Study On Parameter Sensitivity And Construction Key Technology Of Steel Box Girder Cable-stayed Bridge

With the increasing requirements of transportation in China,steel box girder cable-stayed bridge had become one of the main construction types of modern bridge structure because of its advantages such as superior spanning capacity,pleasing structure and light weight.However,the cable-stayed bridge belongs to the high-order statically indeterminate structure,which is complex in structure,difficult in construction and easy to be affected by environmental factors.In order to ensure the safe and smooth construction of the bridge until the final successful closure and the completion of the bridge meet the design requirements,strict construction control must be carried out in the construction.In this paper,based on the engineering practice,and using the finite element software MIDAS/civil and ANSYS software,the principle of determining the reasonable state of the steel box girder cable-stayed bridge and the advantages and disadvantages of the research methods are described,and the calculation and optimization of the cable force of the completed bridge and the construction tension cable force are carried out;the parameters that may affect the structural mechanical performance are selected,and the change of the control objective under the different degree of deviation of the structural parameters is analyzed The stress condition of temporary consolidation during the main erection and the stress performance of steel box girder during hoisting are studied.The conclusions are as follows::(1)A comprehensive method based on the minimum bending energy method,the unknown load coefficient method and the influence matrix method is proposed to solve a group of cable forces and determine the reasonable completion state of the steel box girder cable-stayed bridge that meets the design requirements and principles.Taking the reasonable completion state as the goal,a group of secondary tension cable forces of the cable are obtained by using the forward installation iterative analysis method to determine the reasonable completion state As the theoretical basis of construction control,the comparison results of the cable forces between the completed bridge and the reasonable completed bridge show that the cable forces of the completed bridge are highly consistent and meet the requirements.(2)Through the sensitivity analysis and research,the results show that these parameters will have different degrees of influence on the structural control objectives after the completion of the bridge,among which the self weight of the main beam,the manufacturing length of the stay cable and the temperature have a greater impact on the structural state of the cable-stayed bridge,which are the main sensitive parameters,as the key monitoring parameters in the construction process.(3)Compared with other control objectives,the change value of girder line shape in the completed state of cable-stayed bridge is larger,which is more sensitive to the change of structural parameters.In the construction control of steel box girder cable-stayed bridge,the girder line shape is selected as the main monitoring object,and the main girder stress as the auxiliary control object.(4)According to the stress law of the most unfavorable working condition of temporary consolidation during the main erection process and the structural checking calculation of temporary fixed structure,it is shown that the checking calculation of tensile and comprehensive bearing capacity and stability meet the construction requirements;through the calculation of lifting steel box girder,the deflection deformation of steel box girder is only 3.25mm,and The maximum combined stress of the temporary lifting lug is less than the allowable stress of the material,it shows that the hoisting scheme is safe and reliable.