Research Of Acceleration Response Spectra For Vertical Ground Motions Based On The Site Division Standard Of Current Seismic Design Code

Generally speaking, the component of vertical ground motion is about1/2～1/3of thecorresponding horizontal one. Compared with the horizontal part, the vertical part hasless impact on buildings, so for the general structure seismic design, the vertical groundmotion is not in the consideration. Seismic Design of Building (GB50011-2010)stipulates the acceleration response spectrum of vertical part: it equals65%of thecorresponding horizontal design response spectrum; the characteristic periods of thevertical response spectrum are adopted according to the design of first group. With theincrease of strong seismographic records, some vertical records are so high that it evenexceeds the motion of horizontal part. At the same time, with the increase of the longspan structures, many kinds of high rise structures and other complex structures, thistrend make the potential destruction of vertical seismic action become bigger and bigger.So further researching the characteristic parameters of vertical ground motion not onlyfeasible, but also has practical engineer value. So the characteristics of vertical designresponse spectra were studied in this paper. The main content of this paper include asfollows:（1） Based on the data of strong earthquake records in western United States, thedifferent parameters of vertical and horizontal ground motion in maximum designspectrums, characteristic periods and so on are considered in this article. The changerules of these parameters under the effect of soil conditions, magnitude and epicentraldistance are also studied in this paper. The article not only proposes the relationshipbetween the maximum of vertical spectrum and horizontal spectrum, but also shows theconnection of vertical and horizontal characteristic periods under the effect ofmagnitude, epicentral distance and soil conditions.（2） With the294vertical strips record actual strong earthquake (strong motionrecords) response spectrum which is classified by the current site categorization criteriaof the Code for Seismic of Building (GB50011-2010) in China, the methods of researchthe effect of site condition on maximum vertical response spectrum at each site areindicated in this article, the method categorize the ground motion intensity with EPAwhich is classified by Class II. The above analysis and comparison conclude that in thesame ground motion intensity, the vertical site coefficient increase with the site becomeweak, on the other hand, in the same site condition, the coefficient of vertical groundhas a tendency to decrease with the increase of ground motion intensity. Through computation and analysis, the proposal solutions of vertical ground coefficient underdifferent site classifications are given in this paper.（3）Site conditions not only have an effect to the maximum of vertical designspectrum, but also have an influence on the corresponding characteristic period. By theanalysis of actual seismic observation data, the rule shows that characteristic period ofvertical spectrum is smaller than the corresponding seismic code. Through computationand study, the article presents the proposed value of characteristic period and thecoefficient of vertical ground under the conditions of different site. Compared therecommended value of vertical design response spectrum with the average verticalresponse spectrum curves recorded by actual observation, the curves meet very well.Finally, the site coefficient and vertical characteristic period of the proposal are given.（4）By the analysis of data from the program of NGA, the focal mechanism and thesite condition’s effect to maximum design spectrum are studied in this paper. Throughcomputation and analysis, the article proposes the suggestion value of coefficient ofhorizontal and vertical ground under the site of strike-slip fault, reverse fault and normalfault.