Study On Seismic Performance Of RC Frame Structures On Thick-Covered Sites

Structural earthquake resistance is not only related to the characteristics of the source,the propagation path,and the characteristics of the structure itself.Site conditions have a greater impact on ground motion and the seismic performance of the structure.The impact of specific site conditions on the seismic performance of specific structures is the planning and engineering of seismic plots.Necessary considerations for seismic assessment.The main factors that influence the site conditions to the building's earthquake damage are the hardness of the soil layer and the thickness of the cover layer,which are manifested by the changes in the spectrum characteristics of the bedrock wave under different conditions,which in turn cause damage to the building.However,for a specific type of site,the refinement of considering the influence of different overlay thicknesses on the seismic performance of the structure is scarce,especially the damage of a particular thick overlay soil site to the seismic resistance of the structure under lowfrequency ground motions,which requires urgent further study.Therefore,based on the current two-parameter site classification standard for seismic codes,this paper selects the actual highwave velocity Class ? sites with different characteristics of soil cover thickness.Taking the RC frame structure based on the code design as an example,it systematically studies the different spectrum characteristics and strength of the bedrock wave excitation.Earthquake response law of site soil layer and seismic performance of structure.The main research work of this article is summarized as follows:(1)Sorted out,deduced and introduced related theories on this subject.It mainly includes three aspects of the frequency spectrum characteristics of ground motion,seismic response of soil layer and structural seismic performance analysis,and discusses the current research status,theoretical basis,research methods,application principles and application procedures of domestic and foreign researches respectively.The application advantages of response and Perform 3D elastoplastic time history analysis are the solid foundation of this project.(2)Using various methods to complete the analysis of the frequency spectrum characteristics of the ground motion.The Fourier transform,wavelet transform,and response spectrum were used to analyze the frequency spectrum characteristics of the real-site vibration records.Comparing the results of the fast Fourier transform and the one-dimensional continuous wavelet transform,the frequency domain characteristics of the two are basically consistent and can reflect the frequency domain characteristics of the ground motion;Response spectrum analysis can concretely transform the characteristics of ground motion into information that is convenient for structural engineers to use.The combination of the three methods can achieve reliable ground motion spectrum analysis.(3)The seismic response analysis of the soil layer considering the influence of soil cover thickness on high-velocity class II sites.A new generation of soil seismic response analysis method FCM is used to study the response law of target high-wave velocity Class ? sites with different soil thickness conditions under different intensity and different frequency characteristics of bedrock wave excitation.The results show that the calculated surface acceleration amplitude deviation meets the limit The site amplification effect under high intensity can be fully taken into account;as the peak acceleration of the bedrock wave input increases,the amplification factor of the surface acceleration response spectrum of the target site gradually decreases;under the same site covering conditions,the peak amplification factor of the bedrock wave It is 3-6 times,and changes slightly with the characteristics of the bedrock wave spectrum.Under different soil cover conditions,as the site cover thickness increases,the excellent period of the acceleration response spectrum develops toward the long period,and the low-frequency double-peak phenomenon is obvious.(4)The seismic performance analysis of the RC frame structure considering the influence of site conditions was completed.The professional seismic evaluation software Perform 3D was used to take the RC frame structure based on the design as an example to analyze the elastoplastic time history.The multi-angle study considered the seismic performance of the structure considering the characteristics of the bedrock wave and the high-velocity type II soil cover thickness.Under the different intensities of the two types of bedrock waves,the maximum peak deviations of the inter-layer displacement angles,interlayer shear forces,and floor displacements are large,and the phenomenon of long-term ground motion damage is significant;the same bedrock waves have different site effects at different strengths,and the goal The most unfavorable response of the structure appears in thick-covered soil,especially under low-frequency and thickcover conditions and the structure is more damaging.