考虑约束扭转的薄壁梁单元刚度矩阵

推导了薄壁空间梁单元刚度矩阵 ,考虑了双向弯曲及截面约束扭转对杆件轴向变形的影响 ;计算了截面的翘曲变形 ,以及二次剪应力对翘曲变形的影响 ,可适用于任意截面 (包括开口、闭口和混合剖面 )的薄壁杆件。计算结果表明 ,考虑约束扭转的薄壁梁单元刚度矩阵有相当好的精确度 ,可以用于薄壁杆件的静动力分析。     

考虑弯扭形变的薄壁箱形梁的非线性后屈曲

在大位移和扭转的前提下,通过一中等弯曲扭转的位移场描述了薄壁箱形梁在偏心载荷作用下的静稳定性问题.该非线性公式可用于分析简支薄壁箱形梁在不同载荷作用下的屈曲和后屈曲行为.采用伽辽金方法将非线性微分系统离散,并通过牛顿-拉普森增量迭代法求解得代数方程组.数值计算结果表明,当前屈曲位移不可忽略时,经典的横向屈曲预测是保守的...     

薄壁杆约束扭转的单肢解析化分析方法

针对薄壁杆件约柬扭转的基本受力反应分析问题,采用与符拉索夫的经典约束扭转理论截然不同的立论途径,将自由扭转刚度视为调整因素,而将剥离了该抗力效应的薄壁杆件基本体系作为主要分析对象,推导出基于翘曲理论并考虑了自由扭转刚度影响的杆件刚度方程及结问荷载的等效措施.此外,提出了基于微段薄壁杆简化单刚的有效数值化分析方法.上述研究表明,对于钢构件等具有薄壁构型截面形式的杆件,这种单肢解析化分析方法无需进行复杂的截面特性如弯、翘曲惯矩或弯、形心坐标等的分析,力与变形的表达简洁、直接,本文的抗力性能分析和表述方式可为薄壁构件的稳定及畸变等研究提供新的思路切入点.     

剪切和扭转工况下微纳米薄壁蜂窝的等效剪切模量计算

分别针对剪切和扭转两种工况给出了微纳米薄壁蜂窝等效剪切模量的解析计算方法.该方法综合考虑了由面板对芯层的约束导致的高度效应和当蜂窝胞壁厚度进入微纳米量级时引起的尺度效应.首先对蜂窝各胞壁选取了可反映面板约束以及受力状态的三角级数位移场,然后在本构关系中引入修正偶应力理论以描述尺度效应,最后应用能量均匀化方法求得蜂窝的等效剪切模量.以典型六边形蜂窝为例,给出了完整的计算过程和结果.与文献中的等效剪切模量结果进行对比,讨论了不同工况下等效剪切模量随芯层高度和胞壁厚度的变化趋势,以及高度效应和尺度效应之间的相互影响.     

A new finite element of spatial thin-walled beams

Based on the theories of Timoshenko＇s beams and Vlasov＇s thin-walled members, a new spatial thin-walled beam element with an interior node is developed. By independently interpolating bending angles and warp, factors such as transverse shear deformation, torsional shear deformation and their Coupling, coupling of flexure and torsion, and second shear stress are considered. According to the generalized variational theory of Hellinger-Reissner, the element stiffness matrix is derived. Examples show that the developed model is accurate and can be applied in the finite element analysis of thinwalled structures.     

The application of graph theory to the limit analysis for torsion of thin-walled bars with complex cross-sections

Graph theory is employed in this paper as a means to establish the topological model of complex thin-walled cross-sections. On this basis, the upper and lower bound theorems of the plastic limit analysis are applied to the analysis of the plastic limit shear flows on the cross-section of thin-walled bars under St. Venant torsion. Corresponding mathematical programming problems are formulated and their duality is shown. After solving the linear programming problem corresponding to the lower bound theorem, the limit torsional moment of a thin-walled cross-section can be calculated according to the shear stress distribution in the limit state. The formula for calculating the limit torsional moment is given. Furthermore, the limit state of thin-walled cross-sections under St. Venant torsion is also discussed and the concept of the limit tree is introduced. A computer program has been developed by the author. Results calculated by the program for typical complex cross-sections are given.     

开口薄壁杆件横截面几何性质计算

基于有限元方法的思想, 给出了厚度线性变化的薄壁结构扇性几何性质 计算的一种方法, 通过数值实施, 表明了所给方法的正确和有效性.     

考虑剪切变形的矩形截面薄壁杆件畸变分析

在以往不考虑剪切变形的畸变分析理论基础上,假设翘曲位移及切向位移的分布函数,考虑剪切变形的影响,利用最小势能原理建立单位均布畸变荷载作用下的畸变角微分方程。采用一般解法对该畸变角微分方程进行求解,并推导求解的初参数法。随之,通过实例验证了本文理论的正确性,结果表明考虑剪切变形的影响大大提高了考虑畸变效应的计算精度。     

扇形截面杆扭转的应力分析

柱体扭转的基本方程为非齐次偏微分方程,在极坐标系下,利用分离变量法及傅立叶级数展开法,求出了扭转应力函数,进一步即可计算出扇形截面杆在外力偶作用下,扭转角和横截面上剪应力的精确解答。这种方法为精确解法,在各种机械及其他工程设备中,对受扭转作用的扇形截面杆设计,有一定实用价值。     

有初应力钢筋混凝土压弯扭构件非线性有限元分析

钢管初应力是钢管混凝土在大跨度桥梁,高层超高层建筑应用中广大工程技术人员关心的问题,本文在钢材随动强化模型和混凝土边界模型的基础上编制了计算有初应力的钢管钢混凝压弯扭构件全过程曲线的非线性有元程序。     

Measurement techniques in the testing of thin-walled structural members

The paper describes methods for measuring displacements and end moments in the testing of thin-walled columns. The complete spatial deformation of a column can be captured by using local and overall deformation measurement frames. The local frame involves spring-loaded levers and roller bearings to mount the frame on to the specimen. The overall frame slides along high-precision shafts using linear ball bearings. Fixed-ended bearings are used to measure minor and major axis bending moments as well as the applied load. The bearings allow the line of action of the applied force to be determined.     

波形钢腹板组合箱梁约束扭转分析

波形钢腹板箱梁相比于传统混凝土箱梁其扭转效应更为明显,为了更加合理地分析其约束扭转效应,在乌曼斯基第二理论的基础上考虑波形钢腹板的手风琴效应及顶底板对腹板的约束作用,通过截面等效的途径,推导了约束扭转正应力和二次剪应力的计算公式,数值算例和ANSYS有限元分析验证了所推导公式的正确性。引入正应力系数反映约束扭转正应力与弯曲正应力的占比关系,引入剪应力系数反映二次剪应力对扭转总剪应力的影响程度。结合数值算例,详细分析了悬臂板宽度和波形钢腹板厚度变化对应力系数的影响规律。研究结果表明,偏心集中荷载作用下,扭转翘曲正应力可达到弯曲正应力的45%,波形钢腹板上下两端区域内的约束扭转正应力可达到弯曲正应力水平,二次剪应力可达到扭转总剪应力的52%,减小悬臂板宽度和增大波形钢腹板厚度可显著降低二次剪应力。     

薄壁杆侧向稳定分析有限杆元模型

根据位移变分原理,建立有限杆元模型,对薄壁杆进行侧向稳定分析。在考虑截面扭转、翘曲同时,特别考虑了反映剪力滞后现象的杆壁中面上剪应交的影响。推导出薄壁杆侧向屈曲能量方程可适用求解常用边界条件,任意棱形截面形状的薄壁杆的屈曲特征值问题。     

The method of solving axisymmetric problems in elastic space by complex function and some examples

This paper proves Love’s stress function of space axisymmetric problem can be represented by choosing two generalized analytic functions of complex variates reasonably^[1], and deduces the expressions of the components of stress displacements and boundary conditions in complex function. To present the feasibility of the method here and examining the truth of the formulae founded in this paper, the problem of circular shaft with globular cavity pressed on the side and pulled at the ends is solved by using power series and the result is the same as that solved by other methods. In the end, the problem of a cone sheared by uniform shear stress on the sideface is solved, and the solution of a cone acted on by gravity is given by converting constant body forces into surface forces.     

考虑剪切变形的薄壁箱梁畸变分析

采用广义坐标法,建立畸变位移模式和几何方程,推导出畸变剪应力;基于混合变分原理,建立了一种新的畸变理论和梁段单元模型,该理论充分考虑了剪切变形的影响。基于新理论,指出了在单箱室箱梁不存在布莱特纯畸变,明确了畸变中心的定义,研究了畸变剪应力成分对剪切变形的影响及其影响程度。结果表明,对于常见的箱梁是可以忽略剪切变形的对畸变效应的影响。     

Fatigue strength of metals and composites under repeated high-cycle torsion

The limiting stresses are determined and constant fatigue life diagrams for high-cycle torsion with repeated stress cycle are plotted using the limiting-state models obtained based on the hypothesis of a unified constant-life diagram, which is invariant to the number of cycles to failure. The unified constant-life diagram is given by a transcendental power function whose exponent is an additional parameter characterizing the sensitivity of the material to the asymmetry of the stress cycle. The calculated results and experimental data for carbon and alloyed steels and composite materials are in good agreement __________ Translated from Prikladnaya Mekhanika, Vol. 44, No. 2, pp. 19–28, February 2008.     

Free vibration of horizontally curved thin-walled beams with rectangular hollow sections considering two compatible displacement fields

A finite element is presented for vibration analyses of horizontally curved thin-walled rectangular hollow beams. Eight cross-section deformation modes are employed to describe the mid-surface contour displacement field with the modal superposition method. Focused on the in-plane moment equilibrium condition and the displacement continuity condition, two compatible displacement fields are constructed to calculate the strain energy and the kinetic energy of the beam, respectively. With the application of Hamilton’s principle the dynamic governing equations are formulated, and then approximated for the finite element implementation. Finally, numerical examples are illustrated to verify the validity of the present theory.     

薄壁箱梁的翘曲连续性条件

基于薄壁杆件理论,分析了薄壁箱梁弯曲剪流和约束扭转翘曲剪流计算时的翘曲连续性条件. 从翘曲连续性条件出发,推导了薄壁箱梁约束扭转翘曲剪流的一般公式,此外,还指出了有关文献中的错误并进行了更正. 最后对一个悬臂箱梁的约束扭转翘曲剪流进行了计算比较.     

调液阻尼器对结构扭转耦联振动控制的优化设计

提出了利用调液柱型阻尼器(Tuned Liquid Column Dampers,简称TLCD)和环形调液阻尼器(Circular Tuned Liquid Column Dampers,简称CTLCD)来控制偏心结构在多维地震作用下扭转耦联振动的方法。采用遗传算法,在双向地震作用下,对调液阻尼器的相关参数进行优化。选取了两种目标函数,一种只考虑最大的楼层反应,另一种考虑结构所有自由度的反应。用一个12层的偏心结构作为算例,进行优化计算,结果表明,采用第二种目标函数得到的阻尼器的参数,能有效降低结构的平动反应和扭转反应。     

平面应力下薄壁管材连续矫直压弯量力学模型与数值解法

薄壁管材在连续矫直过程中,各矫直辊组的压弯量作为核心工艺参数直接决定了薄壁管材的矫直精度。而目前现场仍沿用经验图表结合人工经验和反复试矫对其进行估定,亟待建立针对性的压弯量数学模型以指导生产。为此从薄壁管材的结构特点和矫直辊系组成出发,构建了针对压弯量计算的简化悬臂结构模型,基于相关假设和弹塑性相关理论,分别确定了平面应力状态下弹性区和弹塑性区管材横截面的弯矩模型,运用虚功原理建立了矫直辊压弯量力学模型,并给出了数值计算方法,完成了程序开发。经有限元动态仿真试验证明了模型的正确性和适用性,通过对典型管材数据的计算绘制了一系列工艺参数曲线,得到管材轴线弯曲半径和压弯量随管材直径、壁厚和屈服极限的变化关系,为现场压弯量的调整提供理论依据。