Study Of Bidirectional Maximum Acceleration Response Spectrum Of Ground Motion

With the increase of the number of ground motion records and in-depth knowledge of earthquakes’ laws, our country has experienced several big adjustments of the seismic design response spectra, but so far, all the adjustments is to take the two horizontal components as two independent ground motion records for processing. In this paper, call the acceleration response spectrum calculated by this way as one-way acceleration response spectrum.For the same earthquake ground motion, as the earthquake instrument placed the different direction, the two horizontal components’ data is also different, thus the calculated one-way acceleration response spectrum value under certain period will also change, in this paper, call the the maximum value among the different values as the bidirectional maximum acceleration response spectrum value, and call the curve according to these values under different periods as bidirectional maximum acceleration response spectrum, be short of Bd M spectrum.In order to obtain Bd M spectrum characteristics and their similarities and differences between one-way spectrum characteristics, this paper conducted the following research work:① First describes the measurement and processing method of earthquake ground motion records. By learning the processing procedure of the most accepted digital earthquake acceleration records data, a brief narrative isintroduced from the following aspects:ground vibration measuring instruments, the ground motion record error analysis, seismic data processing method, and the application of ground motion records. This is the foundation for the analysis and calibration of ground motion records which will be discussed later in this paper.② Conclude the so far different definitions of the representation of two horizontal components,and specifically introduces the definitions of the representation in the recent version of the seismic zoning map used by USGS(U.S. Geological Survey).③ From the latest Pacific Earthquake Engineering Research Center(PEER) database collect 1702 set of ground motion records which is equivalent to Ⅱ site conditions of Chinese seismic code and has enough long effective period. Then classify these records according to the magnitude and distance, establish Bd M spectrum and one-way spectrum, research Bd M spectrum characteristics and their similarities and differences with one-way spectrum characteristics.④ After discussing the domestic and foreign existing two-way ground motion record selection and calibration methods, raise up a new method of two-way selection and calibration of ground motion records based on Bd M spectrum.⑤ To demonstrate the application of the method raised up by this paper, there will be an engineering example, which is established by 3D inelastic analysis program, PERFORM-3D, and then select 7 sets of ground motion records which is based on the raised up method of two-way selection and calibration of ground motion records. Finally, by inelastic dynamic nalysis of the engineering example under severe level earthquake, this paper compared its analysis results with the results calculated according to the Chinese seismic design code.Through the above work, the main conclusions are obtained:① Compared with the early use of analog earthquake records, a new generation of digital earthquake instruments’ meter band features have made a lot of improvement, based on the digital earthquake instrument recorded, ground motion records can provide more accurate long period component.② After the statistical analysis of 1702 sets of ground motion records, the conclusions are as follows: with the comparison of the spectra shape, Bd M spectrum is almost the same with one-way spectrum in the average level; With the comparison of the spectral statistical average value, Bd M spectrum is a one-way spectrum of 1.2-1.4 times, and with the comparison of the standard deviation, the former is roughly 1.1 to 1.4 times of the latter.③ Use inelastic analysis program PERFORM-3D to build the engineering example model, and then select ground motion records respectively according to the proposed method of two-way selection and calibration of ground motion records in this paper, based on the Bd M spectrum, and the method of Chinese seismic design code. Analyse the model under those selected records using inelastic dynamic way, then compared the two kinds of analysis results, the conclusion is as follows: Compared to the analysis results calculated according to the China’s seismic code, the analysis results calculated based on the Bd M spectrum of two-way selection and calibration method are significantly larger. From the aspect of the biggest displacement angle between the layers, the latter is about 1.55% ~ 25.50% and 5.13% ~ 24.51% larger than the former in X and Y direction respectively, and the average lager amplitude of X and Y were 14.39% and 14.08%; From the aspect of the biggest displacement of the vertices, the latter is about-0.65% ~ 23.90% and 6.01% ~ 26.53% larger than the former in X and Y direction respectively, and the average lager amplitude of X and Y were 15.41% and 16.66%; From the aspect of the largest base shear, the latter is about-0.17%~9.85% and 3.32%~13.62% larger than the former in X and Y direction respectively, and the average lager amplitude of X and Y were 5.5% and 8.27%; From the aspect of the maximum shear between the layers, the latter is about 3.0% ~ 9.8% and 3.3% ~ 13.6% larger than the former in X and Y direction respectively, and the average lager amplitude of X and Y were 6.2% and 8.3%.