On Methods Of Calibrating Seismic Design Spectrum

Seismic design spectrum is the fundamental basis of the seismic design ofengineering structures. However, different regions and specifications give differentseismic design spectra. This is because one the one hand, data used in statistics isdifferent, and on the other, is also different. These statistical calibration methods,which have advantages and disadvantages, are strongly needed to be modified. Firstly,based on recent earthquake seismogram, this paper made a comparison of threetypical design spectra for statistical calibration method and point out the problemsexisting in various methods. Secondly, a simplified single-frequency ground motioncomponent model was introduced, and characteristics of ground motion werediscussed using this model. Based on the above comparison and analysis, optimizationimprovements made to the calibration method of seismic design spectra are as follows:(1) because ground vibration peak statistic PGV/PGA, PGA·PGD/PGV2are discrete,methods like weighted average replace the simple average, classify ground motionaccording to statistics are brought forward. These can improve statistical stability ofthe ground motion parameters.(2) a new normalized parameter was constructed using peak ground of PGA, PGV,PGD. This parameter makes coincident better with the trend of ground motionresponse spectra. What’s more, the design spectra can reflect characteristics of PGA,PGV, PGD in the short, medium and long three cycle segments.(3) points with clear meaning were selected as control points of segment fitting anddesign spectral calibration, which makes fitting calibration method have greatermaneuverability, and calibration results fit quite well with the original curve.With the improvements above, a new statistical calibration method of designspectrum was obtained. Then, the advantages and the problems of this method werediscussed. Finally, results of method were compared with results obtained from othermethods and causes of these differences are discussed followed. This paper canprovide references for the study of new seismic design spectra.