A comparative study of bridge damage due to the Wenchuan, Northridge, Loma Prieta and San Fernando earthquakes

A comparative study of selected bridge damage due to the Wenchuan, Northridge, Loma Prieta and San Fernando earthquakes is described in this paper. Typical ground motion effects considered include large ground fault displacement, liquefaction, landslide, and strong ground shaking. Issues related to falling spans, inadequate detailing for structural ductility and complex bridge configurations are discussed within the context of the recent seismic design codes of China and the US. A significant lesson learned from the Great Wenchuan earthquake, far beyond the opportunities to improve the seismic design provisions for bridges, is articulated.     

2008年青海大柴旦Mw6.3地震地面运动模拟

2008年11月10日在青海柴达木盆地北缘发生了大柴旦M_W6.3地震,为了研究该地震的区域地震波传播与地面运动特征,本文利用地质资料和地壳速度结构研究成果,构建了柴达木盆地及周边区域三维传播介质模型,采用有限差分方法模拟了大柴旦地震波场传播过程以及地面运动分布特征.结果表明,柴达木盆地对波场传播有明显影响,表现为地震波传入盆地后在边界产生次生面波,盆地沉积物对地震波具有围陷作用,地震地面运动在盆地内振幅增大、持时延长.模拟结果给出的地震地面运动峰值速度分布以及理论地震图均和观测结果符合较好,反映数值模拟较好地给出了观测地面运动的主要特征以及传播介质模型的合理性.     

Modelling non‐linear ground response of non‐liquefiable soils

A non‐linear finite element (FE) model is presented to account for soil column effects on strong ground motion. A three‐dimensional bounding surface plasticity model with a vanishing elastic region, appropriate for non‐liquefiable soils, is formulated to accommodate the effects of plastic deformation right at the onset of loading. The elasto‐plastic constitutive model is cast within the framework of a FE soil column model, and is used to re‐analyse the downhole motion recorded by an array at a Large‐Scale Seismic Test (LSST) site in Lotung, Taiwan, during the earthquake of 20 May 1986; as well as the ground motion recorded at Gilroy 2 reference site during the Loma Prieta earthquake of 17 October 1989. Results of the analysis show maximum permanent shearing strains experienced by the soil column in the order of 0.15 per cent for the Lotung event and 0.8 per cent for the Loma Prieta earthquake, which correspond to modulus reduction factors of about 30 and 10 per cent respectively, implying strong non‐linear response of the soil deposit at the two sites. Copyright © 2000 John Wiley & Sons, Ltd.     

一种利用单台强震记录计算任意场地三分量地面运动的方法

本文利用近场理论格林函数反褶积的方法计算土层的地震反应.解答中包含了产生地面运动的各种反射、透射和转换波震相,也计入了土层与基底介质的相互作用.将计算的土层响应与已获得的近场加速度记录褶积,可算出不同土层场地上垂直向和水平向三分量的地面运动.文中利用1982年卢龙地震的近场加速度记录,检验了方法的可行性.     

一种利用单台强震记录计算任意场地三分量地面运动的方法

本文利用近场理论格林函数反褶积的方法计算土层的地震反应.解答中包含了产生地面运动的各种反射、透射和转换波震相,也计入了土层与基底介质的相互作用.将计算的土层响应与已获得的近场加速度记录褶积,可算出不同土层场地上垂直向和水平向三分量的地面运动.文中利用1982年卢龙地震的近场加速度记录,检验了方法的可行性.     

Study on the severest real ground motion for seismic design and analysis

How to select the adequate real strong earthquake ground motion for seismic analysis and design of trucures is an essential problem in earthquake engineering research and practice.In the paper the concept of the severest design ground motion is proposed and a method is developed for comparing the severity of the recorded strong ground motions.By using this method the severest earthquake ground motions are selected out as seismic inputs to the structures to be designed from a database that consists of more than five thousand significant strong ground moton records collected over the world.The selected severest ground motions are very likely to be able to drive the structures to their critical response and thereby result in the highest damage potential.It is noted that for different structures with diffferent predominant natural periods and at different sites where structures are located the severest design ground motions are usually different.Finally.two examples are illustrated to demonstrate the rationality of the concept and the reliability of the selected design motion.     

黄土丘陵河谷场地地震动特征研究

研究黄土丘陵河谷场地在地震作用下强地面运动特征的变化情况,可以揭示强震对该类场地上震害的触发机理。结合黄土高原的地貌特征,建立具有代表性的动力数值分析模型,通过输入不同幅值、频谱特性和持续时间的地震波,对起伏地形和覆盖黄土层共同影响下的黄土河谷场地进行地震反应分析。结果表明:黄土层和地形耦合作用控制了地表的PGA变化,使其趋于复杂,在同一输入波不同振幅作用下,与基岩河谷各测点相比,黄土覆盖河谷场地的地震动频谱幅值均有所增加,并且频谱主峰均向高频移动。在不同地震波输入下,场地不同部位的固有频率受地形高程和土层影响;而地震动大小和频谱幅值不仅与场地的基本频谱和地形起伏有关,也与输入地震波的频谱成分相关。输入波PGA与地震频谱特征都不变时,同一场地输出的地震频谱形状具有相似的特征,随着地震持时增长,能量向场地基本频率附近集中,从而可能导致场地上相应频率建筑物震动幅值增加,造成累积破坏。     

Ultrasonic modelling research of earthquake response of underground lifeline engineering

Earthquake response of underground lifeline engineering is investigated by the method of ultrasonic model experiments in this paper. From general field conditions, two models of underground lifeline engineering, one for non-uniform field and the other for uniform field, are designed based on the similarity principle. Besides analysis of seismic phases, a series of analyses especially on particle vibration are carried out. The results show that: The shorter the epicentral distance, the greater are the intensity variation and the change rate of intensity variation of earthquake ground motion, so the more disadvantageous to underground pipelines. In soft covering layer, compressional waves mainly cause radial flexures deformation, but shear wave result in axial dilation deformation of the pipelines; when the thickness of the covering layer is smaller (less than seismic wave length), the rhythmic variation of the intensity of earthquake ground motion is controlled mainly by the wave length of seismic waves in the bedrock. The property of the covering layer has considerable effect on earthquake ground motion. For different covering layers, their effect on each component of earthquake ground motion is not the same. Owing to the effect of wave propagation, the ground is in different states of particle vibration at different times, and there is considerable difference in phase and intensity of particle vibration between two different covering layers near their junction line or surface. Because underground lifelines tend to vibrate with the particles of the earth around it, this results in different deformation of underground pipelines under different conditions. So, it is necessary to take corresponding anti-seismic countermeasures for pipelines according to their practical situations. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, 104–110, 1992. This paper is part of the research supported by Funds of Doctoral Faculty of National Education Committee.     

最不利设计地震动研究

实际记录到的真实地震动在工程结构的抗震研究、分析和设计中往往作为一种施加到结构上使结构振动，直至破坏的地震荷载．如何合理选择真实的地震动记录作为研究结构地震反应的输入，一直是国内外抗震研究和设计中引人关注的重要问题．本文首先提出了最不利设计地震动的概念；然后在收集到的国内外5000余条被认为有重要意义的地震动记录基础上，利用综合估计地震动潜在破坏势的方法，对４种场地类型分别给出了长周期、短周期和中周期结构的国内外最不利设计地震动；最后通过几类不同结构的地震反应分析，初步验证了本文所确定的最不利设计地震动的可靠性和合理性．      

竖向地震动对大跨度高断面Y形柱地铁车站地震响应分析研究

以北京地铁6号线新华大街站公共区Y型柱地铁车站为工程背景,利用FLAC3D有限差分程序数值模拟分析,研究超浅埋大跨度、高断面、Y形柱地铁车站结构分别在仅输入水平向地震动和同时输入水平向与竖向地震动情况下的地震响应特性。结果表明:(1)与仅输入单向地震动相比,双向地震动耦合作用下车站各测点的峰值加速度和应力值均增大,而相对水平位移减小,且随着输入地震动强度的增加,竖向地震动影响率呈递减趋势;(2)双向地震动作用下,同一工况Y形柱叉支处各测点的竖向位移明显增大,且各测点的竖向位移值较为均匀,而单向水平地震动作用下各测点竖向位移差异较大;(3)与单向水平地震动相比,竖向地震动的输入对各测点间的水平方向地震动特性规律影响较小。     

Earthquake ground motion modeling of induced seismicity in the Groningen gas field

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, M_L 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.     

准稳态地震动模拟和场地放大率的计算

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。     

2014年2月12日新疆于田地震强地面运动初步模拟及烈度预测

2014年2月12日新疆自治区于田县发生了M_S7.3级地震.在已知的三维介质模型、地形数据基础上,利用震源运动学初步反演模型（张勇等,2014）,作者采用曲线坐标网格三维曲线有限差分方法模拟了于田地震波场传播过程,并计算了模拟区域地震烈度分布.结果表明：地震最大烈度为7度,距离震中最近的于田县城烈度约为5度,断层西北侧地面震动略强于断层东南侧.另外模拟结果还显示地震动在山脊处具有较大的幅度.该地震本身主要能量释放区域在中地壳,主要滑动未及地表,因此对地表造成的破坏有限,这与目前尚无人员伤亡报告的情况相符合.     

特殊长周期地震动的参数特征研究

近断层脉冲型地震动和远场软土层场地类谐和地震动是两类特殊的长周期地震动,当前的规范均很少对这两类地震作用进行具体的规定。研究了近断层脉冲型和远场类谐和地震动的幅值、幅值比（V／A,D／V）、傅里叶幅值谱和反应谱的差别,分析了相位角和作用循环周期数对简单脉冲的影响,并用于解释两类特殊地震动的工程特征。以集集地震动为数据基础,分析了两类长周期地震动的傅里叶谱和反应谱特征;将平均加速度和位移规准反应谱分别与规范设计谱进行了比较。建议设计谱在长周期段考虑近断层作用和软土场地面波效应的影响。     

特征地震强地面运动参数衰减公式拟合

计算机仿真模拟设定地震断层动态破裂传播和近断层强地表运动响应的结果表明, 对于特征地震而言,近断层附近的地表运动特征与断层破裂传播的方向性有着强烈的依赖关系. 当场地（观测点）至断层的距离给定时,正向于破裂传播方向的场地（场地A）的地表质点运动（位移、速度、加速度）,远远大于震中附近（场地B）和反向于破裂传播方向的场地（场地C）的地表质点运动,而且沿断层垂直分量所辐射的SH波的传播起到了主导作用. 对应于场地A,B和C,统计分析结果表明,峰值加速度的几何平均值之比为2.15:1.5:1, 而且各自的均方差分别为0.12, 0.11和0.13. 如果将所得的研究结果应用于概率地震危险性分析中,对于较低的年超越频度,近断层附近的地表峰值加速度的估算值可下降15%~30%. 因此,考虑到断层破裂传播方向性对地表运动的影响,区域衰减曲线的回归分析模型应该给予恰当的修正.      

合成地震动方法用于研究强地震动长周期特性的探讨

合成地震动一直是地震学研究中一个非常跃的领域。针对２长周期结构物抗震设计缺少宽频带强震记录的现状,利用“反射率法”和“围道积分法”等合成地震动方法对地震动长周期特性进行了探讨。结果表明：合成地震动方法是研究地震动长周特性的一个有效方法;在地震动长周期成份中,面波起着重要作用。因此长周期结构物的抗震设计必须考虑面波的影响。     

断层破裂面倾角变化对断陷盆地强地面运动的影响

地震事件中,断层破裂面的倾角大小直接影响到地表强地震动的分布状态,尤其在断陷盆地中,强地面运动特征还可能受到盆地结构及盆地内多条围限断层的影响.本文模拟了银川断陷盆地内的活动断层--银川隐伏断层南段发生M_w6.5特征地震时,断层破裂面倾角在30°~85°范围内变化时引起的强地面运动,探讨了断层破裂面倾角变化对盆地内强地面运动分布特征和强度的影响.结果表明:破裂面倾角较缓时,银川盆地内的强地面运动分布区域不仅仅决定于发震断层的产状,同时还受到断层上盘距离最近的芦花台断层的影响,致使强地面运动集中于两条断层所围限的区域;随着发震断层破裂面的倾角逐渐增大,强地面运动以发震断层产状的影响为主,强震集中区向发震断层靠近并分布于发震断层上盘,且沿断层走向方向出现了强度不同的地震动反射区;尤其是发震断层破裂面倾角接近垂直时,受银川盆地"西陡东缓"结构和盆地西边界贺兰山东麓断裂反射作用的影响,竖向地震动反射区强度在远离发震断层的西北方向明显增大,致使芦花台断层附近区域与银川断层南段上盘区域成为地震发生时可能遭受震害最严重的地区.本文探讨结果提醒我们在类似区域的活动断层附近进行建(构)筑规划和地震工程设计时,有必要考虑发震断层破裂面倾角大小和盆地内其它断层构造的共同影响,综合评价潜在地震对盆地内近断层地表及各类建(构)筑物的危害性.     

Ground motion characteristics of the Chi‐Chi earthquake of 21 September 1999

The purpose of this paper is to investigate the ground motion characteristics of the Chi‐Chi earthquake (21 September 1999) as well as the interpretation of structural damage due to this earthquake. Over 300 strong motion records were collected from the strong motion network of Taiwan for this earthquake. A lot of near‐field ground motion data were collected. They provide valuable information on the study of ground motion characteristics of pulse‐like near‐field ground motions as well as fault displacement. This study includes: attenuation of ground motion both in PGA and spectral amplitude, principal direction, elastic and inelastic response analysis of a SDOF system subjected to near‐field ground motion collected from this event. The distribution of spectral acceleration and spectral velocity along the Chelungpu fault is discussed. Based on the mode decomposition method the intrinsic mode function of ground acceleration of this earthquake is examined. A long‐period wave with large amplitude was observed in most of the near‐source ground acceleration. The seismic demand from the recorded near‐field ground motion is also investigated with an evaluation of seismic design criteria of Taiwan Building Code. Copyright © 2000 John Wiley & Sons, Ltd.     

Some considerations on the physical mea-sure of seismic intensity

Introduction In1564,an Italian man named Jacopo Gastaldi(XIE,1958)presented the first macroseismic intensity scale in the world,which based on the building damage and the ground surface failure after an earthquake.Today the seismic intensity has developed into an indispensable important concept,which applies to seismology and earthquake engineering,however it was just used to de-scribe earthquake damage while the concept of intensity was established.With this concept,seis-mologist can estima…     

保定市设计地震动参数的研究

本文根据保定市及周围地区的地震地质环境，在地震危险性分析的基础上，采用等效线性一维波动方程进行土层的地震反应分析。给出50年超越概率63％、10％、2％基岩和地面的水平向峰值加速度、反应谱（场址基本烈度Ⅶ度）和地震影响系数最大值。该结果为抗震设计提供了可靠依据，具有应用价值。