共查询到19条相似文献，搜索用时 372 毫秒
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为了模拟车辆/列车通过多跨变截面桥梁时的耦合动力响应,采用有限元法将移动车辆作为移动质量处理,使用Euler-Bernoulli变截面梁单元模拟桥梁结构,讨论了移动质量在梁桥模型上作匀变速运动下的有限元离散模式.在假定变截面模式的基础上,推导了梁高呈线性变化及抛物线性变化的矩形截面梁单元刚度矩阵和质量矩阵,并对多个变速移动荷载作用下的梁桥结构动力响应进行了数值模拟.运用该方法可以使变截面梁的分析简化,计算结果可作为工程设计和科学研究时的参考. 相似文献
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随着数值模拟的发展,有限单元法已成为当今工程分析中最广泛应用的数值计算方法。本文采用有限元分析了变截面压杆的稳定问题,并用ANSYS分析结果与解析分析结果进行对比,分析表明杆剪应力对杆受荷的影响,使荷载偏小。 相似文献
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小根开塔(窄基塔)是输电线路一种新塔型,属于风敏感结构,风与结构的相互作用十分复杂,风荷载常常是设计的主要控制荷载。本文以某一220 kV同塔双回路直线窄基塔为工程背景,建立了详细的有限元计算模型,获得了结构的自振动力特性。在考虑节点风荷载空间相关性的基础上,利用Kaimal谱对结构的风荷载进行了准确的数值模拟。结合动力时程积分法,计算得到了结构的风致振动响应时程。研究了结构位移平均值、位移均方根值和加速度均方根值的分布特点,同时分析了结构各层的荷载风振系数和位移风振系数,并与我国规范进行了对比。通过研究,揭示了窄基塔的风致振动特性,结果可作为窄基塔结构抗风设计的参考。 相似文献
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为了研究车辆在桥面上行驰过程中突然刹车对桥梁产生的冲击振动的影响,考虑了车轮处的摩擦力与刹车制动力共同作用时移动质量模型对车桥的耦合振动现象进行数值模拟。对于工程中常用的变截面箱梁,推导了平面内呈线性和抛物线形变化时的质量阵,采用Romberg数值积分方法得到刚度矩阵中的系数项。对于变速行驰在桥面上的车辆出现紧急刹车的现象,考虑了车轮与桥面间的摩擦并引入冲击系数模拟刹车力对桥面的作用,探讨了摩擦系数与冲击系数对车桥耦合振动的影响。 相似文献
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针对组合拼接建筑结构下钢筋搭接抗震性分析还是一个全新的课题,受到结构复杂性的影响,当前的测试方法具有一定的局限性,为此提出一种考虑传力性能的空间反应谱以及精细时程积分的抗震性分析方法,分析组合拼接建筑结构下钢筋搭接的强度退化率、粘结强度以及附加搭接长度三个传力性能指标,根据这些指标构建组合拼接建筑结构下,钢筋搭接结构动力模型,采用空间反应谱以及精细时程积分方法,获取不同振动加速度下的钢筋搭接结构的移动结果,完成钢筋结构的线性动力抗震分析。实验结果表明,所提方法具有较高的抗震分析性能以及鲁棒性,不受振动波的干扰,取得了令人满意的效果。 相似文献
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输电塔属于风敏感结构,风与结构的相互作用十分复杂,风荷载常常是设计的主要控制荷载。本文以某一高185 m的500 kV输电跨越塔结构为工程背景,建立了详细的有限元计算模型,获得了结构的自振动力特性。在考虑节点风荷载空间相关性的基础上,利用Kaimal谱对结构的风荷载进行了准确的数值模拟。结合改进显示积分法的优点,计算得到了结构的风致振动响应时程。研究了结构位移平均值、位移均方根值和加速度均方根值的分布特点,同时分析了结构各层的荷载风振系数和位移风振系数,并与多种规范进行了对比。通过研究,揭示了超高输电铁塔的风致振动特性,结果可作为输电塔结构抗风设计的参考。 相似文献
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特高压输电线路中塔身极高,采用传统的反应谱法不能准确反应塔的抗震能力,抗震分析时需采用精细的三维有限元方法。本文采用谐波合成法数值模拟了地震加速度时程曲线,并用时程分析法计算了输电塔在地震激励下的动力响应。计算结果表明该塔强度满足抗震设计要求。 相似文献
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首先介绍了拉索-TMD系统的参数及有限元软件Ansys模拟所用的单元,再通过Matlab模拟脉动风功率谱和风速时程得到相关数据转化成风荷载,导入Ansys中进行模拟计算。通过有限元模拟探讨在一定范围内改变TMD的质量参数、刚度参数、阻尼比,得到拉索在数值模拟的风荷载作用下的减振效果。最终可针对拉索的一阶模态振动,进行TMD参数的最优配置以达到抑制拉索振动的效果。由此可对实际工程中TMD的配置具有一定的参考作用。 相似文献
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钢混组合梁在长期荷载作用下的动力特性受到混凝土徐变的影响,为研究动力因素与混凝土徐变因素耦合作用下的部分相互作用组合梁的动力特性,本文选择适当的状态变量来建立状态空间公式,然后得到两端简支边界条件下自由振动的频率特征方程和对应的各阶模态。公式是基于节点处的受力平衡与应变兼容性的基本力学微分方程利用D’Alembert原理推导出的,在此基础上还额外加入了考虑混凝土的徐变影响的系数项。然后采用模态叠加法计算部分相互作用组合梁在均布简谐荷载、集中移动荷载作用下的非齐次方程解以及动力响应。无论荷载类型如何,该数值模型都可以成功地用于模拟任意跨连续梁的时变结构行为。最后通过给出分析结果与数值结果的比对研究和若干相关参数研究,验证了数值模型的有效性。 相似文献
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A mechanical integraph has been developed which plots continuously the integral of the product of two functions. It uses the principle of the electrical integrating watthour-meter combined with a moving table. Errors of the machine have been reduced to an average of 1 per cent. for common uses. By cross-connecting the device in a simple mechanical way, it is possible to solve certain types of integral equations. A link motion has been added which plots the product of two given functions. Various uses have been made of the instrument for solving problems in connection with electrical circuits, continuous beams, etc., and certain problems involving integral equations. 相似文献
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Walter T. White 《Journal of The Franklin Institute》1948,245(1):25-36
In this paper integral equations are applied for the calculation of the normal modes of vibrating beams. Both exact and approximate methods of solving the integral equation are considered. The Green's function, or kernel, of the integral equation is constructed for both uniform and nonuniform beams. Solutions for the normal modes of a uniform cantilever are given. A nonuniform, naturally-twisted turbine blade is studied in detail and the first and second normal modes are calculated by the integral-equation method. 相似文献
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This paper presents solution of the optimal linear-quadratic controller problem for unobservable integral Volterra systems with continuous/discontinuous states under deterministic uncertainties, over continuous/discontinuous observations. Due to the separation principle for integral systems, the initial continuous problem is split into the optimal minmax filtering problem for integral Volterra systems with deterministic uncertainties over continuous/discontinuous observations and the optimal linear-quadratic control (regulator) problem for observable deterministic integral Volterra systems with continuous/discontinuous states. As a result, the system of the optimal controller equations are obtained, including the linear equation for the optimally controlled minmax estimate and two Riccati equations for its ellipsoid matrix (optimal gain matrix of the filter) and the optimal regulator gain matrix. Then, in the discontinuous problems, the equation for the optimal controller and the equations for the optimal filter and regulator gain matrices are obtained using the filtering procedure for deriving the filtering equations over discontinuous observations proceeding from the known filtering equations over continuous ones and the dual results in the optimal control problem for integral systems. The technical example illustrating application of the obtained results is finally given. 相似文献
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This series of papers addresses three interrelated problems: the solution of a variational problem, the solution of integral equations, and the solution of an initial valued system of integrodifferential equations. It will be shown that a large class of variational problems requires the solution of a nonlinear integral equation. It has also been shown that the solution of a nonlinear integral equation is identical to the solution of a Cauchy system. In this paper, we by-pass the nonlinear integral equations and show that the minimization problems directly imply a solution of the Cauchy system. This second paper in the series looks at semi-quadratic functional and scalar functions. 相似文献
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In this brief, a switching fault-tolerant control (FTC) scheme is presented for a moving vehicle-mounted flexible manipulator subject to state constraints. The dynamic characteristics of the system are represented by coupled ordinary differential equations and partial differential equations (ODEs–PDEs). When actuators are healthy, vibration control and position regulations can be realized without violation of the given constraints based on a Barrier Lyapunov Function (BLF). Moreover, a switching strategy is introduced to prevent the transgression of constraints even under actuator failure by detecting actuator faults as-assisted by the proposed monitoring functions. The closed-loop states are kept within the given bounds under FTC laws. By extending LaSalle's Invariance Principle to an infinite dimension, the asymptotic stability of the fault-free closed-loop system is strictly verified. Simulation results demonstrate the effectiveness of the proposed approach. 相似文献
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Changqing Yang 《Journal of The Franklin Institute》2012,349(3):947-956
In the current work, the Chebyshev collocation method is adopted to find an approximate solution for nonlinear integral equations. Properties of the Chebyshev polynomials and operational matrix are used in the integral equation of a system consisting of nonlinear algebraic equations with the unknown Chebyshev coefficients. Numerical examples are presented to illustrate the method and results are discussed. 相似文献
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《Journal of The Franklin Institute》2023,360(6):4378-4398
Dynamic path planning for mobile robots is an urgent issue that needs to be solved because of the growing use of mobile robots in daily life and industrial operations. This work focuses on avoiding moving obstacles in dynamic situations. The computational effort required by some current algorithms makes them difficult to utilize for path planning in dynamic situations whilst the computational effort required by other methods makes them simple yet prone to local minima. In this paper, an improved simulated annealing (SA) algorithm for dynamic path planning is proposed. To reduce its computational effort, the initial path selection method and deletion operation are introduced. Simulation results show the improved SA algorithm outperforms other algorithms and provides optimal solutions in static and dynamic environments. 相似文献
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The difficulties in solving Fredholm integral equations of the first kind are well known. A classical method has been to convert the equation into a set of m linear algebraic equations in n unknowns (m?n). For computational convenience, it is customary to force m = n and solve the resulting ill-conditioned system using one technique or other. In the general case, a feasible solution, if it exists, can be found by determining the generalized inverse of the coefficient matrix. One method of finding the generalized inverse is to reformulate the problem and observe the steady state response of a system of ordinary differential equations with prescribed initial conditions. Results obtained from this reformulation are found to be comparable in quality to those obtained earlier by other methods. Analog and digital computer implementations are discussed. 相似文献