共查询到20条相似文献,搜索用时 203 毫秒
1.
2.
3.
关于“拟协调元”的若干问题及在构造拱单元上的应用 总被引:1,自引:0,他引:1
本文根据加权余值法构造了与文献同样的拟协调元,并提出位移型拟协调元.本文论证了拟协调元通过分片试验和满足刚体位移条件.还探讨了杂交元与拟协调元异同之处.最后以扁拱为例,通过数值计算说明扁拱拟协调单元不仅精度高,而且精确地满足刚体位移条件. 相似文献
4.
普通截锥壳单元是分析旋转壳结构的常用单元,但应力计算的精度较差;而渐近传递函数解在圆锥壳的应力分析方面具有很高的计算精度。本文针对一般截锥壳单元应力计算精度不高的缺点,将传递函数法与有限元法进行结合,以圆锥壳的渐近传递函数解为插值函数,直接构造了一种高精度的截锥壳单元,该单元位移插值模式满足相容性和完备性要求,并具有力学概念清楚、计算精度高等特点。数值算例表明,采用该单元进行圆锥壳的内力和自由振动 相似文献
5.
6.
7.
8.
扁壳单元中引入结点转角自由度可以在不增加结点的情况下,增加位移场的阶次,提高计算精度,从而显著地提高单元性能。同时在单元中引入泡状位移场,能有效地扩大了单元位移场的解空间,所构造的单元具有计算精度高、对计算网格畸变不敏感的优良特性。本文利用广义协调薄板单元RGC-12的位移函数作为扁壳元的法向位移,利广义协调矩形膜元的位移函数作为扁壳面的切向位移,通过附加面内转动自由度构造了一个具有24个自由度的4结点广义协调曲面矩形扁壳元GRC-S24。在此基础上再增加一个广义泡状位移,又构造了一个具有更高计算精度的曲面矩形扁壳元GRC-S24M。并通过实例分析对这两个单元的收敛性和精度进行了验证。 相似文献
9.
10.
钢管初应力对钢管砼拱桥承载力影响非线性分析 总被引:1,自引:0,他引:1
基于非线性问题的平衡方程和空间梁单元非线性几何方程,推导了一般线弹性关系下计入初应力影响的空间梁单元显式切线刚度矩阵。针对钢管混凝土哑铃型截面的构造特点,提出了组合空间梁单元法,较好解决了哑铃型截面钢管初应力的计算与存储问题,并给出了承载力分析时单元划分的具体方法,编制了专用计算程序,计算结果与试验吻合良好。开展了不同钢管初应力系数、不同截面含钢率和不同跨径对钢管混凝土拱桥承载力的影响分析。结果表明,钢管初应力将使钢管混凝土拱桥的承载力降低,降低幅度与拱肋截面型式有关,承载力最大降低值可超过30%。最后给出了三种考虑钢管初应力影响的常用拱肋截面型式拱桥承载力影响系数实用计算公式。 相似文献
11.
Mario M. Attard Jianbei Zhu David C. Kellermann 《Archive of Applied Mechanics (Ingenieur Archiv)》2014,84(5):693-713
The in-plane buckling behavior of funicular arches is investigated numerically in this paper. A finite strain Timoshenko beam-type formulation that incorporates shear deformations is developed for generic funicular arches. The elastic constitutive relationships for the internal beam actions are based on a hyperelastic constitutive model, and the funicular arch equilibrium equations are derived. The problems of a submerged arch under hydrostatic pressure, a parabolic arch under gravity load and a catenary arch loaded by overburden are investigated. Buckling solutions are derived for the parabolic and catenary arch. Subsequent investigation addresses the effects of axial deformation prior to buckling and shear deformation during buckling. An approximate buckling solution is then obtained based on the maximum axial force in the arch. The obtained buckling solutions are compared with the numerical solutions of Dinnik (Stability of arches, 1946) [1] and the finite element package ANSYS. The effects of shear deformation are also evaluated. 相似文献
12.
几何缺陷浅拱的动力稳定性分析 总被引:3,自引:1,他引:2
研究了几何缺陷对粘弹性铰支浅拱动力稳定性能的影响。从达朗贝尔原理和欧拉-贝努利假定出发推导了粘弹性铰支浅拱在正弦分布突加荷载作用下的动力学控制方程,并采用Galerkin截断法得到了可用龙格-库塔法求解的无量纲化非线性微分方程组。同时引入能有效追踪结构动力后屈曲路径的广义位移控制法,对含几何缺陷浅拱的响应曲线进行几何、材料双重非线性有限元分析。用这两种方法分析了前三阶谐波缺陷对浅拱动力稳定性能的影响,其中动力临界荷载由B-R准则判定。主要结论有:材料粘弹性使浅拱动力临界荷载增大且结构响应曲线与弹性情况差别很大;二阶谐波缺陷影响显著,它使动力临界荷载明显下降且使得浅拱粘弹性动力临界荷载可能低于弹性动力临界荷载。 相似文献
13.
The nonlinear in-plane instability of functionally graded carbon nanotube reinforced composite (FG-CNTRC) shallow circular arches with rotational constraints subject to a uniform radial load in a thermal environment is investigated. Assuming arches with thickness-graded material properties, four different distribution patterns of carbon nanotubes (CNTs) are considered. The classical arch theory and Donnell’s shallow shell theory assumptions are used to evaluate the arch displacement field, and the analytical solutions of buckling equilibrium equations and buckling loads are obtained by using the principle of virtual work. The critical geometric parameters are introduced to determine the criteria for buckling mode switching. Parametric studies are carried out to demonstrate the effects of temperature variations, material parameters, geometric parameters, and elastic constraints on the stability of the arch. It is found that increasing the volume fraction of CNTs and distributing CNTs away from the neutral axis significantly enhance the bending stiffness of the arch. In addition, the pretension and initial displacement caused by the temperature field have significant effects on the buckling behavior. 相似文献
14.
The behavior of a bistable strut for variable geometry structures was investigated in this paper. A fixed shallow arch subjected to a central concentrated load was used to study the equilibrium path of the bistable strut. Based on a nonlinear strain–displacement relationship, the critical loads for both the symmetric snap-through and asymmetric bifurcation buckling modes were obtained. Moreover, the principal of virtual work was also used to establish the post-buckling differential equilibrium equations of the arch in the horizontal and vertical directions. Therefore, the whole mechanical behavior before and after the buckling of fixed arches is investigated. 相似文献
15.
基于大变形动力学微分方程并利用有限差分离散分析,研究了子弹撞击作用下固支浅圆拱的弹塑性动力响应。通过对响应不同时刻内力分布特征的分析,阐明了圆拱的响应模式和变形机制。研究表明,弹塑性响应过程可分为六个阶段。在响应早期,拱的变形以塑性弯曲挠动由撞击点向拱根部传播为主;在响应后期,则主要以轴力主导下的轴向拉伸变形为主。在高速撞击下,塑性弯曲挠动的不均匀性可以引起浅拱的反向弯曲变形。固支浅圆拱的动力响应对撞击速度的某个变化范围非常敏感,在此范围内,撞击速度的较小增加可以导致响应的很快增长,但动力响应随撞击速度连续变化,未发生突然的跳跃失稳。本文中计算结果同实验数据吻合较好。 相似文献
16.
《应用数学和力学(英文版)》2019,(7)
The nonlinear dynamic behaviors of a double cable-stayed shallow arch model are investigated under the one-to-one-to-one internal resonance among the lowest modes of cables and the shallow arch and external primary resonance of cables. The in-plane governing equations of the system are obtained when the harmonic excitation is applied to cables. The excitation mechanism due to the angle-variation of cable tension during motion is newly introduced. Galerkin's method and the multi-scale method are used to obtain ordinary differential equations(ODEs) of the system and their modulation equations, respectively. Frequency-and force-response curves are used to explore dynamic behaviors of the system when harmonic excitations are symmetrically and asymmetrically applied to cables. More importantly, comparisons of frequency-response curves of the system obtained by two types of trial functions, namely, a common sine function and an exact piecewise function, of the shallow arch in Galerkin's integration are conducted.The analysis shows that the two results have a slight difference; however, they both have sufficient accuracy to solve the proposed dynamic system. 相似文献
17.
Thin shallow arches may become unstable under transverse loading as the built-up internal compressive forces reach a limiting value beyond which the structure undergoes a sudden large displacement towards a new stable configuration. This phenomenon could be both desirable (in toggle switches) and disastrous (collapse of a dome or truss). Hence, it is important to carry out the so-called snap- or limit-load analysis to reveal the factors influence the phenomenon and to give guidelines in designing structures to behave favorably. Although energy methods are a common means of this analysis, the phenomenon could also be analyzed by considering the equations governing the displacement of the arch and by monitoring the load-displacement characteristic of the structure until it reaches the limit point. This is the procedure adopted here. Researches on the subject mostly consider constant thickness arches with common pin-ended or fixed supports. Here the thickness is varied along the arch in three forms: power-law, exponential, and logarithmic. The supports are considered to be nonrigid fixed; i.e., pinned ends are equipped with torsional springs with constant stiffness. By changing these stiffnesses, various combinations of pinned and/or fixed states, or an intermediate state at each end could be developed. By considering the analytical solution for the transverse displacement for the general power-law case, the limit-load is obtained by numerical solution of the limit-load condition, which is a highly complicated function of the derived displacement field. Several parameter studies, such as that of the effects of shallowness and slenderness of arch and spring stiffnesses on the critical load, are carried out. The results are verified by those of simpler cases available in the literature, as well as those from a finite-element approach. 相似文献
18.
《Fluid Dynamics Research》1994,13(3-4):197-215
The evolution of topographically generated interfacial motion is considered in a two-layer model. A system of two non-linear equations, similar to the Boussinesq equations for shallow water waves, is derived. The consequences of the cubic non-linearity of these equations on the nature of the solitary wave solutions are explored. A dispersion relation for solitary waves implies the existence of maxima for speed and displacement in a wave. The limiting values are shown to agree with other studies. The growth of solitary and/or cnoidal waves is studied for finite pulses of displacement and for internal bores. 相似文献
19.
In this paper an integral equation solution to the linear and geometrically nonlinear problem of non-uniform in-plane shallow arches under a central concentrated force is presented. Arches exhibit advantageous behavior over straight beams due to their curvature which increases the overall stiffness of the structure. They can span large areas by resolving forces into mainly compressive stresses and, in turn confining tensile stresses to acceptable limits. Most arches are designed to operate linearly under service loads. However, their slenderness nature makes them susceptible to large deformations especially when the external loads increase beyond the service point. Loss of stability may occur, known also as snap-through buckling, with catastrophic consequences for the structure. Linear analysis cannot predict this type of instability and a geometrically nonlinear analysis is needed to describe efficiently the response of the arch. The aim of this work is to cope with the linear and geometrically nonlinear problem of non-uniform shallow arches under a central concentrated force. The governing equations of the problem are comprised of two nonlinear coupled partial differential equations in terms of the axial (tangential) and transverse (normal) displacements. Moreover, as the cross-sectional properties of the arch vary along its axis, the resulting coupled differential equations have variable coefficients and are solved using a robust integral equation numerical method in conjunction with the arc-length method. The latter method allows following the nonlinear equilibrium path and overcoming bifurcation and limit (turning) points, which usually appear in the nonlinear response of curved structures like shallow arches and shells. Several arches are analyzed not only to validate our proposed model, but also to investigate the nonlinear response of in-plane thin shallow arches. 相似文献