Optimization Design Method Of Transmission Tower Based On Adaptive Surrogate Model

With the rapid development of national economy and the great improvement of people’s living standard,the state has put forward higher requirements for the development and future planning of the electric power industry.In order to build a safe,reliable,efficient and excellent transmission line project,it is very important to improve the research and design level of transmission tower system and reduce the cost input.As the main infrastructure of transmission line engineering,transmission tower structure has high steel consumption and high cost.Therefore,under the premise of ensuring the safety of the structure,it has important practical significance and great economic benefit to reduce the steel consumption of transmission tower by structural optimization design.Traditional structural optimization design method searches for optimal design points by constantly updating design variable values,and each update of design variables corresponds to a structural analysis.Therefore,the traditional optimization method is difficult to be applied to large and complex engineering structures,such as transmission tower structure,because of its high calculation cost and long time consuming.In view of this,the study first discusses and develops the surrogate model method used to approximate response function from the theoretical level,and then introduces the developed surrogate-based optimization method into the optimization design of transmission tower structure in practical engineering.In particular,the following work has been carried out and completed:(1)Based on the shortcomings of the existing methods of sequential sampling for surrogate model,an improved error tracking-Voronoi adaptive sequential sampling method for arbitrary surrogate models is proposed.By using the Voronoi method,the whole design space is divided,and the k-fold cross-validation prediction errors of sample points is introduced to evaluate the spatial region.Finally,a new sample points are extracted according to the maxmin criterion.The proposed method is independent of the surrogate model and can be applied to different types of engineering problems which has a wide range of applications.Though the exploration of design space and the exploitation of local area,the algorithem selects sample points effectively,which has strong adaptability,low computational cost and high modeling efficiency.(2)Based on the basis idea of global exploration and local exploitation,a modelindependent hybrid infill sampling criterion is proposed firstly,and a surrogate-based optimization design method based on hybrid infill sampling criterion is developed.During the process of optimization,the proposed method can guide the optimization to the global optimal direction by adaptively sampling in the local area near the minimum value of the current surrogate model and the region with large fluctuation of function and strong nonlinear,avoiding the issue that conventional surrogate-based optimization design method is easy to fall into the local optimal solution.The examples demonstrate that,compared with conventional method,the proposed method can keep the tradeoff of accuracy and efficiency,which has great global optimization characteristics and robustness.(3)Based on the geometry and mechanical characteristic of semi-rigid joints,the optimization design framework and corresponding mathematic optimization model is proposed.Then,the mathematical function expressions of ultimate moment bearing capacity and maximum rotation displacement of semi-rigid joints in transmission tower are fitted by surrogate model,and the discrete surrogate-based optimization design method of semi-rigid joints in transmission tower is carried out.It is certified that the proposed method can reduce the number of calls of complicated finite element analysis model during optimization and cut down the cost of optimization design calculation effectively,which provide a powerful way to solve the problem of optimization design of practical semi-rigid joints in transmission tower.(4)In order to efficiently evaluate the mechanical properties of semi-rigid joints in transmission tower and explore their effect on the force-deformation performance of transmission tower,a method based on the RBF surrogate model is proposed to predict the moment-rotation relationship of the semi-rigid joints in transmission tower in this paper.Then,the influence of semi-rigid joints is considered in the structure of transmission tower,and the response analysis of transmission tower considering semirigid connection is carried out.The results show that there are large errors in the finite element model of transmission tower which ignores the influence of semi-rigid connection.Furthermore,the optimization design of transmission tower considering semi-rigid connection is also carried out,and the mathematical model and design scheme of optimal design of transmission tower considering semi-rigid connection are provided.