剪力墙结构基于性能抗震设计的目标层间位移确定方法

结构层间变形的计算和性能水平的划分,是基于性能的抗震设计中确定目标位移的关键问题之一。该文根据剪力墙结构的受力特点,将楼层位移分为有害位移和刚体位移,将层间位移分为名义层间位移和有害层间位移;分析了剪力墙结构的名义层间位移、有害层间位移及楼层转角之间的关系,给出有害层间位移的近似计算公式并进行误差分析;对结构层间变形的计算方法进行改进,提出采用有害层间位移角作为剪力墙结构的性能指标,进行结构性能水平的划分,并采用有害层间位移角和顶点位移角两个参数来控制剪力墙结构的变形。最后,给出剪力墙结构目标层间位移的确定方法,以此确定其目标侧移曲线,可进行直接基于位移的抗震设计。     

高精度电容式位移传感器校准方法的研究

介绍一种使用激光干涉仪结合单轴精密位移台对电容式位移传感器进行校准的方法。建立了一套高精度电容式位移传感器校准装置,利用单轴精密位移台位移与电压之间的关系产生纳米级的微小位移,同时使用激光干涉仪和待校准电容式位移传感器测量单轴精密位移台的微小位移。该装置可实现电容式位移传感器线性度、测量重复性以及测量分辨率的校准。实验验证了此校准方法的准确性和实用性,对影响校准的主要因素进行了分析,其综合不确定度为2.2 nm。     

等强残余位移系数谱研究

针对双线性单自由度体系定义了残余位移系数,然后选取100条地震波,通过弹塑性动力时程分析,建立了等强残余位移系数谱,分析了其影响因素,并建立了拟合公式,最后对残余位移和最大位移之间的关系进行了研究。结果表明:在总体上,结构周期越小,强度越低,屈服后刚度系数越小,其残余位移系数越大;结构周期较大时,残余位移系数和周期之间关系不大;结构周期越小,结构强度对残余位移系数的影响越大;残余位移和最大位移基本呈线性关系。     

电涡流位移传感器在设备监测诊断中的应用

<正>设备监测诊断的概念:通过实时监测设备的横向位移、纵向位移、轴向位移,分析对比位移情况和振动幅度来测量压缩机的振动情况,测出振动曲线,分析后得出设备位移量。这种方式称之为设备监测诊断。目前我厂的设备主要有往复式压缩机和离心式压缩机,我们的工作主要是对这两种压缩机的位移情况进行测量,确保位移在允许偏差之内。我     

聚丙烯纤维水泥稳定碎石断裂性能试验研究

通过30个尺寸为100mm×100mm×515mm的聚丙烯纤维水泥稳定碎石和普通水泥稳定碎石三点弯曲试件断裂试验,探讨了聚丙烯纤维对水泥稳定碎石断裂韧度(KIC)、断裂能(GF)、临界裂缝嘴张开位移(CMODC)、临界裂缝尖端张开位移(CTODC)、极限裂缝嘴张开位移(CMODmax)和极限裂缝尖端张开位移(CTODmax)的影响。试验结果表明:聚丙烯纤维的掺入可增大水泥稳定碎石的断裂韧度、断裂能、临界裂缝嘴张开位移、极限裂缝嘴张开位移、临界裂缝尖端张开位移和极限裂缝尖端张开位移;随着聚丙烯纤维体积掺量的增加,断裂韧度、临界裂缝嘴张开位移和临界裂缝尖端位移的变化无明显规律,但断裂能、极限裂缝嘴张开位移和极限裂缝尖端位移基本上呈线性增加的。     

连续梁桥横桥向等位移准则

首先分析了单自由度等位移准则与结构屈服程度的关系,然后针对典型连续梁桥的特点,定义了名义屈服位移和名义屈服曲率,并通过改变主梁特性、桥墩特性和地震动输入等进行参数分析,将等位移准则由单自由度推广到多自由度。研究表明,当连续梁桥的主要振型的周期均大于对应单自由度等位移准则的周期下限,并且主要振型的质量参与系数之和超过90%时,非线性时程方法得到的位移与弹性反应谱方法得到的位移接近,等位移准则成立,可以采用弹性位移评估其非弹性位移。多自由度等位移准则的应用较大程度简化了相当一部分连续梁桥的横桥向位移需求的计算,为其基于位移的抗震设计提供了基础。     

基于长短时记忆神经网络的大跨拱桥温度-位移相关模型建立方法

建立温度-位移相关模型是开展基于位移响应的大跨桥梁性能评估的关键步骤。该文提出一种基于长短时记忆(LSTM)神经网络的多元温度-位移相关模型建立方法。充分利用LSTM神经网络能够考虑位移时滞效应和适合处理超长数据序列的优势,采用自适应矩估计方法对LSTM神经网络进行优化,并引入丢弃正则化技术提升模型的预测能力。在此基础上,基于一座三跨连续系杆拱桥长期同步监测的温度和位移数据,讨论了影响该桥主梁竖向位移的主要温度变量,并建立了多元温度-位移的LSTM神经网络模型,与基于误差反向传播(BP)神经网络的多元温度-位移相关模型进行了比较。研究结果表明:构件有效温度与主梁竖向位移具有明显的非线性关系,构件间温差和主拱温度梯度与主梁竖向位移呈线性相关性;主拱有效温度和主梁与主拱的温差是引起该桥主梁竖向位移的主要温度变量;相比于BP神经网络模型,该文提出的LSTM神经网络模型能够大幅降低温度位移的重构误差和预测误差。     

基于土层位移差的地下结构抗震分析的反应位移法

采用平面弹性理论的复变函数方法,推导了具有小孔的无限介质在无限远处受到剪应力时的水平位移,得出有小孔时和无小孔时的位移关系,可以应用在基于土层位移差的反应位移法的土层位移的求解。为了验证该方法的适用性,设定某地质条件下的典型的圆形盾构隧道和矩形地下车站为基准模型,使用不同的方法求解土层位移,再用反应位移法计算土体刚度变化时的结构内力。结果表明：基于土层位移差的反应位移法适用于埋深较大的地下结构,不适用硬土的情况,对地基弹簧刚度的求解精度要求较高。     

位移传感器测量方法

针对位移传感器的检定校准,提出一种采用测长机测量位移传感器示值误差的新方法,可以实现对拉线位移传感器、激光位移传感器、光栅式或电感式位移传感器等各类位移传感器的校准,并应用此方法进行了实例测量和误差分析,为实际应用提供指导.     

类旗帜型滞回模型体系的近断层等损伤位移谱

面向于近断层区域自复位体系的抗震设计需求,为了揭示自复位体系的弹塑性行为,基于Park-Ang双参数损伤模型建立了类旗帜型滞回模型的等损伤位移谱,研究损伤指标模型参数和滞回模型参数对位移谱的影响,分别对比分析了等损伤与等延性位移谱以及近断层脉冲型与无脉冲地震动作用下等损伤位移谱的差异,通过回归分析建立等损伤位移谱预测方程。研究表明:采用脉冲周期进行周期标准化能够反映脉冲效应在短周期段内对位移谱的局部放大作用,同时能降低中长周期段内位移谱的离散性;极限延性系数对短周期段内位移谱值的影响超过20%;等损伤及等延性位移谱的对比分析说明,累积滞回耗能对自复位体系位移需求的影响不能忽视;与无脉冲地震动位移谱值相比,近断层脉冲型地震动位移谱值在标准化周期约为0.5和1.0时增大20%左右。构建的等损伤位移谱预测模型可用于近断层区域自复位体系位移响应的预测。     

地震作用下冷弯薄壁型钢结构房屋弹塑性位移简化计算研究

针对地震作用下冷弯薄壁型钢结构房屋弹塑性位移的简化计算,基于层间剪切模型和冷弯薄壁型钢组合墙体的恢复力模型,对2层~7层冷弯薄壁型钢结构房屋进行弹塑性时程分析。通过对滞回耗能沿楼层高度分布规律的研究,确定了冷弯薄壁型钢结构房屋薄弱楼层的位置;研究了楼层屈服剪力系数、楼层数、结构自振周期和不同地震记录对弹塑性层间位移增大系数的影响;通过大量参数统计分析,提出了冷弯薄壁型钢结构房屋弹塑性层间位移增大系数与楼层屈服剪力系数和楼层数的定量关系,为罕遇地震作用下冷弯薄壁型钢结构房屋弹塑性位移验算提供依据。     

考虑翘曲效应的薄壁曲梁几何非线性分析

利用UL法研究了开口薄壁曲线梁几何非线性分析问题。采用多项式插值函数表示位移场。考虑了翘曲自由度及曲率效应模拟开口薄壁曲梁的结构行为。所有位移参数定义于截面形心以便在弹性应变能中包括弯扭耦合项。利用修正的弧长法求解非线性方程,跟踪荷载位移曲线。用算例对提出的方法进行了验证,表明了薄壁曲梁的分析中翘曲变形不可忽略。     

Elastoplastic analysis of compact and thin-walled structures using classical and refined beam finite element models

The paper presents results on the elastoplastic analysis of compact and thin-walled structures via refined beam models. The application of Carrera Unified Formulation (CUF) to perform elastoplastic analysis of isotropic beam structures is discussed. Particular attention is paid to the evaluation of local effects and cross-sectional distortions. CUF allows formulation of the kinematics of a one-dimensional (1D) structure by employing a generalized expansion of primary variables by arbitrary cross-section functions. Two types of cross-section expansion functions, TE (Taylor expansion) and LE (Lagrange expansion), are used to model the structure. The isotropically work-hardening von Mises constitutive model is incorporated to account for material nonlinearity. A Newton–Raphson iteration scheme is used to solve the system of nonlinear algebraic equations. Numerical results for compact and thin-walled beam members in plastic regime are presented with displacement profiles and beam deformed configurations along with stress contour plots. The results are compared against classical beam models such as Euler–Bernoulli beam theory and Timoshenko beam theory, reference solutions from literature, and three-dimensional (3D) solid finite element models. The results highlight: (1) the capability of the present refined beam models to describe the elastoplastic behavior of compact and thin-walled structures with 3D-like accuracy; (2) that local effects and severe cross-sectional distortions can be detected; (3) the computational cost of the present modeling approach is significantly lower than shell and solid model ones.     

基于Novozhilov理论薄壁弯箱位移参数的动态Bayes估计

基于Novozhilov理论推导了薄壁弯箱结构的有限曲条控制方程,并首次建立了薄壁弯箱位移参数的动态Bayes误差函数,推导了参数的动态Bayes均值和方差表达式,提出步长的一维自动搜索方案后,并结合共轭梯度法推导了薄壁弯箱位移参数的动态Bayes估计公式,同时给出了具体计算步骤。通过算例分析,总结了薄壁弯箱位移参数先验信息准确性判定方法及位移参数动态Bayes估计的其它重要结论。     

Coupled deflection analysis of thin-walled Timoshenko laminated composite beams

For the deflection analyses of thin-walled Timoshenko laminated composite beams with the mono- symmetric I-, channel-, and L-shaped sections, the stiffness matrices are derived based on the solutions of the simultaneous ordinary differential equations. A general thin-walled composite beam theory considering shear deformation effect is developed by introducing Vlasov’s assumptions. The shear stiffnesses of thin-walled composite beams are explicitly derived from the energy equivalence. The equilibrium equations and force-deformation relations are derived from energy principles. By introducing 14 displacement parameters, a generalized eigenvalue problem that has complex eigenvalues and multiple zero eigenvalues is formulated. Polynomial expressions are assumed as trial solutions for displacement parameters and eigenmodes containing undetermined parameters equal to the number of zero eigenvalues are determined by invoking the identity condition to the equilibrium equations. Then the displacement functions are constructed by combining eigenvectors and polynomial solutions corresponding to nonzero and zero eigenvalues, respectively. Finally, the stiffness matrices are evaluated by applying the member force-displacement relations to the displacement functions. In addition, the finite beam element formulation based on the classical Lagrangian interpolation polynomial is presented. In order to verify the validity and the accuracy of this study, the numerical solutions are presented and compared with the finite element results using the isoparametric beam elements and the detailed three-dimensional analysis results using the shell elements of ABAQUS. Particularly the effects of shear deformations on the deflection of thin-walled composite beams with the mono-symmetric I-, channel-, and L-shaped sections with various lamination schemes are investigated.     

Free vibration analysis of reinforced thin-walled plates and shells through various finite element models

Abstract

This article deals with free vibration analysis of thin-walled structures reinforced by longitudinal stiffeners using refined one-dimensional (1D) models.The 1D theory, which is used in the present article, has hierarchical features and it is based on the Carrera Unified Formulation (CUF). The displacement field over the cross section is obtained by means of Taylor (TE) or Lagrange (LE) expansions. Finite element (FE) method is applied along the beam axis to obtain weak form solutions of the related governing equations. The obtained results are compared with those from classical finite element formulations based on plate and shell (2D), beam (1D), and solid (3D) elements that are available in commercial software. When solid formulation is used to build the FE solutions, stringers and skin are modeled with only 3D elements while, in the 2D-1D FE models, shell and beam elements are used for skin and stringers, respectively. Three benchmark problems are analyzed: a flat plate, a curved panel, and a thin-walled cylinder. When TE models are used, different orders of expansion, N, are considered, where N is a free parameter of the formulation. As far as Lagrange expansions are concerned, four-node (LE 4) and nine-node (LE 9) elements are used to build different meshes on the cross section. The results show that the present 1D models are able to analyze the dynamic behavior of complex structures and can detect 3D effects as well as very complex shell-like modes typical of thin-walled structures. Moreover, the 1D-CUF elements yield accurate results with a low number of degrees of freedom.     

关于薄壁构件总势能方程的理论探讨

薄壁构件的总势能方程在结构稳定分析和工程设计中具有十分重要的地位和意义,是进行结构稳定计算的基础和钢结构设计规范中制定相关设计公式的依据。多年来薄壁构件的总势能方程一直存在着多种形式,一些设计规范依据的总势能方程也不尽相同。该文采用典型的薄壁构件纵向位移表达式,从理性力学的角度,对薄壁构件的总势能方程进行了严格的推导,得到了应用较多、具有代表性的几种表达式,对产生总势能方程不同形式的原因进行了理论上的剖析,该文认为主要是推导者所采用的基本假定不同、采用的构件纵向位移表达式不同、推导方法上的差异以及工程梁理论本身不完善所造成的;理论的分析证明了经典理论下薄壁构件的总势能方程是最为准确合理的表达式。     

考虑剪切变形的薄壁杆件稳定分析

本文提出了一种基于势能原理的薄壁杆件稳定分析的半离散方法。采用转换Ｂ３样条函数作为横截面纵向位移的插值函数，通过变分原理，导出控制微分方程及自然边界条件，利用常微分方程求解器求解。分析时放弃了古典理论关于杆壁中线剪应变为零或剪力流为常数的假设，很好地描述了剪力滞后现象。本方法适用于任意截面形状的薄壁杆件，能够灵活、精确、有效地进行薄壁杆件在轴压与纯弯作用下的稳定分析。算例的快速收敛说明了计算结果的可靠性。     

Instantaneous response of elastic thin-walled structures to rapid heating

A generalized modelling and analysis approach of thermally induced coupled vibrations of elastic thin-walled configurations with arbitrary open cross-sections are presented in conjunction with a unified implicit transient methodology. Limited research which takes into account the influence of rapid thermal heating effects on structures involving various forms of coupling appears in the literature. As a consequence, the dynamic response of such thin-walled structures of arbitrary open cross-section to rapid heating are described here. Effects involving triple, double, and no coupling between bending and torsional vibrations caused by sudden heating on these structures are examined. Numerical test cases are presented which describe the influence of sudden heating on elastic thin-walled structures of arbitrary open cross-sections.     

Stress analysis of multi-layered hollow anisotropic composite cylindrical structures using the homogenization method

This paper presents a general and efficient stress analysis strategy for hollow composite cylindrical structures consisting of multiple layers of different anisotropic materials subjected to different loads. Cylindrical material anisotropy and various loading conditions are considered in the stress analysis. The general stress solutions for homogenized hollow anisotropic cylinders subjected to pressure, axial force, torsion, shear and bending are presented with explicit formulations under typical force and displacement boundary conditions. The stresses and strains in a layer of the composite cylindrical structures are obtained from the solutions of homogenized hollow cylinders with effective material properties and discontinuous layer material properties. Effective axial, torsional, bending and coupling stiffness coefficients taking into account material anisotropy are also determined from the strain solutions for the hollow composite cylindrical structures. Examples show that the material anisotropy may have significant effects on the effective stiffness coefficients in some cases. The stress analysis method is demonstrated with an example of stress analysis of a 22-layer composite riser, and the results are compared with numerical solutions. This method is efficient for stress analysis of thin-walled or moderately thick-walled hollow composite cylindrical structures with various multiple layers of different materials or arbitrary fiber angles because no explicit interfacial continuity parameters are required. It provides an efficient and easy-to-use analysis tool for assessing hollow composite cylindrical structures in engineering applications.