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以我国近海海域工程场地为研究对象,充分考虑上覆海水的自重影响,构建典型的饱和海底自由场计算模型,运用动力有限差分法开展二维地震反应分析,探讨以不同幅值的SV波、P波作为基底输入条件下上覆海水厚度对海底地震动峰值和反应谱的影响,总结上覆有水和无水场地的地震动结果差异,并分析差异产生的原因。结果表明:当基底输入SV波时,上覆有水场地海床表面峰值加速度小于上覆无水场地地表峰值加速度,海水层厚度对峰值加速度的影响可以忽略;当基底输入P波时,上覆有水场地海床表面峰值加速度大于上覆无水场地地表峰值加速度,且随着海水层厚度的增大,海床表面峰值加速度逐渐减小。 相似文献
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《地震工程与工程振动》2021,41(5)
SV波以大角度斜入射时,场地伴随更大的竖向地震作用,这很可能使得地铁隧道地震响应特点异于小角度斜入射情况。基于粘弹性人工边界理论,采用频域刚度矩阵法计算任意角度斜入射SV波的地震动输入等效节点力,通过ABAQUS有限元软件建立自由场模型,验证了0°、30°、40°和50°斜入射SV波地震动输入的准确性;在此基础上建立任意角度斜入射SV波作用下的地下双线并行圆形地铁隧道地震响应分析数值模型,从场地类别、隧道埋深和双隧道间距等方面分析SV波入射角度对隧道结构横断面地震响应的影响。研究表明:入射角度0°及略大于SV波临界角的入射角度是浅埋圆形地铁隧道结构抗震的最不利角度,尤其对于Ⅱ类场地,若仅在临界角以内研究衬砌结构的地震响应,将显著低估衬砌结构的动力响应;此外,隧道埋深对衬砌动弯矩、动轴力峰值具有显著影响,这种影响与场地类别密切相关;Ⅱ类和Ⅲ类场地中小隧道间距条件下隧道间的动力相互作用对衬砌结构动力响应具有一定的增大效应,而Ⅳ类场地中可忽略隧道间的动力相互作用对衬砌结构动力响应所产生的影响。 相似文献
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以美国Garner Valley Downhole Array(GVDA)竖向观测台阵的强震观测记录为基础,利用水平与竖向谱比(Horizontal-to-Vertical Spectral Ratio,HVSR)方法与传统谱比方法研究了多次地震作用下竖向台阵场地的波动传播规律,探讨了该场地HVSR曲线与传递函数(Transfer Function,TF)曲线的差异,综合利用频域求解一维层状场地P、SV波入射情况下场地响应的土层地震反应分析方法和合成理论地震图的波数积分法解释了二者差异可能的原因,在此基础上研究了HVSR方法应用于地震作用下场地效应分析的适用性.研究结论表明:竖向地震动场地效应是HVSR与传递函数产生差异的主要原因,竖向地震动场地效应主要是由竖向地震动中的P波成分引起的.在场地竖向放大可以忽略的频段范围内,HVSR可以作为传递函数研究地震作用下的场地效应. 相似文献
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覆水场地地震反应分析 总被引：3，自引：0，他引：3
随着各种海洋结构物的兴建,覆水场地的地震反应逐渐成为研究热点。基于任意拉格朗日-欧拉描述,推导时变区域上的流体运动方程,给出流场、结构的接触条件和流场网格运动控制方法。对于平坦覆水场地,水平向地震动作用下,根据Couette流理论证明该类场地流体作用可以忽略;竖向地震动激励下,横向均匀场地可以通过动水压力公式准确考虑流体作用,横向非均匀场地则需要通过流固耦合方法考虑流体作用,以海底隧道为例加以说明。对于起伏场地,天然起伏场地在地震动激励下的动力反应具有明显的流固耦合特征,以三角形起伏场地为算例;结构物的兴建造成的人工起伏场地同样需要考虑流固耦合效应,以某沉管隧道在水平向地震动激励下的动力反应为算例,并根据结果初步提出该类结构物流固耦合分析的简化计算方法。 相似文献
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《国际地震动态》2016,(3)
钢筋混凝土水池在供水系统中承担着净水、储水的重要功能,是典型的储液结构。裂缝的出现会加速钢筋锈蚀、降低结构耐久性,且结构设计中裂缝宽度限值很大程度上决定了配筋量。水池在地震作用下易出现裂缝,裂缝可能导致储液渗漏,造成水池服务功能下降甚至丧失,并在一定程度上影响整个系统的功能。震后储液结构的裂缝开展情况及由此导致储液渗漏程度是评判水池地震破坏等级的主要标准。目前,已有研究成果表明,混凝土裂缝在与水接触条件下会发生自愈使原有裂缝宽度减小,水池由于储水为裂缝的自愈提供了必要条件。因此,应考虑承载力、耐久性、服务功能、经济性、裂缝自愈性能及震后维修加固可行性等因素综合确定水池结构设计和地震破坏等级划分标准中的裂缝限值。储液结构在地震作用下存在液固耦合效应且液体会发生晃动,储液的存在改变了结构的动力特性和地震响应。水池结构除受到结构本身惯性力和静水压力外,其底部和侧壁还承受液体在垂直壁面方向上产生的动水压力。水池在抗震设计中需考虑液面晃动和动水压力的影响。现阶段,对钢筋混凝土水池裂缝自愈性能、渗漏特性及水池在地震作用下的液固耦合动力特性和地震响应的研究尚不完善。本文通过钢筋混凝土水池壁板弯曲裂缝和贯通裂缝自愈、渗漏试验研究混凝土裂缝的自愈性能及渗漏特性,采用大型有限元软件ADINA进行圆形水池地震响应分析,研究液固耦合系统的动力特性、储液晃动、动水压力及破坏特征等。论文主要完成了如下工作:(1)设计并完成了钢筋混凝土水池壁板弯曲裂缝和贯通裂缝的自愈及渗漏试验。进行了材料性能试验;对静水环境中弯曲微裂缝、流动水环境中贯通裂缝的自愈性能进行了测试,给出了弯曲微裂缝在静水环境中短期内的自愈合宽度,证实了贯通裂缝在流动水环境中仍会发生自愈合;在裂缝上施加实际水头作用测试了弯曲裂缝和贯通裂缝的渗漏特性,研究了弯曲裂缝宽度、受压区高度及作用水头对液体渗漏的影响,分析了贯通裂缝水的渗漏率与累计时间和水头高度之间的关系。通过试验得到裂缝特性与自愈及渗漏之间的关系,为水池结构设计和地震破坏等级划分提供参考。(2)对地面式圆形水池进行了液固耦合动力特性分析,液固耦合系统包括刚体模态、储液晃动模态和液固耦联振动模态3种形式。研究了储水高度、水池半径、液体表面重力波对液固耦合系统动力特性的影响。此外,对比了圆形水池储液晃动频率的理论和有限元计算结果,验证了模型的可靠性,且推导得到圆形水池储液晃动基本周期计算公式。(3)分析了单向水平地震作用下不同水池半径、不同储水高度圆形水池的液面最大晃动波高,拟合得到了圆形水池单向地震作用下的液面最大晃动波高计算公式。公式可用于储液结构地震作用下的最大晃动波高估计和储液结构最大晃动波高设计。结合储液结构长周期抗震设计反应谱和阻尼比修正系数,提出了储水水池液面最大晃动波高计算方法。(4)研究了单向水平地震作用下,不同水池半径、不同储水高度圆形水池池壁、底板环向和径向位置的动水压力数值及分布情况,并与理论计算结果进行了对比;分析了地震动峰值加速度、储水高度、水池半径对动水压力的影响;确定了对流压力与脉冲压力的叠加方法;拟合得到对流压力、脉冲压力及动水压力计算公式;结合底板环向动水压力分布,综合给出单向水平地震作用下圆形水池动水压力标准值,与较复杂的理论计算方法和仅考虑脉冲压力的规范法相比,计算更简便且与实际相符。此外,还分析了液面和池底动水压力的时程变化。(5)进行了双向水平地震动作用下圆形水池的地震响应分析,提取了液面最大晃动波高和动水压力计算结果;基于单向水平地震动作用下的响应结果,通过合理的组合方式给出了双向水平地震动作用下的液面最大晃动波高和动水压力计算公式,建立了双向水平地震作用下储水水池液面最大晃动波高和动水压力计算方法;并对双向水平地震作用下圆形水池地震破坏特征和易损性进行了分析。 相似文献
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波浪作用对单柱式桥墩地震反应特性的影响 总被引：2，自引：1，他引：1
以ABAQUS有限元软件为计算平台,建立了考虑波浪作用影响的单柱式桥墩-桩-土体系非线性地震反应分析二维有限元模型,土体以四节点实体单元离散,采用土体粘塑性记忆型嵌套面本构模型描述土的动力特性;桥墩以及桩以两节点梁单元离散,采用动塑性损伤模型描述混凝土的动力特性;根据Stokes五阶波浪理论,将基于Morison公式计算所得的波浪力以分布力的形式施加于桥墩之上,比较了静水条件下和考虑波浪作用时不同地震动激励下单柱式桥墩结构的地震反应特性,结果表明:波浪作用的影响使桥墩墩身相对墩底的位移反应、桥墩墩底的剪力和弯矩反应有较明显的增大,但对桥墩墩身加速度反应的影响可忽略不计,波浪作用影响的大小与输入地震动特性有关.在单柱式桥墩的抗震设计中考虑波浪作用的影响是必要的。 相似文献
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新型随机地震动模型 总被引：2，自引：0，他引：2
在研究结构的随机地震反应时，要用大量的符合场地条件的地震记录作为输入数据。但强震历史记录却不是每个地区都有的，因此根据符合场地条件的现有地震记录建立随机地震动模型具有重要意义。本文利用中国抗震规范2001版修正选取的样本波作为目标波，考虑了幅值和频率的双重非平稳性，建立了新型随机地震动模型——改进的时变ARMA模型随机地震动模型。通过使用残差的卡方检验法，对多种非平稳ARMA模型生成的模拟波进行检验；同时又比较丁模拟波与目标波的功率谱密度图和反应谱图。结果证明：此法能够更精确地反映不同场地条件地震动的频谱和幅值的真实内容，从而建立符合目标场地条件的更为有效的模拟地震动，为相关研究与工程设计架起一座桥梁。 相似文献
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新疆乌恰2次5.1级地震加速度记录特征对比分析 总被引：1，自引：0，他引：1
分析新疆乌恰两次5.1级地震4个强震台的强震动记录,第1次地震4个台记录卓越频率在4.25 Hz-13.59 Hz;第2次地震4个台记录卓越频率为2.45 Hz-3.61 Hz.从谱比曲线可以看出,2次地震在同一观测场地的场地效应基本相似,基岩台场地效应在高频部分有明显放大作用,土层场地在高频部分有明显的减小作用. 相似文献
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基于应用透射人工边界条件的显式有限元法计算断层破碎带宽度及力学参数变化、地震动入射角变化时二维断层场地模型P波入射下地表地震动场的分布。结果表明:(1)低速度破碎带的存在导致整个场地都有P波转换为SV波的分量,且在断层破碎带的区域出现断层陷波;(2)低速度破碎带的存在使输入场地恒定的能量向破碎带集聚放大,随着破碎带宽度增大或其介质波速降低集聚放大效应增大;(3)场地放大效应是频率相关的,宽度较宽或介质波速较低的断层破碎带对输入地震动中较低的频率成份放大显著;(4)竖向断层破碎带能阻隔斜入射地震P波,随着入射角增加隔震效应更显著。 相似文献
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The effect of seawater on vertical ground motions is studied via a theoretical method and then actual offshore ground motion records are analyzed using a statistical method. A theoretical analysis of the effect of seawater on incident plane P and SV waves at ocean bottom indicate that on one hand, the affected frequency range of vertical ground motions is prominent due to P wave resonance in the water layer if the impedance ratio between the seawater and the underlying medium is large, but it is greatly suppressed if the impedance ratio is small; on the other hand, for the ocean bottom interface model selected herein, vertical ground motions consisting of mostly P waves are more easily affected by seawater than those dominated by SV waves. The statistical analysis of engineering parameters of offshore ground motion records indicate that:(1) Under the infl uence of softer surface soil at the seafl oor, both horizontal and vertical spectral accelerations of offshore motions are exaggerated at long period components, which leads to the peak spectral values moving to a longer period.(2) The spectral ratios(V/H) of offshore ground motions are much smaller than onshore ground motions near the P wave resonant frequencies in the water layer; and as the period becomes larger, the effect of seawater becomes smaller, which leads to a similar V/H at intermediate periods(near 2 s). These results are consistent with the conclusions of Boore and Smith(1999), but the V/H of offshore motion may be smaller than the onshore ground motions at longer periods(more than 5 s). 相似文献
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地震作用下含软弱夹层顺层岩质边坡表面放大效应研究 总被引：8，自引：0，他引：8
为了研究地震作用下含软弱夹层顺层岩质边坡表面的放大效应,借用FLAC3D软件,建立了含软弱夹层顺层岩质边坡动力分析数值模型;在合理考虑地震动输入、边界条件、网格划分与模型参数的基础上,分析了地震动峰值、频率、持时以及初动方向等因素影响下的边坡表面放大效应。研究结果表明：①地震动峰值、频率和初动方向对边坡表面放大效应的影响较显著,而地震动持时对边坡表面放大效应的影响微小;②随着地震动峰值的增加,放大效应由软弱夹层之上的坡面及坡顶面向坡肩点逐渐增大,坡肩点的放大效应最大;③当输入地震动频率小于边坡的自振频率时,边坡表面加速度放大倍数较小,且频率越小,放大倍数越小,当输入地震动频率大于边坡的自振频率时,边坡表面加速度放大倍数较大,且频率越大,放大倍数亦越大。 相似文献
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基于确定性震源模型的方法主要用于计算低频(11 Hz)地震动常用经验格林函数法或随机方法,对低频地震动模拟不够准确．本文在确定性震源模型方法基础上,尝试采用分解给定的震源模型的方法来模拟宽频带(0.1——10 Hz)强地面运动,即采用分级离散断层面和分解断层面破裂单元上升时间的方法,增加震源时间函数中的高频信号,从而避免了对地震记录丰富程度和准确性的依赖．文中模拟计算了汶川MS8.0地震在8个地震观测台的地震动,将模拟结果和观测记录进行了加速度时程曲线和傅里叶振幅谱的对比分析．对比结果显示,模拟估计的地震动峰值加速度和持续时间与观测记录的数据基本在plusmn;50%的精度范围内相同,傅里叶振幅谱显示模拟结果有得到10 Hz左右的高频成分. 四川盆地中的台站模拟结果高频衰减比观测记录要快,原因是模拟过程没有考虑场地效应.对强地震动模拟还是要综合考虑震源、传播路径和场地的影响．研究结果表明,此改变震源输入的确定性方法可应用于模拟近断层宽频强地面运动． 相似文献
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A physics‐based numerical approach is used to characterize earthquake ground motion due to induced seismicity in the Groningen gas field and to improve empirical ground motion models for seismic hazard and risk assessment. To this end, a large‐scale (20 km × 20 km) heterogeneous 3D seismic wave propagation model for the Groningen area is constructed, based on the significant bulk of available geological, geophysical, geotechnical, and seismological data. Results of physics‐based numerical simulations are validated against the ground motion recordings of the January 8, 2018, ML 3.4 Zeerijp earthquake. Taking advantage of suitable models of slip time functions at the seismic source and of the detailed geophysical model, the numerical simulations are found to reproduce accurately the observed features of ground motions at epicentral distances less than 10 km, in a broad frequency range, up to about 8 Hz. A sensitivity analysis is also addressed to discuss the impact of 3D underground geological features, the stochastic variability of seismic velocities and the frequency dependence of the quality factor. Amongst others, results point out some key features related to 3D seismic wave propagation, such as the magnitude and distance dependence of site amplification functions, that may be relevant to the improvement of the empirical models for earthquake ground motion prediction. 相似文献
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以云南鲁甸6.5级地震中房屋建筑破坏严重的龙头山集镇斜坡地形为例,通过地脉动测试分析得出斜坡及坡顶测点相对于坡脚参考点谱比峰值均＞1,顺坡向谱比峰值大于垂直坡向谱比峰值,且谱比峰值从斜坡坡脚到坡顶逐渐增大,坡顶处约为3;顺坡向谱比峰值对应的频率为4.57～5.39 Hz,垂直坡向谱比峰值对应的频率稍高,为5.42～5.96 Hz。通过结合黏弹性边界的时域动力有限元方法分析斜坡地形在垂直入射地震动作用下的响应,数值模拟结果表明,斜坡坡顶处的位移放大作用显著,坡脚处放大作用较小;介质剪切波速对斜坡地震动的影响较明显,尤其是坡顶点处不同介质剪切波速模型位移峰值差异较大。由于斜坡地形复杂的散射效应,在斜坡及附近测点均出现明显的转换面波,坡顶点处波形转换最显著。数值模拟结果进一步验证了龙头山集镇依坡而建的房屋建筑破坏严重是由局部地形地震动放大效应与地震动差动共同作用引起的。 相似文献
16.
Existing studies for site response analysis in geotechnical earthquake engineering have widely concentrated on the horizontal component of the ground motion. However, strong vertical ground motions have been repeatedly observed, resulting in significant vertical compression damage of engineering structures. Furthermore, for the seismic design of critical structures(e.g. large-scale dams and nuclear power plants), the ground motions in all three directions should be considered. Therefore, there is a need to investigate the site response subjected to the vertical component of the ground motion, especially for the seismic design of critical structures. Consequently, in this study, a numerical program for vertical site response analysis is proposed based on the commonly used analytical transfer function method. The proposed program is then validated against well-documented case studies obtained from the Japanese KiK-net(Kiban Kyoshin network) downhole array monitoring system. Results show that the response spectra at the ground surface are well predicted in the low frequency range(5 Hz), while discrepancies are observed in the high frequency range. However, the high frequency discrepancies do not significantly affect the overall prediction accuracy, as the overall seismic response of geotechnical structures are usually dominated by low frequency vibrations. Furthermore, the limitations in the analysis are also discussed. 相似文献
17.
本文讨论的是没有强震资料的地区在做地震动模拟时遇到的一些问题。模拟的地震动时程曲线基于统计的衰减数据,如地面加速度峰值或速度反应谱。由于这些数据并不包含有关地震频率成分的信息,要使用相同的统计反应谱对地震动可以随机模拟为稳态或准稳态的设想加以证明。 相似文献
18.
Based on our numerical model for wave scattering problems due to P and SV wave incidences and the frequency domain analysis procedure, the effect of canyon topographic and geologic conditions on ground motion due to P and SV earthquake wave incidences has been extensively studied in this paper. The numerical results from this research illustrated that: (1) canyon topographic and geologic conditions can dramatically affect both peak value and frequency contents of the free field motion along the canyon surface during an earthquake; (2) a canyon may be subjected to stronger ground motion when its predominant frequency is in coincidence with the predominant frequency of the incident earthquake wave; (3) a stronger wave mode conversion effect can be induced by a steeper canyon bank or a softer weathered stratum on the canyon surface in the case of an earthquake wave incidence; (4) compared with harmonic wave incidences, the amplification effect of a canyon on the incident earthquake wave is a little weaker due to the average self-healing effect of the earthquake wave. 相似文献
19.
Site response in the Qionghai Basin in the Wenchuan earthquake 总被引：2，自引：1，他引：1
Amplification effects of soil site response can significantly impact ground motions, and must be considered in the seismic fortification of buildings/structures to prevent or mitigate this potential seismic hazard. Utilizing acceleration time histories from the main shock of the Wenchuan earthquake recorded at four stations (i.e., one on bedrock and three on soil) in the Qionghai Basin, the site responses from three soil sites are studied by using the traditional spectral ratio method. The bedrock site is selected as a reference site. This study found that peak ground accelerations (PGAs) on the soil sites are much larger than on bedrock, with EW, NS and UD components of 3.96–6.58, 6.27–10.98, and 3.17–6.66 times those of the bedrock site, respectively. The amplification effects of the soil sites on ground motions in the frequency range of 0.1 Hz to 10 Hz are significant, depending on the thickness of the soil layer and the frequency content of the site. A significant amplification occurs with high frequency components of ground motion at shallow soil sites, and low and high frequency components of ground motion at intermediate soil sites. 相似文献
20.
In order to deeply understand the characteristics of influence factors of ground motion in Southwest Yunnan, and better serve the related research of seismic fortification and earthquake prediction in the target area, 242 groups of three-component strong earthquake recordings in Southwest Yunnan from 2007 to 2019 were analyzed by using the two-step non-parametric generalized inversion method. By separating and solving the ground motions observed on the surface in frequency domain, the empirical relationship of the quality factors of 0.5 ~ 20 Hz in this area was given, and the site effect of 26 strong earthquake stations in the study frequency band were obtained, which were compared with the HVSR results. Based on the grid search method, the seismic moment M0, corner frequency fc and source model parameters of 35 seismic events are determined, and the calibration relationship among some source parameters is obtained by fitting. The results show that the relationship between Q value and frequency of quality factor in Southwest Yunnan is Q=94.23f 0.43. Compared with HVSR method, the site response determined by non-parametric generalized inversion method is generally higher, but the site effect spectra obtained by the two methods are consistent. The source parameters such as corner frequency, seismic moment and stress drop are mutually dependent. 相似文献