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1.
弹塑性地震反应谱的长周期特性研究 总被引：3，自引：1，他引：3
在基于性能抗震设计中弹塑性反应谱在计算结构地震位移反应方面越来越受到重视。利用统计分析方法研究了等强度的延性需求谱和等延性的强度折减系数谱的长周期(至5 s)区段的特性,关注的重点是等位移准则和场地条件影响。给出了若干具有工程价值的结论:一是周期介于1.5Tg(地震动特征周期)和2.5 s之间的结构可近似认为等位移准则成立且与场地条件关系不大,这样确定的强度折减系数当位移延性系数小于等于4时结果将是偏于安全的;二是结构周期大于2.5 s后以硬土场地等延性强度折减系数谱或等强度延性需求谱代替软土场地谱求解系统强度需求或延性需求,将会得到偏于安全的结果。 相似文献
2.
3.
This paper aims at implementing and introducing the use of conditional mean spectrum (CMS) and conditional spectrum (CS) as the main input parameters in the practice of seismic safety evaluation (SSE) in China, instead of the currently used uniform hazard spectrum (UHS). For this purpose, a procedure for M-R-epsilon seismic hazard deaggregation in China was first developed. For illustration purposes, two different typical sites in China, with one to two dominant seismic zones, were considered as examples to carry out seismic hazard deaggregation and illustrate the construction of CMS/CS. Two types of correlation coefficients were used to generate CMS and the results were compared over a vibration period range of interest. Ground motion records were selected from the NSMONS (2007–2015) and PEER NGA-West2 databases to correspond to the target CMS and CS. Hazard consistency of the spectral accelerations of the selected ground motion records was evaluated and validated by computing the annual exceedance probability rate of the response spectra and comparing the results to the hazard curve corresponding to each site of concern at different periods. The tools developed in this work and their illustrative application to specific case studies in China are a first step towards the adoption of CMS and CS into the practice of seismic safety evaluation in this country. 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.
本文人工合成了36条代表不同频谱特性的地震动,构造了简单的平台地形,并利用人工合成地震动作为平台地形计算输入地震波,获得了地表观测点的时程和反应谱.在此基础上,分析了具有不同高度、侧向坡降和介质阻尼等的平台地形对地震动特征周期值的影响.研究的结果表明:当平台高度与入射地震波优势波长相比较小时,平台的高度、侧向坡降、阻尼比等对地震动特征周期值的影响不大,此时单个平台地形地表地震动的特征周期主要依赖于入射地震动的特征周期,而且一般比入射地震动的特征周期略有增大;当平台高度与入射地震波优势波长相比较大时,平台高度对地表地震动特征周期影响较大. 相似文献
6.
Jorge M. Gaspar-Escribano Manuel Navarro Belén Benito Antonio García-Jerez Francisco Vidal 《Bulletin of Earthquake Engineering》2010,8(6):1547-1567
An approach that relates results from a regional seismic hazard assessment study with local-scale site-effect characterizations
in an area of low-to-moderate seismic activity such as Andalusia (southern Spain), is presented. Results of a previous probabilistic
seismic hazard analysis of Andalusia on rock conditions are disaggregated to infer hazard controlling earthquakes for different
target motions. A collection of controlling magnitude-distance pairs and the corresponding site-specific response spectra
at main capital cities of the region are obtained. These spectra are first-order approximations to expected seismic actions
required in local earthquake risk assessments. In addition, results of independent, local-scale studies developed in Almeria
City (SE Andalusia) are used to derive an updated seismic zonation of the city. These include predominant soil period estimates
and shear-wave velocity profiles at different locations. If a local seismic risk assessment study or an earthquake-resistant
structural design is to be developed, it may be recommended the use of different seismic actions on sites characterized by
distinct response to seismic shaking (as derived from the seismic zonation). The seismic action related to worst-case scenarios
may be modeled through a hazard-consistent response spectrum, obtained by hazard disaggregation at the spectral acceleration
with period matching the prevailing resonant period of the target site or structure. 相似文献
7.
Correlation in spectral accelerations for earthquakes in Europe 总被引：1，自引：0，他引：1
Gian Paolo Cimellaro 《地震工程与结构动力学》2013,42(4):623-633
The shape of a uniform hazard spectrum has been criticized to be unrealistic for a site where the spectral ordinates of the uniform hazard spectrum at different periods are governed by different scenario events and conservative for long‐return‐period earthquake shaking. The conditional mean spectrum considering epsilon (CMS‐ε) takes into account the correlation of spectral demands (represented by values of ε) at different periods, to address these issues. This paper proposes new prediction models for the correlation coefficient of ε(T1) and ε(T2), a key component for developing a CMS, using Pan‐European earthquake records from a European ground motion database. Epsilon (ε) for each record is computed using the 2005 Ambraseys ground‐motion prediction equation. The model can be used to develop CMS for European sites, and it can be incorporated in the European seismic standards. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
8.
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
9.
In a companion paper, an overview and problem definition was presented for ground motion selection on the basis of the conditional spectrum (CS), to perform risk‐based assessments (which estimate the annual rate of exceeding a specified structural response amplitude) for a 20‐story reinforced concrete frame structure. Here, the methodology is repeated for intensity‐based assessments (which estimate structural response for ground motions with a specified intensity level) to determine the effect of conditioning period. Additionally, intensity‐based and risk‐based assessments are evaluated for two other possible target spectra, specifically the uniform hazard spectrum (UHS) and the conditional mean spectrum (CMS, without variability).It is demonstrated for the structure considered that the choice of conditioning period in the CS can substantially impact structural response estimates in an intensity‐based assessment. When used for intensity‐based assessments, the UHS typically results in equal or higher median estimates of structural response than the CS; the CMS results in similar median estimates of structural response compared with the CS but exhibits lower dispersion because of the omission of variability. The choice of target spectrum is then evaluated for risk‐based assessments, showing that the UHS results in overestimation of structural response hazard, whereas the CMS results in underestimation. Additional analyses are completed for other structures to confirm the generality of the conclusions here. These findings have potentially important implications both for the intensity‐based seismic assessments using the CS in future building codes and the risk‐based seismic assessments typically used in performance‐based earthquake engineering applications. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
10.
SMART-1台阵记录的长周期反应谱特性 总被引：3，自引：0，他引：3
利用台湾SMART－1台阵的数字强震仪加速度记录分析了同类场地上的地震动长周期分量特性，结果表明：同一次地震震中距基本相同的同类场地加速度反应谱短周期部分有较明显的差别，长周期部分则基本相同；震级和震中距对短周期反应谱影响明显，对长周期反应谱也有一定影响。最后将SMART－1台阳场地的平均谱与新的建筑抗震设计规范修订稿中提出的设计反应谱作了比较。 相似文献
11.
Regional variation of spectral parameters for seismic design from broadband probabilistic seismic hazard analysis 
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下载免费PDF全文 The characterisation of the seismic hazard input is a critical element of any seismic design code, not only in terms of the absolute levels of ground motion considered but also of the shape of the design spectrum. In the case of Europe, future revisions of the seismic design provisions, both at a national and a pan‐European level, may implement considerable modifications to the existing provisions in light of recent seismic hazard models, such as the 2013 European Seismic Hazard Model. Constraint of the shape of the long‐period design spectrum from seismic hazard estimates on such a scale has not been possible, however, owing to the limited spectral period range of existing ground motion models. Building upon recent developments in ground motion modelling, the 2013 European Seismic Hazard Model is adapted here with a new ground motion logic tree to provide a broadband Probabilistic Seismic Hazard Analysis for rock sites across a spectral period range from 0.05 seconds to 10.0 seconds. The resulting uniform hazard spectra (UHS) are compared against existing results for European and broadband Probabilistic Seismic Hazard Analysis and against a proposed formulation of a generalised design spectrum in which controlling parameters can be optimised to best fit the uniform hazard spectra in order to demonstrate their variability on a European scale. Significant variations in the controlling parameters of the design spectrum are seen both across and within stable and active regions. These trends can help guide recalibrations of the code spectra in future revisions to seismic design codes, particularly for the longer‐period displacement spectrum. 相似文献
12.
The selection of representative input ground motions (IGMs) is important for a proper nonlinear response time history analysis (NLRHA) of modern structures. The prevailing IGM selection procedure requires that the response spectra of selected ground motions are matched with the code-specified design spectra, while the effect of the frequency contents combination in the time domain on the multimode interactions is not considered. Ignoring the effect of the frequency contents combination in the time domain of IGMs may cause significant variations in the analysis results for selected IGMs, although they are matched to the same design spectrum. In this paper, a modal-based ground motion selection (MGMS) procedure is proposed as a supplement to spectrum matching-based IGM selection procedures for selecting proper IGMs that can sufficiently induce the multimode interactions. In the proposed procedure, three equivalent single-degree-of-freedom (ESDOF) systems are developed by pushover analysis. NLRHA is then conducted for these ESDOF systems with a set of 20 seed IGMs chosen by the spectrum-matching–based selection procedure. Finally, seven IGMs are selected from the seed IGMs for NLRHA in the full structural model. To verify MGMS, seismic demands of high-rise buildings were computed by NLRHA with seven MGMS-selected IGMs, seven IGMs with closest spectrum matching, and groups of seven randomly selected IGMs derived from three different sets of 20 seed IGMs. The computed seismic demands with MGMS-IGMs show very good agreement with the mean demands determined using the whole set of seed IGMs, while the deviation is much lesser compared with those groups of randomly selected IGMs. 相似文献
13.
当前,合理确定地震动峰值加速度与反应谱特征周期是工程场地地震动参数确定工作的主要内容。本文以北京地区典型中硬场地为研究对象,分析场地条件对不同周期地震动反应谱值的影响。首先,计算不同震级、震中距条件下的基岩地震动加速度反应谱,合成基岩输入地震动时程;再利用110个工程场地的钻孔资料进行土层地震反应计算,分析中硬场地条件对不同输入环境下的地震动加速度反应谱值的放大效应。结果表明,中硬场地对高、中频震动放大效应明显,尤其是对0.2-0.5s周期段地震动加速度反应谱值的放大倍数大多在1.3以上;场地覆盖层厚度变化对不同频段地震动加速度反应谱值的放大倍数所产生的影响是不同的,与场地自振周期的相关性很强;在不同的地震动输入环境下,中硬场地对不同频段地震动加速度反应谱的影响是不同的,这一结论对实际的抗震设防工作具有一定参考价值。 相似文献
14.
Hazard-consistent response spectra in the Region of Murcia (Southeast Spain): comparison to earthquake-resistant provisions 总被引：1，自引：1，他引：0
Jorge M. Gaspar-Escribano Belén Benito Julián García-Mayordomo 《Bulletin of Earthquake Engineering》2008,6(2):179-196
Hazard-consistent ground-motion characterisations of three representative sites located in the Region of Murcia (southeast
Spain) are presented. This is the area where the last three damaging events in Spain occurred and there is a significant amount
of data for comparing them with seismic hazard estimates and earthquake-resistant provisions. Results of a probabilistic seismic
hazard analysis are used to derive uniform hazard spectra (UHS) for the 475-year return period, on rock and soil conditions.
Hazard deaggregation shows that the largest hazard contributions are due to small, local events for short-period target motions
and to moderate, more distant events for long-period target motions. For each target motion and site considered, the associated
specific response spectra (SRS) are obtained. It is shown that the combination of two SRS, for short- and long-period ground
motions respectively, provides a good approximation to the UHS at each site. The UHS are compared to design response spectra
contained in current Spanish and European seismic codes for the 475-year return period. For the three sites analysed, only
the Eurocode 8 (EC8) type 2 spectrum captures the basic shape of the UHS (and not the EC8 type 1, as could be expected a priori).
An alternative response spectrum, anchored at short- and long-period accelerations, is tested, providing a close match to
the UHS spectra at the three sites. Results underline the important contribution of the frequent, low-to-moderate earthquakes
that characterize the seismicity of this area to seismic hazard (at the 475-year return period). 相似文献
15.
Consecutive combined response spectrum 总被引：1，自引：1，他引：0
Appropriate estimates of earthquake response spectrum are essential for design of new structures, or seismic safety evaluation of existing structures. This paper presents an alternative procedure to construct design spectrum from a combined normalized response spectrum(NRSC) which is obtained from pseudo-velocity spectrum with the ordinate scaled by different peak ground amplitudes(PGA, PGV, PGD) in different period regions. And a consecutive function f(T) used to normalize the ordinates is defined. Based on a comprehensive study of 220 strong ground motions recorded during recent eleven large worldwide earthquakes, the features of the NRSC are discussed and compared with the traditional normalized acceleration, velocity and displacement response spectra(NRSA, NRSV, NRSD). And the relationships between ground amplitudes are evaluated by using a weighted mean method instead of the arithmetic mean. Then the NRSC is used to define the design spectrum with given peak ground amplitudes. At last, the smooth spectrum is compared with those derived by the former approaches, and the accuracy of the proposed spectrum is tested through an analysis of the dispersion of ground motion response spectra. 相似文献
16.
针对上海及邻近区域划分的46 个潜在震源区,采用概率地震危险性分析方法计算上海中心地区基岩地震动参数,分析对反应谱不同周期起主要影响的潜在震源区,并研究主要潜在震源区对不同周期反应谱的概率贡献。研究结果表明:对于长周期反应谱,远距离高震级潜在震源区概率贡献随着周期的增加而增大,甚至超过场地所在潜在震源区的概率贡献;在上海地区进行长周期项目地震安全性评价中,应充分考虑150 km以外的高震级潜在震源区的影响;对于上海地区的超高层建筑等长周期建筑物而言,长江口、南黄海等地区的地震影响风险较大,郯城地区的地震影响也不容忽视,应引起重视。 相似文献
17.
条件均值谱（CMS）已成为目前国内外广受关注及认可的结构抗震时程分析选波的目标谱,但其无法同时兼顾多个周期点谱加速度具有相同的地震危险水平,对于须考虑多阶振型影响的长周期结构尚存局限。Newmark-Hall三联谱是基于加速度峰值（PGA）、速度峰值（PGV）和位移峰值（PGD）并联合短、中、长周期相关放大系数建立的反应谱,与短、中、长周期结构均具有天然良好的相关性,其与概率地震危险性分析（PSHA）结合较弱及具有经验化特征。将两种反应谱的优势相结合,即将CMS的“条件分布”理念引入Newmark-Hall三联谱,建立了条件Newmark-Hall三联谱（即CN-H）,并提出了以CN-H为目标谱的选波方法（即CN-H方法）。以美国SAC计划设计的3层和9层抗弯钢框架结构为例,将CN-H方法与以CMS为目标谱的选波方法所得结果进行了对比。CN-H方法对于结构反应均值的估计与CMS方法具有一致的准确性,且所得结构反应的离散性也较低,可见CN-H方法对于结构弹塑性时程分析选波具有良好的适用性。 相似文献
18.
Brendon A. Bradley 《地震工程与结构动力学》2013,42(15):2235-2253
This paper compares the seismic demands obtained from an intensity‐based assessment, as conventionally considered in seismic design guidelines, with the seismic demand hazard. Intensity‐based assessments utilize the distribution of seismic demand from ground motions that have a specific value of some conditioning intensity measure, and the mean of this distribution is conventionally used in design verification. The seismic demand hazard provides the rate of exceedance of various seismic demand values and is obtained by integrating the distribution of seismic demand at multiple intensity levels with the seismic hazard curve. The seismic demand hazard is a more robust metric for quantifying seismic performance, because seismic demands from an intensity‐based assessment: (i) are not unique, with different values obtained using different conditioning intensity measures; and (ii) do not consider the possibility that demand values could be exceeded from different intensity ground motions. Empirical results, for a bridge‐foundation‐soil system, illustrate that the mean seismic demand from an intensity‐based assessment almost always underestimates the demand hazard value for the exceedance rate considered, on average by 17% and with a large variability. Furthermore, modification factors based on approximate theory are found to be unreliable. Adopting the maximum of the mean values from multiple intensity‐based assessments, with different conditional intensity measures, provides a less biased prediction of the seismic demand hazard value, but with still a large variability, and a proportional increase the required number of analyses. For an equivalent number of analyses, direct computation of the seismic demand hazard is a more logical choice and provides additional performance insight. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
19.
The inelastic (design) spectra characterizing a seismic hazard are generally obtained by the scaling‐down of the elastic (design) spectra via a set of response modification factors. The component of these factors, which accounts for the ductility demand ratio, is known as the strength reduction factor (SRF), and the variation of this factor with initial period of the oscillator is called an SRF spectrum. This study considers scaling of the SRF spectrum in the case of an elasto‐plastic oscillator with strength and stiffness degradation characteristics. Two models are considered: one depending directly on the characterization of source and site parameters and the other depending on the normalized design spectrum characterization of the seismic hazard. The first model is the same as that proposed earlier by the second author, and is given in terms of earthquake magnitude, strong‐motion duration, predominant period, geological site conditions, ductility demand ratio, and ductility supply‐related parameter. The second model is a new model proposed here in terms of the normalized pseudo‐spectral acceleration values (to unit peak ground acceleration), ductility demand ratio and ductility supply‐related parameter. For each of these models, least‐square estimates of the coefficients are obtained through regression analyses of the data for 956 recorded accelerograms in western U.S.A. Parametric studies carried out with the help of these models confirm the dependence of SRFs on strong‐motion duration and earthquake magnitude besides predominant period and site conditions. It is also seen that degradation characteristics make a slight difference for high ductility demands and may lead to lower values of SRFs, unless the oscillators are very flexible. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
20.
To develop uniform and seismic environment-dependent design spectrum, common acceleration response spectral characteristics need to be identified. In this paper, a bi-normalized response spectrum (BNRS) is proposed, which is defined as a spectrum of peak response acceleration normalized with respect to peak acceleration of the excitation plotted vs. the natural period of the system normalized with respect to the spectrum predominant period, Tp. Based on a statistical analysis of records from the 1999 Chi-Chi earthquake, the conventionally normalized response spectrum(NRS) and the BNRS are examined to account for the effects of soil conditions, epicentral distance, hanging wall and damping. It is found that compared to the NRS, the BNRS is much less dependent on these factors. Finally, some simple relationships between the BNRS for a specified damping ratio and that for a damping ratio of 5%, and between the spectra predominant period and epicentral distance for different soil types are provided. 相似文献