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1.
I. C. Simpson 《地震工程与结构动力学》1978,6(3):247-263
A two-dimensional soil-structure interaction analysis is carried out for transient Rayleigh surface waves that are incident on a structure. The structure is modelled by a three-degree of freedom rigid basemat to which is attached a flexible superstructure, modelled by a single mass-spring system. The structural responses to a given Rayleigh wave train are compared with those that would have been obtained if the free-field acceleration-time history had been applied as a normally incident body wave. The results clearly exhibit the [frequency filtering] effects of the rigid basemat on the incident Rayleigh waves. It is shown that, if seismic excitation of a structure is, in fact, due to Rayleigh surface waves, then an analysis assuming normally incident body waves can considerably over-estimate structural response, both at basemat level for horizontal and vertical motions and for vertical oscillations of the superstructure. However, in the examples considered here, relatively large rocking effects were induced by the Rayleigh waves, thus giving maximum horizontal accelerations in the superstructure that were of comparable magnitude for Rayleigh and normally incident body waves. 相似文献
2.
《地震研究进展（英文）》2022,2(4):100179
In this study, A time-domain seismic response analysis method and a calculation model of the underground structure that can realize the input of seismic P, SV and Rayleigh waves are established, based on the viscoelastic artificial boundary elements and the boundary substructure method for seismic wave input. After verifying the calculation accuracy, a comparative study on seismic response of a shallow-buried, double-deck, double-span subway station structure under incident P, SV and Rayleigh waves is conducted. The research results show that there are certain differences in the cross-sectional internal force distribution characteristics of underground structures under different types of seismic waves. The research results show that there are certain differences in the internal force distribution characteristics of underground structures under different types of seismic waves. At the bottom of the side wall, the top and bottom of the center pillar of the underground structure, the section bending moments of the underground structure under the incidences of SV wave and Rayleigh wave are relatively close, and are significantly larger than the calculation result under the incidence of P wave. At the center of the side wall and the top floor of the structure, the peak value of the cross-sectional internal force under the incident Rayleigh wave is larger than the calculation result under SV wave. In addition, the floor of the underground structure under Rayleigh waves vibrates in both the horizontal and vertical directions, and the magnification effect in the vertical direction is more significant. Considering that the current seismic research of underground structures mainly considers the effect of body waves such as the shear waves, sufficient attention should be paid to the incidence of Rayleigh waves in the future seismic design of shallow underground structures. 相似文献
3.
Building foundation-soil interaction is studied in the frequency domain using a two-dimensional analytical model. The building is represented by an infinitely long shear wall resting on a circular foundation, embedded into an elastic homogeneous half-space. Deep and shallow foundations are considered (with depth-to-half-width ratios of 1 and 0·5). Both the dynamic interaction and the wave passage effects are included. The excitation is a plane P- or SV-wave,or a surface Rayleigh wave. The results show that for incident waves which are long relative to the width of the foundation, the foundation driving forces are larger when the embedment is deeper. For shorter incident waves, the input base rotation is larger for shallow foundations and, therefore, the relative building response may then be larger. It is also shown that the input base rotation may contribute significantly to the building excitation and that neglecting it may cause nonconservative estimates for the forces in the building. 相似文献
4.
The effect of topography and subsurface inhomogeneity on surface motion is investigated in the case of Rayleigh waves. In the previous paper, the same effect was investigated in the case of SV waves. Several types of topography, such as cliffs both with and without a soft layer at the foot of the slope, are considered. Computations are made using a new hybrid method combining a particle model with a finite element method. In cases of harmonic Rayleigh waves, surface motions with amplitudes as large as 1.5 to 5 times the horizontal surface displacement of the incident Rayleigh waves are produced near the slope and the sloping interface. When a Rayleigh wave propagating through a hard single-layered ground encounters a sloping interface where hard ground and soft ground make contact with each other, Rayleigh waves having two different, phase velocities are produced and they correspond to the fundamental mode, and the first mode determined by Haskell's method. In addition, the transient response when Rayleigh waves propagate through the cliff is also simulated. Assuming the vertical component of the Tokachi-oki Earthquake (1968) measured on the surface to be a Rayleigh wave, the incident Rayleigh wave can be obtained by a Fourier synthesis of eigenfunctions of Rayleigh waves. 相似文献
5.
Foundation soil interaction is studied using an analytical two-dimensional model, for circular foundations embedded in a homogeneous elastic half-space and for incident plane P- and SV- and for surface Rayleigh waves. The scattered waves are expanded in complete series of cyclindrical wave functions. A detailed analysis is presented of the foundation response to unit amplitude incident waves as a function of the type of incident waves and angle of incidence, the depth of the embedment and the foundation mass per unit length.It is shown that free-field translations and point rotation approximate well the foundation input motion only for very long incident waves. For shorter incident waves, those in general overestimate the foundation input motion. Neglecting the rotation of the foundation input motion (which is usually done in practice) may eliminate a major contribution to the base excitation of buildings and may cause nonconservative estimates of the forces in these buildings. Incident waves appear as ‘longer’ to a shallow foundation than to a deeper foundation. Therefore, deeper foundations are more effective in reflecting and scattering the short incident waves. 相似文献
6.
采用间接边界元法（IBEM）,对Rayleigh波入射下两邻近山体的地震响应进行了定量分析。结果表明:与单个山体在Rayleigh波入射下的地震响应相比,两山地形的地震反应规律更为复杂,反应特征受控于入射波频率和山体间距等因素。总体上看:入射Rayleigh波频率较低时,两山间距对双山地形地震反应影响较大。低频波入射,受邻近山体影响,迎波面山体水平位移峰值约为入射波水平位移的6.3倍,放大效应可达单山作用的1.5倍。且山体山脚处竖向位移的频谱振荡更为剧烈,特定频率下山脚的竖向位移反应可达单山放大效应的1.6倍。较高频波入射时,迎波面一侧山体受邻近山体影响较小,且对波表现出明显的屏障效应,背波面山体地震反应强度被削弱。 相似文献
7.
基于Biot多孔介质波动模型,研究了非均匀饱和土层对平面P-SV波入射时的动力响应.考虑饱和土地基的物理力学特性沿厚度方向连续变化,利用亥姆霍兹矢量分解原理和动力刚度法,分析了平面入射P-SV波在非均匀饱和土层中的反射和透射,并给出了基岩表面和自由表面处反射系数和透射系数的计算表达式.基于理论推导结果,数值分析了平面SV波入射下非均匀饱和土自由场地的动力响应,其中假设饱和土地基的物理力学性质沿土层深度按幂律梯度变化.数值结果表明,平面SV波入射所引起的地面位移与基岩位移之比均随土层厚度和土体的非均匀程度、波的入射角和入射频率的增加而减小,且其竖向位移比的减小更为显著,厚土层对地震波的耗散作用尤为明显. 相似文献
8.
A time domain Boundary Element-Finite method is employed to determine the dynamic response of flexible surface two-dimensional foundations under conditions of plane strain placed on an elastic soil medium and subjected either to transient external forces or to obliquely incident seismic waves. The elastic, isotropic, and homogeneous soil medium is treated by the time domain Direct Boundary Element Method, while the flexible foundation is treated by the Finite Element Method. The two methods are appropriately combined through equilibrium and compatibility considerations at the soil-foundation interface. Parametric studies examining the effect of the relative stiffness between the foundation and the soil and the spatial distribution of the dynamic disturbances on the foundation response are presented. 相似文献
9.
在远场地震作用下单桩横向地震响应研究的基础上,引入相互作用因子,研究了远场地震作用下成层地基中桩与桩的横向动力相互作用,得到了桩间距、桩土刚度比、桩顶约束条件、瑞利波入射角度、震动频率是影响群桩横向动力相互作用主要因素的结论,为进一步研究远场地震作用下群桩的横向地震响应打下了基础。 相似文献
10.
结合延安新区强夯加固地基工程,进行强夯振动加速度测试现场试验。选取填方区场地,结合地形设计监测方案,以测试强夯波沿水平方向和斜坡的传播规律。在选定试验段的某级填方场地上布置多组加速度传感器,运用多个8通道24位高速采集卡记录强夯振动加速度在平面和斜坡的传播和衰减过程,探讨强夯振动波沿水平面和斜坡的传播规律以及能级对振动加速度的影响。结果表明:径向和竖向加速度值均随与夯点距离的增大而减小;在与夯击点距离相同处,强夯振动波沿水平方向传播的径向和竖向加速度值要大于沿斜坡方向;随着能级的增大,强夯产生的夯击波增强,在与夯击点相同距离处产生的径向和竖向加速度均明显增大。 相似文献
11.
Rayleigh波入射情形下的断层效应 总被引：1，自引：0，他引：1
本文运用数值模拟方法对Rayle igh波入射情形下的断层效应进行分析,结果表明:断层对Ray-le igh面波具有隔震作用,随断层深度的增加其隔震效果更加明显,且水平向的隔震效果强于竖向。在入射波一侧,由于断层的作用使接触带附近的反应增强,随着断层破碎带宽度的增加,竖向反应变化特征明显不同于水平向反应变化特征。 相似文献
12.
This paper shows an effective implementation of the half-plane Green function for surface strip impulses (Lamb's problem), which was previously developed in a closed form by the authors, into the time-domain boundary element method for the analysis of related initial boundary value problems. The time-stepping algorithm utilizing Heaviside step function makes the solution process free from the Rayleigh wave front singularity. Illustrative analyses performed include that: First, the response due to an impulsive uniform strip loading is dealt with in order to check the accuracy of the present solution and to interpret the associated wave motion in the medium. Second, a rigid massless strip surface foundation is analysed when subjected to various impulsive loadings in vertical, horizontal and rotational directions to observe which wave is most concerned with the respective foundation motion. The field response is also of interest with respect to distance attenuation. Third, the dynamic cross-interaction between active and passive foundations through soil is investigated when multiple strip foundations are placed separately on a half-space with a certain distance. 相似文献
13.
Rabindra Kumar Bhattacharyya 《Pure and Applied Geophysics》1996,146(3-4):677-688
In this paper the smooth perturbation technique is employed to investigate the problem of reflection of waves incident on the plane boundary of a semi-infinite elastic medium with randomly varying inhomogeneities. Amplitude ratios have been obtained for various types of incident and reflected waves. It has been shown that an incidentSH orSV type of wave gives rise to reflectedSH, P andSV waves, the main components beingSH andP, SV in the respective cases. The reflected amplitudes have been calculated depending upon the randomness of the medium to the square of the small quantity , where measures the deviation of the medium from homogeneity. An incidentP-type wave produces mainly aP component and also a weakSH component to the order of 2. The reflected amplitudes obtainable for elastic media are also altered by terms of the same order. The direction of the reflected wave is influenced by randomness in some cases. 相似文献
14.
Under the action of Rayleigh waves, pile head is easy to rotate with a concrete pile cap, and pure fixed-head condition is rarely achieved, which is a common phenomenon for it usually occurs on the precast piles with insufficient anchorage. In addition, the propagation characteristics of Rayleigh wave have been changed significantly due to the existence of capillary pressure and the coupling between phases in unsaturated soil, which significantly affects the pile-soil interaction. In order to study the above problems, a coupled vibration model of unsaturated soil–pile system subjected to Rayleigh waves is established on the basis that the pile cap is equivalent to a rigid mass block. Meanwhile, the soil constitution is simplified to linear-elastic and small deformations are assumed to occur during the vibration phase of soil–pile system. Then, the horizontal dynamic response of a homogeneous free-field unsaturated soil caused by propagating Rayleigh waves is obtained by using operator decomposition theory and variable separation method. The dynamic equilibrium equation of a pile is established by using the dynamic Winkler model and the Timoshenko beam theory, and the analytical solutions of the horizontal displacement, rotation angle, bending moment and shear force of pile body are derived according to the boundary conditions of flexible constraint of pile top. Based on the present solutions, the rationality of the proposed model is verified by comparing with the previous research results. Through parametric study, the influence of rotational stiffness and yield bending moment of pile top on the horizontal dynamic characteristics of Rayleigh waves induced pile is investigated in detailed. The analysis results can be utilized for the seismic design of pile foundation under Rayleigh waves. 相似文献
15.
Tapendra Nath Maulik 《Pure and Applied Geophysics》1964,58(1):49-62
Summary It has been found that when seismic energy propagates along the surface of the homogeneous crust beside usual Rayleigh waves, it produces certain instability in layers through which it propagates. In the light of this instability, a type of motion corresponding to longitudinal wave will be prominent in horizontal component compared to the vertical component; while transverse wave will be prominent in the vertical component but weak in the horizontal component, a contradiction with the existing knowledge. This has been identified withP
F
phase. On taking the medium of propagation as slightly heterogeneous which allows existence of low velocity layer, a few larger number of such instabilities have been found. Velocity equation for Rayleigh waves for such media reveals existence of different velocities corresponding to vertical and horizontal components. Table for these velocities has been furnished. 相似文献
16.
An evaluation of the wave passage effects on the relevant dynamic properties of structures with flexible foundation is presented. A simple soil–structure system similar to that used in practice to take into account the inertial interaction effects by the soil flexibility is studied. The kinematic interaction effects due to non‐vertically incident P, SV and Rayleigh waves are accounted for in this model. The effective period and damping of the system are obtained by establishing an equivalence between the interacting system excited by the foundation input motion and a replacement oscillator excited by the free‐field ground motion. In this way, the maximum structural response could be estimated from standard free‐field response spectra using the period and damping of the building modified by both the soil flexibility and the travelling wave effects. Also, an approximate solution for the travelling wave problem is examined over wide ranges of the main parameters involved. Numerical results are computed for a number of soil–structure systems to identify under which conditions the effects of wave passage are important. It comes out that these effects are generally negligible for the system period, but they may significantly change the system damping since the energy dissipation within the soil depends on both the wave radiation and the diffraction and scattering of the incident waves by the foundation. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
17.
The problem of the dynamic response of rigid embedded foundations subjected to the action of external forces and seismic excitation is analysed. It is shown that to calculate the response of rigid embedded foundations, or the response of flat rigid foundations subjected to non-vertically incident seismic waves, it is necessary to obtain not only the impedance matrix for the foundation, but also the forces induced by the incident seismic waves. Under these general conditions, rocking and torsional motion of the foundation is generated in addition to translation. The case of a two-dimensional rigid foundation of semi-elliptical cross-section is used as an example to illustrate the effects of the embedment depth and angle of incidence of the seismic waves on the response of the foundation. 相似文献
18.
以西安万寿寺塔纠偏工程为研究背景,分别建立增加圈梁、圈梁-地梁组合以及圈梁-地梁-托盘组合模型下的塔体与基础协同工作模型。采用时程分析法,对不同基础刚度条件下塔体的地震响应进行分析及评估,结果表明:(1)增大基础刚度的同时结构的地震位移响应将会被放大,但应力时程曲线的波动范围随之缩小、幅值减小;(2)增设圈梁时由于塔底三向受力,塔底应力将被放大;(3)进行基础完全托换能够大幅改善塔底在地震作用下的受力状态。在塔体加固维修时应综合考虑地震作用下塔体的位移放大效应与塔体应力分布的影响,选取合适的基础刚度。 相似文献
19.
激光雷达观测得到的密度、温度等数据被广泛应用于大气重力波研究.瑞利激光雷达可以获取激光路径上的大气密度、温度数据.对于大气中的三维波动而言,单条路径上的观测参量能提取得到的波动信息有限.本文首先以单色重力波为例,分析了利用激光雷达直接观测三维波动结构的可行性.激光雷达垂直观测即可得到重力波的垂直波长,当激光雷达以一定的天顶角斜向测量时,所得到的波长包含了重力波的垂直波长以及水平波长信息.因此,利用激光雷达同时以三个方向(垂直、向南(天顶角30°)以及向西(天顶角30°))测量,可以提取得到重力波的垂直波长和水平波长.本文利用中国科学院国家空间科学中心研制的车载532nm瑞利激光雷达的经向系统和纬向系统同时以不同的指向角观测大气重力波,对利用激光雷达获取三维波动结构的方法进行了分析研究.本文给出了北京地区激光雷达观测重力波的诸多案例,分析了30~60km高度范围内北京地区大气重力波的垂直及水平波长信息.并以2017年11月7日观测的准单色重力波为例,结合再分析资料的风场数据,分析了该重力波的水平波长,垂直波长及传播方向等信息. 相似文献
20.
地震动入射角度对地下结构地震响应的影响 总被引：1，自引：0，他引：1
考虑土-结构接触面效应和场地初始静应力影响,基于大型商用有限元软件ANSYS和粘弹性人工边界条件,采用动力松弛法的分析思路,建立了一种地震动斜入射条件下地下结构的接触非线性动力反应分析模型和方法,并讨论了地震动入射角度对地下结构动力反应的影响。结果表明：地震波斜入射使得结构的整体反应发生明显变化;随着入射角度的增加,节点的水平向应力反应明显增大,竖向应力峰值较小,增大程度也相对较小;节点的位移峰值随输入加速度峰值的增大也有一定的变化。因此,在分析近源地震作用下的地下结构动力响应时,需要考虑地震动的非一致输入问题。 相似文献