Design Parameter Analysis And Experimental Study Of Cable Hoisting System Of Wuzhou Xijiang Fourth Bridge

During the construction of long-span bridges,it is necessary to hoist and transport prefabricated components of large sections.Cable hoisting system has become the first choice for long-span bridge construction because of its advantages such as easy operation,convenient construction,no need to erect supports,and strong environmental adaptability.With the continuous development of bridge construction scale and construction strength in China,the structural form of bridges is also developing towards large-span and multi span.In the construction process of multi span arch bridges,if the single span cable hoisting system scheme is adopted,the steel used for the main cable and tower will have high performance requirements,large consumption and high cost due to the large side and middle span of the cable system;And in the urban construction environment,there is no condition to build large anchors on both banks.Compared with the single span cable hoisting system,the multi tower multi span cable hoisting system can reduce the span of each span,the height of the cable tower,the tension of the main cable and the scale of the anchorage,and can carry out hoisting operations synchronously between the spans,which is more suitable for the construction of multi span arch bridges.Due to the complex stress of the multi span cable hoisting system structure,and the research on the structural form of the multi span cable hoisting system is relatively few in China at present,further research is needed on the stress characteristics of the multi span cable hoisting system and the layout form to optimize its structural stress.Taking the cable hoisting system of Wuzhou Xijiang fourth bridge,the first multi tower multi span cable hoisting system in China,as the engineering background,this paper adopts the method of establishing finite element models of cable hoisting system with different structural design parameters for comparative analysis,and combines with the trial hoisting test project of Wuzhou Xijiang fourth bridge,and obtains the following results:(1)Two calculation theories of the main cable of the cable hoisting system,parabola method and catenary method,are analyzed,and the calculation methods of the main cable line shape,unstressed cable length and main cable tension of the multi span cable hoisting system are proposed,which provide a basis for the follow-up theoretical calculation and analysis of the main cable.The parabola theory and catenary theory are compared and calculated,and the calculation deviation of the two theoretical methods under different vertical span ratios of main cables is obtained.(2)By changing the design parameters such as the angle of back cable,the design vertical span ratio of main cable and the height of side span main tower,several finite element comparative analysis models are established.The influence of the change of angle of back cable,the design vertical span ratio and the height of side span main tower on the stress of main cable is analyzed,and the optimal design range for the stress of main cable is obtained.(3)By changing the design parameters of the cable tower,such as the angle of the rear cable,the height of the side span tower and the stiffness of the cable tower,the influence of the change of the angle of the rear cable,the height of the side span tower and the stiffness of the cable tower on the stability of the cable tower is studied.The influence of different load combinations on the overall stability of the cable tower is calculated and analyzed,and the surface function is fitted,which can provide theoretical support for the design and construction of multi tower multi span cable hoisting system.(4)Relying on the trial hoisting test project of Wuzhou Xijiang No.4 bridge,it is verified that the cable hoisting system of Wuzhou Xijiang No.4 bridge has good mechanical performance and ensures the safety and stability of the hoisting construction process.At the same time,the comparison between the measured value of the load test and the theoretical value proves the reliability of the calculation theory of the multi tower multi span cable hoisting system.