Research On Robust Design Methods For Engineering Structures Considering Parameter Uncertainty

There are varieties of uncertainties in the design and analysis of engineering structures,which cause structural response to deviate from the target value,and there is even a risk of structural failure.With the lasting raising of complexity and diversity of engineering structures,the importance of uncertain structure design is increasing.Robust design method is an effective tool to deal with uncertainties of structures,which has been widely used in mechanical engineering,aerospace,automobile and ship,vibration control,processing and manufacturing and many other fields,but there are still relatively few applications in the civil engineering field.With the consideration of probabilistic and interval uncertainties of structural parameters,this paper studies in depth the key technical issues involved in the robust design method for engineering structures based on Taguchi method and optimization theory,so as to provide ideas and methods for the concrete implementation of robust design of engineering structures.This paper focuses on the following work and conclusions listed as follows:(1)For the engineering structure required simultaneous optimization of multiple responses,a robust parameter design method based on improved grey-TOPSIS model is proposed.On the basis of grey Taguchi method,the principal component analysis method is used to solve the correlation and conflict problem existing among multiple responses;the improved grey-TOPSIS model is established using the weighted combination of Euclidean distance and grey relational degree,which defines the grey relative closeness degree as a new kind of robustness index,reflecting the relative position and change trend of the responses' data sequences simultaneously;and then the robust parameter design results can be obtained based on the factor effect analysis of the grey relative closeness degree.For the section type selection of the subway station structure,the proposed method is superior to other methods;and there are no specific requirements for sample size and distribution of data,so this method has good adaptability.(2)For the engineering structure involved with nonlinear dynamic response,a robust parameter design method based on Kriging model is proposed.The mean value and standard deviation of response variance within the parameter variation range are used to represent the fluctuation of nonlinear dynamic response.Because Kriging approach has the advantage in improving model accuracy and dealing with nonlinear problems,the proposed method develops the variation model and response model using Kriging models,and then defines a new kind of robust criterion based on mean square error to optimize the settings of control factors.The proposed method is applied to optimize geometric parameters of the double-layer three-center cylindrical reticulated shell,which reduces the mean value and fluctuation of maximum node displacement for reticulated shell structure under the action of seismic waves;the results indicate that compared with traditional deterministic optimization,the structural performance of three-center cylindrical reticulated shell after robust optimization has been better improved.(3)For the engineering structure considered tolerance control,a robust optimization design method based on improved physical programming is proposed.Because physical programming method has the good processing capacity for the multi-objective optimization problem,the proposed method first improves the traditional physical programming method by using the unit interval and piecewise parabola to establish the preference function,so as to make the preference function simpler,more universal and ensure the overall continuity.And then,the cost-based tolerance control model is established with weighted combination of preference functions of each tolerance,which can better reflect the contribution of different tolerances in the cost;the dynamic constraint processing strategy based on dynamic factor and soft preference function is developed,which can enhance the ability of handling complex constraints and searching feasible solutions.The application in the truss structure illustrates the effectiveness of the proposed method;compared with traditional physical programming method,the proposed method has a faster speed in searching the optimum value.(4)For the engineering structure whose probability distribution of uncertain parameters is difficult to obtain accurately,a robust optimization design method based on interval analysis is proposed.Using interval variables to describe uncertain parameters,the robustness of interval objective function and interval constraint function are analyzed respectively,and a new kind of interval possibility degree model is adopted to deal with constraints.Based on this,the robust optimization model with consideration of interval uncertainties is established;furthermore,the interval boundaries of objective and constraint functions are obtained by solving the Taylor linear approximation at the midpoint of the interval,thus no optimization procedure is required for the inner loop,avoiding the large increase of the computational burden due to double-looped structure.The proposed method is applied to optimize the cross-section size of the single-layer Kiewitt reticulated shell;the results indicate that compared with before optimization,the single-layer reticulated shell after robust optimization can reduce the mass of rods,simultaneously improve the stability.