浅谈结构的刚度和变形

为解决结构的刚度和变形问题，就截面刚度、构件刚度和结构刚度的概念进行了阐述，以一座塔楼的几种结构方案为例，探讨了提高刚度的方法，指出只有提高截面刚度和构件刚度才能提高结构刚度。     

玻璃纤维增强塑料夹砂管的环刚度分析

<正>通过对玻璃纤维增强塑料夹砂管的环刚度、管刚度、刚度等级概念进行分析,明确了环刚度的内涵是管道在外载作用下抵抗变形的一种能力,管刚度与环刚度并不是同一个概念,而刚度等级是管材初始特定环刚度的级别。由环刚度的相关概念分析了环刚度设计与测试的基本方法,并根据设计规范的要求对实际工程中所需要的刚度等级从变形和稳定性两个方面进行了分析,得到了确定刚度等级的基本原则和方法及其与埋设条件     

玻璃纤维增强塑料夹砂管的环刚度分析

通过对玻璃纤维增强塑料夹砂管的环刚度、管刚度、刚度等级概念进行分析,明确了环刚度的内涵是管道在外载作用下抵抗变形的一种能力,管刚度与环刚度并不是同一个概念,而刚度等级是管材初始特定环刚度的级别。由环刚度的相关概念分析了环刚度设计与测试的基本方法,并根据设计规范的要求对实际工程中所需要的刚度等级从变形和稳定性两个方面进行了分析,得到了确定刚度等级的基本原则和方法及其与埋设条件之间的关系。对正确理解玻璃纤维增强塑料夹砂管的环刚度以及环刚度的设计、测试及选择都具有一定的参考意义。     

任意地基中桩的刚度计算

本文采用基于温克尔假定的弹性地基梁计算法,提出了水平分层地基中,受竖向荷载作用桩的刚度传递计算法和受水平荷载作用桩的柔度传递计算法。并且分析了桩土条件对桩的竖向刚度、水平刚度、摇摆刚度及水平摇摆刚度的影响,然后根据等效桩和桩侧土刚度矩的概念,研究了任意地基中桩刚度与它的等效桩及桩侧土刚度矩之间的关系,从而提出了任意地基中桩刚度的近似计算方法。     

基于基频法的预应力混凝土箱梁疲劳刚度退化试验

开展了基于基频法的预应力混凝土箱梁桥模型疲劳试验; 详细介绍了基于基频法的疲劳多级变幅试验加载过程及疲劳加载方案和采集方案; 梳理了动刚度和静刚度的基本原理、基于基频的动刚度计算方法和基于挠度的静刚度计算方法; 对预应力混凝土箱梁的疲劳动刚度和静刚度退化规律进行了研究。结果表明:箱梁构件疲劳裂缝分布、裂缝走向和破坏敏感位置与矩形梁不同,模型梁均首先在腹板产生斜裂缝,腹板斜裂缝主要分布在从支座到1/4跨范围内,不断向顶板和底板斜向延伸; 预应力混凝土箱梁疲劳动刚度和静刚度二者退化规律相同,均呈现为先快速、后平稳的2阶段变化规律; 在疲劳初期,动刚度和静刚度退化率均在40%以上; 疲劳荷载上限值是桥梁结构疲劳刚度退化的一个重要影响因素,疲劳荷载上限值越大,动刚度和静刚度退化幅值就越大,且疲劳剩余刚度越小; 因为二者计算原理不同,所以计算的动静刚度数值也不同,但二者刚度退化规律相同,可相互对比、补充、验证,共同来探究预应力混凝土箱梁疲劳刚度的退化规律。     

首层架空层转换结构的侧向刚度控制参数探讨

通过一系列在首层架空层设置转换层的高层建筑的有限元分析,对楼层侧向刚度比、等效剪切刚度比和等效侧向刚度比三种转换层结构侧向刚度控制参数进行了探讨。讨论了在不同首层层高条件下,转换层下部结构侧向刚度改变对这三种侧向刚度比控制参数的影响。结果表明,首层层高较高且与相邻层层高相差悬殊时,楼层侧向刚度比和等效剪切刚度比容易大幅度超过现行规范限值,但并不能由此判断转换层下部结构侧向刚度严重不足。这种情况下,等效侧向刚度比较好地体现了转换层上下结构的侧向刚度关系,宜按等效侧向刚度比对结构侧向刚度进行控制,但其上限取值有待进一步研究。     

下部支承刚度对索拱结构力学性能的影响分析

为了研究下部支承刚度对索拱结构力学性能的影响,建立了跨度为60m,矢跨比分别为0.2,0.3,0.4的纯拱结构和索拱结构模型,采用支座刚度对下部支承的刚度进行等效处理。研究了五种不同支座水平刚度下索拱结构的强度、刚度和稳定性。结果表明,下部支承刚度对纯拱结构和索拱结构的强度和静力稳定性影响较小,但对其刚度有一定影响;该索拱结构在不同刚度的下部支承情况下力学性能良好。     

结构设计中刚度的应用

刚度概念在结构设计中贯穿整个过程,本文对刚度的相关概念进行了介绍,并通过举例,叙述了刚度在结构高宽比中、在平面布置上和竖向中的应用.通过对刚度的了解和应用,保证了结构的安全性,受力的合理性同时获得最佳的经济性.     

高层建筑结构层侧向刚度计算方法的研究

对高层建筑结构层侧向刚度的计算方法进行了讨论,提出了新的高层建筑结构层侧向刚度计算方法。对剪力墙、框筒及部分框支剪力墙结构的工程案例采用不同方法进行了侧向刚度、侧向刚度比的对比分析。建议的计算方法较好地反映了层竖向构件截面、层高和材料的刚度特征及两端转动约束的实际状况,其计算结果能较好地反映结构的真实侧向刚度,可供工程师在设计高层建筑结构时参考。     

不同边界条件下叠层橡胶支座的水平刚度分析

为了研究边界条件对叠层橡胶支座水平刚度的影响,定义了四类边界条件,采用弯剪模型,用直接积分法推导了在压剪作用下叠层橡胶支座的水平刚度方程。通过算例分析支座顶面与底面的转动约束参数k0和kh以及竖向荷载p对叠层橡胶支座水平刚度的影响,对比了不同边界条件下水平刚度的变化。结果表明:边界条件对于叠层橡胶支座的水平刚度影响明显,在相同参数k0和kh以及竖向荷载p作用下,边界条件一(k0≈∞和kh≈∞)时水平刚度KR,I最大,边界条件四(k0和kh较小)时水平刚度KR,IV最小,当边界条件相同时随着参数k0和kh的增大,边界条件二、三、四下叠层橡胶支座的水平刚度增大且向边界条件一接近,随着竖向荷载p的增大各类水平刚度降低。     

Timoshenko模型桩水平振动的非线性动力刚度

基于桩水平振动的非线性土阻抗,将桩等效为Timoshenko梁,研究非线性黏弹性土层中端承桩水平振动的动力特性,给出频率域内桩头非线性动力刚度的半解析解,得到桩头动力刚度和阻尼随频率的响应,考察物性和几何参数等对桩头动力刚度和阻尼的影响。结果表明:土非线性降低桩头刚度和阻尼,在第一共振频率处,桩头动力刚度取极小,并且随着桩振幅的增加,土层非线性效应逐步增强,这些结果可以为工程设计提供参考和帮助。     

Simplified analysis of façade rigger braced high‐rise structures

A simplified method of analysis for the preliminary design of tall building structures with façade riggers subjected to lateral loading is presented. A façade rigger braced structure comprises a series of interior walls and façade riggers placed in the exterior frames of the building parallel to the horizontal load on the structure. The method of analysis requires only four stiffnesses representing a uniform structure up the height: the bending stiffness of the walls, an axial stiffness parameter representing the contribution of the columns in the end frames and bending as well as racking shear stiffnesses of the façade riggers. The analysis yields the optimum location of the façade rigger, the deflection at the top of the structure and the forces in the four structural components such as the bending moment reduction in the walls. It allows a rapid assessment of the influence of the façade rigger stiffnesses on the overall behaviour of the structure in graphical form. It is suggested that the bending and racking shear stiffnesses of the façade riggers not be ignored in the preliminary design. Copyright © 2000 John Wiley & Sons, Ltd.     

Numerical and experimental analysis of penetration grouting in jointed rock masses

The reinforcement effect of penetration (or permeation) cement grouting injected into jointed rock masses is investigated in this paper. For this, anisotropic material properties of jointed rock masses with and without grouting are derived based on the mechanics of composite material. Derived anisotropic material properties are not only functions of the material properties of the intact rock and grouting, but are also related to the geometric and mechanical properties of rock joints, such as dip angle, spacing and stiffness. Two in situ seismic tests were also performed to obtain information on the ground improvement. Finally, a back analysis methodology is proposed to quantify the reinforcement effect. Here, joint stiffnesses of the rock masses are selected as the dominant parameter to be determined. The so-called back analysis shows that, after grouting, the stiffnesses of the filled joints are increased upto 6 times compared with those of the ungrouted joints.     

Vibrations of rectangular plates with elastic intermediate line-supports and edge constraints

A set of static beam functions, which are the solutions of an elastically point-supported beam under a Fourier series of static sinusoidal loads distributed along the length of the beam, are developed as the admissible functions to analyze the vibrations of orthotropic rectangular plates with elastic intermediate line-supports using the Rayleigh–Ritz method. Both the elastic rotational and the elastic translational constraints along the edges of the plate are also considered simultaneously. Unlike conventional admissible functions, this set of static beam functions not only can automatically adjust to the stiffnesses of the intermediate line-supports but also can properly describe the discontinuity of shear forces at the line-supports so that higher accuracy and faster convergence can be expected for the dynamic analysis of such plates. The suggested approach is effective even for various limiting cases by letting the corresponding stiffnesses approach their natural limits of zero or infinity. The present method is theoretically sound and mathematically simple, with each of the static beam functions being only a third-order polynomial plus a sine function. A common and efficient computational program can be compiled because of the fact that a change of the line-support parameters (locations, number and stiffnesses) and the boundary conditions of the plate only results in a corresponding change of the coefficients of the polynomial in the static beam functions. Several numerical examples are presented and the results obtained, where possible, are compared with the known solutions in literature. The present method has proved to be extremely effective for solving the aforementioned problems.     

梯形分布荷载作用下钢筋混凝土框架梁挠度计算公式

提出了梯形（三角形）分布荷载作用下钢筋混凝土框架梁、连续梁的挠度计算公式,其原理基于阶梯形变刚度梁的初参数法,并与挖处理方法的计算结果作了分析比较。     

Natural response of non-rigidly connected rectangular plates

The effect of a finite rotational restraint along two opposite edges of a rectangular plate is investigated for a range of mode numbers, aspect ratios and joint stiffnesses. Some practical applications are discussed by reference to welded joints. The extension of the theory to plate assemblies is briefly discussed.     

高层建筑结构设计中扭转效应的控制方法

结合工程实例,介绍在高层建筑结构设计中控制扭转效应的具体方法,即在建筑物外围尽可能均匀、对称布置抗侧力结构,减小裙房与主楼上下刚度偏心,防止小高层建筑结构平面过于狭长。     

侧扭屈曲的波形钢腹板钢筋混凝土连续组合梁的转动刚度

在负弯矩区,连续组合梁将达到由腹板刚度以及混凝土板和剪力连接刚度所产生的侧扭屈曲的极限状态。这3种刚度构成了组合梁的转动刚度。EC4在平面钢腹板组合梁中定义了这种刚度,但对于波形钢腹板组合梁结构中的刚度尚未有结论性研究。文中提出了一个公式,并基于以下几点来对波形腹板型材组合梁的转动刚度进行评估:1)倒U框架模型的4种代表性的试验结果;2)使用ANSYS有限元软件对数值模型进行构建和标定;3)68个数值模型的计算过程。在这些模型中,研究人员试图改变影响转动刚度的所有参数,例如腹板高度和厚度、平板的大小与类型(混凝土板或组合板)、横截面的剪力连接件的数量以及连接件的纵向间距。     

有限单元法计算分层地基上的弹性地基梁

本文用有限单元法计算分层地基上的弹性地基梁,编制了EFB程序,可在Apple-Ⅱ微机上进行计算。通过典型实例,将分层地基模式、弹性半空间地基模式和温克勒地基模式进行了比较,并探讨了梁的不同刚度和不同地基条件对计算结果的影响,得出了有实用意义的结论。     

Rotational stiffness of continuous composite beams with sinusoidal-web profiles for lateral-torsional buckling

In the hogging bending moment region, continuous composite beams are subjected to the ultimate limit state of lateral-torsional buckling, which depends on web stiffness as well as concrete slab and shear connection stiffnesses. These three stiffnesses compose the rotational stiffness of composite beams. Eurocode 4 defines this stiffness in composite beams with plane webs, but there are no conclusive studies on the stiffness of composite beams with sinusoidal-web profiles. This paper presents a formulation to evaluate the rotational stiffness of composite beams with sinusoidal-web steel profiles presented based on (a) test results for four representative prototypes of the inverted U-frame model, (b) the development and calibration of a numerical model using the ANSYS commercial finite element software, and (c) the computational processing of sixty-eight numerical models. In these models, the researchers attempted to vary all the parameters that could influence the rotational stiffness, such as web height and thickness, slab size and type (concrete or composite), number of shear connectors in the cross-section and longitudinal spacing of connectors.