Characteristic Analysis On Vertical Acceleration Peak And Response Spectrum Of LuShan Earthquake

In seismic design,it usually requires that the structure must satisfy the horizontal and vertical component of ground motion of the load requirements.It often ignores the vertical seismic loads only considering the gravity.In seismic design code of China,only in highly seismic region or near-field of large span structure,cantilever structure and tall structures the effect of vertical ground motion needs to be considered,and it takes 1/2 ~ 2/3 of the horizontal component based on experience.In recent years,with the increasing of strong motion record and the appearance of various kinds of special structures,the engineers and researchers put a value on the vertical seismic actions.This paper uses the strong motion records data of 171 set of major aftershocks of the 7.0 Lushan earthquakes in 2013,to systematically analyze the characteristics of the vertical ground motion,and have obtained some meaningful results.This paper mainly completed the following research works:1.The recent progress and the status of the vertical seismic action were summarised,the relevant provisions of the various vertical seismic actions on the domestic and international seismic code were concluded.The problems existed and the achievements obtained in this field were commented,and its effect on the seismic design of structure was analyzed.2.50 set of original records and 143 set of aftershock records of 8 bedrocks and 50 non-bedrocks in Sichuan and Yunnan province were collected.The regional geological structure and local site conditions were analyzed.This paper also analyzed 171 set of earthquake data and classified the sites of the records.3.The relationship between the vertical ground motion and horizontal ground motion.This article extracted the epicenter distance and peak accelerations of the three components from the strong motion records,and obtained the three components of absolute acceleration response spectrum according to the acceleration time history.Given the ratio F of the vertical peak acceleration(aVmax)and the horizontal peak acceleration(aHmax),and calculated the ratio P(T)of the vertical acceleration response spectrum(SaV)and horizontal acceleration response spectrum(SaH)in the same period.It also discussed and analyzed the influence of the data characteristics and major aftershock,site classification,epicenter distance,hanging wall and footwall on the ratio F and P(T)values,some engineering meaningful conclusions are obtained.4.The vertical ground motion parameters were counted.Based on the ground motion acceleration time history,the paper puts forward the amplification factor spectrum of each set of records,using the calibration of the sectional least square fitting method based on coordinate transformation to get the design spectrum,using the design spectrum statistical platform to get the three parameters of value,characteristics period and attenuation index.The influence of the site classification,epicenter distance and the major aftershock on these three parameters were discussed and analyzed.The paper put forward the value of vertical ground motion platforms,the characteristics period and attenuation index.This paper used the strong ground motion data of the Lushan earthquake to analyze the characteristics of vertical ground motions.It is obviously that the conclusions have its limitations.With the increasing density of seismic strong motion networks and new requirements of seismic design,it can foresee that the study of vertical ground motion is an important issue.The author hopes this article can promote the development of research in the vertical ground motion.Of course,due to the limited level of the author,some aspects of the issue cannot be exposited deeply,so an outlook of the further study in the future was proposed at the end of this paper.