轻型变截面门式刚架梁-柱端板连接转动模型研究

以门式刚架端板竖放连接节点滞回试验为基础,对节点域的弯矩-转角转动关系进行研究,其中节点域定义为节点、1.0倍柱大端截面、1.5倍梁大端截面长度区域,节点域包含结构破坏位置,可反映出整个门式刚架的受力情况。首先,基于强化双线性模型,通过理论分析得到节点域的初始刚度K_0和极限弯矩M_u的计算公式;其次,根据节点试验结果,确定了分段系数β=0.87,衰减系数α=0.63;最终,建立了门式刚架端板竖放连接的节点域M-θ模型。同时,根据试验结果,拟合出弹塑性阶段卸载刚度Ku的计算公式,并给出滞回规则,建立节点域的弯矩-转角滞回模型。本文的研究可为门式刚架抗震性能简化分析奠定理论基础。     

节点连接刚性对门式刚架结构承载能力的影响

分别按《建筑结构荷载规范》（GBJ9－87）和《门式刚架轻型房屋钢结构技术规程》（CECS102。98）附录A的荷载规定对一门式刚架中摇摆柱节点连接刚性对结构承载能力的影响进行了分析。在分析中引入了节点弹簧单元,使摇摆柱与横梁的连接节点刚性从完全不考虑刚性（即铰接）到半刚性连接直至完全刚性连接之间变化,发现当适当考虑节点的连接刚性时,部分构件的内力将与完全忽略节点连接刚性时有较大差别,而与节点完全刚性连接时的内力比较接近,考虑工程实际情况,指出在结构分析中,将非刚性连接节点分别按铰接和半刚性连接处理,按最不利情况进行结构设计,对保证结构的可靠性是非常必要的,通过对比按两种荷载规定计算的结果发现,按前者分析的结果较后者的大很多,即前者的规定较后者保守。     

无侧移半刚性连接组合框架的稳定分析:(Ⅰ)柱的有效长度系数方程

本文基于钢结构设计规范GB50017-2003,利用三柱子框架模型,考虑了连接的非线性弯矩-转角关系和楼板组合效应的影响,推导了无侧移半刚性连接组合框架柱的有效长度系数方程式,同时考虑了梁端和柱远端不同约束情况对有效长度系数的影响。另外,分析了GB50017规范附录D表D-1求解的精确性。研究表明,当柱远端刚接时,推导的方程式类似于GB50017规范附录D表D-1给出的无侧移刚接框架柱的有效长度系数计算公式;对于三柱子框架模型,当柱远端铰接时,用GB50017规范附录D表D-1得到的有效长度系数设计柱是不安全的,但最大误差只有11%。     

解算有侧移多层框架柱计算长度系数的电算程序

1.程序的功能 本程序可解算下列有侧移各柱的计算长度系数: (1)单层工业厂房,带有弹性横梁的阶形柱。可为等高厂房,亦可为高低跨处的厂房阶形柱,横梁刚度可为无限大,亦可为横梁与柱铰接。     

无侧移半刚性连接组合框架的稳定分析:(Ⅱ)连接转动刚度和算例分析

计算半刚性连续框架柱的有效长度系数时,必须先确定梁柱连续转动刚度。本文提出了计算无侧移框架梁柱连接转动刚度的简化方法:用梁线理论和弯矩-转角曲线确定切线连接刚度。另外,通过两个算例:门式组合框架和三层两跨组合框架,研究了连接的非线性弯矩-转角特征和荷载水平大小对有效长度系数的影响,比较了本文简化方法、Barakat-Chen简化方法与精确方法计算的有效长度系数。研究表明,本文简化方法具有很好的精确性,可以代替精确方法用于无侧移半刚性连接组合框架的稳定分析和设计。     

变截面门式刚架结构分析的微分求积单元法

本文采用一种精确、简便的数值计算方法——微分求积单元法(DQEM)对变截面门式刚架结构进行了力学分析。首先建立了一般荷载作用下变截面构件的平衡微分方程，并采用微分求积法进行离散，进而得出了较为精确的分析变截面构件的单元力学模型。该模型的刚度方程不仅反映了单元的刚度性质，而且反映了单元的实际荷载作用，可较为精确地分析变截面门式刚架结构在分布载荷作用下的受力性能。通过与有限元法计算结果的比较，表明了微分求积单元法在变截面刚架的力学分析中的正确性和优越性。微分求积单元法可用于任意形状的刚架结构的静力分析。     

基于梁-柱连接转动模型变截面门式刚架抗震承载力分析

轻型门式刚架结构变形能力小、延性性能较低,地震对其影响不可忽略。传统计算中梁柱连接通常按刚性节点考虑,但端板连接节点具有明显的半刚性特征,考虑节点转动影响的抗震承载力计算对于结构设计有着重要意义。本文在变截面门式刚架梁-柱端板连接转动关系研究的基础上,将节点域转动模型导入整体结构中,以转动弹簧形式模拟梁柱连接。针对简化模型进行分析,与试验以及全尺寸实体单元有限元模型计算结果比较发现,其在承载力计算上精度较高,误差在10%以内,满足工程应用要求。本文研究将简化变截面门式刚架结构的抗震承载力计算,具有较好的理论与工程意义。     

含刚性斜杆的平面有侧移刚架内力计算

在结构分析中,为简化计算常假定结构体系中某些杆件或杆件沿某个方向为无限刚性,含刚性杆结构的内力分析是结构力学的教学难点。在位移法教学中常涉及有侧移刚架,若刚架中含斜杆和刚性杆件,杆端位移将受到限制,结构体系中必有非独立结点位移出现。本文通过引入刚架中刚性约束的约束方程,获得约束方程的系数矩阵,根据系数矩阵秩的计算确定结构体系的基本未知量。并根据约束方程确定结构体系非独立结点位移与独立结点位移间的关系式,应用位移法分析刚架内力。     

二维边坡稳定性分析的最小势能法新解

针对最小势能法研究的不足,通过条块虚位移方向的静力平衡方程确定滑面上剪应力的解析解,构建了一种新的剪切势能计算模型.同时,提出了一种多地层边坡稳定性分析方法.算例结果表明:剪切势能对边坡稳定性系数会产生影响,使得计算结果更为合理;运用文中方法计算得到边坡稳定性系数与极限平衡法的结果较为一致,表明文中的计算方法是可行且合理的;文中多地层边坡的计算模型,考虑了土层滑面长度以及法向力对边坡抗剪强度的贡献,且计算简便,易于工程人员使用.     

光伏支架柱平面内有侧移失稳计算长度系数研究

光伏支架是一种典型的不等高单层框架,有侧移失稳的光伏支架柱计算长度系数需考虑多方面因素的影响,无法直接套用现有规范公式．综合考虑了光伏支架短柱和长柱的刚度比γ、短柱和长柱的高度比β以及梁柱线刚度比K1的影响,进行了理论推导,得出了不等高单层框架柱有侧移失稳计算长度系数的计算公式,并制作表格以便工程人员查阅使用．然后以某典型光伏支架实际工程为算例,建立了有限元数值分析模型,并分别进行了线性屈曲分析和考虑几何非线性以及材料非线性的极限承载力分析．分析结果表明,提出的理论公式和计算表格能够精确地计算光伏支架有侧移失稳的极限承载力．     

Preclude failure: A philosophy for materials selection and simulated service testing

Failure of products in service under foreseeable conditions often subject manufacturers to legal liability when personal injuries occur; hence, the care used (or the philosophy employed) in material selection, design, analyses, fabrication and maintenance must be sufficient to preclude failure. Failure analysis requires careful sorting of a wide variety of information to determine how and why a metal part failed in service or in testing and to determine what can be done to prevent a recurrence. Valuable knowledge is available in the literature from documentation of prior failures that may be used to develop logical approaches to the design and development of new components. A philosophy of design and prototype evaluation based on the prevention of failure is more sound and workable than the stereo-typed application of empiricisms, codes, specifications and factors of safety now commonly used. Reliance on design for static loadings and for factors of safety based on tensile strength as a criterion are frequently erroneous and dangerous. If a part does not fulfill its intended function satisfactorily, it “fails” by: (a) excessive deformation, (b) fracture, (c) surface disintegration, and (d) deterioration of properties. A variety of failures will be discussed to emphasize the factors that must be considered in selection of an optimum material and in prescribing an effective method of simulated-service testing. Considerable latitude in use and misuse of equipment must be foreseen in order to predict possible modes of failure. A broad consideration of service environment is necessary for correcting faulty design and selecting proper materials which will withstand modifications due to processing, fabrication, maintenance or repair operations that lead to failure.     

Escape factors in zero-dimensional radiation-transfer codes

Several zero-dimensional non-LTE radiation-transfer codes are in common use within the laser-plasma community (for example, RATION, FLY, FLYCHK and GALAXY). These codes are capable of generating calculated emission spectra for a plasma of given density and temperature in the presence of a radiation field. Although dimensionless in nature, these codes can take into account the coupling of radiation and populations by use of the escape factor method, and in this sense the codes incorporate the finite size of the plasma of interest in two ways – firstly in the calculation of the effect of the radiation on the populations and secondly when using these populations to generate a spectrum. Different lengths can be used within these two distinct operations, though it has not been made clear what these lengths should be. We submit that the appropriate length to use for the calculation of populations in such zero-dimensional codes is the mean chord of the system, whilst when calculating the spectrum the appropriate length is the size of the plasma along the line of sight. Indeed, for specific plasma shapes using the appropriate escape factors it can be shown that this interpretation agrees with analytic results. However, this is only the case if the correct escape factor is employed: use of the Holstein escape factor (which is in widely distributed versions of the codes mentioned above) is found to be significantly in error under most conditions. We also note that for the case where a plasma is close to coronal equilibrium, some limited information concerning the shape of the plasma can be extracted merely from the ratio of optically thick to optically thin lines, without the need for any explicit spatial resolution.     

超大跨度空间X撑结构屈曲强度特性研究

为了深入研究深水导管架平台超大跨度空间X撑结构的承载机理,合理地指导工程设计,本文在已有理论模型的基础上,研究了空间X撑结构(有面外支撑X撑结构)在典型的载荷模式、刚度特性、端点约束以及长度因子(交点位置)等参数下屈曲长度系数的变化规律,结合实际工程深水导管架结构,辅助有限元计算对超大跨度有面外支撑X撑结构进行了屈曲强度分析,最后得到了可为工程设计提供有效技术支撑的多个结论。     

复合砂浆钢绞线网加固RC梁受弯性能计算研究

分析了复合砂浆钢绞线网加固钢筋混凝土梁的受弯性能, 不同材料加固梁的受弯性能可采用同一公式进行计算, 研究表明加固梁受弯性能受本体梁的初始受力状态和是否采用三面U型加固影响较大. 采用正截面极限平衡法, 推导出复合砂浆钢绞线网加固钢筋混凝土梁极限抗弯承载力计算公式; 在混凝土结构设计规范公式基础上, 提出加固梁裂缝宽度和裂缝间距计算公式, 加固梁公式计算值与试验值吻合较好.     

An effective way to couple FEM meshes and Peridynamics grids for the solution of static equilibrium problems

Peridynamics is a continuum theory based on a non-local approach and capable of dealing with discontinuous displacement fields. The paper presents a technique to couple Peridynamic grids and finite element meshes to solve static equilibrium problems. The domain is divided in two zones: one discretized by the Peridynamic grid and the other where the Finite Element Method is applied. The coupling is achieved by considering that Peridynamics bonds act only on Peridynamic nodes, whereas finite elements apply forces only on finite element nodes. The proposed method was applied to study 1D and 2D examples. No problem in the zone of the structure where the two approaches are merged is observed. The results show that the coupling method is very effective and its simplicity suggests it can be easily introduced in commercial finite element codes.     

热电材料孔边周期裂纹问题的热电弹分析

论文研究了均匀电流密度和能量流作用下,热电材料中带4k个周期径向裂纹的圆形孔口问题.考虑非渗透型电和热边界条件,运用复变函数理论和保形映射方法,得到了热电材料中电流密度、能量密度和应力场的精确解.依据断裂力学理论,运用Cauchy积分公式得到了周期裂纹的电流、能量和应力强度因子.数值结果分析了场强度因子随各个参数的变化...     

Buckling of sandwich wide columns

The paper deals with the theoretical prediction of buckling loads for sandwich columns with metallic and laminated facings and foam or honeycomb core. The loading is a uniform axial compression, applied statically (very slowly) and suddenly with constant magnitude and infinite duration (step loading). The effect of length and boundary conditions is assessed and results are presented for the following cases: for a cantilever column, a simply supported column and a clamped column, for several lengths. Several fiber materials are used in the laminated facings. Two types of core were examined: alloy-foam or hexagonal glass/phenolic honeycomb. The facings are Boron/Epoxy, Graphite/Epoxy and Kevlar/Epoxy laminates with 0° orientation with respect to the column axis and a metallic one made out of aluminum. These various materials are employed to provide comparative data that can be used in design. Results, for the static case are generated by computer codes as well as by the use of closed form theoretical solutions. For the dynamic case, results are generated by the DYNA3D code.     

A solution of transport in porous media with equilibrium and kinetic reactions

A solution is presented to verify numerical computer codes of reactive transport with both equilibrium and kinetic reactions. A synthetic model of A ↔ B ↔ C → chain reactions is proposed to describe operator-splitting numerical schemes used in numerical computer codes. A reaction matrix is derived for both the equilibrium and the first-order kinetic reactions and further decoupled as a diagonal matrix. Therefore, the partial differential equations (PDEs) coupled by the reaction matrix can be transformed into independent PDEs, for which closed-form solutions exist or can be derived. The solution derived in this study is compared with numerical results.     

On the Optimal Design of Composite Material Tubular Helical Springs

A method is presented for the design of helical springs, with particular reference to those made from composite material and having a hollow circular section. Given the technical specifications, (e.g. stiffness, maximum deflection, ...), the method allows to define the spring geometrical and mechanical parameters in order to get the best compromise among spring performances (minimum mass, maximum strength, ...), with constraints on local and global stability, on resonance frequency, ... The method is based on Multi-Objective Programming (a branch of Operations Research), which provides a theoretically correct way for defining the values of many design variables when many objectives (performance indexes) have to be taken into account. Mathematical models are developed for describing the mechanical behaviour of the spring. The models have been validated with satisfactory results. The design solutions coming from the application of the method suggest the best parameter setting for obtaining the desired spring performances.