Study On Soil Site Amplification Effect Based On Site Period

Site conditions have an important effect on the propagation of seismic waves.It has been a focus of seismic engineering field at home and abroad to study the effect of site conditions on ground motion to reduce the potential earthquake risk of buildings.At present,according to some physical and mechanical indexes,the engineering site is divided into different types of sites,and the corresponding design ground motion parameters are stipulated accordingly.It is a common practice to distinguish the effects of site conditions on ground motion in seismic design codes of various countries.Overall,method of site classification achieved significant effect,played an important role in engineering anti-seismic,however,the current mainstream of site classification method is relatively rough,only considering two indicators,the shear wave velocity and ground cover layer thickness,ignore the influence of other factors,when the soil structure is relatively complex,may give the wrong site category discriminant result,bring dangers to seismic safety of engineering structures.This paper summarizes the existing research results at home and abroad,double parameters of site classification method in our country is taken as an example,for it can't reflect the infulence of soil structure and the ground motion parameter,put forward to the site period use for site classification index of the new site classification scheme,and statistical analysis of the various categories of the ground motion parameter.This paper mainly completed the following aspects of the research work.1.This paper summarizing the representative site classification methods at home and abroad,focusing on the advantages and disadvantages of site classification method in our country were analyzed,for the problem of the calculation depthon of equivalent shear wave velocity is shallow and can not be well reflect the effects of soil structure on the dynamic response,put forward by site period for site classification index to the idea of site category division,discussed the scientific and feasibility of the idea.2.In this paper,the concept of site period is expounded and reclassified,the determination methods of various site periods are systematically summarized,and based on the evaluation of various site period calculation formulae,the basic site period calculation formulae of layer by layer single degree of freedom method which can reflect the influence of soil structure are emphatically introduced.3.Drilling data were collected from 436 different types of sites nationwide.The basic period of different sites is calculated by using the single-degree-of-freedom method layer by layer,the distribution form of site period of different sites is analyzed,and a new site classification scheme with site period as index is proposed according to the distribution form of site period4.The calculation model of soil layer seismic response of the collected 436 sites was established,and 54 representative man-made ground motions were used as ground motion input to calculate the ground motion parameters of each site.Under the new site classification scheme,the amplification coefficient and the characteristic period of response spectrum of different types of sites are calculated,and the corresponding recommended values for reference in seismic design are given.