Comparative Analysis On Design Of Isolated Frame Structures Based On Time History Method And Response Spectrum Method

After the actual earthquake,the frame structure shows concrete failure,such as concrete crushing,lateral displacement and steel yielding.The ultimate failure mode of the frame structure is "strong beam and weak column".In order to enhance the seismic performance of the frame structure,the traditional seismic design generally increases the sectional area of the structure and increases the cross-section reinforcement,so that the designed building structure meets the seismic requirement of "small earthquake is not bad,moderate earthquake can be repaired,big earthquake does not fall”.This design method is mainly through the structure of the carrying capacity of its own resist earthquake action.Due to the large cross-section,the large stiffness of the building structure itself also plays the role of "amplifier",leading to an increase in seismic action,neither economic,and can not guarantee structural safety and structural facilities within the intact.With the development of science and technology,the government and residents' consciousness of preventing and reducing earthquake disaster is improving,and the traditional seismic design method can not meet the actual demand of engineering.So a new design method of seismic damping "base isolation technology" came into being.China's current code for the base isolation structure design gives more guidance,not for enforcement.At present,for the design of the base-isolated frame structure,the commonly used design method is the response spectrum method with the horizontal damping coefficient.The method is based on the principle of modal decomposition response spectrum,and the horizontal shock absorption coefficient is calculated by the time history analysis method under moderate earthquake action.The seismic response of the upper structure is reduced by the horizontal shock absorption coefficient.The isolation design method and the design flow are easy to be understood by the designers.However,this method does not consider the nonlinearity of the upper structure and the isolation layer and the limitation of the response spectrum method,which is not conducive to the checking and optimization of structural design.In order to discuss the application of time history analysis method in the design of base isolation structure,the finite element dynamic response analysis software ETABS and SAP2000 are used to calculate the structure of isolated frame structure based on time history analysis and response spectrum method under the effect of medium earthquake.And the actual frame structure is taken as the object of study.The differences between the calculation results of the internal force of the structure are analyzed and analyzed by the response spectrum reduction method and the time history analysis method.The preparation of Matlab program helps to finish the internal force data extraction and statistical comparison,and through the chart to visually compare the two design methods of the upper structure of internal force differences.In this paper,the frame structure as an example,the main work is as follows:1.The selected structure is selected as the object of study,and the mass and vibration period of the model are compared and the consistency of the model is ensured by comparing the ETABS isolation model(non-isolated)and the SAP2000 seismic isolation model.2.Study on Input Seismic Wave.(Slightly greater than 180)artificial wave was generated by using YJK according to the fortification intensity,maximum influence coefficient,peak acceleration and characteristic period.The first three order isolation period and the first three order seismic period were compared and contrasted.Point on the"spectrum" and "standard response spectrum" value of the difference does not exceed 20%that meet the requirements.According to the engineering parameters,the artificial wave is generated,and the average of the shearing force,the overturning moment,the displacement angle and the internal force of the member under different wave numbers are compared to determine the reasonable wave number of the engineering design.3.Analysis of Horizontal Damping Coefficient.The method of solving the horizontal damping coefficient is used in the reactive spectrum reduction method.The difference of ?between the internal force component of the single component and that of the traditional isolation design method is obtained by taking a artificial wave similar to the normalized response spectrum.4.The results are compared with the results obtained by seismic isolation analysis using the time-history analysis method using the horizontal damping coefficient to reduce the response spectrum.In this framework,20 artificial waves and 3 natural waves are selected to compare the time-averaged value of seismic isolation and response spectrum reduction method and the internal force of single component,and the relevant rules are obtained,and then the design of frame structure is proposed.