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叶海青 《五邑大学学报(社会科学版)》1993,(3)
为了确保计算稳定性和提高计算精度,本文改进了砼梁单元在双向应力作用下的本构关系,自编了钢筋砼梁非线性平面有限元计算程序RCNFEA,对简支梁和两跨连续梁进行了非线性全过程分析,着重研究了连续梁的内力重分布规律,并详细分析了弯矩调幅对低配筋连续梁使用阶段裂缝宽度和挠度的影响,所得结果与试验分析结果基本一致。 相似文献
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为了能够简捷、快速地得到一般平面弹性力学问题的结果,将一个平面弹性体假想为由若干正方形组成的近似结构,这个结构可以简单地用二维数组直接进行描述。以梁弯曲为例,引用"节点领域"的差分法推导每个节点与周围节点的平衡关系,利用每个节点的关系方程进行迭代计算,从而编写程序实现了模拟梁弯曲变形的过程。总结了适合于程序编写、供各种基本边界条件下,联立方程组迭代求解弹性体的位移分布的简单思路。 相似文献
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苏英志 《邢台职业技术学院学报》2007,24(1):25-28
本文对基于模态振型的结构损伤识别方法进行了研究，提出一个新的模态参数——振型差值曲率，阐述了用它作为参数进行结构损伤识别的思想与方法，然后建立了一个悬臂梁的数值模型，用有限元分析计算结果作为损伤诊断的依据，对不同的模拟损伤用本丈所研究的方法进行了识别，结果表明采用振型差值曲率法可找到结构损伤的位置并确定结构损伤的程度，分析判断简便有效。 相似文献
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用积分法和中点材料法形成单元刚度阵对非均匀材料进行结构分析。用函数形式表达材料参数,通过在每个三角形区域里对弹性系数进行积分,得到单元刚度矩阵,从而真实地反映了材料的非均匀性;另一种简化方法是用三角形中心处的材料参数代替整个三角形单元的材料参数,使每一个三角形单元为均匀单元。文章比较了两种方法的计算结果和时间,同时用COMSOL对这两种方法进行了验证。 相似文献
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建立了一种基于广义梁理论(GBT)的非线性显式动力梁有限元模型,该模型可用于等截面薄壁钢构件的冲击响应模拟.考虑冲击加载时的应变率强化及绝热升温引起的热软化效应,当前模型采用了一种修正的Cowper-Symonds率相关本构模型.用GBT截面变形模态构建单元截面位移场,因此新模型可考虑构件截面的畸变、屈曲及任意的翘曲剪切等局部效应.此外,用三次非均匀B样条基函数拟合各个GBT截面变形模态的幅值函数.用Kirchhoff薄板假设构造弯曲相关位移场.用Green-Lagrange应变张量和PK2应力分别描述材料点的应变和应力,假设各材料点处于平面应力状态.为了验证所提模型的有效性,给出了3组薄壁构件的冲击分析算例,将当前模型的结果和壳有限元(Ls-Dyna)分析结果进行了对比,结果表明:当前模型和壳有限元模型的位移解和应力解具有等效精度,但所提模型的计算效率更高,并具备更好的结构明晰性. 相似文献
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王焕定、焦兆平编著的《有限单元法基础》这本教材,以能量法为纽带,通过能量法求解杆件结构、平面问题、空间问题。通过建立单元的位移模式,得到单元的应变与应力;通过求单元的应变能与外力势能,从而得到单元的总势能;用最小势能原理求单元刚度矩阵与等效节点载荷。最后由单元刚度矩阵组集总纲,引入边界条件,解线性方程组,求出节点位移。再将求出的节点力代入相应单元,求得单元应力与应变。 相似文献
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基于势能驻值原理和广义坐标法原理推导出考虑截面畸变效应的梁单元刚度矩阵.根据此梁单元刚度矩阵,编制了计算薄壁钢箱梁结构的有限元程序,且此程序可以考虑截面畸变效应和扭转效应.运用自编程序,分析横隔板间距对薄壁钢箱梁受力性能的影响.通过数值计算,得出布置横隔板对畸变正应力的影响最大,对弯曲正应力的影响很小.畸变荷载作用下,只有当横隔板布置间距小到一定数值时,薄壁箱梁的畸变正应力才会减小.最后,引入畸变翘曲影响系数γ,简化了薄壁箱形梁纵向正应力的计算方法.当横隔板布置间距L与薄壁箱梁横截面最大尺寸H的比值小于2时,畸变翘曲影响系数γ趋于1,表明薄壁箱形梁的畸变正应力趋于零,可以忽略畸变效应的影响. 相似文献
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Xue-ping LI Wei-qiu ZHU Zu-guang YING 《浙江大学学报(A卷英文版)》2008,9(3):330-337
An optimization method for time-delayed feedback control of partially observable linear building structures subjected to seismic excitation is proposed. A time-delayed control problem of partially observable linear building structure under horizontal ground acceleration excitation is formulated and converted into that of completely observable linear structure by using separation principle. The time-delayed control forces are approximately expressed in terms of control forces without time delay. The control system is then governed by Itoe stochastic differential equations for the conditional means of system states and then transformed into those for the conditional means of modal energies by using the stochastic averaging method for quasi-Hamiltonian systems. The control law is assumed to be modal velocity feedback control with time delay and the unknown control gains are determined by the modal performance indices. A three-storey building structure is taken as example to illustrate the proposal method and the numerical results are confirmed by using Monte Carlo simulation. 相似文献
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语气副词是表达语气的语法成分，也常常跟语用因素直接关联。语气副词既可出现于动态句子中，也可以用于静态短语中。本文援引“小句中枢说”和生成语法的“X-阶标理论”讨论不同位置上的语气副词的句法特征和语用功能的差异。我们进而认为，按照最简方案下“广义左向合并理论”，语气副词一律都是在语段生成时左向附加上去的，可以附加于VP，vP和TP等多种不同的句法节点，并非必然地附加于句子的最外层。 相似文献
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To consider the bending collapse of the pipes in the latticed frames, based on the multi-scale simulation, the collapsed parts of the pipe are meshed by the shell elements as micro-scaled models, and the other parts are meshed by beam elements macro-models. The incremental displacement constraint equations for the nodes on the section between the two models are established based on the plane section premise of classical beam theory. The method to introduce the constraint equations is derived based on the Updated Largrangian method. The location of the micro-model is predicted by the stress field of the beam element, and the length of the collapsed part is adjusted by the plastic energy in the micro model. Several examples are included to illustrate the efficiency and accuracy of this method. 相似文献
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杨杰 《成都航空职业技术学院学报》2010,26(3):54-56
本文利用有限元分析软件SAP2000对一座十五层钢筋混凝土框架结构进行改进模态Pushover分析,并将其结果与动力时程方法进行比较。由于该方法所得结果考虑了高阶振型的影响,其结果有较高的准确性。 相似文献
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Additive summation is observed when more responses are emitted to the simultaneous presentation (tone-plus-light) of independently conditioned stimuli (tone and light) than to either stimulus presented alone. The current experiment sought to determine if this increased rate during tone-plus-light was a function of a new modal interresponse time (IRT) or a differential mixing of pauses with a modal IRT characteristic of the responding in tone and light alone. Three rats were trained on a three-component multiple schedule where tone and light were each associated with a variable-interval 30-sec schedule while a variable-interval 100-sec operated in the simultaneous absence of these stimuli, tone-off and light-out. Baseline response rates were 2–4 times as high in tone or light as in their absence. In testing, more responses were emitted to tone-plus-light than to tone or light by all animals, but the modal IRT was in the 0.2–0.4-sec IRT bin for all test conditions. Tone-plus-light controlled fewer long IRT values and more responses in the short modal category than tone or light alone. These results support the response mixing hypothesis of stimulus control; i.e., no “new” behavior was observed during the novel combination of stimulus elements, only a mixture of previously reinforced behavior patterns in different proportions. 相似文献
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为了分析塔式起重机的动力特性及在不同水平下的地震响应,首先借助ANSYS有限元分析软件,对塔式起重机进行模态分析;其次对塔式起重机的有限元模型分别输入EI Centro、Taft及汶川什邡八角站三种激励地震波,分析塔身和水平横梁节点地震响应,最后讨论塔式起重机的抗震设计要点及隔震措施。结果表明：塔式起重机的塔臂疲劳主要由地震反应谱中的窄带过程控制,反之,塔臂的折断破坏是由宽带过程起主要作用。 相似文献
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情态动词是情态系统最为核心的表达形式,也是各种语言实现情态意义最为重要的方式与载体。已有研究发现,不同母语背景学习者在情态动词习得上都存在不同程度的问题。其原因有二:一是情态动词具有多义性,其意义会随着语境的改变而改变,情态动词的多义性造成了自身的复杂性;二是受传统教学方法的影响。文章以认知教学法为基础,以范畴化理论与心理空间理论为例来探讨认知理论应用于情态动词教学的方法与原则。与传统教学方法相比,认知方法只能作为一种补充,在教学实践中不能完全替代传统教学方法。 相似文献
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应用Pro/E对平板式半挂车车架进行三维实体建模。对该模型进行简化处理、抽中面和修补后导入ANSYS。采用壳单元建立平板式半挂车车架的有限元模型,对车架进行静力分析和模态分析。结果表明,车架在弯曲和扭转工况下,刚度和强度满足要求;车架结构的低阶模态频率不在路面激励频带之内,不会产生共振现象。 相似文献
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This paper presents an elements-grouped morphogenesis method for the design of grid shells based on finding the linkage mechanism system shape that corresponds to the state of minimum potential energy. This method assigns the elements to several groups according to architectural design intentions and requirements to optimize a structural shape. A shape transformation equation is derived to constrain the total length of elements in each element group in the morphogenesis process and the generalized inverse matrix theory is then used to resolve the equation. The positions of nodes are, thus, progressively updated until the system reaches the minimum potential energy state. This method is characterized by the settings of element groups, temporary elements, and temporary forces. Finally, several numerical examples illustrate the characteristics and effectiveness of the proposed method. 相似文献
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1 Introduction a The crack problem has always been an important topic to researchers in engineering mechanism. Some initial defects, like microcrack for example, will exist in the manufacturing procedure of real materials, they will grow or coalesce gradu… 相似文献