Shaking Table Test And Numerical Investigation For Evaluation Of Long Cycle Section Of Response Spectrum

The response spectrum of seismic design is the main basis for calculating seismic action in engineering design in many countries.The seismic design of structures using response spectrum method can meet the goal of seismic design in most cases.Some existing studies show that there may be some unreasonableness in the design of the long period of response spectrum,which leads to the difficulty of meeting the requirements for the design of super high-rise building structures in actual design.With the increasing application of super high-rise buildings in China,the research on the seismic response characteristics of long-period structures and the long-period period of seismic design spectrum has attracted more and more attention from engineering circles and experts and scholars.This paper is based on this background.The acceleration response of multi-story and high-rise model structures is obtained by shaking table test combined with numerical simulation analysis.Based on the SRSS rule in China's seismic code,the dynamic amplification coefficients of the single-degree-of-freedom system corresponding to the structural modes are deduced,and the complete spectrum curve of dynamic amplification coefficients is fitted to evaluate the long period of response spectrum of seismic design in China's code.Reliability and rationality are compared with the proposed seismic design response spectrum in reference [32].The main research work is as follows.1.Shaking table test of 40-layer perspex test model was carried out.Three seismic records,Northridge wave,Chi-Chi wave and artificial seismic wave,with rich low frequency and long period components,and a typical seismic record,El Centro wave,were selected as input excitation for the platform.The stations were determined according to the fortified intensity of 7-degree frequent earthquakes,7.5-degree frequent earthquakes,8.5-degree frequent earthquakes and 8.5-degree frequent earthquakes.Surface input acceleration was tested in four groups(A,B,C,D)in four time periods.In the test,three seismic waves are selected from the above four seismic waves for testing with different seismic intensity.2.The floor acceleration response data of the shaking table test model are analyzed and processed,and the dynamic amplification coefficients of the single-degree-of-freedom system corresponding to the first three modes of the test model structure X can be deduced by using SRSS rules.3.According to the same conditions as the test,a number of structures with different natural vibration periods are established for numerical calculation to calculate the floor acceleration response under multiple seismic excitations.Finally,a complete dynamic amplification coefficient spectrum of the single-degree-of-freedom system is formed.It is compared with the spectrum of dynamic amplification coefficient given in Chinese code and the recommended spectrum of dynamic amplification coefficient in reference [32].The analysis results are as follows.1.Through reasonable deduction and analysis,the dynamic amplification coefficient obtained from the test and numerical analysis can be decomposed into SDOF dynamic amplification coefficients corresponding to the structural modes of each order,and a complete spectrum of SDOF dynamic amplification coefficients can be fitted.2.The dynamic amplification coefficients obtained at the vertex of the structure and the equivalent SDOF height are calculated respectively and the spectrum of the dynamic amplification coefficients of SDOF is fitted.The trend of the curve change and the spectrum value of the two coefficients are smaller.This shows that the dynamic amplification coefficient spectrum of SDOF is independent of the height and position of the structure,but only related to the damping ratio and natural frequencies of the structure modes.It also shows that this method is feasible to evaluate seismic design spectrum.3.In the long period,with the increase of the natural vibration period,the average SDOF dynamic amplification coefficient spectrum and the standard dynamic amplification coefficient spectrum attenuate continuously,but the attenuation trend of the standard dynamic amplification coefficient spectrum is abnormal,its attenuation range is small,and the value is larger in the long period,which is conservative.It shows that the seismic design spectrum of the code does not reasonably reflect the dynamic response of long-period structures under earthquake excitation.