L形无孔钢板连接式方钢管混凝土组合异形柱压弯性能简化模拟研究

对2根偏心距不同的L形无孔钢板连接式方钢管混凝土组合异形柱进行压弯简化模拟研究,并对简化模型及实体模型进行了破坏模态、竖向承载力、侧向位移3方面的对比,结果表明:简化模型基本能够合理有效地模拟L形无孔钢板连接式方钢管混凝土组合异形柱的压弯性能;在简化模型的基础上,对异形柱的压弯性能进行了参数化分析,分析发现提高钢材强度能有效改善柱承载力,提高混凝土强度、连接板厚度对柱承载力及延性没有明显影响,柱承载力会随着偏心距的增加而不断下降,且下降程度不断减小。     

Investigation of FRP strengthened circular columns under biaxial bending

This paper presents the analysis and design of cylindrical reinforced concrete (RC) columns confined with fiber reinforced polymer (FRP) composites. The columns studied are under combined axial loads and biaxial bending moments. The fiber method modeling (FMM) together with finite element analysis (FEA) are adopted to investigate the behavior of such columns. The procedure finds the inclination and depth of the neutral axis that satisfy the equilibrium conditions. Moreover, the proposed analysis is capable of solving slender columns under biaxial bending through a developed computer program. The finite element derivation of a general stiffness matrix that accounts for the loss of symmetry of the cross-section due to material nonlinearity and biaxial moments is presented herein. The derivation starts from the principle of virtual work and develops an updated Lagrangian procedure for geometric nonlinear analysis. It should be noted that the stiffness for an elastic-plastic cross-section is a function of the current state and the past history of the strain of the column section as well as the stress-strain relations for each of concrete, steel and the fibers used. Therefore the cross-section is partitioned into a number of small elemental areas and a step-by-step application of the force-deformation equilibrium equation is applied. Interaction diagrams for columns under uniaxial bending are plotted and compared with experimental results conducted in the literature review. Moreover, contour lines for columns under biaxial bending are plotted. A parametric study was carried out to investigate the effect of various parameters on the strength of the column. The parameters include unconfined concrete strength, type of FRP used, thickness of FRP and the column height to the cross-sectional diameter (H/D) ratio. The developed diagrams provide the designer with an easy and reliable way to analyze and design such columns.     

基于网络的结构远程试验系统的探讨

结构远程试验研究是目前国际结构工程研究的前沿领域,本文作者仅对实现结构远程试验的几个关键技术及其体系结构等进行了探讨,并对国内外在该方向的研究动向进行了简单介绍.     

双向压弯钢筋混凝土L形柱之平截面假定的分析与讨论

通过对等肢L形钢筋混凝土柱在双向压弯作用下利用ANSYS软件进行空间有限元分析,讨论了平截面假定的正确性与适用性,研究结果表明,平截面假定仅在一定范围内适用,并提出了相应的设计建议.     

Behaviour of reinforced and concrete-encased composite columns subjected to biaxial bending and axial load

An experimental investigation of the behaviour of reinforced concrete columns and a theoretical procedure for analysis of both short and slender reinforced and composite columns of arbitrarily shaped cross section subjected to biaxial bending and axial load are presented. In the proposed procedure, nonlinear stress–strain relations are assumed for concrete, reinforcing steel and structural steel materials. The compression zone of the concrete section and the entire section of the structural steel are divided into adequate number of segments in order to use various stress–strain models for the analysis. The slenderness effect of the member is taken into account by using the Moment Magnification Method. The proposed procedure was compared with test results of 12 square and three L-shaped reinforced concrete columns subjected to short-term axial load and biaxial bending, and also some experimental results available in the literature for composite columns compared with the theoretical results obtained by the proposed procedure and a good degree of accuracy was obtained.     

Effective flexural stiffness of slender reinforced concrete columns under axial forces and biaxial bending

Most of the design codes (ACI-318-2008 and Euro Code-2-2004) propose the moment magnifier method in order to take into account the second order effect to design slender reinforced concrete columns. The accuracy of this method depends on the effective flexural stiffness of the column. This paper proposes a new equation to obtain the effective stiffness EI of slender reinforced concrete columns. The expression is valid for any shape of cross-section, subjected to combined axial loads and biaxial bending, both for short-time and sustained loads, normal and high strength concretes, but it is only suitable for columns with equal effective buckling lengths in the two principal bending planes. The new equation extends the proposed EI equation in the “Biaxial bending moment magnifier method” by Bonet et al. (2004) [6], which is valid only for rectangular sections. The method was compared with 613 experimental tests from the literature and a good degree of accuracy was obtained. It was also compared with the design codes ACI-318 (08) and EC-2 (2004) improving the precision. The method is capable to verify and design with sufficient accuracy slender reinforced concrete columns in practical engineering design applications.     

混凝土双向受弯梁斜截面受剪承载力的计算

以32根集中荷载作用下混凝土双向受弯梁斜截面受剪性能试验为依据,将混凝土框架柱双向受剪承载力计算方法用于计算双向受弯梁斜截面受剪承载力。结果表明,该方法的计算值是试验值的偏下限,具有足够的安全度,该方法适用于混凝土双向受弯梁斜截面受剪承载力计算。     

Full plastic capacity of equal angle sections under biaxial bending and normal force

Steel angle members are usually designed by elastic methods, which may lead to uneconomical design. In order to make use of the plastic reserves of the section, the knowledge of its exact failure surface is important. In this study, it is shown that idealizing the section with lines of no thickness, which is common in the literature, entails a significant error when the neutral axis intersects a leg at a small angle. A simple interaction formula is proposed, which is shown to be very accurate based on an exhaustive analysis of all common angle sections listed in the tables. Further increase in accuracy is achieved through analytical relations for the cross-sectional properties, both elastic and plastic, that are derived. The proposed analysis forms the base of inelastic design and does not address stability issues.     

The influence of the weak axis on the behavior of high strength RC slender columns subjected to biaxial bending

This paper focuses on the behavior of high strength reinforced concrete columns subjected to biaxial bending. Experimental research with 56 high strength columns was carried out to achieve this purpose. The analyzed parameters were: the slenderness, the eccentricity, and the skew angle of the applied load.The coupling of the second order effects in each main direction of bending was analyzed. It has been observed that the behavior of the column was strongly influenced by the flexibility of the weak axis. However, the proposed simplified approaches in ACI-318(05) and EC-2 (2004) do not take it into account.The experimental results have been compared with a numerical simulation and with simplified approaches based on moment magnification factors such as that proposed by ACI-318(05) and by EC-2 (2004). Numerical simulation provided good agreement with displacement-load results and failure loads from the tests. In general, the simplified approaches are conservative in the case of the smaller eccentricities and result unsafe in the case of larger eccentricities.     

钢筋混凝土双向偏心受力异形柱的计算研究

本文采用非线性有限元数值分析方法，对双向偏心受力异形柱的设计计算进行分析研究，并编制了计算机程序，本文算法与18根L型模型柱和146根矩形截面模型柱实验结果比较，说明该算法和程序正确，该程序可解决截面设计，截面验算；可供设计时使用。     

Elastic biaxial bending and torsion of thin-walled members

This paper presents a detailed treatment of the non-linear elastic biaxial bending and torsion of thin-walled open section members. The treatment is valid for uniform members of linear elastic material, and is limited to small strains and rotations, and moderate deflections. Shear straining of the mid-surface of the member wall is neglected, and it is assumed that the member does not distort or buckle locally. The effects of initial deformations, loads, stresses, and strains are incorporated.

The treatment is based on non-linear strain-displacement relationships, and these are used to derive the non-linear equilibrium and tangent stiffness equations in forms which are suitable for computer solution by the finite element method.

Approximate linear and non-linear differential equilibrium equations are derived, as are the differential equilibrium equations and the energy equation for neutral equilibrium at bifurcation buckling, and these are then related to the classical equations developed by Timoshenko, Vlasov, and others.