Study On Site Amplification Coefficient And Dynamic Amplification Coefficient Of Seismic Design Response Spectrum

As the primary basis of seismic design of structures and an important method ofdetermining earthquake loading, design response spectrum directly influences safety andeconomical efficiency of engineering seismic design. Scientific, reasonable and accurateseismic design response spectrum is still an important subject of seismic research anddesign in the world. With the technological advancements and rapid building of stations allover the world, a solid grounding of database and technical support are provided for studyon response spectrum.The maximum seismic effect coefficient in current Chinese seismic design code（GB50011-2010） only considers effect of the basic intensity, but not site condition.Earthquake damage shows the amplification of ground motion is different in various sites.The paper using715horizontal strong earthquake records grouped according to sitecondition, magnitude and epicenter distance, has got a group of site amplificationcoefficient, using peak ground acceleration of class II as earthquake ground motionintensity and the effective peak acceleration （the average of acceleration responsespectrum in0.1⁰.5s divided by2.5with5%damping ratio） as the calculation standard.The result shows site amplification coefficient increases with the softening of sites underthe same seismic intensity; site amplification coefficient increases as the ground motionintensity strengthens in the same site. On the basis of results, it has given proposed siteamplification coefficient applicable to10seismic design code.In the aspect of dynamic amplification coefficient, the paper briefly introducesdevelopment history of seismic design code and origin of β_max=2.25. Research suggests itonly considers the influence of site condition, but not magnitude and epicenter distance.dynamic amplification coefficient is studied as single factor and mult-factor consideringthe effects of site condition, magnitude and epicenter distance. The results shows thestatistics has great differences under various factors. And only considering the influence ofsite condition, it is very close to the value of seismic design code. To sum up, the groupconsidering site condition, magnitude and epicenter distance is more representative of theunderstanding level of seismic ground motion. Based on the statistical results, the proposed value of dynamic amplification coefficient is2.5.