Structural Design Response Spectrum Research And Engineering Analysis Based On Strong Earthquake Records In Yunnan Province

Yunnan is one of the provinces with severe earthquake damage in China due to frequent earthquakes.Eighteen earthquakes more than 5 levels occurred in Yunnan within recent 10 years.There are two devastating earthquakes each year.In order to reduce earthquake disasters,Yunnan provincial government has issued regulations on accelerating the development and application of seismic isolation technology and construction management regulations supporting engineering in recent years.Nowadays,the number of isolated buildings in Yunnan accounts for more than half of the country.As for the isolation structure,there are China Building Earthquake Code and China Isolation Building Design Specification that is being compiled.The design response spectra in both codes is based on absolute acceleration spectra.The seismic force calculated by absolute spectrum corresponds to structural inertia force,which includes elastic restoring force and damping force,and the seismic force calculated by pseudo-spectral corresponds to structural elastic restoring force.For structure design,elastic restoring force is the design action value.Through data statistics,it is found that when the damping is small,the difference between absolute spectrum and pseudo spectrum is small and should be ignored.When the damping ratio is greater than 0.15,the difference between two spectral is relatively large,and the difference ratio can reach more than 10% when the period is greater than 2.5 s,exceeding engineering error range.The additional damping ratio of the structures with seismic isolation technology can reach 20%.High-rise and isolation buildings have long period and large damping ratio.If absolute spectrum is still used to calculate the earthquake effect,it will tend to be conservative.U.S.,Europe,and Japan Seismic standards of waterproofing and site categories were converted to the chinese corresponding standards of waterproofing and site classification,and the seismic response spectra for the four seismic fortifications were compared.It is found that the response spectrum segment of China earthquake resistance code.is much smaller than other normative response spectra in shortperiod,but is much larger than the others in long-period phase.The main reason is that characteristic spectrum period,damping adjustment coefficient,and attenuation index of China design spectrum are a little unreasonable,so it is necessary to correct the design response spectrum.Based on the above two points,the proposes of the paper is to establish a structure design response spectrum applicable to the Yunnan region.The response spectrum is applicable to both general structures and long-period,large damping high-rise structures and seismic isolation structures.Due to the characteristics of isolated buildings in long-period and large-damping,the paper uses isolation buildings as the object of analysis to study the structural response spectrum of Yunnan.The article collected more than 2,000 seismic records in Yunnan region since 2007 through Yunnan Earthquake Administration.The site response spectrum under different site and design groupings are obtained through classification and calibration,and the recommended values of the feature period are given.The classification calibration result show that the amplification factor,attenuation index and damping adjustment coefficient of the response spectrum are no significant correlation in different site category.The attenuation index formula and the damping adjustment coefficient formula are obtained by fitting the attenuation index and the mean value of the DRF spectrum at different damping ratios.The article provides reference for correcting design response spectrum of Yunnan region.