Improvement Of Real Mode Superposition Response Spectrum Method Of Isolated Structures And Research On Optimization Method Of Isolation Bearings Arrangement

After years of theoretical research and engineering practice,the design method of isolation structure has become increasingly mature,However it is very difficult for general engineers to master the time history analysis method as stipulated in the code for seismic design of buildings,or the complex mode superposition response spectrum method as specified in the code of design for seismic isolation buildings,at the same time,the parameters and arrangement of isolation bearings should be adjusted for trial calculation in the design of isolation structures,and the results might not optimal and the design efficiency is low.these all have great impact on the isolation technology promotion and application.Therefore,this paper researches on the practical optimization design of isolation structure,firstly,the calculation precision of the real mode superposition response spectrum method is improved to meet the engineering design requirements.secondly,the optimization method is applied to complete the optimized arrangement of isolation bearings.The main research contents and conclusions are as follows:(1)The theoretical background of the real mode superposition method and the complex superposition method for isolated structures is analyzed,through an example of isolation engineering,the calculation error of the real mode superposition method which forced decoupling is discussed,the results show that,when the damping ratio of the isolation layer is not more than 20%,the error caused by the forced decoupling is not more than 5%;when the damping ratio of the isolation layer is 30%,the error caused by the forced decoupling reach to 10%;with the increase of the damping ratio of the isolation layer,the errors caused by forced decoupling increase and the trend is more significant.(2)In addition to the forced decoupling method,other factors affecting the calculation accuracy of the real mode superposition response spectrum method of isolated structures are discussed,including the equivalent linearization parameters of the isolation layer,the calculation of damping parameters and the design response spectrum.Based on the analysis of three factors,an improved real mode superposition response spectrum method for the isolated structure is proposed,after calculation of three typical engineering examples,it is shown that compared with the time history analysis results,the error of the improved real mode superposition response spectrum method about 5%,which can meet the requirements of engineering design.(3)An optimal arrangement method of isolation bearings is presented.In this method the problem of optimal arrangement of isolation bearings is divided into two optimization problems,firstly,the multiple population genetic algorithm is used to determine the optimal design parameters of isolation layer.Then,based on the optimal design parameters of the isolation layer,the linear programming method is adopted to determine the model,parameters and arrangement of isolation bearings.(4)With MATLAB programming,the program for optimiz ing bearing arrangement of isolated structures is realized.Using the genetic algorithm toolbox function of MATLAB and the SAP2000 OAPI,using MATLAB to realize the genetic algorithm,the dynamic analysis of the isolation structure is completed by SAP2000,the optimal design parameters of the isolation layer are finally determined.with the help of the optimization toolbox function of MATLAB,the optimal arrangement of isolation bearings is achieved.The analysis of two practical isolation projects shows that the optimized isolation scheme is better than the original design scheme,whether seismic isolation effect or economic benefit.