L形截面钢纤维高强钢筋混凝土柱及复合柱偏心加载试验

研究钢纤维对L形截面高强钢筋混凝土柱和混凝土复合柱的性能的影响。对16根L形截面钢纤维柱进行试验研究。主要参数为混凝土抗压强度、荷载偏心率、长细比影响以及钢纤维含量。对L形截面钢筋混凝土柱的试验结果进行了讨论。此外,基于材料的非线性特性对试样进行了分析。采用ACI318规范中的弯矩放大法对长细比影响加以考虑。结果表明:高强混凝土中加入钢纤维能够增强L形截面钢筋混凝土柱和复合柱的结构特性,有利于抵抗双向弯曲和轴向加载。     

钢管钢纤维混凝土圆柱的试验研究

进行了钢管钢纤维混凝土圆柱的性能研究。制作了16根钢管混凝土柱,并进行了双向压弯试验。主要参数有:横截面尺寸、柱长、混凝土抗压强度、荷载偏心。考虑材料非线性和几何非线性,提出计算钢管混凝土柱的极限承载力和荷载-位移曲线的理论方法,将普通钢管混凝土柱和钢管钢纤维混凝土柱的极限承载力和荷载-位移曲线的试验数据与理论分析进行对比。结果表明,钢纤维对钢管混凝土的性能有很大影响。     

Experimental study on steel tubular columns in-filled with plain and steel fiber reinforced concrete

An experimental investigation on the structural behaviour of steel tubular columns in-filled with plain and steel fiber reinforced concrete is presented in this study. A total of 16 concrete-filled steel tubular columns were constructed and tested subjected to biaxial bending and short-term axial load. The main variables considered in the test study were the cross section, slenderness, concrete compressive strength and the load eccentricity. In the presented study, a theoretical method for the prediction of ultimate strength capacity and load-deflection curves of concrete filled steel tube columns is proposed. In the analysis procedure, the nonlinear behaviour of the materials is considered and the slenderness effect has been taken into account. The experimental ultimate strength capacities and load-deflection curves of both plain and steel fiber concrete-filled tube columns have been compared with the analysis results and discussed in the paper. The results indicate that the addition of steel fibers in core concrete has considerable effect on the behaviour of concrete-filled steel tube columns.     

L形截面钢骨混凝土柱正截面承载力试验研究

为探索一种承载力高且便于施工的钢骨混凝土异形柱, 研究其破坏的一般规律和极限承载力,进行了3根以粗钢筋和型钢为钢骨的不等肢L形截面混凝土柱试件在双向偏心压力作用下的试验.试验得到试件中的钢骨及混凝土在不同荷载时的应变、裂缝开展情况以及极限承载力等相关数据.表明在双向偏心压力作用下,这种柱子破坏过程与普通钢筋混凝土构件相似,横截面平均应变符合平截面假定,极限承载力比相同截面普通钢筋混凝土异形柱有显著提高;粗钢筋作为钢骨可以有效利用钢筋与混凝土的粘结力,不必在钢骨间设置钢腹杆.粗钢筋作为钢骨便于施工.     

一种分析型钢混凝土T形柱双向压弯受力性能数值模拟方法：试验验证与极限承载力分析

为研究型钢混凝土T形柱双向压弯受力性能,提出一种基于OpenSees零长单元并考虑加载角度影响的高效数值模拟方法,采用该数值算法对已有文献有关弯曲型破坏的型钢混凝土T形柱进行全过程受力分析,以此验证该数值模拟技术的合理性。在此基础上,深入分析轴压比、加载角度、混凝土强度、型钢配钢率与强度、肢高肢厚比等变化参数对型钢混凝土T形柱极限受弯承载力的影响,并推导型钢混凝土T形柱双向受弯承载力计算公式。结果表明：在界限轴压比范围内,提高轴压比、混凝土强度、型钢配钢率、型钢强度和肢高肢厚比均能提高型钢混凝土T形柱极限受弯承载力;但当轴压比大于界限轴压比时,提高轴压比和混凝土强度反而降低其极限受弯承载力;型钢混凝土T形柱的薄弱加载方向为90°（即沿翼缘方向）;加载角度和混凝土强度对型钢混凝土T形柱的界限轴压比影响显著,当加载角度为45°时,其界限轴压比最高;提高混凝土强度会降低其界限轴压比;轴压比在0～0.4、0.4～0.9、0.9～1.4之间,型钢混凝土T形柱双向受弯承载力关系曲线分别为矩形、椭圆形和菱形。     

钢管混凝土叠合柱轴压性能研究

为研究钢管混凝土叠合柱轴压性能,基于合理的钢材和混凝土本构关系模型,采用纤维模型法和有限元法分析方法计算叠合柱轴压荷载-变形关系曲线。将理论计算结果与试验结果进行对比,验证了理论分析模型的正确性。在此基础上,对叠合柱的破坏模态、轴向荷载分配以及组成钢管混凝土叠合柱的外围钢筋混凝土、钢管和钢管内部混凝土之间相互作用等进行分析,提出了叠合柱的轴压承载力简化计算式,简化计算结果与试验结果吻合较好。为保证外围钢筋混凝土和内部钢管混凝土较好地协同工作,建议外围钢筋混凝土中箍筋的约束指标与内部钢管混凝土的约束效应系数比值不应小于0.188。     

基于修正压力场理论的型钢超高强混凝土柱受剪承载力研究

为分析型钢超高强混凝土柱受剪机理,并准确计算其受剪承载力,基于修正压力场理论提出型钢超高强混凝土柱的受剪承载力计算模型。该模型通过柱端部截面中心正应变ε0来考虑轴力、弯矩和剪力的相互作用,并通过关键参数混凝土主压应力角θ和平均纵向应变εx来反映剪跨比、轴力以及配箍对柱受剪承载力的影响。推导出型钢超高强混凝土柱受剪承载力的计算式,并分析其两种剪切破坏形式。通过两组型钢超高强（高强）混凝土柱的低周反复试验结果对该受剪模型进行验证。研究表明：模型能合理考虑轴力、弯矩和剪力的相互作用,反映剪跨比、轴力和箍筋对受剪承载力的影响;模型计算所得受剪承载力与试验值吻合较好。     

Experimental study on the static performance of steel reinforced concrete columns with high encased steel ratios

The static performances of 12 steel reinforced concrete (SRC) columns with high encased steel ratios subjected to biaxial bending and axial loadings are studied experimentally. The main design parameters of the specimens in this experiment are the encased steel ratio, axial compression ratio, and shape distribution of the encased steel section. The crack formation, failure processes, bearing capacity, and ductility of the specimens are investigated in detail. The experimental results show that the increased encased steel ratio results in the increased bearing capacity and ductility of the specimens. Furthermore, the stiffness of the specimen degenerates gradually beyond the peak point with an increase in the axial compression ratio. In addition, a more extensive shape distribution of an encased steel section has a positive influence on the ductility of the specimen. A comparison of the yield and peak bearing capacities between the experimental results of this study and the predictions according to Eurocode 4 also highlights that Eurocode 4 would underestimate the bearing capacity of SRC columns with high encased steel ratios because it ignores the confinement of concrete provided from the steel section and hoops and it employs a conservative prediction approach for the simplified axial load‐bending moment curve.     

使用预拱钢板对矩形预应力混凝土柱进行轴向加固

钢套常用于钢筋混凝土(RC)柱加固。之前的试验研究评估了钢套柱的延性和抗剪性能。然而,实践中常使用预压轴向荷载对RC柱进行加固。尚未对预应力引起的传统柱和新型套管之间的应力滞后效应进行研究。使用一种简单的新型卸载方法,利用预拱钢板提高预应力RC柱的轴向承载力,试验证明该方法能够有效提高RC柱的轴向承载力。提出相应理论模型来计算钢板加固柱的轴向承载力,将模型的预测结果与试验结果相比较,验证了该模型的准确性。     

外套钢管自密实混凝土加固钢筋混凝土圆形截面短柱轴压性能试验研究

提出外套钢管自密实混凝土加固钢筋混凝土柱的复合加固方法。通过11个加固钢筋混凝土圆形截面短柱试件（其中2个为增大截面加固柱试件、9个为复合加固柱试件）和2个未加固钢筋混凝土圆形截面短柱试件的轴压试验,对不同方法加固的钢筋混凝土圆形截面短柱承载力、刚度和延性进行研究,分析加载方式、含钢率、后浇自密实混凝土强度、界面处理方式等因素对复合加固柱轴压性能的影响。试验结果表明：复合加固柱试件的承载力和延性均优于未加固钢筋混凝土圆柱试件和增大截面加固柱试件。仅核心混凝土受压的试件承载力略大于全截面受压的试件;随着含钢率的增大,复合加固柱试件的承载力和延性提高显著;随着后浇自密实混凝土强度的提高,复合加固柱试件的承载力略有提高,但延性有所下降;界面处理方式对复合加固柱试件轴压性能影响不显著。在试验研究的基础上,提出复合加固钢筋混凝土圆形截面短柱的承载力计算式,得出的计算结果与试验结果吻合良好。     

型钢-方钢管自密实高强混凝土轴压短柱受力性能的试验研究

提出了一种重载柱设计的模式,即型钢-方钢管自密实高强混凝土柱。该组合柱是在方钢管中填充自密实高强混凝土和型钢而形成。通过13根型钢-方钢管自密实高强混凝土短柱的轴心受压试验,研究了该组合柱的受力性能。试验结果表明自密实试件与经过振捣的试件的受力性能几乎没有差别;型钢的存在有效地延缓或抑制了高强混凝土中剪切裂缝的产生从而提高了构件的延性;混凝土强度、方钢管的宽厚比和型钢的用量对构件的强度和延性有着显著影响。最后给出了型钢-方钢管自密实高强混凝土轴心受压短柱强度承载力的计算公式,计算结果与试验结果吻合良好。     

Nonlinear analysis of short concrete-filled steel tubular beam-columns under axial load and biaxial bending

This paper presents a nonlinear fiber element analysis method for determining the axial load-moment strength interaction diagrams for short concrete-filled steel tubular (CFST) beam-columns under axial load and biaxial bending. Nonlinear constitutive models for confined concrete and structural steel are considered in the fiber element analysis. Efficient secant algorithms are developed to iterate the depth and orientation of the neutral axis in a composite section to satisfy equilibrium conditions. The accuracy of the fiber element analysis program is verified by comparisons of fiber analysis results with experimental data and existing solutions. The fiber element analysis program developed is employed to study the effects of steel ratios, concrete compressive strengths and steel yield strengths on axial load-moment interaction diagrams and the C-ratio of CFST beam-columns. The proposed fiber element analysis technique is shown to be efficient and accurate and can be used directly in the design of CFST beam-columns and implemented in advanced analysis programs for the nonlinear analysis of composite columns and frames.     

规则钢筋混凝土框架中考虑双向随机偏心距的柱承载力抗震可靠度分析

地震作用下RC框架柱大多处于双偏压受力状态。为考虑双向偏心距随机特性的影响,采用Monte Carlo方法分析了RC框架柱的承载力抗震可靠度。基于已有的试验数据,分析了GB 50010—2010《混凝土结构设计规范》中双偏压构件抗力计算模式的不确定性及其对极限状态方程的影响。以按规范设计的典型RC框架角柱、边柱和中柱为例,结合已有荷载和抗力变量的统计概率参数,通过对荷载效应以及抗力进行抽样,分别按单偏压和双偏压情形计算了RC柱的承载力抗震可靠度。结果表明：对于规则框架结构,双偏压情形下使柱具有较低可靠度的地震作用方向(沿结构主轴)与单偏压情形并不相同;考虑双向随机偏心距后,RC柱的承载力抗震可靠度会较单向随机偏心距下的可靠度有较大程度的降低。     

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.     

钢管高强混凝土组合柱轴心抗压数值分析

为研究钢管高强混凝土组合柱的轴心抗压性能,利用高强混凝土和钢管混凝土本构关系,对组合柱轴心抗压受力全过程进行了数值计算,计算轴力-纵向应变曲线与试验结果吻合良好;并与钢筋混凝土柱进行了对比,定量分析了套箍指标、混凝土强度和配箍特征值对轴压承载力和纵向应变延性的影响.     

高层建筑框架柱轴压比限值的讨论

本文从框架柱大小偏心受压破坏角度出发,阐述了规定轴压比限值对保证压弯构件延性的必要性,并根据国内外学者的研究成果,就普通混凝土柱、高强混凝土柱、劲性混凝土柱各自轴压比的定义式及其限值进行了分析与比较,从概念上说明了以上各限值的大小关系。介绍了劲性骨架高强混凝土压弯柱的低周伪静力试验研究结果,结合试验结果提出了其轴压比和轴力比限值的建议     

Axial load behavior and strength of tubed steel reinforced-concrete (SRC) stub columns

This paper presents experimental and analytical studies on the behavior of tubed SRC stub columns subjected to axial compressive load. Fourteen circular tubed SRC (CTSRC) and fifteen square tubed SRC (STSRC) stub columns were tested to investigate the failure mode and axial loaded behavior of tubed SRC columns. The effect of diameter/width to thickness ratio of the tubes was studied. The effect of height to diameter/width ratio of the separated tubes in tubed SRC columns was studied to investigate the effect of bond and friction between tube and concrete on the behavior of tubed SRC columns. The test results indicated that tubed SRC stub columns exhibited higher axial load capacity than common SRC columns with the same volumetric steel ratio. Elastic–plastic analysis on the steel tube was employed to study the mechanism of tubed SRC stub columns subjected to axial compression. Equations for the prediction of the axial load strength of tubed SRC stub columns were also proposed based on the proposed experimental results.     

Nonlinear inelastic time-history analysis of truss structures

This paper presents a reliable numerical procedure for the nonlinear inelastic analysis of concrete-filled steel tubular frames. Geometric nonlinearities are taken into account by the use of stability functions derived from the exact stability solution of a beam–column subjected to axial force and bending moments. The spread of plasticity over the cross section and along the member length is captured by tracing the uniaxial stress–strain relationships of each fiber on the cross sections located at the selected integration points along the member length. The nonlinear equilibrium equations are solved using an incremental-iterative scheme based on the generalized displacement control method because of its general numerical stability and efficiency. The accuracy of the proposed procedure is verified by comparisons of the obtained results with experimental data and existing solutions. The proposed numerical procedure proves to be a reliable tool for the nonlinear analysis of concrete-filled steel tubular structures.     

空间钢构架混凝土柱的试验研究与设计建议

通过 2根空间钢构架混凝土轴心受压短柱及 1根普通钢筋混凝土轴心受压短柱的对比试验研究 ,以及 4根空间钢构架混凝土偏压短柱的试验研究 ,分析了空间钢构架混凝土柱的破坏特征 ,提出了其设计计算方法和构造要求。     

Performance-based analysis of concrete-filled steel tubular beam–columns,Part II: Verification and applications

The theory and algorithms of a performance-based analysis (PBA) technique for the nonlinear analysis and performance-based design of thin-walled concrete-filled steel tubular (CFST) beam–columns with local buckling effects were presented in a companion paper. Initial local buckling and effective strength/width formulas for steel plates are incorporated in the PBA program to account for local buckling effects. Performance indices are used in the PBA program to quantify the section, axial ductility and curvature ductility performance of thin-walled CFST beam–columns. This paper presents the verification and applications of the PBA program developed. The axial load–strain curves, ultimate axial loads and moment–curvature curves for thin-walled CFST columns predicted by the PBA program are verified by experimental data. The PBA program is then utilized to investigate the effects of local buckling, depth-to-thickness ratio, concrete compressive strengths, steel yield strengths and axial load levels on the stiffness, strength and ductility performance of thin-walled CFST beam–columns under axial load and biaxial bending. The PBA technique developed is shown to be efficient and accurate and can be used directly in the performance-based design of thin-walled CFST beam–columns and implemented in advanced analysis programs for composite columns and frames.