Research On The Characteristic Parameters Of Response Spectrum In Seismic Design Code

Seismic design response spectrum is the foundation for seismic structural design and the basis of determining the strong ground motion input in seismic design.The standard response spectrum in code for seismic design of buildings in China is given in the form of seismic influence coefficient curve.The shape of seismic design response spectrum is controlled by several characteristic parameters,among which the most important ones are the characteristic period and platform value ?max(maximal influence coefficients of ground motion).Therefore,to determine the reasonable of characteristic periods and platform values play a key role in seismic design.Influence of site condition should be considered in the related studies of response spectrum and proposed to use of H/V spectral ratio method for site classification on the basis of system analysis the existing site classification methods.The main contents of this paper as follows:(1)The 2423 strong ground motion records during 1933~2015 from 166 sites with detailed borehole data in the Western United States are collected,including 1650 horizontal and 773 vertical.The station sites are sorted according to the site classification standards of the Chinese code for seismic design of building(GB 50011-2010).The records are divided into groups according to magnitude,epicentral distance and site classification,the strong ground motion records database are established.(2)The 1237 horizontal strong ground motion records are selected and each peak ground acceleration is more than 10 Gal.The platform values and the characteristic periods of response spectrum are extracted according to Chinese Code for Seismic design of buildings(GB 50011-2010).The influences of site,magnitude and epicentral distance on characteristic period of response spectrum are discussed.The averages of the characteristic period of response spectrum with different sites based on design earthquake classification in the Code are statistically analyzed,and compared with the characteristic period values in the Code for Seismic Design of Buildings in China.(3)Statistical analysis the single factor and the three factors including the site classification,the magnitude,the epicentral distance which influences on the value of platform.The design earthquake classification is considered for the border of characteristic periods in the partition of earthquake ground motion.Effects of design earthquake classification on the response spectrum platform values are discussed.The results show that the influence of site classification on the platform values should be considered.The feasibility of research on the platform values according to the design earthquake classification are verified.The peak flat values of class?,? and ? site in each classification of design earthquake are provided.(4)The 1546 strong motion records including horizontal and vertical are selected.Then statistical analysis the magnitude and the epicentral distance which influences on the curve of horizontal to vertical spectral ration on different sites.The feasibility of H/V spectral ratio method is used for site classification are verified.The standard spectral ratio curves on each sites are calculated based on the H/V spectral ratio method.Then the method could be provided references to study the site classification of Chinese strong-motion stations.An indicators of site classification was proposed based on the peak value of spectral ratio and the value of spectral ratio from 0.50 to 0.65 seconds.The results show that the two indicators have more higher accuracy on site ?,? class.