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1.
Ground motion selection for seismic slope displacement analysis using a generalized intensity measure distribution method 
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下载免费PDF全文 《地震工程与结构动力学》2018,47(5):1352-1359
Selecting ground motions based on the generalized intensity measure distribution (GIMD) approach has many appealing features, but it has not been fully verified in engineering practice. In this paper, several suites of ground motions, which have almost identical distributions of spectral acceleration (SA) ordinates but different distributions of non‐SA intensity measures, are selected using the GIMD‐based approach for a given earthquake scenario. The selected ground motion suites are used to compute the sliding displacements of various slopes. Comparisons of the resulting displacements demonstrate that selecting ground motions with biased distribution of some intensity measures (ie, Arias intensity) may yield systematic biases (up to 60% for some slope types). Therefore, compared to the ground motions selected based only on the distribution of SA ordinates, the ground motion suite selected by the GIMD‐based approach can better represent the various characteristics of earthquake loadings, resulting in generally unbiased estimation in specific engineering applications. 相似文献
2.
Although for many years it was thought that amplitude scaling of acceleration time series to reach a target intensity did not introduce any bias in the results of nonlinear response history analyses, recent studies have showed that scaling can lead to an overestimation of deformation demands with increasing scale factors. Some studies have suggested that the bias can be explained by differences in spectral shape between the response spectra of unscaled and scaled records. On the basis of these studies, some record selection procedures assume that if records are selected using spectral-shape-matching procedures, amplitude scaling does not induce any bias on the structural response. This study evaluates if bias is introduced on lateral displacement demands and seismic collapse risk estimates even when spectral shape is carefully taken into consideration when selecting ground motions. Several single-degree-of-freedom and multiple-degree-of-freedom systems are analyzed when subjected to unscaled and scaled ground motions selected to approximately match the mean and the variance of the conditional spectrum at the target level of intensity. Results show that an explicit consideration of spectral shape is not enough to avoid a systematic overestimation of lateral displacement demands and collapse probabilities as the scale factor increases. Moreover, the bias is observed in practically all cases for systems with strength degradation and it increases with decreasing period and decreasing lateral strength relative to the strength required to remain elastic. Key reasons behind the bias are presented by evaluating input energy, causal parameters, and damaging pulse distributions in unscaled and scaled ground motion sets. 相似文献
3.
A broader consensus on the number of ground motions to be used and the method of scaling to be adopted for nonlinear response history analysis (RHA) of structures is yet to be reached. Therefore, in this study, the effects of selection and scaling of ground motions on the response of seismically isolated structures, which are routinely designed using nonlinear RHA, are investigated. For this purpose, isolation systems with a range of properties subjected to bidirectional excitation are considered. Benchmark response of the isolation systems is established using large sets of unscaled ground motions systematically categorized into pulse-like, non-pulse-like, and mixed set of motions. Different subsets of seven to 14 ground motions are selected from these large sets using (a) random selection and (b) selection based on the best match of the shape of the response spectrum of ground motions to the target spectrum. Consequences of weighted scaling (also commonly referred to as amplitude scaling or linear scaling) as well as spectral matching are investigated. The ground motion selection and scaling procedures are evaluated from the viewpoint of their accuracy, efficiency, and consistency in predicting the benchmark response. It is confirmed that seven time histories are sufficient for a reliable prediction of isolation system displacement demands, for all ground motion subsets, selection and scaling procedures, and isolation systems considered. If ground motions are selected based on their best match to the shape of the target response spectrum (which should be preferred over randomly selected motions), weighted scaling should be used if pulse-like motions are considered, either of weighted scaling or spectral matching can be used if non-pulse-like motions are considered, and an average of responses from weighted-scaled and spectrum-matched ground motions should be used for a mixed set of motions. On the other hand, the importance of randomly selected motions in representing inherent variability of response is recognized and it is found that weighted scaling is more appropriate for such motions. 相似文献
4.
The conditional spectrum (CS, with mean and variability) is a target response spectrum that links nonlinear dynamic analysis back to probabilistic seismic hazard analysis for ground motion selection. The CS is computed on the basis of a specified conditioning period, whereas structures under consideration may be sensitive to response spectral amplitudes at multiple periods of excitation. Questions remain regarding the appropriate choice of conditioning period when utilizing the CS as the target spectrum. This paper focuses on risk‐based assessments, which estimate the annual rate of exceeding a specified structural response amplitude. Seismic hazard analysis, ground motion selection, and nonlinear dynamic analysis are performed, using the conditional spectra with varying conditioning periods, to assess the performance of a 20‐story reinforced concrete frame structure. It is shown here that risk‐based assessments are relatively insensitive to the choice of conditioning period when the ground motions are carefully selected to ensure hazard consistency. This observed insensitivity to the conditioning period comes from the fact that, when CS‐based ground motion selection is used, the distributions of response spectra of the selected ground motions are consistent with the site ground motion hazard curves at all relevant periods; this consistency with the site hazard curves is independent of the conditioning period. The importance of an exact CS (which incorporates multiple causal earthquakes and ground motion prediction models) to achieve the appropriate spectral variability at periods away from the conditioning period is also highlighted. The findings of this paper are expected theoretically but have not been empirically demonstrated previously. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
5.
地震动记录的合理选取对预测结构响应有着重要的作用。本文通过对风雨操场建筑混合结构的抗震性能分析,提出了一种对水平及竖向地震动频谱特性均进行控制的改进选波方法。为了评价不同选波方法的可靠性和有效性,根据初选条件选取55组三向地震动记录,并以55组地震动的统计反应谱作为目标反应谱,以55组记录计算的结构响应均值作为"预测值",通过与单周期点和双频段选波方法的计算结果对比,分析表明:改进选波方法计算的结构基底剪力、柱顶位移、支座位移和网架竖向位移的相对误差和变异系数均小于前两种选波方法,其计算结果更加可靠有效。 相似文献
6.
Newmark design spectra have been implemented in many building codes, especially in building codes for critical structures. Previous studies show that Newmark design spectra exhibit lower amplitudes at high frequencies and larger amplitudes at low frequencies in comparison with spectra developed by statistical methods. To resolve this problem, this study considers three suites of ground motions recorded at three types of sites. Using these ground motions, influences of the shear-wave velocity, earthquake magnitudes, source-to-site distances on the ratios of ground motion parameters are studied, and spectrum amplification factors are statistically calculated. Spectral bounds for combinations of three site categories and two cases of earthquake magnitudes are estimated. Site design spectrum coefficients for the three site categories considering earthquake magnitudes are established. The problems of Newmark design spectra could be resolved by using the site design spectrum coefficients to modify the spectral values of Newmark design spectra in the acceleration sensitive, velocity sensitive, and displacement sensitive regions. 相似文献
7.
Structure-specific selection of earthquake ground motions for the reliable design and assessment of structures 总被引：1，自引：1，他引：0
A decision support process is presented to accommodate selecting and scaling of earthquake motions as required for the time domain analysis of structures. Code-compatible suites of seismic motions are provided being, at the same time, prequalified through a multi-criterion approach to induce response parameters with reduced variability. The latter is imperative to increase the reliability of the average response values, normally required for the code-prescribed design verification of structures. Structural attributes like the dynamic characteristics as well as criteria related to variability of seismic motions and their compliance with a target spectrum are quantified through a newly introduced index, δ sv–sc , which aims to prioritize motions suites for response history analysis. To demonstrate the applicability of the procedure presented, the structural model of a multi-story building was subjected to numerous suites of motions that were highly ranked according to both the proposed approach (δ sv–sc ) and the conventional one (δ conv ), that is commonly used for earthquake records selection and scaling. The findings from numerous linear response history analyses reveal the superiority of the proposed multi-criterion approach, as it extensively reduces the intra-suite structural response variability and consequently, increases the reliability of the design values. The relation between the target reliability in assessing structural response and the size of the suite of motions selected was also investigated, further demonstrating the efficiency of the proposed selection procedure to achieve higher response reliability levels with smaller samples of ground motion. 相似文献
8.
An efficient method for selecting and scaling ground motions matching target response spectrum mean and variance 下载免费PDF全文
下载免费PDF全文 The purpose of this study is to propose an accurate and efficient method for selecting and scaling ground motions matching target response spectrum mean and variance, which does not require excessive computation and simulation. In the proposed method, a desired number of ground motions are sequentially scaled and selected from a ground motion library without iterations. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
9.
Response spectrum matching is commonly used to generate ground motions with response spectra matching a scenario target spectrum. There is some debate in the literature about whether spectrum‐matched motions lead to biased structural analysis results. Furthermore, there are no objective, quantitative criteria available for deciding whether a ground motion has been manipulated excessively by spectrum matching, and whether large modification may also lead to bias. This study investigates both of these issues by presenting the results of structural analysis using two reinforced concrete moment frame models and two earthquake scenarios, with suites of unmatched and matched ground motions. Through comparison with a robust benchmark, it is shown that no significant bias is introduced by spectrum matching. The period range and target damping values for matching are also investigated, and matching up to three times the fundamental period is shown to be beneficial in reducing dispersion in the results. Finally, these analyses were also used to investigate whether large changes in the ground motion lead to biased analysis results. Several potential measures of change are investigated, including those based on peak absolute ground motion, cumulative squared ground motion (absolute or normalized), and input energy into single‐degree‐of‐freedom systems. Although no systematic, statistically significant correlation is found for the analysis results in terms of any of these measures of change, tentative criteria are proposed, which may be used by analysts to aid in the decision of whether to accept or reject a spectrum‐matched motion. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
10.
在PEER地震动数据库(PGMD)的基础上, 结合近几年国内外特大地震的地面运动记录, 建立了地面运动数据库, 同时根据日本MW9.0特大地震获得的141组记录进行统计回归建立加速度反应谱衰减关系, 并采用条件均值反应谱法, 即设定地震与结构概率需求结合的方法选择地面运动. 选波实例表明, 当设定地震为特大地震时, 基于条件均值反应谱法选取地面运动记录时, 扩展数据库中大震记录并建立符合大震记录加速度反应谱的衰减关系是十分必要与迫切的. 该思路为进一步研究结构动态时程分析中地面运动记录选取问题及所选记录提供了依据. 相似文献
11.
双向地震动作用的拟等延性系数谱 总被引：1，自引：0，他引：1
首先建立了以强度折减系数表述的恢复力特性满足二维屈服面模型的理想弹塑性单质点系统(它在2个相互垂直的主轴方向上分别具有水平平动自由度)在双向地震动作用下的归一化运动方程。然后引入单向地震动作用下等延性系数的强度折减系数谱,给出了双向地震动作用的拟等延性系数谱(定义为系统分别承受双向和单向地震动作用,在同一主轴方向上的最大位移反应之比)最后通过硬土场地10组双向地震动记录拟等延性系数谱的统计平均结果,分析了结构周期、位移延性系数和阻尼等因素对谱值及结构双向地震反应的影响。结果表明,双向地震动作用与单向地震动作用相比主要增加结构较长周期方向的最大位移反应。若在基于位移的抗震设计中降低结构较短周期方向的设计位移延性系数,可在一定程度上降低双向地震动的不利影响。因定义的谱为比值形式,阻尼对其影响不大。 相似文献
12.
The validity of the response spectrum concept for determining loads in structures excited by differential earthquake ground motion is examined. It is shown that the common definition of response spectrum for synchronous ground motion can be reconciled to remain valid in cases when the columns of extended structures experience different motions. Then, a relative displacement response spectrum for design of first-storey columns, SDC(T, δ, ζ, τ), is defined. In addition to natural period, T, and fraction of critical damping, ζ, this spectrum depends also on the ‘travel time’, τ (of the waves in the soil over distances about one half width, or length of the structure), and on a factor, δ, specifying the relative displacement of the first floor. It is shown how this spectrum can be determined using existing empirical scaling equations for relative displacement spectra SD(T, ζ) and for peak velocity and peak acceleration of strong ground motion. These new spectra are illustrated for a horizontal component of a record in the near field of the 1994 Northridge earthquake. The results show that differential motions are more important for short period (stiff) than for longer period (flexible) structures, and for structures founded on softer ground (small shear wave velocity). © 1997 by John Wiley & Sons, Ltd. 相似文献
13.
Iunio Iervolino Carmine Galasso Roberto Paolucci Francesca Pacor 《Bulletin of Earthquake Engineering》2011,9(6):1761-1778
This paper introduces REXELite, an internet version of REXEL, a software for automatic selection of ground motion suites for
nonlinear dynamic analysis of structures. REXELite was developed with the aim of integrating an advanced earthquake records’
repository, such as the ITalian ACcelerometric Archive (ITACA), with a tool to define seismic input for engineering seismic
analysis according to international standards (with priority to Europe). In fact, REXELite allows to define target design
spectra according either to Eurocode 8 or to the Italian building code, and to search ITACA for suitable sets of seven records
(comprised of one or two horizontal ground motion components) matching such target spectra: on average, in a user-specified
period range, and with the desired tolerance. The records in the set also have, individually and according to some criteria,
the most similar spectral shape with respect to that of the code. Selection options include magnitude, source-to-site distance,
soil conditions and, if desired, linear scaling of records to reduce further record-to-record variability of the selected
suite. 相似文献
14.
A novel ground motion selection and modifications method to perform response history analysis of structures is presented in this paper. Currently, the accessibility of ground motion information permits the analysis of structures using real ground motion data. Predicting the dynamic behavior of structures is a primary objective; therefore, the selection of a set of ground motions that shows a reduction in the variability of the structural response and accuracy in preserving the median demand is a challenging task. The new selection and scaling procedure emerges from comparing a set of horizontal ground motions at various ranges of frequency. In this study, the conditional mean spectrum and the design response spectrum are used as target spectra, and the records that give an applicable and compelling contribution to the hazard are considered. It is possible to obtain a set of ground motions with similar seismic severity by matching the target spectrum at the period of interest T ref , where the scaled spectrum should have an equivalent Housner intensity in the period range 0.2T ref –2T ref . The horizontal components for every band of frequency is obtained using a specific index that depends on the energy-frequency trend’s shape as well as on its scattering degree around the mean value. This allows obtaining a set of spectrum-compatible records with almost identical severity and low dispersion of the structural response parameters. The methodology has been tested showing a significant effectiveness in terms of low variability of parameters and accuracy in preserving the median demand for a given hazard scenario. 相似文献
15.
在传统地震动反应谱频域拟合方法的基础上,提出了拟合加密控制点目标反应谱的地震动合成方法,并在此基础上利用实际算例与传统方法进行了对比.本文方法在每次迭代调整过程中均考虑了对地震动加速度强度包络函数的模拟,并且对调整后的地震动进行了基线校正,从而确保最终合成的地震动时程既能以一定精度拟合加密目标反应谱,又能满足目标包络函数的要求,同时保证积分所得位移曲线不产生基线漂移.数值算例分析结果表明,本文方法与传统非加密控制点目标谱拟合方法相比,在地震动时程曲线合成、反应谱拟合精度以及收敛速度等方面均具有一定的优势. 相似文献
16.
17.
In this paper the effect of causal parameter bounds (e.g. magnitude, source‐to‐site distance, and site condition) on ground motion selection, based on probabilistic seismic hazard analysis (PSHA) results, is investigated. Despite the prevalent application of causal parameter bounds in ground motion selection, present literature on the topic is cast in the context of a scenario earthquake of interest, and thus specific bounds for use in ground motion selection based on PSHA, and the implications of such bounds, is yet to be examined. Thirty‐six PSHA cases, which cover a wide range of causal rupture deaggregation distributions and site conditions, are considered to empirically investigate the effects of various causal parameter bounds on the characteristics of selected ground motions based on the generalized conditional intensity measure (GCIM) approach. It is demonstrated that the application of relatively ‘wide’ bounds on causal parameters effectively removes ground motions with drastically different characteristics with respect to the target seismic hazard and results in an improved representation of the target causal parameters. In contrast, the use of excessively ‘narrow’ bounds can lead to ground motion ensembles with a poor representation of the target intensity measure distributions, typically as a result of an insufficient number of prospective ground motions. Quantitative criteria for specifying bounds for general PSHA cases are provided, which are expected to be sufficient in the majority of problems encountered in ground motion selection for seismic demand analyses. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
18.
作为一种特殊的地震动,长周期地震动对结构的危害已引起国内外学者的关注。选取10条KiK-net、K-NET台网中典型的长周期地震动,以及10条国内外的短周期地震动,对比分析两者时程特征和反应谱特征的差异。将所选长、短周期地震动输入钢框架结构模型;通过非线性时程分析,研究钢框架结构在长、短周期地震动作用下的响应差异。结果表明：短周期地震动的平均地面峰值加速度是长周期地震动的3.26倍,而平均地面峰值位移比长周期地震动低10.89%;短周期地震动作用下,钢框架结构顶点加速度响应平均值是长周期地震动的5.16倍,结构顶点位移响应平均值仅比长周期地震动多0.91%;长周期地震动作用下,钢框架结构层间位移角响应较大,结构底部受影响范围更广。对于长周期地震动隐患地区的高层钢框架结构,应对长、短周期震害分别进行考虑;对于中、长周期钢框架结构,建议选用峰值位移作为抗震分析指标。 相似文献
19.
为了进一步提高人造地震动时程对目标反应谱的拟合精度和效率,本文提出了一种人造地震动反应谱非线性拟合方法.在人造地震动反应谱非线性拟合过程中,认为Fouricr幅值谱与反应谱调整项之间满足非线性(幂指数)关系.通过比例拉伸和折叠等数值技巧以促使模拟加速度向目标加速度逼近.算例分析结果表明,人造地震动反应谱非线性拟合方法具... 相似文献
20.
Ground motion selection for scenario ruptures using the generalised conditional intensity measure (GCIM) method 总被引：1，自引：0，他引：1 下载免费PDF全文
下载免费PDF全文 In this paper, the generalised conditional intensity measure (GCIM) method is extended to ground motion selection for scenario earthquake ruptures. The selection algorithm is based on generating random realisations of the considered intensity measure (IM) distributions for a specific rupture scenario and then finding the prospective ground motions that best fit the realisations using an optimal amplitude scale factor. Using different rupture scenarios and site conditions, two important aspects of the GCIM methodology are scrutinised: (i) different weight vectors for the various IMs considered and (ii) quantifying the importance of replicate selections for ensembles with different numbers of desired ground motions. It is demonstrated that considering only spectral acceleration (SA) ordinates in the selection process, as is common in many conventional selection procedures, may result in selected motions with a biased representation for duration and cumulative ground motion effects. In contrast, considering IMs other than SA ordinates (in particular, significant duration, cumulative absolute velocity, and Arias intensity) results in ensembles with an appropriate representation of these IMs, without a practically significant effect on SA ordinates. The benefit of conducting replicate selections to obtain a suite of motions with an improved representation for the distribution of the considered IMs is demonstrated, and a minimum number of replicates are suggested for different ground motion ensemble sizes. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献