Improvement Of Major Engineering Design Response Spectrum Shape And Calibration Method

In the field of engineering seismic and geotechnical engineering,response spectrum is a method used to express the intensity of earthquake ground motion,which is the basis of seismic design.The design response spectrum is derived from the seismic response spectrum,which is an expression of the average response of the dynamic response of different sites under the action of different strength earthquakes.The research on the design,expression and calibration methods of the design response spectrum shape is a basic issue that has long been concerned in the field of engineering earthquake resistance.How to give a design response spectrum curve that can more realistically reflect the spectral characteristics of the ground motion and the dynamic characteristics of the site is one of the hot issues in the seismic field of major engineering projects.Based on the existing research,this paper selects 1227 strong earthquake records at home and abroad for statistical analysis,carries out in-depth research on the shape and calibration method of the design response spectrum,gives a new design response spectrum expression method,and proposes New calibration method for site-specific response spectra.The main research contents and results are as follows:(1)The development process of seismic design response spectrum is summarized and sorted out,and the calibration principle of design response spectrum is introduced and commented in detail.By comparing and analyzing Newmark's three-parameter calibration method,two-parameter calibration method,least squares calibration method,differential evolution algorithm and genetic algorithm,the characteristics and applicability of various current calibration methods are discussed.Through analysis and discussion,the stipulation of the expression form and shape of the design response spectrum is the key issue to realize the reasonable calibration of the design response spectrum.(2)Based on the study of a large number of seismic acceleration response spectrum curves,a variety of regression analysis methods are used to fit the seismic acceleration response spectrum curve in pieces.Based on this,a new three-stage design is summarized and proposed.The response spectrum curve calibration model improves the current design response spectrum shape and calibration method.Different sections of the improved design response spectrum curve are composed of a quadratic function curve,a cubic function curve,and an exponential decline curve,respectively.The new design response spectrum uses curve fitting instead of the straight line fitting of the traditional design response spectrum in the rising section and the platform section,to a certain extent,reducing the dispersion caused by the expression of the original design response spectrum platform section to the calibration of the seismic response spectrum.(3)According to the three factors of site type,magnitude and epicentral distance,the 1,227 strong earthquake records participating in the statistics were grouped,and each response spectrum curve was calibrated according to the new design response spectrum expression form.By analyzing the calibration results,the characteristic parameters of the newly designed response spectrum(the maximum value of the design response spectrum ?max and the characteristic period Tg)are given,and the effects of the site type,magnitude,and epicentral distance on the design response spectrum expression and characteristic parameters are discussed.(4)In order to meet the needs of seismic safety evaluation of major engineering sites in China,a new calibration method of site-related response spectrum is proposed,and the new calibration method is compared with the commonly used calibration methods.At the same time,the application of the new method of site-specific response spectrum calibration proposed in this paper in engineering is realized through engineering examples.The results of the comparative analysis show that the calibration method proposed in this paper has relatively high accuracy and can more reasonably reflect the characteristics of the site-specific response spectrum.The design response spectrum is a kind of stipulation for the input of ground motion in the seismic design of the structure,and the rational design of the design response spectrum and the input method of the ground motion is the cornerstone of the seismic design of the structure.Since scientists applied seismic response spectrum to the field of engineering seismic design in the middle of the last century,most national seismic design codes have adopted acceleration response spectrum as the design spectrum,and the spectral parameters of different risk levels are used as the controlling ground motion parameters of the seismic design of the structure.In more than half a century of engineering applications,scientists and engineering technicians have never stopped researching and perfecting the design response spectrum to make it more reasonable to reflect the characteristics of site ground motion.The work in this paper has important scientific significance for enriching the theory of response spectrum,and has important practical value for promoting the engineering application of response spectrum.