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1.
空间相关的多点地震动合成(Ⅱ)合成实例 总被引：18，自引：3，他引：15
本文应用已提出的自功率谱、相干函数、视速度模型生成了空间相关的多点地震动时程。采用分段合成、乘强度包络函数的方法近似地考虑了地震动强度和频率尬发的非平稳性、生成的地震动符合空间相关性、传播性、随机性和非平稳性,可用于长结构多点输入地震反应分析。 相似文献
2.
2012年9月7日我国西南云贵交界彝良-威宁地区连续发生两次MS5.5和MS5.6中强地震,其时间间隔短,震中位置接近,震级相差很小,为中强地震地震动的随机特性分析研究提供了难得的强震动数据. 本文从集系与样本函数两方面考虑,通过加速度时程的相关函数研究了地震动随机过程的相关特性. 结果表明: 两次地震集系的相关矩阵均为随机相关,互相关矩阵较自相关矩阵表现出更强的随机性;两次地震在同一个台站记录的加速度时程所构成的集系,其相关性较两次地震单独构成的集系好;样本函数的相关函数均呈现不规则震荡衰减的特点,且两个采样值间时滞越大,其样本函数相关性越小. 相比大震(如我国台湾地区的集集地震),中强地震地震动记录的相关矩阵及分解后的自相关函数均表现出不同的特点. 由于这两次地震的地震动幅值相比大震较小,土层非线性影响较弱,故本文结果为认识地震动的随机特性提供了新的参考依据. 相似文献
3.
Djilali Berkane Hakima Harichane Zamila Çelebi Erkan Elachachi Sidi Mohammed 《地震工程与工程振动(英文版)》2019,18(3):497-509
The goal of this study is to provide a stochastic method to investigate the effects of the randomness of soil properties due to their natural spatial variability on the response spectra spatial variation at sites with varying conditions. For this purpose, Monte Carlo Simulations are used to include the variability of both incident ground motion and soil parameters in the response spectra by mean of an appropriate coherency loss function and a site-dependent transfer function, respectively. The approach is built on the assumption of vertical propagation of SH type waves in soil strata with uncertain parameters. The response spectra are obtained by numerical integration of the governing equation of a single-degree-of-freedom(SDOF) system under non-stationary site-dependent and spatially varying ground motion accelerations simulated with non-uniform spectral densities and coherency loss functions. Numerical examples showed that randomness of soil properties significantly affects the amplitudes of the response spectra, indicating that as the heterogeneity induced by the randomness of the parameters of the medium increases, the spectral ordinates attenuate. 相似文献
4.
H. HAO 《地震工程与结构动力学》1996,25(6):599-610
Due to the inherent difficulty in directly recording the rotational ground motions, torsional ground motions have to be estimated from the recorded spatially varying translational motions. In this paper, an empirical coherency function, which is based on the recorded motions at the SMART-1 array, is suggested to model the spatial variation of translational motions. Then, the torsional ground motion power spectral density function is derived. It depends on the translational motion power spectral density function and the coherency function. Both the empirical coherency function and the torsional motion power spectral density function are verified by the recorded motions at the SMART-1 array. The response spectra of the torsional motions are also estimated. Discussion on the relations between the torsional motion response spectrum and the corresponding translational motion response spectrum is made. Numerical results presented can be used to estimate the torsional ground motion power spectral density function and response spectrum. 相似文献
5.
This paper presents a novel approach to model and simulate the multi-support depth-varying seismic motions (MDSMs) within heterogeneous offshore and onshore sites. Based on 1D wave propagation theory, the three-dimensional ground motion transfer functions on the surface or within an offshore or onshore site are derived by considering the effects of seawater and porous soils on the propagation of seismic P waves. Moreover, the depth-varying and spatial variation properties of seismic ground motions are considered in the ground motion simulation. Using the obtained transfer functions at any locations within a site, the offshore or onshore depth-varying seismic motions are stochastically simulated based on the spectral representation method (SRM). The traditional approaches for simulating spatially varying ground motions are improved and extended to generate MDSMs within multiple offshore and onshore sites. The simulation results show that the PSD functions and coherency losses of the generated MDSMs are compatible with respective target values, which fully validates the effectiveness of the proposed simulation method. The synthesized MDSMs can provide strong support for the precise seismic response prediction and performance-based design of both offshore and onshore large-span engineering structures. 相似文献
6.
This paper studies the effect of coherency loss and wave passage on the seismic torsional response of three‐dimensional, multi‐storey, multi‐span, symmetric, linear elastic buildings. A model calibrated against statistical analyses of ground motion records in Mexico City is used for the coherency function. The structural response is assessed in terms of shear forces in structural elements. Incoherence and wave passage effects are found to be significant only for columns in the ground level of stiff systems. The increase of column shears in the ground level is much higher for soft than for firm soil conditions. For the torsionally stiff systems considered, it is found that incoherent and phase‐delayed ground motions do not induce a significant rotational response of the structure. The use of a code eccentricity to account for torsion due to ground motion spatial variation is assessed. On firm soil, the use of a base shear along with an accidental eccentricity results in highly overestimated shear forces; however, for soft soil conditions, code formulations may result in underestimated shear forces. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
7.
A criterion is developed for the simulation of realistic artificial ground motion histories at soft‐soil sites, corresponding to a detailed ground motion record at a reference firm‐ground site. A complex transfer function is defined as the Fourier transform of the ground acceleration time history at the soft‐soil site divided by the Fourier transform of the acceleration record at the firm‐ground site. Working with both the real and the imaginary components of the transfer function, and not only with its modulus, serves to keep the statistical information about the wave phases (and, therefore, about the time variation of amplitudes and frequencies) in the algorithm used to generate the artificial records. Samples of these transfer functions, associated with a given pair of soft‐soil and firm‐ground sites, are empirically determined from the corresponding pairs of simultaneous records. Each function included in a sample is represented as the superposition of the transfer functions of the responses of a number of oscillators. This formulation is intended to account for the contributions of trains of waves following different patterns in the vicinity of both sites. The properties of the oscillators play the role of parameters of the transfer functions. They vary from one seismic event to another. Part of the variation is systematic, and can be explained in terms of the influence of ground motion intensity on the effective values of stiffness and damping of the artificial oscillators. Another part has random nature; it reflects the random characteristics of the wave propagation patterns associated with the different events. The semi‐empirical model proposed recognizes both types of variation. The influence of intensity is estimated by means of a conventional one‐dimensional shear wave propagation model. This model is used to derive an intensity‐dependent modification of the values of the empirically determined model parameters in those cases when the firm‐ground earthquake intensity used to determine these parameters differs from that corresponding to the seismic event for which the simulated records are to be obtained. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
8.
Stochastic simulation of regionalized ground motions using wavelet packets and cokriging analysis 
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下载免费PDF全文 Performance‐based earthquake engineering often requires ground‐motion time‐history analyses to be performed, but very often, ground motions are not recorded at the location being analyzed. The present study is among the first attempt to stochastically simulate spatially distributed ground motions over a region using wavelet packets and cokriging analysis. First, we characterize the time and frequency properties of ground motions using the wavelet packet analysis. The spatial cross‐correlations of wavelet packet parameters are determined through geostatistical analysis of regionalized ground‐motion data from the Northridge and Chi‐Chi earthquakes. It is observed that the spatial cross‐correlations of wavelet packet parameters are closely related to regional site conditions. Furthermore, using the developed spatial cross‐correlation model and the cokriging technique, wavelet packet parameters at unmeasured locations can be best estimated, and regionalized ground‐motion time histories can be synthesized. Case studies and blind tests using data from the Northridge and Chi‐Chi earthquakes demonstrate that the simulated ground motions generally agree well with the actual recorded data. The proposed method can be used to stochastically simulate regionalized ground motions for time‐history analyses of distributed infrastructure and has important applications in regional‐scale hazard analysis and loss estimation. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
9.
This paper proposes a computational procedure for the conditional simulation of spatially variable seismic ground motions for long span bridges with multiple supports. The seismic ground motions, with part of their time histories measured at some supports, are regarded as zero‐mean nonstationary random processes characterized by predefined evolutionary power spectral density. To conditionally simulate unknown seismic ground motion time histories at other supports, the Kriging method is first described briefly for the conditional simulation of a random vector comprised of zero‐mean Gaussian variables. The multivariate oscillatory processes characterized by the evolutionary power spectral density matrix are then introduced, and the Fourier coefficients of the oscillatory processes and their covariance matrix are derived. By applying the Kriging method to the random vector of the Fourier coefficients and using the inverse Fourier transform, unknown nonstationary seismic ground motion time histories can be simulated. A numerical example is selected to demonstrate capabilities of the proposed simulation procedure, and the results show that the procedure can ensure unbiased time‐varying correlation functions, especially the cross correlation between known and unknown time histories. The procedure is finally applied to the Tsing Ma suspension bridge in Hong Kong to generate ground accelerations at its multiple supports using limited seismic records. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
10.
A previously developed simplified model of ground motion amplification is applied to the simulation of acceleration time histories at several soft‐soil sites in the Valley of Mexico, on the basis of the corresponding records on firm ground. The main objective is to assess the ability of the model to reproduce characteristics such as effective duration, frequency content and instantaneous intensity. The model is based on the identification of a number of parameters that characterize the complex firm‐ground to soft‐soil transfer function, and on the adjustment of these parameters in order to account for non‐linear soil behavior. Once the adjusted model parameters are introduced, the statistical properties of the simulated and the recorded ground motions agree reasonably well. For the sites and for the seismic events considered in this study, it is concluded that non‐linear soil behavior may have a significant effect on the amplification of ground motion. The non‐linear soil behavior significantly affects the effective ground motion duration for the components with the higher intensities, but it does not have any noticeable influence on the lengthening of the dominant ground period. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
11.
This paper investigates the effects of random variations of soil properties on site amplification of seismic waves. First, based on attenuation laws and the filtered Tajimi–Kanai spectrum, seismic motion at the base rock of a soil site is stochastically generated according to an assumed earthquake with a given magnitude and epicentral distance. Motions on the surface of this layered random soil site are calculated by nonlinear wave propagation methods, and by assuming the incoming seismic wave consisting of SH wave or combined P and SV waves. Soil properties, including shear modulus, damping ratio and mass density, as well as ground water level are considered as random in the numerical calculation. The Rosenblueth method is used to solve the random dynamic responses of the soil site. Parametric calculations are performed to investigate the effects of various parameters on site amplification of seismic waves. The mean and maximum ground motions on surface of the site are estimated. Numerical results indicate that the estimated surface motions differ substantially if the random variations of soil properties and soil saturation level are taken into consideration in the analysis. 相似文献
12.
The performance‐based design of lifeline systems requires spatially variable seismic excitations at the structures' supports that are consistent with prescribed seismic ground motion characteristics and an appropriate spatial variability model—such motions can be obtained through conditional simulation. This work revisits the concept of conditional simulation and critically examines the conformity of the generated motions with the characteristics of the target random field and observations from data recorded at dense instrument arrays. Baseline adjustment processing techniques for recorded earthquake accelerograms are extended to fit the requirements of simulated and conditionally simulated spatially variable ground motions. Emphasis is placed on the use of causal vs acausal filtering in the data processing. Acceleration, velocity and displacement time histories are evaluated in two example applications of the approach. The first application deals with a prescribed synthetic time history that incorporates nonstationarity in the amplitude and frequency content of the motions and depends on earthquake magnitude, source–site distance and local soil conditions; this example results in zero residual displacements. The second application considers as prescribed time history a recording in the vicinity of a fault and yields nonzero residual displacements. It is shown that the conditionally simulated time histories preserve the characteristics of the prescribed ones and are consistent with the target random field. The results of this analysis suggest that the presented methodology provides a useful tool for the generation of spatially variable ground motions to be used in the performance‐based design of lifeline systems. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
13.
Hong Hao 《地震工程与结构动力学》1998,27(1):91-103
During the recent major earthquakes, some bridges suffered severe damage due to the pull-off-and-drop collapse of their decks. This is due to the large differential movements of the adjacent spans of bridges during strong shaking compared to the seating lengths provided. The differential movements are primarily due to the different vibration properties of adjacent spans and non-uniform ground excitations at the bridge supports. This paper analyses the effects of various bridge and ground motion parameters on the required seating lengths for bridge decks to prevent the pull-off-and-drop collapse. The random vibration method is used in the analysis. A two-span bridge model with different span lengths and vibration frequencies and subjected to various spatially varying ground excitations is analysed. Non-uniform spatial ground motions are modelled by the filtered Tajimi–Kanai power spectral density function and an empirical coherency function. Ground motions with different intensities, different cross-correlations and different site conditions are considered in the study. The required seating lengths for bridge decks are calculated. Numerical results are presented and discussed with respect to different bridge vibration and ground motion properties. © 1998 John Wiley & Sons, Ltd. 相似文献
14.
It is shown that the observed loss of coherency of synthetic strong motion on ground surface for separation distances less than about 100 m can be described in terms of the dispersion of strong motion waves. Additional contributions to the loss of coherency from variations of material properties in the soil and from geometrical departures from perfectly flat ground surface and irregular layer geometries are not considered in this paper. It is also shown that the synthetic surface displacements over a large rectangular area (100×100 m) on ground surface can be described well by a flat surface undergoing translations and rotations only, and with only minor departures from the plane flat surface. 相似文献
15.
16.
Coherency analysis of accelerograms recorded by the UPSAR array during the 2004 Parkfield earthquake 下载免费PDF全文
下载免费PDF全文 Spatial variability of near‐fault strong motions recorded by the US Geological Survey Parkfield Seismograph Array (UPSAR) during the 2004 Parkfield (California) earthquake is investigated. Behavior of the lagged coherency for two horizontal and the vertical components is analyzed by separately examining the decay of coherency with frequency and distance. Assumptions, approximations, and challenges that are involved in estimation of the coherency from recorded data are presented in detail. Comparison of the UPSAR coherency estimates with coherency models that are commonly used in engineering practice sheds light on the advantages and limitations of different approaches to modeling the coherency, as well as on similarities and differences in the spatial variability exhibited by seismic ground motion arrays at different sites. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
17.
土层场地对地震动的影响较大,建(构)筑物的选址及其抗震设防必须考虑土层场地的放大作用,以避免或减轻其震害.汶川地震中,布设在渭河盆地中的数字强震动台网共有27个台站(包括2个基岩台站和25个土层台站)获得良好的主震加速度时程.利用这些加速度时程,选择汤峪台做为参考场地,基于考虑几何衰减的传统谱比法分析研究了25个土层场... 相似文献
18.
Probabilistic seismic hazard analysis (PSHA) was performed to determine two alternate magnitude-distance combinations for the 475 yr event, and the worst-case scenario event in Perth, Western Australia. Regional strong ground motion (SGM) time histories on rock sites are used to modify an eastern North America (ENA) seismic model to suit southwest Western Australian (SWWA) conditions. This model is then used to stochastically simulate a set of 475 yr design events and a set of worst-case scenario event for rock sites in the Perth metropolitan area (PMA). The simulated time histories are then used as input to typical soft soil sites in the PMA to estimate surface ground motions. The spectral accelerations of the ground motions on rock and soil sites are calculated and compared with the corresponding design spectra defined in current and previous Australian earthquake loading code. Discussions of the adequacy of the code spectra and the differences to ours, along with implications on structural response and damage are made. 相似文献
19.
Risk assessment of spatially distributed building portfolios or infrastructure systems requires quantification of the joint occurrence of ground‐motion intensities at several sites, during the same earthquake. The ground‐motion models that are used for site‐specific hazard analysis do not provide information on the spatial correlation between ground‐motion intensities, which is required for the joint prediction of intensities at multiple sites. Moreover, researchers who have previously computed these correlations using observed ground‐motion recordings differ in their estimates of spatial correlation. In this paper, ground motions observed during seven past earthquakes are used to estimate correlations between spatially distributed spectral accelerations at various spectral periods. Geostatistical tools are used to quantify and express the observed correlations in a standard format. The estimated correlation model is also compared with previously published results, and apparent discrepancies among the previous results are explained. The analysis shows that the spatial correlation reduces with increasing separation between the sites of interest. The rate of decay of correlation typically decreases with increasing spectral acceleration period. At periods longer than 2 s, the correlations were similar for all the earthquake ground motions considered. At shorter periods, however, the correlations were found to be related to the local‐site conditions (as indicated by site Vs30 values) at the ground‐motion recording stations. The research work also investigates the assumption of isotropy used in developing the spatial correlation models. It is seen using the Northridge and Chi‐Chi earthquake time histories that the isotropy assumption is reasonable at both long and short periods. Based on the factors identified as influencing the spatial correlation, a model is developed that can be used to select appropriate correlation estimates for use in practical risk assessment problems. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
20.
K. AfifChaouch B. Tiliouine M. Hammoutene R. Sigbjörnsson R. Rupakhety 《Bulletin of Earthquake Engineering》2016,14(4):1195-1217
Spatial variability of ground motions has significant influence on dynamic response of extended structures such as bridges and tunnels. In this study, the widely used finite-source ground motion simulation approach, the so-called Empirical Green’s Function (EGF) method, is extended to synthesize seismic motions across an array of stations located at bedrock in the epicentral region of the 1980 El-Asnam region (North-West Algeria). The target event being simulated is the October 10 1980 \( M_{s} = 7.2 \) Earthquake, and the EGF is obtained from the ground motion recorded at Sogedia Factory station during the 8 November 1980 \( M_{L} = 5.6 \) aftershock. Coherency functions are then estimated from the simulated ground accelerations. A parametric study investigating the influence of shear wave velocity, earthquake magnitude, and epicentral distance is conducted by simulating ground acceleration for different scenarios using the Hybrid Green’s Function method. The main finding of the study is that finite source effects can cause significant loss in coherency at bedrock in the near-field. In the far-field, the source effect alone does not seem to produce incoherent motion, which implies that scattering and local site effects could be dominating there. Furthermore, coherency functions are found to be more sensitive to inter-station separation in the near-field than in the far-field. Increasing shear wave velocity seems to increase coherency functions, and larger earthquakes seem to produce more incoherent motion than smaller ones. The simulation method presented here produces incoherent motion mainly due to the finite source effect, while path effects are partially accounted for through the EGF, and local site effects are not considered. In this sense, the estimated coherency functions represent that of plane waves. A parametric model of plane wave coherency is calibrated and presented based on the simulation results. The results indicate that the parametric model can be used as a first approximation, and at least an upper bound of lagged coherency in the near-field region of the El-Asnam Earthquake scenario. This model could be useful in random vibration analysis or generation of spatially variable ground motion for time history analysis of lifeline structures in the study area. 相似文献