Design And Optimization Of The Isolated Structure Based On Repair Cost Ratio

Multiple seismic measurements have shown that the isolated structure can significantly reduce the damage of the buildings,maintain the building function,and reduce the loss of the buildings.But how to clarify the impact of the isolation technology on the seismic loss of the buildings,or use the minimum building seismic loss as the judging by the criteria for the quality of isolation design,the current design methods and seismic performance of the structure have not been considered.Isolated structure design is usually carries out based on deterministic analysis,and the damping coefficient of the superstructure and the displacement of bearing are used as performance index.Due to the uncertainty of ground motion and structural dynamic characteristics,deterministic dynamic analysis and structural performance parameters are not good for assessing the expected seismic losses of isolated structures.Therefore,this paper introduces the concept of "repair cost ratio".The repair cost ratio refers to the ratio of the expected repair cost of the structure to the total cost of the structure caused by earthquake.The repair cost ratio is smaller,the expected loss risk of the building is lower,and the seismic performance of the structure is better.The isolated structure design with the minimum repair cost ratio as optimization goal can consider the uncertainty of the ground motion and the dynamic characteristics of the structure,and can link the design parameters with the performance parameters of structural.Therefore,to clarify the influence of seismic isolated structure parameters on the seismic loss and seismic resistance of the buildings,which is more convenient for engineers and owners to select and make decisions.This paper gives a design method of isolated structure based on the repair cost ratio,the main research is following:(1)Give the concept and calculation of the structural repair cost ratio,which is related to the probability of failure in each state of damage to the structure and to the cost of the structural components.(2)To establish a 3D nonlinear finite element model of the isolated structure,through incremental dynamic analysis(IDA),to obtain the failure probability of each state of damage the isolated structure.(3)Carry out analysis of the fragility curves of different isolation bearing arrangement scheme to obtain a uniform repair cost ratio functional surface of the isolated structure.(4)The optimized design of isolated structures based on the repair cost ratio is completed using multiple group optimization methods with the minimum cost ratio of structural repair as an objective function.Through the above study,the following main conclusions were drawn:(1)The fragility curves for each limit state of the isolated structure satisfy the normal distribution.In the small ground earthquake,both the superstructure and the isolated layer will hardly be damaged In the basic ground earthquake,both the superstructure and the isolated layer will be slightly damaged,and in the rare ground earthquake,the protection of the structure by isolation is still relatively effective.In the very rare ground earthquakes,the superstructure will be moderately damaged,but the structure doesn't collapse,the isolation bearing will have a greater probability of damage,and the isolated layer will have a greater probability of failure than the superstructure.(2)The repair cost ratio is related to the probability of structural failure,and can be used as a performance index for isolated structures.Different isolated schemes have uniform repair cost ratio functional surfaces.The uniform repair cost ratio function of the isolated structure can be expressed as a function of the maximum inter-story drift ratio of the superstructure and the maximum shear deformation of the isolation bearing.By using the uniform repair cost ratio function,there is no need to calculate the failure probability of the structure,only the EDP value of the structure needs to be solved to directly obtain the structure repair cost ratio,which can greatly simplify the design process.(3)The minimum repair cost ratio of the structure was regarded as the optimization goal,the multi-population genetic algorithm was used for optimization,to achieve the optimized design of isolated structure based on repair cost ratio,which programming is combined with SAP2000 and MATLAB genetic algorithm toolbox Through an example of isolated engineering,the analysis resulted in an optimized solution.Compared with the original scheme,the probability of structural failure under each performance parameter and each limit state of the optimized scheme is reduced.In the design life,the frequent ground earthquake,the basic ground earthquake,the rare ground earthquake corresponding to the maximum repair cost ratios have been reduced,when the frequent ground earthquake to reduce the most obvious,up to 61%.The total cost of repair can be reduced by 48%.It is expressed that the optimization result of this method is reasonable,which can effectively improve the design quality and design efficiency of isolated engineering.