This article describes a hybrid simulation method to generate artificial ground motion time histories that are compatible with specified peak seismic acceleration, velocity and displacement as well as the target respo...This article describes a hybrid simulation method to generate artificial ground motion time histories that are compatible with specified peak seismic acceleration, velocity and displacement as well as the target response spectrum of absolute acceleration. First, based on traditional methods that match the target spectrum in the frequency domain, an initial acceleration time history was synthesized to satisfy the specified peak acceleration, target spectral acceleration and intensity envelope. Second, by using the inversion formula of the seismic input to a linear single-degree-of-freedom system and by superimposing a series of narrow-band time histories in the time domain, the initial time history is further modified to allow its peak velocity and displacement to approach the targets and improve its matching precision with the target spectrum. Numerical examples are provided to demonstrate that the proposed method achieves good agreement with the target values.展开更多
In this paper, response spectral characteristics of one-, two-, and three-lobe sinusoidal acceleration pulses are investigated, and some of their basic properties are derived. Furthermore, the empirical mode decomposi...In this paper, response spectral characteristics of one-, two-, and three-lobe sinusoidal acceleration pulses are investigated, and some of their basic properties are derived. Furthermore, the empirical mode decomposition （EMD） method is utilized as an adaptive filter to decompose the near-fault pulse-like ground motions, which were recorded during the September 20, 1999, Chi-Chi earthquake. These ground motions contain distinct velocity pulses, and were decomposed into high-frequency （HF） and low-frequency （LF） components, from which the corresponding HF acceleration pulse （if existing） and LF acceleration pulse could be easily identified and detected. Finally, the identified acceleration pulses are modeled by simplified sinusoidal approximations, whose dynamic behaviors are compared to those of the original acceleration pulses as well as to those of the original HF and LF acceleration components in the context of elastic response spectra. It was demonstrated that it is just the acceleration pulses contained in the near-fault pulse-like ground motion that fundamentally dominate the special impulsive dynamic behaviors of such motion in an engineering sense. The motion thus has a greater potential to cause severe damage than the far-field ground motions, i.e. they impose high base shear demands on engineering structures as well as placing very high deformation demands on long-period structures.展开更多
In this paper, a method, which synthesizes the artificial ground motion compatible with the specified peak velocity as well as the target acceleration response spectrum, was proposed. In this method, firstly, an initi...In this paper, a method, which synthesizes the artificial ground motion compatible with the specified peak velocity as well as the target acceleration response spectrum, was proposed. In this method, firstly, an initial acceleration time history α8^（0） （t）, which satisfies the prescribed peak ground acceleration, the target spectral acceleration ST（ω, ζ）,and the specified intensity envelope, is generated by the traditional method that generates the requency domain; secondly,α8^（0） （t）is further modulated by superimposing narrow-band time histories upon it in the time domain to make its peak velocity, approach the target peak ground velocity, and at the same time to improve its fitting precision to the target spectrum. Numerical examples show that this algorithm boasts high calculation precisions.展开更多
In order to study the differences in vertical component between onshore and offshore motions,the vertical-to-horizontal peak ground acceleration ratio(V/H PGA ratio) and vertical-to-horizontal response spectral ratio(...In order to study the differences in vertical component between onshore and offshore motions,the vertical-to-horizontal peak ground acceleration ratio(V/H PGA ratio) and vertical-to-horizontal response spectral ratio(V/H) were investigated using the ground motion recordings from the K-NET network and the seafloor earthquake measuring system(SEMS).The results indicate that the vertical component of offshore motions is lower than that of onshore motions.The V/H PGA ratio of acceleration time histories at offshore stations is about 50%of the ratio at onshore stations.The V/H for offshore ground motions is lower than that for onshore motions,especially for periods less than 0.8 s.Furthermore,based on the results in statistical analysis for offshore recordings in the K-NET,the simplified V/H design equations for offshore motions in minor and moderate earthquakes are proposed for seismic analysis of offshore structures.展开更多
In this paper,two new methods are introduced to fit response spectrum in generating earthquake acceleration time history.The first method is Adding Harmonic Wave in Time Domain(AHWTD).In this method, a control point o...In this paper,two new methods are introduced to fit response spectrum in generating earthquake acceleration time history.The first method is Adding Harmonic Wave in Time Domain(AHWTD).In this method, a control point of response spectrum is adjusted by adding a harmonic time history to the adjusted one.Three features of the method are that it has small cross interference,small amount of computation and it can give consideration to the amplitude envelope.The second one is Approximating Response Spectrum as a Whole(ARSW).This method has following feature. When adjust a time history that is decided by amplitude spectrum A k and phase spectrum φ k(k =0, 1, 2, …, n ), the mean square root of every relative error E j(j= 1, 2, …, M ) between response spectrum and object spectrum V r=∑Mj=1E 2 j/M is used to decide adjusting direction of any amplitude spectrum A k . Because E j and V r are functions of A k and φ k , the problem of fitting response spectrum in generating earthquake acceleration time history can be changed to a problem of finding minimum point of V r . Restricted by Nyquist frequency, AHWTD is not suitable for high frequencies of response spectrum. Restricted by frequency distribution of FFT, the density of control points in the low frequency part can′t be too dense for ARSW. But two methods can replenish each other and get such a good fitting effect that we can fit the given peak ground acceleration and peak ground velocity well at the same time.展开更多
基金National Natural Science Foundation of ChinaUnder Grant No.50278090
文摘This article describes a hybrid simulation method to generate artificial ground motion time histories that are compatible with specified peak seismic acceleration, velocity and displacement as well as the target response spectrum of absolute acceleration. First, based on traditional methods that match the target spectrum in the frequency domain, an initial acceleration time history was synthesized to satisfy the specified peak acceleration, target spectral acceleration and intensity envelope. Second, by using the inversion formula of the seismic input to a linear single-degree-of-freedom system and by superimposing a series of narrow-band time histories in the time domain, the initial time history is further modified to allow its peak velocity and displacement to approach the targets and improve its matching precision with the target spectrum. Numerical examples are provided to demonstrate that the proposed method achieves good agreement with the target values.
基金Natural Science Foundation of China Under Grant No. 50278090
文摘In this paper, response spectral characteristics of one-, two-, and three-lobe sinusoidal acceleration pulses are investigated, and some of their basic properties are derived. Furthermore, the empirical mode decomposition （EMD） method is utilized as an adaptive filter to decompose the near-fault pulse-like ground motions, which were recorded during the September 20, 1999, Chi-Chi earthquake. These ground motions contain distinct velocity pulses, and were decomposed into high-frequency （HF） and low-frequency （LF） components, from which the corresponding HF acceleration pulse （if existing） and LF acceleration pulse could be easily identified and detected. Finally, the identified acceleration pulses are modeled by simplified sinusoidal approximations, whose dynamic behaviors are compared to those of the original acceleration pulses as well as to those of the original HF and LF acceleration components in the context of elastic response spectra. It was demonstrated that it is just the acceleration pulses contained in the near-fault pulse-like ground motion that fundamentally dominate the special impulsive dynamic behaviors of such motion in an engineering sense. The motion thus has a greater potential to cause severe damage than the far-field ground motions, i.e. they impose high base shear demands on engineering structures as well as placing very high deformation demands on long-period structures.
基金National Natural Science Foundation of China (50278090).
文摘In this paper, a method, which synthesizes the artificial ground motion compatible with the specified peak velocity as well as the target acceleration response spectrum, was proposed. In this method, firstly, an initial acceleration time history α8^（0） （t）, which satisfies the prescribed peak ground acceleration, the target spectral acceleration ST（ω, ζ）,and the specified intensity envelope, is generated by the traditional method that generates the requency domain; secondly,α8^（0） （t）is further modulated by superimposing narrow-band time histories upon it in the time domain to make its peak velocity, approach the target peak ground velocity, and at the same time to improve its fitting precision to the target spectrum. Numerical examples show that this algorithm boasts high calculation precisions.
基金Project(2011CB013605)supported by the National Basic Research Development Program of China(973 Program)Projects(51178071,51008041)supported by the National Natural Science Foundation of ChinaProject(NCET-12-0751)supported by the New Century Excellent Talents Program in University of Ministry of Education of China
文摘In order to study the differences in vertical component between onshore and offshore motions,the vertical-to-horizontal peak ground acceleration ratio(V/H PGA ratio) and vertical-to-horizontal response spectral ratio(V/H) were investigated using the ground motion recordings from the K-NET network and the seafloor earthquake measuring system(SEMS).The results indicate that the vertical component of offshore motions is lower than that of onshore motions.The V/H PGA ratio of acceleration time histories at offshore stations is about 50%of the ratio at onshore stations.The V/H for offshore ground motions is lower than that for onshore motions,especially for periods less than 0.8 s.Furthermore,based on the results in statistical analysis for offshore recordings in the K-NET,the simplified V/H design equations for offshore motions in minor and moderate earthquakes are proposed for seismic analysis of offshore structures.
文摘In this paper,two new methods are introduced to fit response spectrum in generating earthquake acceleration time history.The first method is Adding Harmonic Wave in Time Domain(AHWTD).In this method, a control point of response spectrum is adjusted by adding a harmonic time history to the adjusted one.Three features of the method are that it has small cross interference,small amount of computation and it can give consideration to the amplitude envelope.The second one is Approximating Response Spectrum as a Whole(ARSW).This method has following feature. When adjust a time history that is decided by amplitude spectrum A k and phase spectrum φ k(k =0, 1, 2, …, n ), the mean square root of every relative error E j(j= 1, 2, …, M ) between response spectrum and object spectrum V r=∑Mj=1E 2 j/M is used to decide adjusting direction of any amplitude spectrum A k . Because E j and V r are functions of A k and φ k , the problem of fitting response spectrum in generating earthquake acceleration time history can be changed to a problem of finding minimum point of V r . Restricted by Nyquist frequency, AHWTD is not suitable for high frequencies of response spectrum. Restricted by frequency distribution of FFT, the density of control points in the low frequency part can′t be too dense for ARSW. But two methods can replenish each other and get such a good fitting effect that we can fit the given peak ground acceleration and peak ground velocity well at the same time.
