Research On The Adaptability Of Algorithms In Dynamic Optimization Of Rope-fixing Systems In Pontoon Bridge

In the pontoon bridge structure,the main function of the rope-fixing system is to resist the lateral dynamic load of the pontoon bridge and ensure the hydrodynamic stability of the pontoon bridge.Compared with anchor-cable system,the rope-fixing system has a general adaptability.Because it is installed on both sides of the river,it is not affected by the soil quality,water depth and velocity of the river bottom.Due to the strong nonlinearity of the rope-fixing system,the calculation theory is very complicated,and there are few related researches.This paper carries out structural dynamic optimization design of the rope-fixing system in the pontoon bridge structure,through the combination of ANSYS finite element simulation and MATLAB optimization analysis.The results can provide a reliable reference for similar structural design and structural research.In the optimization design of the rope-fixing system in the pontoon bridge structure,the section size of main cable and the section size of tower structural members are the key parameters of structural design.The single-parameter analysis method used in conventional optimization analysis does not take into account the coupling effect between the various parameters.It requires a lot of trial and error to get a better feasible solution.It is difficult to obtain the optimal plan of section size of the main cables and the section size of the tower members in a large number of combinations of multiple parameters.In this paper,the optimization analysis based on mathematical analysis is used to carry out the following optimization research for the rope-fixing system in the pontoon bridge structure:1.Three constrained nonlinear optimization analysis modules are compiled with MATLAB language and validity is verified.The results of several numerical examples show that the three optimization modules have high convergence and obvious optimization effect,which can be used for the subsequent research on the adaptability of various algorithms to the dynamic optimization of pontoon bridge structure.(1)Optimizing module 1: Solve the mathematical model based on the penalty function method and the conjugate direction method.In this module,Taylor expansion is used to describe the constraint function with linear expression;(2)Optimizing module 2: The response surface method was used to establish the constraint function,and then the penalty function method and the conjugate direction method were used to find the optimal solution;(3)Optimizing module 3: Based on the genetic algorithm optimization model to solve nonlinear constraint optimization model.2.The finite element model for dynamic analysis of the rope-fixing system of a heavy-duty pontoon bridge is established in ANSYS,and the transient analysis is performed by applying hydrodynamic load to study and analyze the dynamic response of the structure.Based on catenary theory,the linear iteration program of main cable is programmed with APDL language,and the effectiveness of the program is verified;The connection between the tower and the main cable needs to simulate the sliding contact.Contact178 unit is used to simulate the connection between the main cable and the tower,and the accuracy of the simulation is verified by an example.Research shows that in the rope-fixing system preliminary design scheme,the existence of the main cable breaking security hidden danger,tower components and stability is the waste material.Therefore,it is necessary to further optimize the dynamic response of the ropefixing system.3.The conjoint analysis framework of multi-dimensional constrained nonlinear optimization problems based on ANSYS finite element analysis and self-designed optimization module is established to carry out optimization analysis for the rope-fixing system in the pontoon bridge structure.The total weight of the rope-fixing system was reduced by 14.188%,14.381% and 16.138% respectively after the optimization of module 1,module 2 and module 3,on the premise that the dynamic response peaks of the rope-fixing system met the requirements of the specification.The optimization result of module 3 was the most ideal.The total calculation time of the three optimization modules is 198.3h,211.7h and 348.2h respectively,and the optimization module 1 has the highest calculation efficiency.From the perspective of comprehensive optimization structure and total calculation time,the conjoint analysis framework based on response surface method has the best adaptability in dynamic optimization design of pontoon bridge structure,which not only ensures the calculation efficiency,but also makes the objective function well optimized.