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1.
The effect of reservoir length on seismic performance of gravity dams to near- and far-fault ground motions 总被引：1，自引：1，他引：0
In this article, the effect of reservoir length on seismic performance of gravity dams to near- and far-fault ground motions
is investigated. For this purpose, four finite element models of dam–reservoir–foundation interaction system are prepared
by using the Lagrangian approach. In these models, the reservoir length varies from H to 4H (H: the height of dam). The Folsom gravity dam is selected as a numerical application. Two different ground motion records of
1989 Loma Prieta earthquake are used in the analyses. One of ground motions is recorded in near fault; the other is recorded
in far fault. Also, the two records have the same peak ground acceleration. The study mainly consists of three parts to assess
the effects of reservoir length on the seismic performance of the concrete gravity dam. In the first part, the linear time-history
analyses of the four finite element models prepared for the Folsom gravity dam are performed. In the second part, the seismic
performance of the dam is evaluated according to demand–capacity ratio and cumulative inelastic duration. Finally, the nonlinear
time-history analyses of the finite element models of the dam are carried out by using Drucker–Prager yield criteria for dam
concrete. It is seen from the analyses results that the seismic behavior of the concrete gravity dams is considerably affected
from the length of the reservoir. The reservoir length of 3H is adequate for concrete gravity dams. The selection of ground motion is on of the important parts of seismic evaluation
of gravity dams. Also, the frequency characteristics of the ground motion having the same peak ground acceleration affect
the seismic performance of the dam. The near-fault ground motions are generally creates more stress on the dam body than far-fault
ground motions. The used performance approach provides a systematic methodology for assessment of the seismic performance
and necessity of nonlinear analyses for dam systems. 相似文献
2.
Comparison of near-fault and far-fault ground motion effects on geometrically nonlinear earthquake behavior of suspension bridges 总被引：2，自引：1，他引：1
Süleyman Adanur Ahmet Can Altuni?ik Alemdar Bayraktar Mehmet Akk?se 《Natural Hazards》2012,64(1):593-614
This paper presents a comparison of near-fault and far-fault ground motion effects on geometrically nonlinear earthquake behavior of suspension bridges. Bo?azi?i (The First Bosporus) and Fatih Sultan Mehmet (Second Bosporus) suspension bridges built in Istanbul, Turkey, are selected as numerical examples. Both bridges have almost the same span. While Bo?azi?i Suspension Bridge has inclined hangers, Fatih Sultan Mehmet Suspension Bridge has vertical hangers. Geometric nonlinearity including P-delta effects from self-weight of the bridges is taken into account in the determination of the dynamic behavior of the suspension bridges for near-fault and far-fault ground motions. Near-fault and far-fault strong ground motion records, which have approximately identical peak ground accelerations, of 1999 Chi-Chi, 1999 Kocaeli, and 1979 Imperial Valley earthquakes are selected for the analyses. Displacements and internal forces of the bridges are determined using the finite element method including geometric nonlinearity. The displacements and internal forces obtained from the dynamic analyses of suspension bridges subjected to each fault effect are compared with each other. It is clearly seen that near-fault ground motions are more effective than far-fault ground motion on the displacements and internal forces such as bending moment, shear force and axial forces of the suspension bridges. 相似文献
3.
Dams constructed on the seismically active regions have a high-risk potential for downstream life and property. Strong ground
motion can result in instability of the dam and strength loss of foundation. Active faults within the foundation of dam have
the potential to cause damaging displacement of the structures. Appropriate design measures should be considered to obtain
rational solution to the problem of catastrophic release of water from the reservoir, and especially to resist earthquake
loads. Safety concerns for dams under the earthquake loads involve the seismic hazard evaluation of dam site for the overall
stability of structure. Various types of analyses can be used, ranging from a simplified analysis to more complex procedures
based on ground motion parameters and response spectra. This paper briefly evaluates seismic hazard analyses for dam structures,
and introduces the analyses for thirty-six dams with height ranging from 15 to 195 m in Kızılırmak basin, Turkey. The seismic
hazard analyses have indicated that peak ground acceleration varies within a wide range (0.09–0.45 g) for the dam sites of
the basin. 相似文献
4.
对国家强震动台网中心紫坪铺面板堆石坝区域台站实测主震记录以及大坝台网实测余震记录进行分析,研究主震与强余震地震动的基本特征。分别选取茂县地办、郫县走石山、成都中和这3组基岩台站实测主震地震动,紫坪铺台站2008年11月6日实测余震地震动以及按水工抗震规范人工生成地震动作为数值计算的地震动输入,对紫坪铺大坝进行三维动力有限元分析,并与实测结果进行对比。研究表明,郫县走石山与成都中和2个远场台站位于断层下盘,其实测地震动的加速度反应谱长周期（0.65 s以后）分量过于丰富,不宜作为断裂带附近紫坪铺大坝的地震动输入;紫坪铺大坝台站实测的余震地震动1 Hz附近（大坝基频）的频率成分相对较少,且持续时间较短,以至于难以激发大坝响应;对比坝顶实测地震动加速度反应谱和数值计算反应谱,建议汶川地震中紫坪铺大坝动力计算时可采用茂县地办台站实测地震动或按抗震设计规范反应谱人工生成地震动。 相似文献
5.
6.
针对现行水工抗震规范中对近断层地震缺乏考虑这一实际问题,首先讨论了近断层、远场地震动的差别,对比了近断层、远场地震动对地下洞室地震响应的影响,继而提出一种新的人工合成近断层地震动时程的方法,并采用合成的近断层地震动时程对某水电站地下洞室群进行了近断层地震稳定性专门研究。结果表明：与常规地震分析中考虑的远场地震动相比,近断层脉冲型地震动的主要特征为Vmax/Amax和Dmax/Amax（Vmax、Dmax、Amax分别为速度峰值、位移峰值、加速度峰值）指标更大,且近断层脉冲型地震动的主要能量集中在1 Hz以下的频段;在相同峰值加速度幅值、相同反应谱的前提下,近断层地震动对高边墙、大跨度地下工程的破坏程度远比远场地震动大;较之前人的研究方法,文中提出的近断层脉冲型地震动合成方法考虑了[1/Tp, 1] Hz这一频段内的地震波信息,更具合理性;在设定的计算条件下,地下厂房洞室群有在近断层地震动作用下发生失稳的危险性,需要进一步针对近断层地震动进行专项风险性评价,以讨论是否需要增设针对性的抗震支护措施。 相似文献
7.
场地条件对地震动和震害有重要影响。本文简要回顾了场地条件对地震动和震害影响的研究历史,总结和评述了这一领域的研究进展。重点对地形地貌、岩土类型、覆盖层厚度、土层结构、地下水、岩土动力性质及物理地质现象等对地震动和震害的影响进行了总结和评述。提炼和概括了目前场地条件对地震动和震害影响研究中比较一致的几点认识。在此基础上,提出了这一领域当前应进一步研究的问题,主要包括地震现场资料调查、局部地形几何尺度、场地分类、覆盖层安全厚度界限、近断层地震动参数分布规律、活断层避让距离,以及强震资料积累等关键问题。 相似文献
8.
基于小波分析方法,从NGA数据库的3 551条地震记录中选取189条速度脉冲地震动,地震动均转换成发生最强脉冲的方向。基于Newmark方法,分析了近断层速度脉冲地震动作用引起的边坡永久位移值。结果表明：近断层速度脉冲地震动对边坡产生特殊的破坏作用,表现在滑动位移值大、滑动体破坏力强等方面;边坡永久位移值与速度脉冲地震动的峰值速度具有高度相关性,位移值较大时尤为明显。建立了基于单变量形式的峰值速度及双变量形式的峰值速度、峰值加速度两种边坡永久位移预测模型,模型简单实用,与回归数据具有很好的相关性,前者更适用于预测对实际工程影响较大的永久位移值,且离散性较小。提出的预测模型为考虑近断层地震动速度脉冲特性影响的边坡永久位移值的概率地震灾害分析提供了基础。 相似文献
9.
考虑场地和震源机制的近断层地震动衰减特性的研究 总被引：9，自引：1，他引：8
在收集了世界范围内自由场地的近断层地震记录基础上 ,综合考虑台站场地和震源构造机制的差别 ,应用统计分析方法对近断层地震动的峰值加速度、峰值比、特征比值及特定周期处的反应谱的衰减关系进行了研究 ,并和集集地震得到的结果进行了比较 ,发现场地和震源机制的共同作用对近断层地震动的影响是很显著的 ,为抗震设计规范的研究提供了参考 相似文献
10.
通过动力有限元时程法分析了金沙江阿海混凝土重力坝在设计地震动(0.344g)作用下的动态响应,计算模型考虑了动水压力作用、大坝-岩基相互作用,用黏弹性吸波边界模拟了地震动能量向无限远域逸散的地基“辐射阻尼”效应。通过将坝体惯性力时程极大值与振型分解反应谱法的惯性力极值对比,从而验证了复杂动力数值模拟结果的正确性,为后续分析打下了基础。采用沿滑面的应力积分法得到了大坝沿建基面的瞬态抗滑安全系数时程。计算结果表明：阿海重力坝在设计地震动(0.344g)作用下的安全系数时程的极小值为1.146,大坝整体稳定性良好,可不采取提高整体抗滑 相似文献
11.
Natural Hazards - This study presents a numerical investigation on the seismic behaviour of aged concrete gravity dams under near source and far source ground motions. Two-dimensional formulation... 相似文献
12.
Farshid Vahedifard Christopher L. Meehan 《Geotechnical and Geological Engineering》2011,29(6):1023-1034
Predictive displacement-based methods provide a useful index of the seismic performance of earth dams and embankments and
can be used in preliminary assessments of these structures. In practice, simplified Newmark-type sliding block methods are
commonly used for this purpose. Using a database of 122 previously published case histories of permanent deformations of earth
dams and embankments, the performance of six simplified sliding block models was examined. The results show that all six simplified
methods underpredict seismic displacement for many of the embankment and earth dam cases that were examined, sometimes by
a significant amount. An empirical correlation was developed by performing linear multiple regression analysis utilizing multiple
slope and ground motion input parameters. This approach is believed to more properly reflect strong ground motion characteristics
than the use of a single ground motion parameter such as the peak ground acceleration, the approach that has been previously
employed in other correlations of this type. After exploring numerous functional forms, the final resulting seismic displacement
correlation that was proposed was determined to be a function of the critical acceleration, the critical acceleration ratio,
the slope height, the peak ground acceleration, the peak ground velocity, the spectral acceleration, and the predominant period
of earthquake shaking. The proposed empirical equation yields better correlation with the case history database than does
other existing empirical correlations or simplified sliding block models. 相似文献
13.
冶勒沥青混凝土心墙堆石坝最大坝高为124.5 m,坝址区地震烈度高,地质条件复杂,两岸坝基条件严重不对称。大坝上布设了9台强震仪组成的强震监测台阵,曾获得2008年汶川地震和攀枝花地震的大坝强震监测记录。2013年4月20日四川省雅安市芦山县发生里氏7.0级地震,冶勒大坝距震中约212.5 km,坝址区震感较为强烈,强震监测台阵获得了此次地震较为完整的有效记录。对芦山地震主震记录进行时域分析和频谱分析,总结冶勒大坝在芦山地震中的动力反应规律,并与汶川地震时坝体动力反应进行对比分析。研究表明,芦山地震主震时冶勒大坝最大加速度记录为47.043 cm/s2,最长持续时间为76.98 s,坝顶动力放大效应明显;芦山和汶川地震时大坝动力反应规律的差异与地震波频谱特性及大坝自振特性等密切相关。总体而言,冶勒大坝在震后运行安全稳定,芦山地震未对冶勒大坝造成明显不利影响。 相似文献
14.
Abbas Abbaszadeh Shahri Katayoun Behzadafshar Roshanak Rajablou 《Arabian Journal of Geosciences》2013,6(3):881-892
The seismic response of existing earth dams in Iran is important after an earthquake both to provide emergency supplies and to society as well as to ensure structural safety in engineering terms. Better seismic capacity of earth dam results in less structural damage and reduced impacts following an earthquake disaster. Indirect as well as direct costs following earthquakes have gained much attention from both the engineering and socioec onomic research communities in the last few decades. This study is a valuable tool used to study the response of geotechnical structures to infrequent or extreme events such as earthquakes. The Avaj earthquake (2002, Iran) was applied to a series of model tests which was conducted to study the response of soil profiles under seismic loading. The acceleration records at different locations within the soil bed and at its surface along with the settlement records at the surface were used to analyze the soil seismic response. A combination of several software packages with a generated visual user interface computer code by authors named as “Abbas Converter” were employed to evaluate the variation of shear modulus and damping ratio with shear strain amplitude to assess their effects on site response. The proposed method was applied to the Korzan earth dam of Hamedan province in Iran. Site response analysis using the measured shear wave velocity, estimated modulus reduction, and damping ratio as input parameters produced good agreement with the computed site response in this study. 相似文献
15.
基于混凝土塑性损伤本构模型,将可以表征材料和结构渐进破坏的损伤变量作为内变量,考虑了混凝土拉压异性的损伤变量,利用有限元软件ABAQUS,对丰满混凝土重力坝在经受地震作用下的结构损伤区域的发展变化进行安全性评价。在数值计算过程中,对于受地震荷载作用所引起的地面水平运动而导致大坝水位水平运动对坝体的影响,通过扩充后的广义Westergaard公式予以计算模拟。通过分析得到了丰满大坝在地震作用下的塑性损伤破坏情况,并评价了丰满大坝的安全性,亦说明利用损伤力学对大坝进行安全性评价是一个可行的方法。 相似文献
16.
In the case of the dynamic analysis of the structures using the recorded earthquake ground motions, it is usually assumed that the ground motion consists of body waves propagating vertically. However, the response of a long and narrow structure may be influenced by the oblique propagation of body waves and the dispersion of surface waves. In this paper, the effects of the seismic wave propagation on the response of this kind of structure are investigated. The characteristics of the wave propagation were verified using the recorded motions and soil information at the building site. The ground motion at every input point of the building was evaluated using the difference of arrival time of seismic waves calculated by assuming the velocity and the direction of the wave propagation. Using these ground motions, response analyses of the lumped mass model for the structure were performed. By considering the characteristics of the seismic wave propagation, the average response decreased but the local response increased around the end of the roof. Further studies of the structure were also performed in order to restrain the response around the end of the roof. 相似文献
17.
The assessment of local site effects on seismic ground motions is of great importance in earthquake engineering practice.
Several destructive earthquakes in the past have demonstrated that the amplification of ground motion and associated damage
to structures due to local site conditions is a significant consideration in earthquake hazard analysis. A recent paper published
in this journal highlights the hazard posed by earthquakes in the megacity of Kolkata in India due to its seismic and geological
settings. The seismic hazard assessment study speculates that the deep alluvial deposit in the city may increase the seismic
hazard probably due to the amplification of the seismic energies. This paper focuses on the seismic response studies of the
various soil strata (i.e. for local subsurface conditions) obtained from various construction sites in the city for predicted
earthquake. It is very well recognized that site response studies (a part of seismic microhazard zonation for urban areas)
are the first step towards performance-based foundation design or seismic risk analysis and mitigation strategy. One of the
problems for carrying out site-specific study in Kolkata is the lack of recorded strong motion data in the city. Hence, this
paper outlines a methodology to carry out site-specific study, where no strong motion data or seismic data are available.
The methodology uses wavelet-based spectrum compatibility approach to generate synthetic earthquake motions and equivalent
linear method for seismic site response analysis. The Mega City of Kolkata has been considered to explain the methodology.
Seismic hazard zonation map by the Bureau of Indian Standards classifies the City of Kolkata as moderate seismic zone (Zone
III) with a zone factor 0.16. On the other hand, GSHAP(Global Seismic Hazard Assessment Program) map which is based on 10%
probability of exceedance in 50 years specifies a maximum peak ground acceleration (PGA) of 1.6 m/s2 (0.163 g) for this region. In the present study, the seismic response has been carried out based on GSHAP. The results of
the analysis indicate the amplification of ground motion in the range of 4.46–4.82 with the fundamental period ranging from
0.81 to 1.17 s. Furthermore, the maximum spectral accelerations vary in the range of 0.78–0.95 g. 相似文献
18.
Fatih Mosque and its Kulliye (complex) are one of the most important historical monuments in Istanbul. Since it has been built between 1463 and 1470, Fatih Mosque had been subjected to nine strong earthquakes and suffered various degrees of structural damage at every case, including the latest August 17, 1999 Kocaeli Earthquake (Mw = 7.4, epicentral distance approximately 100 km). Recently, a project has been initiated first to study the possible causes of earthquake damage and then develop retrofitting and strengthening techniques to protect this invaluable monument from further damages in the future earthquakes. As part of this investigation, local site soil conditions had been determined and site behavior during earthquakes had been studied in detail. In this paper, the results of 1-D site response analysis, which included convolution and deconvolution analyses utilizing the strong ground motions recorded during the August 17, 1999 Kocaeli Earthquake are presented. The results of the analyses had demonstrated the considerable degree of site amplification, compatible with the recorded motions and the damage suffered. The expected site behavior during a probable future earthquake is also studied using a site specific simulated bedrock motion, and earthquake parameters to be used in dynamic structural analysis are estimated. 相似文献
19.
Repeated earthquakes (EQs) are clear indication of alarming seismicity which can be witnessed across Indian subcontinent. Increase in population density with inappropriate construction practice repeatedly rise alarm that in comparison to damage scenarios experienced during previous major to great EQs in India, future catastrophes would be manifold. Performing regional seismic hazard as well as site response studies can possibly help in accurate estimation of probable future seismic scenario. Site class (SC) of EQ recording stations is an important part of both seismic hazard as well as site response analyses. In seismic hazard analysis, suitable attenuation relations are often selected based on comparison of recorded ground motion with proposed ground motion as per selected attenuation relation for the same SC. Thus, unless SC of recorded ground motions is known, suitability of selected attenuation relation cannot be validated. In addition, recent studies suggest that for same soil column, ground motion may amplify at the surface from minimal to very high depending upon input motion characteristics. Thus again, unless SC of recording station is not known, recorded ground motion cannot be considered with confidence as outcrop or base motion for region specific site response studies. In the present work, SC of eight recording stations located in Tarai region of Uttarakhand, India located adjacent to the Himalayan belt and which are part of PESMOS database, are established by three different methods namely; equivalent linear ground response analysis, generalized inversion technique and horizontal to vertical spectral ratio method. Collectively all these three methods suggest same SC for each of the eight recording stations including Roorkee, Rishikesh, Dehradun etc. Further, obtained SC based on the present study is considerably different from available SC as per PESMOS database. However, present findings are matching with recent published work. Obtained results can be very helpful in developing surface seismic hazard using regional ground motion records towards minimizing future EQ induced damages. 相似文献
20.
While travelling through the subsoil layers, earthquake generated bedrock motions get modified significantly due to local soil and should be quantified using ground response analysis. Present study concentrates on equivalent linear method of site response analysis in SHAKE2000 software. It is a frequency based analysis tool having default frequency set to 15 Hz. While due consideration is given to amplitude, no to very limited information about the frequency content of the input motion to be considered in ground response analysis is available. In the present work, the effect of the maximum frequency of ground motion in site response analysis using SHAKE2000 is examined. Two sets of analyses are carried out in this work based on 30 globally recorded input motions. In the first analyses, input motion up to 15 Hz maximum frequency, which is a default value in SHAKE2000 is considered while second analyses are based on considering each of the 30 input motions up to the Nyquist frequency. Comparing the results from the two sets of analyses highlight that selection of maximum frequency in SHAKE2000 has considerable effect in ground motion amplification at different depths. As a result, even the peak ground acceleration which controls the building behavior and damage scenario, is going to change considerably even in case same input motion is used in the analysis. 相似文献