共查询到19条相似文献,搜索用时 62 毫秒
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某些超静定结构,当弯矩图确立后,应用静力平衡条件无法绘出轴力图.分析该类结构的基本特征和受力特点,利用某些刚架在结点集中力作用下无弯矩、只有轴力的特点和力法的思想,提出解算已知弯矩图轴力超静定结构的计算方法.算例表明该方法简化了力法的计算过程,将其应用于教学,有利于学生对力法的深入理解. 相似文献
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对“用位移法计算超静定结构”论述的商榷徐昌文(上海建筑材料工业学院,上海200434)综观《结构力学》各种教材,一般都有如下的论述:力法和位移法是计算超静定结构的两个基本方法.用位移法解超静定结构是取结点位移作为基本未知量,以单跨超静定梁的组合体作为... 相似文献
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绘制超静定结构的弯矩图形,是土木类专业的主要内容.掌握快速绘制弯矩图的方法,对于土木工程师进行结构的受力分析、计算、校核和检验以及参加注册工程师的考试,都有着非常重要的意义.该文是在多年理论教学与工程实践的基础上,对传统的速画弯矩图的方法进行了总结,归纳出一些进一步提高速画弯矩图的方法.算例表明这些方法简化了超静定结构弯矩图的绘制过程,将其应用于教学,有利于学生对超静定结构的深入理解. 相似文献
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弯矩图确定后轴力不能直接解算问题的探讨 总被引:1,自引:1,他引:0
某些超静定结构,当弯矩图确立后,应用静力平衡条件无法实现对整个结构的支座反力
及内力的完全解算. 通过对此类结构受力特征的分析,定义出现此类情况结构的基本特征,
并在结构力学范畴内,对比可以解决此类问题的计算方法,提出解决思路,给出简便的解算
公式. 相似文献
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将单位支座位移法推广应用于超静定结构的未知支座反力计算,建立并证明了相应的退化虚位移方程,推导指出超静定结构支座反力的影响线即为相应单位支座位移所引起的位移曲线。而且,展示了几个求解超静定梁支座反力的算例. 本文工作可供大学生和教师们在结构力学相关知识的学习和教学中借鉴参考. 相似文献
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对于满足两刚片规则或三刚片规则的简单静定结构,可以证明,用平衡方程进行受力分析时,必可做到一个方程解一个未知力。本文在一个方程解一个未知力的基础上,进一步提出了约束力换算公式及二力杆转化思路,使静定结构的受力分析更加简化。 相似文献
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本文指出“基本结构”与“基本体系”是两个不同的概念,在论述“用过渡法计算超静定结构”时,二者应同时给出. 相似文献
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Aerodynamic force and flow structures of two airfoils in a tandem configuration in flapping motions are studied, by solving
the Navier-Stokes equations in moving overset grids. Three typical phase differences between the fore- and aftairfoil flapping
cycles are considered. It is shown that: (1) in the case of no interaction (single airfoil), the time average of the vertical
force coefficient over the downstroke is 2.74, which is about 3 times as large as the maximum steady-state lift coefficient
of a dragonfly wing; the time average of the horizontal force coefficient is 1.97, which is also large. The reasons for the
large force coefficients are the acceleration at the beginning of a stroke, the delayed stall and the “pitching-up” motion
near the end of the stroke. (2) In the cases of two-airfoils, the time-variations of the force and moment coefficients on
each airfoil are broadly similar to that of the single airfoil in that the vertical force is mainly produced in downstroke
and the horizontal force in upstroke, but very large differences exist due to the interaction. (3) For in-phase stroking,
the major differences caused by the interaction are that the vertical force on FA in downstroke is increased and the horizontal
force on FA in upstroke decreased. As a result, the magnitude of the resultant force is almost unchanged but it inclines less
forward. (4) For counter stroking, the major differences are that the vertical force on AA in downstroke and the horizontal
force on FA in upstroke are decreased. As a result, the magnitude of the resultant force is decreased by about 20 percent
but its direction is almost unchanged. (5) For 90°-phase-difference stroking, the major differences are that the vertical
force on AA in downstroke and the horizontal force on FA in upstroke are decreased greatly and the horizontal force on AA
in upstroke increased. As a result, the magnitude of the resultant force is decreased by about 28% and it inclines more forward.
(6) Among the three cases of phase angles, inphase flapping produces the largest vertical force (also the largest resultant
force); the 90°-phase-difference flapping results in the largest horizontal force, but the smallest resultant force. 相似文献
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《International Journal of Solids and Structures》2006,43(18-19):5658-5673
A numerical method is presented for form-finding of tensegrity structures. Eigenvalue analysis and spectral decomposition are carried out iteratively to find the feasible set of force densities that satisfies the requirement on rank deficiency of the equilibrium matrix with respect to the nodal coordinates. The equilibrium matrix is shown to correspond to the geometrical stiffness matrix in the conventional finite element formulation. A unique and non-degenerate configuration of the structure can then be obtained by specifying an independent set of nodal coordinates. A simple explanation is given for the required rank deficiency of the equilibrium matrix that leads to a non-degenerate structure. Several numerical examples are presented to illustrate the robustness as well as the strong ability of searching new configurations of the proposed method. 相似文献
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Behrooz Farshi Ali Alinia-ziazi 《International Journal of Solids and Structures》2010,47(18-19):2508-2524
This paper describes a new approach to optimum weight design of truss structures. The force method is incorporated in an optimization algorithm based on the method of center points. Design variables are the member cross-sectional areas and the redundant forces evaluated for each independent loading condition acting on the structure. The optimization method utilizes the largest hyperspheres inscribed within the feasible space. The method of hyperspheres has been enhanced here to handle the compatibility equality constraints as well. By including the analysis step in the optimization cycle there is no longer the need to perform separate structural analyses thus saving computation time. The viability and efficiency of the proposed method are demonstrated for truss structures subject to multiple loading conditions and constraints on member stresses, nodal displacement and minimum gage. Numerical results are compared with those reported in the literature. 相似文献
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Nonlinear Dynamics - Basic single-degree-of-freedom mechanical models of force control are presented to achieve desired contact forces between actuators and objects. Nonlinear governing equations... 相似文献
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杆件修改与去除及内力变更时杆系结构分析的矩阵力法 总被引:1,自引:0,他引:1
采用矩阵力法,引入假想初位移的概念,用原始结构在外荷载与某一组假想初位移联合作用下的效应,来替代部分杆件被修改、去除及内力变更的新结构胡该外荷载作用下的效应。这种方法的计算可以仅涉及被修改、去除及内力变更的那部分杆件,并且利用原始结构的计算成果来分析新结构,无须按常规方法从头开始再计算一篇。在许多情况下,这种做法的工作量有可能成倍地甚至几十倍地大幅度减少。文中附有算例,计算结果表明本文提出的简捷计算方法是正确的、可靠的和有效的。 相似文献
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高层建筑结构抗震弹塑性简化方法的研究及其应用 总被引:6,自引:0,他引:6
以地震反应谱理论为依据,建立了可以考虑多阶振型影响的高层建筑结构弹塑性静力分析方法。在此基础上发展了较简单且较为精确的高层建筑结构弹塑性地震反应计算方法。最后给出的算例论证了本文简化方法的可能性及可行性。 相似文献