共查询到19条相似文献,搜索用时 140 毫秒
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采用理论推导与数值模拟相结合的方法,对倒三角形截面板管连接式钢圆弧拱在平面内的弹性屈曲和弹塑性屈曲进行了深入研究。首先,理论推导了拱的截面剪切刚度,并提出了拱在全跨均布径向荷载作用下的弹性屈曲公式。此外,还提出了避免连接板和弦杆在拱发生整体弹性失稳之前发生局部失稳的限制条件。然后,分别研究了在全跨均布径向荷载和全跨均布竖向荷载作用下,拱的整体弹塑性失稳机理。结果表明,在全跨均布径向荷载下,拱在1/4跨和3/4跨附近的弦杆会发生屈服,最终发生拱的整体弹塑性失稳。基于数值结果,建立了拱在全跨均布径向荷载作用下的稳定曲线,并针对拱发生整体弹塑性屈曲提出了相应的稳定承载力设计公式。在全跨均布竖向荷载作用下,钢拱发生整体失稳时,在拱脚两端附近的下弦杆会进入屈服。同样地,本文也提出了拱在全跨均布竖向荷载作用下,发生整体弹塑性失稳时的稳定极限承载力设计公式。本文所建议的公式与有限元结果符合得较好,可供实际工程设计参考。 相似文献
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提出了一种设置反拱结构的拱桥加固方法,该方法是通过在主拱圈拱肋下方设置反拱,在反拱和拱肋之间用竖杆相连,并通过抗弯预埋件和抗剪锚栓把反拱的拱脚和拱肋连接,使反拱结构和原主拱圈共同形成结构受力体系。本文基于有限元参数分析方法,通过设置6个不同参数:拱的矢高f1、拱的拱轴系数m1、反拱的矢高f2、反拱的拱轴系数m2、反拱与待加固拱的等效半径比i、反拱纵向长度与待加固拱的总跨径的比值Kr,以考虑不同拱桥、反拱结构参数对原拱桥关键截面内力、跨中挠度及整体屈曲系数的影响。基于大量计算数据的参数拟合,分别获得跨中弯矩、跨中挠度、拱脚弯矩、拱脚推力、整体屈曲系数的拟合表达式。通过对拟合数据的分析,获得了反拱加固的拱桥结构力学特性的相关变化规律。最后对一个100m跨径拱桥进行加固计算分析,结果表明:本文提出的加固方法不但可以显著提高待加固桥梁的整体刚度与稳定性,而且可有效地降低主拱关键截面的内力。 相似文献
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纸拱桥结构模型优化建模分析——大学生结构设计竞赛谈 总被引:1,自引:0,他引:1
以大学生结构设计竞赛为背景,以纸拱桥结构模型为分析实例,引导大学生讨论如何运用数学规划思想来进行结构优化分析,培养大学生的学习主动性和创造性.通过对拟定的结构竞赛规则下的结构进行受力定性分析,建立了纸拱结构寻优的数学规划模型,以拱桥质量最轻为目标函数,结构在特定荷载作用和材料特性条件下,满足材料强度极限值和稳定性要求作为约束条件,分析求解纸拱结构模型的拱轴线,截面形状与尺寸相关的等决策变量的最优解.求解得到了拱轴线函数的解析解特例,并采用简单迭代运算求解了拱截面尺寸的最优解. 相似文献
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研究了几何缺陷、荷载非均匀分布和支座沉陷对圆弧拱面内屈曲的影响.基于能量的变分原理推导了考虑缺陷的微分方程,得到了外荷载和轴力的关系式以及径向位移的表达式.从微分方程出发用摄动法对屈曲荷载的缺陷敏感性进行了分析,得到了屈曲荷载的近似表达式.结果表明近似解与精确解吻合良好;正对称屈曲荷载对正对称缺陷参数十分敏感;反对称缺陷参数对反对称屈曲荷载影响显著而正对称缺陷参数影响很小. 相似文献
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?????? ?????? 《力学与实践》1993,15(5):35-38
本文根据 Von Karman 大挠度平板理论,采用半解析半能量法对薄壁槽形截面腹板在非均匀压力作用下的屈曲与屈曲后性能进行了理论分析,得到了临界荷载及屈曲后第二平衡路径,以及截面最佳极限承载能力的翼缘与腹板的宽度比,理论分析与试验结果吻合较好. 相似文献
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核心混凝土的徐变会增加钢管混凝土拱肋的屈曲前变形,降低结构的稳定承载力,因此只有计入屈曲前变形的影响,才能准确得到钢管混凝土拱的徐变稳定承载力。基于圆弧形浅拱的非线性屈曲理论,采用虚功原理,建立了考虑徐变和剪切变形双重效应的管混凝土圆弧桁架拱的平面内非线性平衡方程,求得两铰和无铰桁架拱发生反对称分岔屈曲和对称跳跃屈曲的徐变稳定临界荷载。探讨了钢管混凝土桁架拱核心混凝土徐变随修正长细比、圆心角和加载龄期对该类结构弹性稳定承载力的影响,为钢管混凝土桁架拱长期设计提供理论依据。 相似文献
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钢管混凝土拱稳定分析的三维退化层合曲梁单元 总被引:3,自引:0,他引:3
为计算钢管混凝土拱的屈曲荷载,本文在文[1]三维退化梁单元的基础上,采用等效数值积分法,构造,出120-20结点三维退化层合曲梁单元,并考虑几何非线性影响,给出用于层合梁或拱线弹性稳定性分析的有限元列式,最后,以绍兴轻纺大桥为工程背景,计算出轻纺大枯钢管混凝土拱面内及面外屈曲的稳定系数。 相似文献
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槽形截面腹板非均匀受压的屈曲后强度研究 总被引:3,自引:0,他引:3
本根据Vov Karman大挠度平板理论。采用半解析半能量法对薄壁槽形截面腹板在非均匀压力作用下的屈曲与屈曲后性能进行了理论分析,得到了临界荷载及屈曲后第二平衡路径,以及截面最佳极限承载能力的翼缘与腹板的宽度比,理论分析与试验结构吻合较好。 相似文献
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Non-linear in-plane buckling of rotationally restrained shallow arches under a central concentrated load 总被引:2,自引:0,他引:2
This paper investigates the non-linear in-plane buckling of pin-ended shallow circular arches with elastic end rotational restraints under a central concentrated load. A virtual work method is used to establish both the non-linear equilibrium equations and the buckling equilibrium equations. Analytical solutions for the non-linear in-plane symmetric snap-through and antisymmetric bifurcation buckling loads are obtained. It is found that the effects of the stiffness of the end rotational restraints on the buckling loads, and on the buckling and postbuckling behaviour of arches, are significant. The buckling loads increase with an increase of the stiffness of the rotational restraints. The values of the arch slenderness that delineate its snap-through and bifurcation buckling modes, and that define the conditions of buckling and of no buckling for the arch, increase with an increase of the stiffness of the rotational end restraints. 相似文献
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The structural behavior of a shallow arch is highly nonlinear, and so when the amplitude of the oscillation of the arch produced by a suddenly-applied load is sufficiently large, the oscillation of the arch may reach a position on its unstable equilibrium paths that leads the arch to buckle dynamically. This paper uses an energy method to investigate the nonlinear elastic dynamic in-plane buckling of a pinned–fixed shallow circular arch under a central concentrated load that is applied suddenly and with an infinite duration. The principle of conservation of energy is used to establish the criterion for dynamic buckling of the arch, and the analytical solution for the dynamic buckling load is derived. Two methods are proposed to determine the dynamic buckling load. It is shown that under a suddenly-applied central load, a shallow pinned–fixed arch with a high modified slenderness (which is defined in the paper) has a lower dynamic buckling load and an upper dynamic buckling load, while an arch with a low modified slenderness has a unique dynamic buckling load. 相似文献
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This paper is concerned with an analytical study of the non-linear elastic in-plane behaviour and buckling of pinned–fixed shallow circular arches that are subjected to a central concentrated radial load. Because the boundary conditions provided by the pinned support and fixed support of a pinned–fixed arch are quite different from those of a pinned–pinned or a fixed–fixed arch, the non-linear behaviour of a pinned–fixed arch is more complicated than that of its pinned–pinned or fixed–fixed counterpart. Analytical solutions for the non-linear equilibrium path for shallow pinned–fixed circular arches are derived. The non-linear equilibrium path for a pinned–fixed arch may have one or three unstable equilibrium paths and may include two or four limit points. This is different from pinned–pinned and fixed–fixed arches that have only two limit points. The number of limit points in the non-linear equilibrium path of a pinned–fixed arch depends on the slenderness and the included angle of the arch. The switches in terms of an arch geometry parameter, which is introduced in the paper, are derived for distinguishing between arches with two limit points and those with four limit points and for distinguishing between a pinned–fixed arch and a beam curved in-elevation. It is also shown that a pinned–fixed arch under a central concentrated load can buckle in a limit point mode, but cannot buckle in a bifurcation mode. This contrasts with the buckling behaviour of pinned–pinned or fixed–fixed arches under a central concentrated load, which may buckle both in a bifurcation mode and in a limit point mode. An analytical solution for the limit point buckling load of shallow pinned–fixed circular arches is also derived. Comparisons with finite element results show that the analytical solutions can accurately predict the non-linear buckling and postbuckling behaviour of shallow pinned–fixed arches. Although the solutions are derived for shallow pinned–fixed arches, comparisons with the finite element results demonstrate that they can also provide reasonable predictions for the buckling load of deep pinned–fixed arches under a central concentrated load. 相似文献
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《International Journal of Solids and Structures》2002,39(1):105-125
Classical buckling theory is mostly used to investigate the in-plane stability of arches, which assumes that the pre-buckling behaviour is linear and that the effects of pre-buckling deformations on buckling can be ignored. However, the behaviour of shallow arches becomes non-linear and the deformations are substantial prior to buckling, so that their effects on the buckling of shallow arches need to be considered. Classical buckling theory which does not consider these effects cannot correctly predict the in-plane buckling load of shallow arches. This paper investigates the in-plane buckling of circular arches with an arbitrary cross-section and subjected to a radial load uniformly distributed around the arch axis. An energy method is used to establish both non-linear equilibrium equations and buckling equilibrium equations for shallow arches. Analytical solutions for the in-plane buckling loads of shallow arches subjected to this loading regime are obtained. Approximations to the symmetric buckling of shallow arches and formulae for the in-plane anti-symmetric bifurcation buckling load of non-shallow arches are proposed, and criteria that define shallow and non-shallow arches are also stated. Comparisons with finite element results demonstrate that the solutions and indeed approximations are accurate, and that classical buckling theory can correctly predict the in-plane anti-symmetric bifurcation buckling load of non-shallow arches, but overestimates the in-plane anti-symmetric bifurcation buckling load of shallow arches significantly. 相似文献
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In this research work, an exact analytical solution for buckling of functionally graded rectangular plates subjected to non-uniformly
distributed in-plane loading acting on two opposite simply supported edges is developed. It is assumed that the plate rests
on two-parameter elastic foundation and its material properties vary through the thickness of the plate as a power function.
The neutral surface position for such plate is determined, and the classical plate theory based on exact neutral surface position
is employed to derive the governing stability equations. Considering Levy-type solution, the buckling equation reduces to
an ordinary differential equation with variable coefficients. An exact analytical solution is obtained for this equation in
the form of power series using the method of Frobenius. By considering sufficient terms in power series, the critical buckling
load of functionally graded plate with different boundary conditions is determined. The accuracy of presented results is verified
by appropriate convergence study, and the results are checked with those available in related literature. Furthermore, the
effects of power of functionally graded material, aspect ratio, foundation stiffness coefficients and in-plane loading configuration
together with different combinations of boundary conditions on the critical buckling load of functionally graded rectangular
thin plate are studied. 相似文献
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含内埋矩形脱层复合材料圆柱壳屈曲分析的混合变量条形传递函数方法 总被引:1,自引:0,他引:1
提出了一种分析含内埋矩形脱层正交各向异性圆柱壳稳定性问题的混合变量条形传递函数方法。首先基于Mindlin一阶剪切壳理论,通过定义圆柱壳的广义力变量和混合变量,建立了壳的改进混合变量能量泛函;然后,为了便于脱层壳的分区求解,通过引入条形单元,创建了基于混合变量条形传递函数解的含脱层和不合脱层两种超级壳单元;在此基础上,将含内埋矩形脱层的复合材料层合壳划分成两种超级壳单元的组合体,通过各超级壳单元相互之间连接结点处的位移连续和力平衡条件得到脱层壳的屈曲方程;最后由屈曲方程计算含内埋矩形脱层壳的屈曲载荷和屈曲模态。算例分析的结果验证了本方法的正确性,并给出了几种因素对屈曲载荷和屈曲模态的影响。 相似文献
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This paper presents a theoretical analysis for the long-term non-linear elastic in-plane behaviour and buckling of shallow concrete-filled steel tubular (CFST) arches. It is known that an elastic shallow arch does not buckle under a load that is lower than the critical loads for its bifurcation or limit point buckling because its buckling equilibrium configuration cannot be achieved, and the arch is in a stable equilibrium state although its structural response may be quite non-linear under the load. However, for a CFST arch under a sustained load, the visco-elastic effects of creep and shrinkage of the concrete core produce significant long-term increases in the deformations and bending moments and subsequently lead to a time-dependent change of its equilibrium configuration. Accordingly, the bifurcation point and limit point of the time-dependent equilibrium path and the corresponding buckling loads of CFST arches also change with time. When the changing time-dependent bifurcation or limit point buckling load of a CFST arch becomes equal to the sustained load, the arch may buckle in a bifurcation mode or in a limit point mode in the time domain. A virtual work method is used in the paper to investigate bifurcation and limit point buckling of shallow circular CFST arches that are subjected to a sustained uniform radial load. The algebraically tractable age-adjusted effective modulus method is used to model the time-dependent behaviour of the concrete core, based on which solutions for the prebuckling structural life time corresponding to non-linear bifurcation and limit point buckling are derived. 相似文献
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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