Design Parameter Optimization Of Single Tower Asymmetric Self-anchored Suspension Bridge

Self-anchored suspension bridges are structurally characterized by anchoring the main cable at the end of the main girder,eliminating the complex anchorage on both sides,thus saving a lot of money,and also conducive to the use of gravity anchorage in places where geological conditions do not meet the requirements and lack of conditions for the construction of gravity anchorage.The static and dynamic responses of selfanchored suspension bridges are different and more complex than those of ordinary suspension bridges because the force at the end of the cable interferes with the force and deformation of the beam.Therefore,in the analysis of self-anchored suspension bridges,we need to combine the original theoretical knowledge,actively innovate more in-depth theory and new technical methods,to better help the development of selfanchored suspension bridges.Based on an example of an asymmetric self-anchored suspension bridge with a single tower under construction,this paper first analyses the theoretical basis of the self-anchored suspension bridge;secondly,it analyses the influence of some design parameters on the force acting on the bridge structure and the optimization method;secondly,it systematically expounds a numerical analysis method to solve the parameters of the main cable,the length of the non-stress cable of the suspension cable,the pre-deviation of the saddle body and the shape of the empty cable.A new benchmark cable strand erection method is proposed to optimize the erection of empty cables.This paper combines theory with practice to make the following research:(1)The influence of different design parameters of single tower asymmetrical selfanchored suspension bridge on the mechanical characteristics of the structure is analyzed in this paper: the change of the rise-span ratio,the flexural rigidity of stiffening girder and the distance between suspenders is analyzed.By using the control variable method,the Midas model is established with the updated parameters when analyzing a certain parameter.By means of the model,the tension of the main cable,the cable force of the suspender,the axial force of the main girder and the main tower are compared,and the changing rules between the above three parameters and the mechanical performance of the structure are obtained,so as to realize the optimization of the design parameters.(2)Linear parameter analysis of single-tower asymmetric self-anchored suspension bridge: self-anchored suspension bridge belongs to geometric non-linear system,flexible structure,and large displacement characteristics.In order to accurately calculate the stress-free length of main cable and suspender,as well as the parameters such as the shape of empty cable and the pre-deviation of saddle when erecting cable strands,this paper elaborates on the theory of sectional catenary of self-anchored suspension bridge.A numerical analysis method is used to iteratively calculate the optimal combination solution of each parameter,and the corresponding program is programmed by MATLAB to assist the solving process.Finally,the reliability and accuracy of the analytical process are verified by combining the same type of Engineering projects.(3)Adjustment of benchmark strand alignment of single tower asymmetric selfanchored suspension bridge: After obtaining the accurate analysis of the benchmark strand-empty cable alignment,in order to optimize the actual benchmark cable alignment erected at the construction site,many factors need to be considered when erecting,in order to ensure that the completed empty cable alignment meets the theoretical alignment requirements.In this paper,the revised formulas for the deviation and span change of the main tower are sorted out,and a new method of cable adjustment is put forward,that is,fixing one end of the main beam,releasing the other end,adjusting the cable strand shape of the fixed span,and then adjusting the remaining cable strands of the fixed span equally.This method can be used to overcome the problem that the main girder can not adjust the strand shape of the reference cable accurately due to the expansion caused by the temperature change,so that the optimized empty cable shape can be obtained.