非加劲钢板剪力墙的高阶弹性剪切屈曲分析

非加劲钢板剪力墙(SPSW)结构在水平荷载作用下易屈曲,形成主拉压应力场,并以拉力带方式提供水平承载力及抗侧刚度。传统拉杆模型(SM模型)用于非加劲SPSW结构分析或设计时忽略压力场的贡献,一般会低估高厚比较小的非加劲SPSW结构的抗侧能力。非加劲SPSW结构在水平力作用下会形成多波面外变形,与剪力墙板的高阶屈曲相似,可通过在修正的SM模型中引入对应于高阶屈曲的主压应力来反映压力场贡献,提高模型分析精度。考虑剪力墙板高厚比、高宽比及边缘构件刚度的影响,共设计66个单层、单跨和梁柱铰接的非加劲SPSW算例,并进行弹性屈曲分析。分析结果表明,高厚比及边缘构件刚度对非加劲SPSW结构的剪切屈曲系数影响不大;随着剪力墙板高宽比的增加,非加劲SPSW结构的剪切屈曲系数呈增大趋势。采用Matlab程序对66个非加劲SPSW算例的2～5阶剪切屈曲系数结果进行统计分析,并提出了简化公式。     

基于集成化响应面法的薄壁箱梁结构随机剪力滞分析

传统薄壁箱梁结构剪力滞分析方法由于忽略了结构参数的不确定性而不能满足实际工程设计需要。本文将响应面法(RSM)、有限元法(FEM)和蒙特卡罗法(MCS)各自的优点相结合,提出一种新的结构随机剪力滞分析方法-集成化响应面法,并将其成功地应用到一简支梁结构的随机剪力滞分析中,得出了一些有益的结论。     

关于框架-剪力墙结构连续化计算理论的讨论

本文论述框架-剪力墙结构连续化计算理论中刚接体系与铰接体系的对应关系.对于刚接体系引进了总剪力墙广义剪力概念.指出文献[1]关于刚接体系剪力的分析计算是错的....     

金字塔形高层框架结构的自振频率

根据某一金字塔型高层建筑结构的初步设计,将该结构简化为一个二维刚-柔组合结构体系,基于Hamilton原理,建立了该简化结构体系动力响应分析的边界值问题.在此基础上,利用变量分离,给出了其自振频率的特征方程,通过数值计算,考察了斜向剪力墙筒体刚度、中间加强层转动刚度和位置、结构顶部刚性层质量以及金字塔型结构倾角等对自振频率的影响,结果表明:斜向剪力墙筒体抗弯刚度对自振频率有显著的影响,自振频率随剪力墙筒体抗弯刚度的增加而增加;尽管剪力墙筒体发生横向弯曲与轴向拉伸的耦合变形,但其振形的弯曲变形远大于其轴向变形;加强层抗弯刚度对自振频率的影响较小,但其位置对第三自振频率的影响较为明显.同时,斜向剪力墙筒体倾角对自振频率的影响较为复杂.     

基础梁的温度应力

基础梁是工程上广泛采用的一种结构。在实际工程中,基础梁往往出现裂缝,表明基础梁的设计中有必要考虑温度应力,但目前还缺乏一个合适的计算方法。本文提出一个实用的计算方法。 在计算基础梁由外荷载引起的应力时,往往忽略接触面上的剪力,但对于温度应力     

考虑弯曲刚度斜拉索面内面外内共振分析

本文研究桥梁工程中含弯曲刚度斜拉索的面内面外内共振问题．描述了工程中斜拉索变形的三种状态,考虑弯曲刚度、大变形及垂度等因素,忽略斜拉索纵向惯性力的影响,运用Hamilton变分原理建立了含弯曲刚度的斜拉索面内面外耦合偏微分控制方程,采用Galerkin方法对偏微分方程离散,并运用多尺度摄动方法进行了求解,获得了斜拉索可能存在的内共振模式,以工程中一根斜拉索为例,运用有限元法对其进行动力特性分析,列出了斜拉索前10阶面内面外振动频率,找出面内面外可能产生内共振的模态,分别研究了主共振条件下斜拉索面内和面外1:1、2:1内共振情形,获得了有意义的结论．     

钢-混凝土组合梁收缩徐变效应的随机分析

钢-混凝土组合梁是由混凝土板和钢梁通过剪力键连接而成的组合结构。由于混凝土的收缩徐变,将引起结构内力和应力重分布。混凝土收缩徐变具有离散性大的特点,进而导致结构长期响应表现出随机性。本文综合考虑徐变模型、收缩模型、混凝土抗压强度、混凝土弹性模量、环境湿度、钢材弹性模量、荷载以及剪力键刚度的随机性对钢-混凝土组合梁结构响应的影响。利用拉丁超立方抽样技术和基于响应面方法的蒙特卡洛抽样,研究了钢-混凝土组合梁挠度和应力时变效应的概率问题。     

钢-混凝土组合梁收缩徐变效应的随机分析

钢-混凝土组合梁是由混凝土板和钢梁通过剪力键连接而成的组合结构。由于混凝土的收缩徐变,将引起结构内力和应力重分布。混凝土收缩徐变具有离散性大的特点,进而导致结构长期响应表现出随机性。本文综合考虑徐变模型、收缩模型、混凝土抗压强度、混凝土弹性模量、环境湿度、钢材弹性模量、荷载以及剪力键刚度的随机性对钢-混凝土组合梁结构响应的影响。利用拉丁超立方抽样技术和基于响应面方法的蒙特卡洛抽样,研究了钢-混凝土组合梁挠度和应力时变效应的概率问题。     

零泊松比手风琴蜂窝等效模量

柔性蒙皮是变形机翼和风力机叶片的关键组成部分。一维变形的柔性蒙皮不仅要求其支撑结构具有良好的面内变形和面外承载能力,还需要具有零泊松比特性。手风琴蜂窝具有零泊松比特性,可用作一维变形柔性蒙皮支撑。为全面分析其面内外弹性变形特性,综合考虑结构的内力弯矩、轴力和剪力,通过卡氏第二定理对其x向等效弹性模量和x-y面内等效剪切模量进行了推导;利用最小余能原理和最小势能原理确定了x-z面内的等效剪切模量;此外还推导了其y和z向的等效弹性模量以及y-z面内的等效剪切模量;然后通过ANSYS有限元仿真对等效模量理论公式进行了验证;最后将本文理论模型与现有模型进行了比较。结果表明,理论公式和有限元仿真吻合较好,在结构设计时采用较大的斜梁高度系数h和斜梁间距系数g,较小的厚度系数t以及较大的竖直梁厚度系数η,有望获得具有较小面内刚度和较大面外刚度的手风琴蜂窝结构。该结果可用于手风琴蜂窝面内外等效模量的快速预测,为一维变形柔性蒙皮的结构设计提供相应的参考。此外,本文理论模型相比传统模型更为精确且具有更加广泛的应用范围。     

钢筋混凝土剪力墙单元非线性分析模型及其应用

本文简要评述了几种常见的钢筋混凝土剪力墙非线性宏观单元模型后，着重对多垂直杆剪力墙非线性单元模型的几个重要问题如剪力变形的考虑方法，单元刚度矩阵的形式，垂直拉压杆及剪切弹簧的恢复力模型等进行了探讨与改进，最后给出了一个算例，并与试验结果比较，表明非线性宏观墙单元模型具有较好的计算精度。     

一种新的墙单元

本文提出了一种新的空间墙单元模型，这种墙单元把土建中常用的剪力墙作为它的一种特殊情形．本文基于四边形单元所提出的墙单元在平面内是一块膜，它除面内的两个平动自由度外还具有绕平面转动的自由度；平面外是一块弯曲板．因而它是膜和板的一个组合，它的每个节点具有空间的全部六个自由度．由于考虑了空间墙平面内和平面外的刚度，因此这种新的墙单元能够直接与三维框架的梁、柱单元连接．它也能很容易地处理墙的空间变形。     

弯曲动脉的血流动力学数值分析

利用计算流体力学的理论和方法对弯曲动脉中的血流动力学进行数值分析，是研究心血管疾病流体动力学机理的一种行之有效的方法。本文将升主动脉、主动脉弓和降主动脉联系起来作为弯曲动脉几何模型，给出了血液流动的边界条件以及计算条件。根据生理脉动流条件，对狗的弯曲动脉几何模型内发展中的血液流动进行了有限元数值模拟，并利用可视化方法对血液流动的轴向速度、二次流、壁面切应力等计算结果进行了分析。研究结果表明，在弯管内侧壁处，同时存在主流方向和二次流方向的回流，此处容易形成涡流。弯管内侧壁比外侧壁的壁面切应力具有更强的脉动性。     

Stiffness and hysteretic energy loss of a reinforced-concrete shear wall

A static, cyclic test of one of the largest reinforced concrete shear walls to be investigated in a laboratory is reported. The test was performed to study the dynamic characteristics (stiffness and hysteretic energy loss) of the shear wall. Very sensitive displacement gages are needed to measure the small deformations. The large forces required to load the structure make the test results susceptible to deformation of the support fixture. With these concerns in mind, instrumentation and data-reduction methods were developed that could separate model deformations from displacements caused by support motion. Also, model displacements were separated into shear and bending components. Results showed that prior to cracking, overall stiffness as well as the individual components of stiffness are accurately predicted by mechanics of materials beam theory that accounts for shear deformation. Equivalent viscous damping ratios that were determined from the hysteretic energy before and after cracking were similar.     

加权残值法在钢筋混凝土拱桥非线性有限元分析中的应用

本文用圆弧梁离散拱肋;用圆柱拖带坐标、三次位移插值函数及平截面假定来描述单元位形;用加权残值配点法来消除曲梁单元的剪力与膜力闭锁。按基于连续介质力学的Ｕ．Ｌ．列式建立单元增量平衡方程,以考虑几何非线性。假定钢筋为理想弹塑性材料。按三参数各向同性强化塑性模型,建立混凝土的弹塑性本构矩阵。将拱单元分段分块,根据钢筋及砼的本构特性,建立拱单元及梁段单元的弹塑性刚度矩阵,以考虑材料非线性。用编制的程序对两座模型拱桥进行计算,计算结果与模型测试结果接近     

一个基于膜板比拟理论的四节点二十四自由度的平板壳单元

应用膜板比拟关系 ,可以避开 c1 连续性的困难 ,为板单元的构造提供了一种新的途径 ,并已成功地构造出一系列相应的板单元。本文构造了一个四节点二十四自由度的平板壳单元 ,该单元由平面四节点理性元 RQ4(膜部分 )和由膜板比拟理论构造的一个四节点十二自由度的板单元 (弯曲部分 )构成。该单元构造简单 ,数值结果表明具有很好的收敛性和精度。     

钢－混凝土组合梁非线性有限元分析

提出了部分剪力连接钢-混凝土组合梁非线性有限元分析的简化模型，该模型同时考虑了钢、混凝土材料的非线性本构关系和剪力连接件的滑移非线性对组合梁刚度和强度的影响，推导了考虑滑移的剪力连接件单元刚度矩阵。利用该模型计算了连续组合梁的极限荷载、挠度、应力以及滑移，与已有的理论计算结果和实验结果吻合，证明本方法分析钢-混凝土组合梁非线性的可靠性和实用性。     

Eigenanalysis and continuum modelling of pre-twisted repetitive beam-like structures

A repetitive pin-jointed, pre-twisted structure is analysed using a state variable transfer matrix technique. Within a global coordinate system the transfer matrix is periodic, but introduction of a local coordinate system rotating with nodal cross-sections results in an autonomous transfer matrix for this Floquet system. Eigenanalysis reveals four real unity eigenvalues, indicating tension–torsion coupling, and equivalent continuum properties such as Poisson’s ratio, cross-sectional area, torsion constant and the tension–torsion coupling coefficient are determined. A variety of real and complex near diagonal Jordan decompositions are possible for the multiple (eight) complex unity eigenvalues and these are discussed in some detail. Analysis of the associated principal vectors shows that a bending moment produces curvature in the plane of the moment, together with shear deformation in the perpendicular plane, but no bending–bending coupling; the choice of a structure having an equilateral triangular cross-section is thought responsible for this unexpected behaviour, as the equivalent continuum second moments of area are equal about all cross-sectional axes. In addition, an asymmetric stiffness matrix is obtained for bending moment and shearing force coupling, and possible causes are discussed.     

Buckling behavior of a superconducting magnet coil

The buckling behavior of a superconducting magnet coil has been investigated for out of plane perturbations. It has been shown that such a coil becomes unstable due to its own magnetic field for out of plane bending at the operating values of electric currents. A technique devised by the author that computes the inductance change due to deformation, has been incorporated in this study. The evaluation shows that although the magnetic fields external to the coil are important and that there is additional structural stiffness provided by the surrounding structure, the effects of the self magnetic field should be evaluated and incorporated in the design of such coils. However, based on previous studies, both analytical and experimental, it has been established that the out-of-plane deformation is the most critical mode from a stability standpoint. Therefore, this mode has been exclusively addressed in this study.     

Effects of texture on shear band formation in plane strain tension/compression and bending

In this study, effects of typical texture components observed in rolled aluminum alloy sheets on shear band formation in plane strain tension/compression and bending are systematically studied. The material response is described by a generalized Taylor-type polycrystal model, in which each grain is characterized in terms of an elastic–viscoplastic continuum slip constitutive relation. First, a simple model analysis in which the shear band is assumed to occur in a weaker thin slice of material is performed. From this simple model analysis, two important quantities regarding shear band formation are obtained: i.e. the critical strain at the onset of shear banding and the corresponding orientation of shear band. Second, the shear band development in plane strain tension/compression is analyzed by the finite element method. Predictability of the finite element analysis is compared to that of the simple model analysis. Third, shear band developments in plane strain pure bending of a sheet specimen with the typical textures are studied. Regions near the surfaces in a bent sheet specimen are approximately subjected to plane strain tension or compression. From this viewpoint, the bendability of a sheet specimen may be evaluated, using the knowledge regarding shear band formation in plane strain tension/compression. To confirm this and to encompass overall deformation of a bent sheet specimen, including shear bands, finite element analyses of plane strain pure bending are carried out, and the predicted shear band formation in bent specimens is compared to that in the tension/compression problem. Finally, the present results are compared to previous related studies, and the efficiency of the present method for materials design in future is discussed.