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1.
将列车移动荷载简化为多个移动轮轴荷载,基于列车-轨道-路基解析模型推求的列车运行时不同时刻、不同位置时作用于路基的振动荷载时程,采用多点输入方式实现列车荷载的移动施加方式,建立路(地)基-场地体系三维有限元动力分析模型,基于Abaqus软件的并行计算集群平台,对轨道交通振动荷载下路(地)基-场地体系的动力反应进行数值模拟,研究了列车荷载作用线正下方地基中的动应力特征及土单元应力状态变化,分析了列车轮轴荷载移动过程中不同深度处土单元的应力路径和主应力轴的旋转。 相似文献
2.
In this paper, the response of a visco-elastic half-space subjected to moving loads with static and dynamic components is investigated. Four types of vehicle loads are considered, including the moving point load, uniformly distributed wheel load, elastically distributed wheel load, and a train load simulated as a sequence of elastically distributed wheel loads. In each case, the influence of the moving loads traveling in the subsonic, transonic and supersonic ranges on the dynamic responses of the half-space is studied. The parametric study conducted herein enables us to grasp insight into the mechanism of wave propagation for a visco-elastic half-space under moving loads. 相似文献
3.
Dynamic analysis of slab track on multi-layered transversely isotropic saturated soils subjected to train loads 总被引：1，自引：0，他引：1
The dynamic responses of a slab track on transversely isotropic saturated soils subjected to moving train loads are investigated by a semi-analytical approach. The track model is described as an upper Euler beam to simulate the rails and a lower Euler beam to model the slab. Rail pads between the rails and slab are represented by a continuous layer of springs and dashpots. A series of point loads are formulated to describe the moving train loads. The governing equations of track-ground systems are solved using the double Fourier transform, and the dynamic responses in the time domain are obtained by the inverse Fourier transform. The results show that a train load with high velocity will generate a larger response in transversely isotropic saturated soil than the lower velocity load, and special attention should be paid on the pore pressure in the vicinity of the ground surface. The anisotropic parameters of a surface soil layer will have greater influence on the displacement and excess pore water pressure than those of the subsoil layer. The traditional design method taking ground soil as homogeneous isotropic soil is unsafe for the case of RE 1 and RG 1, so a transversely isotropic foundation model is of great significance to the design for high train velocities. 相似文献
4.
Efficiency of trenches along railways for trains moving at sub- or supersonic speeds 总被引：2，自引：0，他引：2
A full 3D analytical approach is adopted to account for trenches on one or both sides close to a railroad. Low-frequency ground vibrations are investigated due to the passing of trains, and open trenches are used as wave barriers. The modelling technique is based on Fourier transforms and Fourier series. The ground is modelled as a layered semi-infinite domain and the embankment with finite layers. The trenches are obtained by simulating the upper surface layer with two or three finite rectangular regions with appropriate widths. A particular boundary condition is adopted at the vertical sides of all finite regions to enable the solution procedure. Rails and sleepers are accounted for with Euler–Bernoulli beams and an anisotropic Kirchhoff plate with transversal isotropy. The wheel loads from the boogie wheel pairs of the train are simulated as moving forces. Hence, no irregularities in rails or wheels are accounted for. 相似文献
5.
混凝土桥梁在工作过程中会产生裂缝,为分析移动荷载对开裂混凝土桥梁结构刚度的影响,对开裂梁动力响应进行分析。建立简支T梁桥有限元模型,并将移动荷载施加至有限元模型中。根据简支T梁桥破坏横向分布位置和强度的不同,研究不同工况下各梁荷载横向分布及不同移动速度对裂缝扩展宽度的影响。结果表明,数值模拟结果能较好地验证计算模型的准确性;在较大的移动荷载作用下,混凝土开裂,导致结构刚度减小、位移增大;随着移动荷载和速度的增加,开裂时间增加,结构刚度降低,持续时间增加,位移增大,使结构响应呈现明显非线性。 相似文献
6.
Based on the Betti–Rayleigh Dynamic Reciprocal Theorem, the reciprocal property of the Green's functions is demonstrated, on the basis of which the analytical solution of soil vibration subjected to moving loads is derived. By application of the Betti–Rayleigh Dynamic Reciprocal Theorem, the moving source problem is converted to the fixed source problem with receiver point moving in opposite direction, which greatly simplifies the complex analytical solution of soil/ground vibration induced by a moving load. A computer code for solving the ground responses subjected to the moving constant load and harmonic load is developed via MATLAB and is employed to perform a case study. The analyzed results show that the ground vibration induced by moving constant load is of typical low-frequency feature; the frequency range of ground vibration is controlled by the Rayleigh's wave velocity of the top layer soil; when the receiver nears the source path, the R-wave contributes to the ground vibration more than the P-wave and the S-wave; while when the receiver is far from the source path, the contribution of the P-wave is more obvious. 相似文献
7.
Gongkang Fu 《地震工程与结构动力学》1998,27(9):977-995
The dynamic behaviour of bridge piers under seismic load is studied here in the context of random vibration. The earthquake excitation is modelled as white noise filtered by the Clough–Penzien filter in cascade with modulation accounting for intensity non-stationarity. The bridge pier modelled as an elastically supported cantilever beam witha lumped mass at the top. An analytical solution is presented for the response statistics, which may be used to develop probabilistic seismic response spectra for design. It is found that the first two modes of the pier approach to rigid-body motion when the stiffness of the elastic support decreases. Seismic responses increase with the top mass, resultingin significantly high displacement and shear but negligible moment at the top, and higher shear and moment at thebase. Lower stiffness of the elastic support increases the pier top displacement and moment responses, but may increase or reduce shear responses. The probabilistic spectrum of the relative displacement between the bridge superstructure and the pier top may depend on the two systems’ relative modal properties. © 1998 John Wiley & Sons, Ltd. 相似文献
8.
J. Glück 《地震工程与结构动力学》1972,1(4):371-376
The solution for transverse vibration frequencies of an elastically supported cantilevered column with continuously varying cross-section under distributed axial load is developed. Boundary conditions are formulated for fixed and elastic support. Values of the fundamental frequency are tabulated for various cross-sections and axial load distributions due to self-weight as functions of the ratios between the rigidities and also the axial loads at the fixed and free ends, the ratio between the actual and critical buckling axial load, the degree of polynomial approximation and the rotational stiffness of the elastic support. 相似文献
9.
This paper explores dynamic soil–bridge interaction in high speed railway lines. The analysis was conducted using a general and fully three-dimensional multi-body finite element–boundary element model formulated in the time domain to predict vibrations caused by trains passing over the bridge. The vehicle was modelled as a multi-body system, the track and the bridge were modelled using finite elements and the soil was considered as a half-space by the boundary element method. The dynamic response of bridges to vehicle passage is usually studied using moving force and moving mass models. However, the multi-body system allows to consider the quasi-static and dynamic excitation mechanisms. Soil–structure interaction was taken into account by coupling finite elements and boundary elements. The paper presents the results obtained for a simply supported short span bridge in a resonant regime under different soil stiffness conditions. 相似文献
10.
The exact analytical solution for the horizontal displacement at the center of the surface of an elastic half space under an impulsive loading having the same spatial distribution as the contact stresses that arise underneath a rigid disk when subjected to a static, horizontal load, is obtained using the Cagniard–De Hoop method. The solution can be used to study the dynamical interaction between soil and structures, and can also be used to assess numerical computations with a finite element or a boundary element program. 相似文献
11.
G. Lefeuve-Mesgouez A. T. Peplow D. Le Houdec 《Soil Dynamics and Earthquake Engineering》2002,22(6):692
The transmission of vibrations over the surface of the ground, due to high-speed moving, vertical harmonic rectangular loads, is investigated theoretically. The problem is three-dimensional and the interior of the ground is modelled as an elastic half-space or a multilayered ground. The transformed solutions are obtained using the Fourier transform on the space variable. A new damping model in the spatial wavenumber domain, presented in Lefeuve-Mesgouez et al. [J. Sound. Vibr. 231 (2000) 1289] is used. Numerical results for the displacements on the surface are presented for loads moving with speeds up to and beyond the Rayleigh wave speed of the half-space. 相似文献
12.
基于Kelvin空间半无限体黏弹性解,以单个轮轴荷载为例,研究地铁列车荷载下地基土动应力状态、应力路径及主应力轴旋转等应力变化规律,并与相应弹性解下的各动应力特征进行对比分析,探讨更适用于工程实际的地基附加动应力特征解。结果表明:弹性地基与黏弹性地基中的各应力状态变化总体趋势、主应力轴旋转变化趋势相同,但极限应力状态各应力分量大小及应力路径形状有明显差别,考虑黏弹性解更符合软土区地铁长期变形实际工况;并对单轮荷载下动应力特征的黏弹性解进行参数分析,发现特征系数对应力分量影响具有不同特性。 相似文献
13.
R. Paolucci A. Maffeis L. Scandella M. Stupazzini M. Vanini 《Soil Dynamics and Earthquake Engineering》2003,23(6):425-433
The ground vibrations induced by a passenger train at the test site of Ledsgaard, Sweden, have been analysed and numerically simulated through a spectral element discretization of the soil. To calculate the spatial distribution of loading due to train passage, the train is decoupled from the track, and a suitable series of static forces is applied. The track and the embankment are modeled as a beam on elastic foundation, using analytical solutions for loads moving at constant velocity. The results of both 2D and 3D modelling assumptions are thoroughly discussed, in terms of prediction of track motion and of attenuation of peak ground velocity with distance. 相似文献
14.
15.
In the railway bridge analysis and design method,dynamic train loads are regarded as static loads enhanced by an impact factor(IF).The IF coefficients for various railway bridges have been reported as a function of span length or frequency of the bridges in Eurocode(2003).However,these IF coefficient values neglect the effects of very high speeds(>200 km/h)and soil-structure interaction(SSI).In this work,a comprehensive study to assess the impact factor coefficients of mid-span vertical displacements for continuous and integral railway bridges subjected to high-speed moving loads is reported.Three different configurations,each for the three-dimensional(3D)continuous and integral bridge,are considered.Also,single-track(1-T)and two-track(2-T)“real train”loading cases for both these bridge types are considered.Subsequently,finite element analysis of the full-scale 3D bridge models,to identify their IF values,considering the effects of SSI for three different soil conditions,is conducted.The IF values obtained from the study for both bridge types are comparable and are greater than the values recommended by Eurocode(2003).The results reveal that with a loss of soil stiffness,the IF value reduces;thus,it confirms the importance of SSI analysis. 相似文献
16.
T. Senjuntichai S. Mani R.K.N.D. Rajapakse 《Soil Dynamics and Earthquake Engineering》2006,26(6-7):626-636
This paper considers time-harmonic vertical vibration of an axisymmetric rigid foundation embedded in a homogeneous poroelastic soil. The soil domain is represented by a homogeneous poroelastic half space that is governed by Biot's theory of poroelastodynamics. The foundation is subjected to a time-harmonic vertical load and is perfectly bonded to the surrounding half space. The contact surface can be either fully permeable or impermeable. The dynamic interaction problem is solved by employing an indirect boundary integral equation method. The kernel functions of the integral equation are the influence functions corresponding to vertical and radial ring loads, and a ring fluid source applied in the interior of a homogeneous poroelastic half space. Analytical techniques are used to derive the solution for influence functions. The indirect boundary integral equation is solved by using numerical quadrature. Selected numerical results for vertical impedance of rigid foundations are presented to demonstrate the influence of poroelastic effect, foundation geometry, hydraulic boundary condition along the contact surface and frequency of excitation. 相似文献
17.
This paper deals with the dynamic response of free-standing statues on the top surface of slender elastically supported cantilevers subjected to horizontal ground motion. Given that there is no link between the base of the statue and the top surface of the monolithic cantilever the statue is in equilibrium in the vertical direction under its own weight. Attention is focused on the determination of the minimum amplitude ground acceleration which leads to the rocking (overturning) instability of the statue whose mass and rotatory inertia are a priory known. It is assumed that the friction between the base of the statue and the top surface of the cantilever is sufficiently large to prevent sliding so that rocking prevails. After simulating the statue by a rigid block freely supported on the top surface of the elastically restrained monolithic cantilever, a theoretical dynamic analysis of the cantilever–rigid block system under horizontal ground motion is comprehensively presented. Two modes of overturning instability of the free standing rigid block are discussed: instability without or with impact. Criteria for overturning instability of the rigid block associated with the minimum amplitude ground acceleration which leads through the vanishing of the angular velocity to an escaped motion in the phase-plane portrait, are properly assessed. 相似文献
18.
R.A.Khan T.K.Datta S.Ahmad 《地震工程与工程振动(英文版)》2005,4(1):83-94
A simplified fragility analysis of fan type cable stayed bridges using Probabilistic Risk Analysis (PRA) procedure is presented for determining their failure probability under random ground motion. Seismic input to the bridge support is considered to be a risk consistent response spectrum which is obtained from a separate analysis. For the response analysis, the bridge deck is modeled as a beam supported on springs at different points. The stiffnesses of the springs are determined by a separate 2D static analysis of cable-tower-deck system. The analysis provides a coupled stiffness matrix for the spring system. A continuum method of analysis using dynamic stiffness is used to determine the dynamic properties of the bridges .The response of the bridge deck is obtained by the response spectrum method of analysis as applied to multidegree of freedom system which duly takes into account the quasi - static component of bridge deck vibration. The fragility analysis includes uncertainties arising due to the variation in ground motion, material property, modeling, method of analysis, ductility factor and damage concentration effect. Probability of failure of the bridge deck is determined by the First Order Second Moment (FOSM) method of reliability. A three span double plane symmetrical fan type cable stayed bridge of total span 689 m, is used as an illustrative example. The fragility curves for the bridge deck failure are obtained under a number of parametric variations. Some of the important conclusions of the study indicate that (i) not only vertical component but also the horizontal component of ground motion has considerable effect on the probability of failure; (ii) ground motion with no time lag between support excitations provides a smaller probability of failure as compared to ground motion with very large time lag between support excitation; and (iii) probability of failure may considerably increase for soft soil condition. 相似文献
19.
J. W. Smith 《地震工程与结构动力学》1972,1(4):357-370
This paper presents a method of analysis for the dynamic response of a simply supported beam and slab bridge under the action of a moving vehicle. The bridge is idealized as an orthotropic plate and, in the analysis, is subdivided into a number of finite strips. The vehicle is idealized as a moving sprung mass. Viscous damping is taken into account for both bridge and vehicle. The results show that there is significant variation of response across transverse sections of the bridge. Furthermore the dynamic magnification is considerably greater than that predicted by a more approximate method in which the bridge is idealized as a simple prismatic beam. 相似文献
20.
Scattering of SH-wave by multiple circular cavities in half space 总被引：17，自引：1，他引：17
In this paper, an analytic method is developed to address steady SH-wave scattering and perform dynamic analysis of multiple
circular cavities in half space. The scattered wave function used for scattering of SH-waves by multiple circular cavities,
which automatically satisfies the stress-free condition at the horizontal surface, is constructed by applying the symmetry
of the SH-wave scattering and the method of multi-polar coordinates system. Applying this scattered wave function and method
of moving coordinates, the original problem can be transformed to the problem of SH-wave scattering by multiple circular cavities
in the full space. Finally, the solution of the problem can be reduced to a series of algebraic equations and solved numerically
by truncating the infinite algebraic equations to the finite ones. Numerical examples are provided for case with two cavities
to show the effect of wave number, and the distances between the centers of the cavities and from the centers to the ground
surface on the dynamic stress concentration around the cavity impacted by incident steady SH-wave. 相似文献