共查询到20条相似文献,搜索用时 0 毫秒
1.
2.
Lu Sun 《国际地质力学数值与分析法杂志》2003,27(1):69-84
A closed‐form deflection response of a beam rest is presented in this paper using the integral transform method. The theory of linear partial differential equations is used to represent the deflection of beam subjected to a moving harmonic line load in integration form. The solution is finally carried out using the inverse Fourier transform. To evaluate the integration analytically, poles of the integrand are identified with the help of algebraic equation theory. Residue theorem is then utilized to represent the integration as a contour integral in the complex plane. Closed‐form deflections and numerical results are provided for different combinations of load frequency and velocity. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
3.
Stratification is a basic characteristic of ground. Due to the influence of ground water, saturated weak interlayers widely exist, particularly in soft soil area. An interlayer of high compressibility and low strength has a substantial effect on dynamic response of the ground, especially under high speed moving load. Thus, a comprehensive investigation in the influence of interlayer is essential and useful in geotechnical and transportation‐related engineering. This paper presents a three‐dimensional semi‐analytical approach to study the dynamic response of a layered ground with a soft saturated interlayer. The ground is modelled as a half‐space consisting of three parts: a viscoelastic upper layer, a saturated poroviscoelastic interlayer governed by Biot's theory and a viscoelastic half‐space. An ‘adapted stiffness matrix’ is proposed to obtain the semi‐analytical solution to the system. Comprehensive parametric study is conducted to investigate the influences of existence, geometrical and physical properties of the interlayer. Depth, thickness, hydraulic permeability of the interlayer, load speed and frequency significantly influence the dynamic response of the ground, among which the interlayer depth plays a dominant role. Resonant frequency exists, which is highly affected by the interlayer thickness, especially in low speed regime. Both hydraulic permeability and boundary conditions of the interlayer influence the characteristics of pore pressure distribution. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
4.
5.
Analytical solutions for the steady‐state response of an infinite beam resting on a visco‐elastic foundation and subjected to a concentrated load moving with a constant velocity are developed in this paper. The beam responses investigated are deflection, bending moment, shear force and contact pressure. The mechanical resistance of the foundation is modeled using two parameters ks and ts — ks accounts for soil resistance due to compressive strains in the soil and ts accounts for the resistance due to shear strains. Since this model represents the ground behavior more accurately than the Winkler spring model, the developed solutions produce beam responses that are closer to reality than those obtained using the existing solutions for Winkler model. The dynamic beam responses depend on the damping present in the system and on the velocity of the moving load. Based on the study, dynamic amplification curves are developed for beam deflection. Such amplification curves for deflection, bending moment, shear force and contact pressure can be developed for any beam‐foundation system and can be used in design. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
6.
移动荷载作用下半无限体的动力响应解 总被引:3,自引:3,他引:3
以Duhamel积分为基础,采用Fourier变换和Floquet变换等方法,给出了移动荷载作用下半无限体中任一点的动力响应在时域、频域和频率-波数域内的表达式。该公式的推出,在交通荷载作用下,可为土体和结构的动力响应分析提供一定的理论基础。 相似文献
7.
根据饱和土比奥理论与最小势能原理及薄板理论,采用子结构法,把上部结构、基础和地基作为一个共同作用的整体,在接触界面上满足变形协调条件,建立移动荷载作用下饱和土体地基-筏板-上部结构共同作用的积分方程。对积分方程的数值求解和相应的Fourier逆变换,得到任意时刻上部结构、筏板的内力和位移以及地基反力。最后通过数值计算,分析了饱和土体参数、移动荷载的速度等对上部结构水平、垂直方向的振动的影响特点。数值结果表明:上部结构各层的水平位移、竖向位移都随荷载速度增大而增加;竖向位移随楼层增加变化不大,当荷载速度较低时,水平位移随上部结构高度的变化曲线平滑少弯折,说明振动较稳定。但当荷载速度较高时,水平位移随楼层变化曲折越明显,层间差异大 相似文献
8.
This paper is dedicated to study the dynamic response of a thin‐plate resting on a layered poroelastic half‐space under a moving traffic load. Based on the dynamic poroelastic theory of Biot, the general solutions of the homogeneous poroelastic foundation are obtained by Fourier translation. By using the transmission and reflection matrices method in the frequency domain, the equivalent stiffness of the layered poroelastic half‐space is presented. Kirchhoff's hypotheses are applied to obtain the vertical displacement of the thin plate. By using the inverse Fourier transform, the time domain solution is obtained. As an example of three layers, the influences of the load velocity, the material properties of poroelastic layers, and the flexural rigidity of the plate on the response of the pavement system are examined. Analyses show that a soft intermediate layer results in the significant increase of vertical displacement of road pavement. Comparison with the existing work validates the present model. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
9.
移动荷载下黏弹性半空间体上双层板的动力响应 总被引:1,自引:0,他引:1
采用黏弹性半空间体上无限大双层板模型模拟路面结构,通过三重Fourier积分变换得到单位脉冲荷载作用下路面动力响应的Green函数。根据线性系统的叠加原理,利用广义Duhamel积分推导出移动荷载作用下路面动力响应的解析解。采用自适应Simpson法编制了计算奇异、振荡函数的广义积分计算程序,完成了路面动力响应从波数-频率域到时间-空间域的转换。结合算例,对移动荷载作用下路面的振动规律进行研究,讨论上、下层板厚度和板材料的弹性模量对路面动力响应的影响,明确了路面结构的振动特性,研究结果可为路面结构的设计、施工提供理论指导。 相似文献
10.
The problem of the dynamic responses of a semi‐infinite unsaturated poroelastic medium subjected to a moving rectangular load is investigated analytical/numerically. The dynamic governing equations are obtained with consideration of the compressibility of solid grain and pore fluid, inertial coupling, and viscous drag as well as capillary pressure in the unsaturated soil, and they can be easily degraded to the complete Biot's theory. Using the Fourier transform, the general solution for the equations is derived in the transformed domain, and then a corresponding boundary value problem is formulated. By introducing fast Fourier transform algorithm, the unsaturated soil vertical displacements, effective stresses, and pore pressures induced by moving load are computed, and some of the calculated results are compared with those for the degenerated solution of saturated soils and confirmed. The influences of the saturation, the load speed, and excitation frequency on the response of the unsaturated half‐space soil are investigated. The numerical results reveal that the effects of these parameters on the dynamic response of the unsaturated soil are significant. 相似文献
11.
埋置简谐扭转荷载作用下广义Gibson饱和地基动力响应 总被引:1,自引:0,他引:1
考虑地基为饱和半空间,研究了广义Gibson饱和地基内作用简谐扭转动荷载时地基的动力响应问题。从Biot饱和地基固结理论出发,结合扭转振动的特点,建立了剪切模量随深度线性变化的饱和地基扭转振动的动力微分方程,通过Hankel变换求解此微分方程,给出了Hankel变换域内的切向位移和剪应力关于待定系数的表达式。根据饱和地基表面为自由表面,荷载作用面位移连续、剪应力差等于动荷载大小,波的辐射条件等边界条件求解出待定系数,借助Hankel逆变换给出地基内的位移和应力的表达式。通过数值算例研究发现:在同一水平面内,地基内的切向位移和剪应力曲线的实部和虚部都呈现出非常明显的波动变化规律;在竖向平面内,动荷载作用面上部区域内随深度逐渐增大时,地基内切向位移和剪应力曲线的实部逐渐增大,而在动荷载作用面下部区域则正好相反;扭转动荷载的影响范围主要是荷载作用面上下2倍半径区域。 相似文献
12.
基于Biot理论,研究了饱和土中带有衬砌的圆形隧洞在移动环形荷载作用下的动力响应。假定衬砌为弹性体,土体为饱和多孔介质,引入两类势函数来表示土体、孔隙水和衬砌的位移,使隧洞的控制方程解耦。结合边界条件及连续条件,通过傅立叶变换得到频率-波数域中衬砌和土体的应力、位移和孔隙水压力解答,最后用傅立叶积分逆变换得到时-空域中的数值解。计算并比较了3种隧洞模型(弹性土体隧洞、饱和土体隧洞和饱和土衬砌隧洞)的动力响应分析。数值分析结果说明:(1)移动荷载速度对3种隧洞动力响应均具有较大影响;(2)弹性土体隧洞和饱和土体隧洞的动力响应具有明显区别,所以在富水地区的隧洞动力响应中土体应该视为饱和土体;(3)衬砌对隧洞动力响应有较大影响,故隧洞的动力分析中不能忽略衬砌作用。 相似文献
13.
Wave propagation and localization in ordered and disordered multi‐span beams on elastic foundations due to moving harmonic loads are investigated by using the transfer matrix methodology. The transfer matrix, as a function of the frequency and velocity of the moving harmonic load, of the periodic beam is formulated in a coordinate system moving with the load. The expressions of critical velocities, cut‐off frequency of an associated uniform beam without discrete spaced supports, are determined through the analysis of the wavenumbers, and the dynamic responses of the beam are also examined. For the ordered and disordered case, the propagation constants and localization factors are respectively employed to identify the velocity and frequency pass bands and stop bands in order to examine whether the perturbation can propagate along the structure or not. The effects of the periodicity, disorder level, excitation frequency, and moving velocity are studied in detail. The validity of the obtained results is confirmed by evaluating the transverse deformation of the beams through the finite element simulations. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
14.
15.
This paper investigates the dynamic response of an axially loaded Timoshenko beam coupled with a multilayered transversely isotropic (TI) half-space subjected to a moving load. An axial force induced by the thermal expansion is taken into account in the Timoshenko beam. The half-space considers the alternate distribution of an arbitrary number of TI elastic and poroelastic layers to model foundation soils with different properties and moisture conditions. To solve the governing equations, Fourier transform is adopted. The stratified foundation is formulated by extending an “adapted stiffness matrix method” to a more general scenario with an arbitrary number of layers. The beam is then coupled with the foundation to derive solutions to the system in the frequency-wavenumber domain. The final results in the time-spatial domain are recovered by the inverse Fourier transform. After confirming the accuracy of the method in this study, the influences of the pore water existence, the transverse isotropy of different parameters, and the axial force are investigated. It can be observed that the effect of pore water existence on the maximum beam deflection can reach 22% in this study. The transverse isotropy of the elastic and shear moduli influences the critical speed of the beam deflection by altering the phase velocity of the first wave propagation mode of the beam-foundation system. The vertical permeability coefficient is more important than the horizontal one in determining the excess pore pressure. The rise of the beam temperature (axial force) decreases the critical speed and magnifies the vibrations. 相似文献
16.
针对交通移动荷载,基于第一动力安定性理论预测了弹塑性半无限空间动力安定性下限值。通过建立无限元边界的三维动力有限元模型,研究了移动荷载作用下弹塑性半无限空间的动应力分布,构造了稳态动应力下的残余应力场,基于残余应力场的构造提出了动力安定性下限值的预测方法,分析了交通动应力下的安定性下限值以及车辆移动速度对安定性的影响,同时分析了均布荷载和Hertz荷载分布对动力安定性下限值的影响。当荷载移动速度低于Rayleigh波速时,安定性极限值随着速度的增加而增加,而当速度超过Rayleigh波速时,随着速度的增加而减小。研究还发现,当荷载和总重相等时采用圆形均布荷载和Hertz荷载的安定性极限值较为相似。 相似文献
17.
18.
煤层气井有杆排采系统悬点动载荷计算 总被引:1,自引:0,他引:1
有杆泵排采设备悬点动载荷是正确设计和选择抽油机和抽油杆以及确定电动机功率的重要影响因素。在分析杆柱和液柱受力状态的基础上,建立了惯性载荷的数学模型,基于弹性体振动理论,建立了振动载荷的计算模型,并给出悬点动载荷的计算方法和变化规律。结果表明,煤层气井悬点载荷的计算需同时考虑惯性载荷和振动载荷,且开采初期,动载荷所占比重较大;随着开采的进行,动载荷所占比重迅速减小,稳定生产时,影响已较小;杆管总变形量明显小于油田,且动变形量相对较小。该算法首次较为精确地计算出煤层气井有杆排采系统的悬点载荷并给出示功图,为有杆排采的设计计算提供了依据。 相似文献
19.