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1.
The natural frequencies and mode shapes of thin and moderately thick rhombic plates are obtained using a 9-noded Lagrangian quadrilateral isoparametric plate element based on Mindlin's theory. The effects of rotatory inertia are included. Plates with a wide range of skew angles and boundary conditions are considered and wherever possible the present results are compared with earlier published work. 相似文献
2.
根据弹性薄板理论和振动理论,运用边界元法(BEM)分析了薄板弯曲自由振动的频率特性,从薄板自由振动的微分方程式出发,采用动态基本解推导出其相应的边界积分方程式,计算中对边界积分方程进行缩减,应用频率扫描的方法研究薄板的动态特性,准确、有效地得到了其相应的固有频率、给出的数值算例证明了本文的方法简单、可行,且具有良好的解析计算精度。 相似文献
3.
Teh Hwei Lee 《地震工程与结构动力学》1979,7(3):235-251
Dynamic response of a thick, horizontal, circular plate supporting a large number of slender rods subjected to uniform boundary motion in the vertical direction has been studied by synthesizing component modes of continuous substructures. The excitation considered corresponds to the vertical component of boundary movement produced by earthquake disturbances and the axisymmetric response problem was solved. Mindlin theory was used to formulate the component equations of the plate which is treated as the main component in a modal synthesis technique. The slender rods, which are attached vertically to the plate, are handled as branch components. Vibration modes of a classical thin plate were used as the initial displacement functions for the Mindlin plate. These functions were subsequently modified by a component mode improvement process to obtain plate modes. System modes were generated by combining the improved plate modes with component modes of rods. Numerical results for the natural frequencies and time-history response of the coupled system are compared with those given by a three-dimensional finite element method. 相似文献
4.
开洞薄钢板剪力墙低周反复荷载试验研究 总被引：5，自引：0，他引：5
薄板墙的滞回曲线在零位移附近有零刚度现象,存在明显的捏缩效应,常规方法是直接采用中厚板或通过强大的加劲体系将薄板转化成中厚板,但这将降低薄板墙的经济性。通过两片开洞薄钢板墙低周反复荷载试验,系统地研究了开洞钢板墙的破坏过程和破坏机理,得到了承载力,侧移刚度,延性和耗能能力等指标。试验结果表明,开洞钢板墙有较高的承载力和侧移刚度,延性和耗能能力很好。开洞不仅可以满足门窗洞口等建筑需求,而且可以减小内填板宽度,调节内填板与框架的刚度比,避免薄板墙的捏缩效应,使构件有更高的安全储备,开洞钢板墙是一种理想的水平抗侧力构件。 相似文献
5.
Curved beam finite elements are presented for out of plane coupled bending and torsional vibration. The element formulation is based upon the exact differential equations of an infinitesimal element in static equilibrium. The effects of shear deformation and rotary inertia are allowed for in the analysis. The element stiffness and mass matrices can be easily restricted to those of a ‘thin’ beam without the secondary effects. Frequencies obtained using either formulation are shown to converge onto exact values using ‘thick’ or ‘thin’ beam theories. 相似文献
6.
复合式多层无孔和开孔矩形薄板是桥梁结构和建筑等结构中的最重要的组成部分。当研究它们的振动问题时,用解析法求解自振频率十分困难,而采用通用的有限元法求解自由度数目多,收敛也比较慢。本文利用三角形薄板广义协调元分析了复合式多层四边简支、四边固定无孔和开孔矩形薄板的自由振动,求出了前几阶频率系数,其结果与用ANSYS软件算出的结果基本接近,当为单层无孔和开孔板时,与文献[8]的结果完全相同,且与文献[10]的解析解吻合较好,证明了本文理论推导及程序编制的正确性,表明广义协调元与有限元相比具有自由度少、精度高、程序简便以及收敛快等优点。 相似文献
7.
Güven Aksu 《地震工程与结构动力学》1984,12(5):709-714
The energy approach using the variational procedure in conjunction with the finite difference technique has been applied for the Mindlin theory dynamic analysis of rectangular plates with cutouts in which account is taken of the effects of both transverse shear deformation and rotary inertia. This study has clearly demonstrated that the discrepancy with the thin plate theory solutions increases with increasing values of thickness ratio β and the error due to the thin plate assumptions increases particularly for the higher modes. It is also concluded that the effect of a cutout becomes more pronounced as the thickness of the plate approaches the size of cutout. 相似文献
8.
孙建刚 《地震工程与工程振动》1995,15(3):69-72
本文以文〔１〕构造的拟协调板弯曲单元为基础，横向剪切应变假设中采用沿厚度二次分布，将其应用于薄板固有振动分析，求解前ｎ阶固有频率，结果表明该单元具有良好的数值特性。 相似文献
9.
This study examines the flexural-gravity wave scattering by a semi-circular ridge submerged in the ocean covered by a thin ice sheet. The ice sheet is treated as an elastic plate and its deflection is modelled using the Euler-Bernoulli beam equation. The fluid motion is described by linear potential theory. The series solutions of velocity potentials for obliquely and normally incident waves are both developed using multipole expansions. The unknowns in the series solutions are determined in terms of the impermeable condition on the ridge surface. Accurate results for the reflection and transmission coefficients of ridge and the deflection of ice sheet are presented. The effects of ridge radius, ice thickness, wave frequency and wave incident angle on the hydrodynamic quantities are shown. 相似文献
10.
Ernian Pan 《Physics of the Earth and Planetary Interiors》1990,60(1-4):254-264
A general method is developed for the study of transient thermoelastic deformation in a transversely isotropic and layered half-space by surface loads and internal sources. A Laplace transform is first applied to the field quantities; Cartesian and cylindrical systems of vector functions are then introduced for reducing the basic equations to three sets of simultaneous linear differential equations. General solutions are obtained from these sets, and propagator matrices from the solutions by a partitioned matrix method.
Source functions for a variety of sources are derived in the Cartesian and cylindrical systems, and the Laplace transformed expressions of the field variables at the surface presented explicitly in the two systems in terms of a layer matrix. The effect of gravity is included by multiplying simply an effect matrix resulting from the modification of continuity conditions at the surface and the layer interfaces.
It should be noted that the present analytical method has great advantages over either the classical thin plate approach or the finite element method, and that the present result can be reduced directly to the solutions of the corresponding isotropic case. 相似文献
11.
采用波函数展开法给出了板的横截面处孔洞在平面P波入射下动应力集中问题的解。本文使用大圆弧假定法来满足板中的自由表面的边界条件。数值结果表明,上表面和孔洞间的距离与下表面和孔洞间的距离都对结果有影响。如果孔洞半径相对板的厚度很小,解近似等于孔洞全空间解。所给出的解是半解析解。因此能被用来验证诸如BEM,FEM,FDM等数值法。 相似文献
12.
An analytical approach is developed to study the dynamic response of a flexible plate on single-layered saturated soil. The analysis is based on Biot's two-phased theory of poroelasticity and also on the classical thin-plate theory. First, the governing differential equations for saturated soil are solved by the use of Hankel transform. The general solutions of the skeleton displacements, stresses, and pore pressures, derived in the transformed domain, are subsequently incorporated into the imposed boundary conditions, which leads to a set of dual integral equations describing the corresponding mixed boundary value problem. These governing integral equations are finally reduced to the Fredholm integral equations of the second kind and solved by standard numerical procedures. The accuracy of the present solution is validated via comparisons with existing solutions for an ideal elastic half-space. Furthermore, some numerical results are presented to show the influences of the layer depth, the plate flexibility, and the soil porosity on the dynamic compliances. 相似文献
13.
Through an energy formulation and the use of a large deflection theory, it is shown that if a thin plate has a slight initial preform, and if its edges are constrained against in–plane displacements, then all of the natural frequencies of the plate will be shifted upward. For a uniform thin plate, the amount of frequency shift depends on the type of boundary conditions and the ratio of the amplitude of preform to the thickness of the plate. Examples of square and rectangular plates preformed in the shape of their first mode shapes are presented. The method holds the promise of shifting or essentially removing a troublesome vibration mode. 相似文献
14.
A thin‐profile buckling‐restrained brace (thin‐BRB) consists of a rectangular steel casing and a flat steel core that is parallel to a gusset plate. A thin configuration reduces the width of the restraining member and thus saves usable space in buildings. However, deformable debonding layers, which cover the steel core plate in order to mitigate the difference between the peak tensile and compressive axial forces, provide a space for the steel core to form high mode buckling waves when the thin‐BRB is under compression. The wave crests squeeze the debonding layers and produce outward forces on the inner surface of the restraining member. If the restraining member is too weak in sustaining the outward forces, local bulging failure occurs and the thin‐BRB loses its compression capacity immediately. In order to investigate local bulging behavior, a total of 22 thin‐BRB specimens with a ratio of steel core plate to restraining steel tube depth ranging from 0.3 to 0.7 and axial yield force capacities ranging from 421 kN to 3036 kN were tested by applying either cyclically increasing, decreasing, or constant axial strains. The restraining steel tube widths of all the specimens were smaller than 200 mm and were infilled with mortar with a compressive strength of 97 MPa or 55 MPa. Thirteen of the 22 thin‐BRB specimens' restraining members bulged out when the compressive core strains exceeded 0.03. A seismic design method of the thin‐BRB in preventing local bulging failure is proposed in this study. Test and finite element model (FEM) analysis results suggest that the outward forces can be estimated according to the BRB compressive strength, steel core high mode buckling wavelength, and the debonding layer thickness. In addition, the capacity of the restraining member in resisting the outward forces can be estimated by using the upper bound theory in plastic analysis. Both the FEM analysis and test results indicate that the proposed method is effective in predicting the possibility of local bulging failure. Test results indicate that the proposed design method is conservative for thin‐BRB specimens with a large steel core plate to restraining steel tube depth ratio. This paper concludes with design recommendations for thin‐BRBs for severe seismic services. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
15.
Electromagnetic induction in the Vancouver Island region for a uniform inducing source field for 300 s period is investigated with the aid of three-dimensional (3-D) numerical and analogue model results and field site measurements. The thin sheet numerical model, based on the subducting Juan de Fuca plate analogue model ofDosso
et al., consists of a 5km thick non-uniform thin sheet (comprising the lateral conductivity contrasts arising from the land, the varying depth ocean, and the sediment) underlain by a four-layer conductive structure. The four-layer conductive structure beneath the non-uniform thin sheet simulates the effect of the Juan de Fuca plate subducting Vancouver Island. To examine the effects of the ocean channel depth between Vancouver Island and the British Columbia (Canada) mainland, numerical results were obtained for two channel depths (0 and 600 m). The results indicate that the channel plays an important role in the geomagnetic response in the central and inner coastal regions of Vancouver Island. The general agreement of the 3-D numerical model induction arrows with the analogue model and field site induction arrows for 300 s supports the premise of a layered conductive substructure dipping at a small angle, at most, beneath Vancouver Island.Lithoprobe Publication No. 311. 相似文献
16.
V. P. Trubitsyn A. A. Baranov E. V. Kharybin 《Izvestiya Physics of the Solid Earth》2007,43(7):533-542
Light continents and islands characterized by a crustal thickness of more than 30 km float over a convective mantle, while the thin basaltic oceanic crust sinks completely in subduction zones. The normal oceanic crust is 7 km thick. However, anomalously thick basaltic plateaus forming as a result of emplacement of mantle plumes into moving oceanic lithospheric plates are also pulled into the mantle. One of the largest basaltic plateaus is the Ontong Java plateau on the Pacific plate, which arose during the intrusion of a giant superplume into the plate ～100 Myr ago. Notwithstanding its large thickness (averaging ～30 km), the Ontong Java plateau is still experiencing slow subduction. On the basis of numerical modeling, the paper analyzes the oceanic crust subduction process as a function of the mantle convection vigorousness and the density, thickness, viscosity, and shape of the crust. Even a simplified model of thermocompositional convection in the upper mantle is capable of explaining the observed facts indicating that the oceanic crust and sediments are pulled into the mantle and the continental crust is floating on the mantle. 相似文献
17.
J. A. S. C. Jayasinghe M. Hori M. R. Riaz M. L. L. Wijerathne T. Ichimura 《地震工程与工程振动(英文版)》2017,16(2):297-309
In this study, a new method for conversion of solid finite element solution to beam finite element solution is developed based on the meta-modeling theory which constructs a model consistent with continuum mechanics. The proposed method is rigorous and efficient compared to a typical conversion method which merely computes surface integration of solid element nodal stresses to obtain cross-sectional forces. The meta-modeling theory ensures the rigorousness of proposed method by defining a proper distance between beam element and solid element solutions in a function space of continuum mechanics. Results of numerical verification test that is conducted with a simple cantilever beam are used to find the proper distance function for this conversion. Time history analysis of the main tunnel structure of a real ramp tunnel is considered as a numerical example for the proposed conversion method. It is shown that cross-sectional forces are readily computed for solid element solution of the main tunnel structure when it is converted to a beam element solution using the proposed method. Further, envelopes of resultant forces which are of primary importance for the purpose of design, are developed for a given ground motion at the end. 相似文献
18.
L. Auersch 《Soil Dynamics and Earthquake Engineering》1996,15(1):51-59
An integral method to calculate the solution of a homogeneous or layered soil due to a harmonic point load is described. An infinite plate at the surface of the soil can be introduced in this integration in wavenumber domain, too. Finite structures on the soil are calculated by a combined finite element and boundary element method, which makes use of the point load solution of the soil. The compliance functions for a vertical point load and some vibration modes are calculated for realistic parameters of the plate and the soil and for a wide range of frequencies. The influence of the stiffness of the soil and the foundation is investigated, showing that the soil mainly affects the low-frequent response whereas the structural properties are more important at higher frequencies. A rigid approximation of flexible plates is only found at low frequencies, if the elastic length
is used as the radius of a rigid disk. At higher frequencies, a characteristic behaviour of the flexible plate of approximately
is observed, what is in clear contrast to the compliance of rigid foundations. A plate on a visco-elastic support (Winkler soil) shows similar displacements as a plate on a homogeneous half-space, but the maximal stresses between the plate and the soil are considerably smaller which is found to be more realistic for a plate on a layered soil. For practical applications, a normalized diagram and some explicit formulas of the exact and the approximate solutions of an infinite plate on a homogeneous half-space are given, which is a useful model to represent the soil-structure interaction of flexible foundations. 相似文献
19.
本文整合了横跨马尼拉海沟北段的21条多道地震层位信息、海底地形以及天然地震数据,分析了研究区内的输入板块性质差异及其对增生楔变形和地震活动性的影响.研究发现,沿马尼拉海沟北段的输入板块在地壳性质、基底起伏和沉积物厚度上存在明显的自北向南的差异:(1)最北段基底埋深大,上覆沉积物厚,地壳厚度较薄,地壳性质可能为初始南海洋壳或者圈闭的菲律宾海洋壳;(2)中段基底埋深浅,上覆沉积物薄,地壳厚度大,地壳属性表现为过渡壳性质,受到岩浆活动的影响,初始的地壳性质可能为华南陆块张裂分离出的微小陆壳块体,或者是南海洋壳;(3)南段基底埋深和沉积物厚度介于中间,存在明显的地磁条带,地壳性质为正常的南海洋壳.这一输入板块性质的不均一性可解释该区的特殊增生楔变形现象,如恒春弱变形带的出现,向海方向内凹的海沟形态以及上陆坡海底的大幅抬升等,同时也影响了研究区内的板片俯冲形态和发震构造的地震活动性.研究结果证实了沿马尼拉海沟北段存在南北向的地球物理性质的差异,但对于地壳属性的最终厘定还需要更多的地质与地球化学证据. 相似文献
20.
本文在各向同性介质假设下,计算了薄层顶、底反射P波和PS波的理论地震图.理论模拟发现薄层的反射P波与PS波是一复合波,包括层内的多次透射和反射转换波型,且具有类似单一界面反射的、脉冲式的波形特征.两类薄层反射整体振幅随着薄层厚度的降低而缩小;在地震子波主频40 Hz条件下,2 m左右厚度的薄层反射相比单一界面反射具有等同的振幅水平.1 m以下极薄层仅有弱反射甚至无反射;薄层反射复合波振幅与炮检距的关系依然成立,但不惟一;单界面反射AVO原理、方法不适用于薄层反射解释与反演. 相似文献