficulty of construction control,the study examines the case of cable-stayed bridge construction using asymmetric methods of stay cables,The sensitivity analysis of multiple parameters in cable-stayed bridge construction control,the reliability of cross-section displacement during construction,and the tolerance interval of construction cable force are all explored.The construction method is compared with the symmetrical tension construction method of the cable.The control method suitable for the asymmetric tensioning construction of long-span steel-concrete composite girder cable-stayed bridge and cable is summarized.The statistical sensitivity analysis of the displacement and internal force of the main beam and the tower section in the bridge and construction stage is carried out by using the test design and significance test method,and the sensitivity parameters affecting the bridge and construction stage are analyzed.The sensitive parameters is selected as a random variable,and the influence range of cable force change on the displacement reliability of main girder and tower top section during construction stage is analyzed by combining experimental design,response surface method and Monte Carlo sampling method.The sensitivity parameters are used as optimization variables,establishing a cable force tolerance interval optimization model based on reliability optimization.The BP neural network optimized by genetic algorithm is used to construct the mapping relationship between the parameters to be optimized and the target and constraint functions.The improved particle swarm optimization algorithm is used to optimize the cable force tolerance interval.The main conclusions are as follows :(1)The sensitivity parameters of key parts of a cable-stayed bridge can be accurately obtained during both completion and construction stages with the use of a statistical sensitivity analysis method.This method is based on a uniform and orthogonal test design,multiple linear regression,and range analysis significance testing.It takes into account the influence of random variability of structural parameters and the combined effects of multiple structural parameters on structural response.For the bridge stage S10,MS10,S9 cable-stayed cable force,steel girder elastic modulus BE1,bridge deck weight DW2,DW4,DW5 main beam and tower section displacement,internal force sensitivity parameters;for asymmetric tension construction,S10,MS10,S9,MS9,S8,MS8,S5 and MS5 cables are the sensitive parameters of displacement of tower top and main beam section.For symmetrical tension construction,S10,MS10,S8,MS8,S9,MS9,S7 and MS7 are the sensitive parameters of the displacement of the tower top and the main beam section.(2)The reliability analysis method based on uniform experimental design,response surface method and Monte Carlo sampling can quickly and accurately fit the complex response relationship between cable force and section displacement,and realize the rapid solution of reliability index.For the mid-span section(21 #)and the tower top section(22 #)of the main span,when the cable force tolerance range is,the reliability indexes of the section displacement are 1.77 and 1.52 respectively when the asymmetric tension construction is adopted,indicating that the structure has 96.2 % and 93.6 % reliability,which meets the engineering requirements.When the cable force tolerance range is,the reliability indexes of the section displacement are 0.91 and 0.72 respectively,and the structural reliability is 81.9 %and 76.4 % respectively.The reliability is low and does not meet the engineering requirements.The symmetrical tension construction is adopted.When the cable force tolerance range is set,the reliability index of section displacement is 2.31 and 2.04 respectively,and the reliability of the structure is 99 % and 97.9 %,which meets the engineering requirements.When the cable force tolerance range is set,the reliability index of section displacement is 1.27 and 0.93 respectively,and the reliability of the structure is 90%and 82.4 % respectively.The reliability of 22 # section is low and does not meet the engineering requirements.With the increase of the tolerance range of cable force,the reliability index of section displacement decreases.In order to ensure the safety of the structure and improve the controllability of the construction process of cable-stayed bridge,it is necessary to clarify the optimal tolerance range of cable force.(3)The cable force tolerance interval optimization method based on BP neural network optimized by genetic algorithm and improved particle swarm optimization algorithm can realize the rapid and accurate prediction of complex nonlinear response,and has good convergence performance in the cable force tolerance interval optimization problem of complex construction cable-stayed bridge.In the asymmetric tension construction,the tension deviation between S8～S10 and MS8～MS10 is 93～165 k N,and the tolerance range is-3.2 %～1.9 %.In the symmetrical tension construction,the tension deviation between S8 ～S10 and MS8～MS10 is 71～142 k N,and the tolerance range is-0.9 %～2.3 %.According to the cable force tolerance interval obtained by this method,the construction control of the target cable-stayed bridge is carried out.The maximum error of the cross-section displacement after the completion of the bridge is 25 mm,and the maximum error of the cable force is 3.4 %,which meets the requirements of the specification and construction monitoring.This method can be applied to the construction tolerance control of long-span cable system bridges and the fault-tolerant design of complex bridge structures.