高温后矩形钢管混凝土双向压弯构件力学性能试验研究

设计了双向压弯构件试验加载和量测装置;对14根高温后矩形钢管混凝土双向压弯构件的残余力学性能进行了试验测试;并对温度、长细比、加载偏心角度、截面高宽比和套箍系数等参数进行了研究。研究发现,温度、长细比、加载偏心角度、套箍系数、截面高宽比是影响高温后矩形钢管混凝土双向偏压构件承载力及延性的主要因素,高温后该类构件仍有较高承载力,所有试件的位移延性系数平均值大于8,表明高温后矩形钢管混凝土双向压弯构件具有较好的延性。     

中空夹层钢管混凝土轴压短柱火灾后剩余承载力的试验研究

对6个中空夹层钢管混凝土轴压短柱开展试验研究,试验的主要参数是截面形式(圆套圆、方套方和方套圆)以及受火与否。试验结果表明,受火后中空夹层钢管混凝土轴压短柱的承载力下降显著。在空心率相同的情况下,方套圆截面形式的试件其剩余承载力最高,而圆套圆截面形式的试件其延性最好。同时还可以发现,火灾后中空夹层钢管混凝土的轴压承载力下降幅度与传统的实心钢管混凝土接近。     

Mechanical behavior of concrete filled double skin steel tubular columns under cyclic pure torsion

为研究中空夹层钢管混凝土柱在扭矩作用下的滞回性能,以截面形式和空心率为主要参数,开展了4个中空夹层钢管混凝土柱试件在扭矩作用下的拟静力试验,得到了中空夹层钢管混凝土柱在往复扭矩作用下的破坏模式和扭矩-转角关系曲线。试验结果表明：中空夹层钢管混凝土柱在往复扭矩作用下的扭矩-转角滞回曲线较为饱满,没有出现“捏拢”现象,卸载刚度与初始弹性刚度接近,具有较好的耗能能力。往复扭矩作用下,圆形截面中空夹层钢管混凝土柱的扭转性能较方形截面中空夹层钢管混凝土柱更优。在截面外轮廓形状和尺寸相同的条件下,空心率对中空夹层钢管混凝土柱在往复扭矩作用下扭转性能的影响不大。     

往复纯扭作用下中空夹层钢管混凝土柱受力性能研究

为研究中空夹层钢管混凝土柱在扭矩作用下的滞回性能,以截面形式和空心率为主要参数,开展了4个中空夹层钢管混凝土柱试件在扭矩作用下的拟静力试验,得到了中空夹层钢管混凝土柱在往复扭矩作用下的破坏模式和扭矩-转角关系曲线。试验结果表明:中空夹层钢管混凝土柱在往复扭矩作用下的扭矩-转角滞回曲线较为饱满,没有出现"捏拢"现象,卸载刚度与初始弹性刚度接近,具有较好的耗能能力。往复扭矩作用下,圆形截面中空夹层钢管混凝土柱的扭转性能较方形截面中空夹层钢管混凝土柱更优。在截面外轮廓形状和尺寸相同的条件下,空心率对中空夹层钢管混凝土柱在往复扭矩作用下扭转性能的影响不大。     

圆锥形中空夹层钢管混凝土偏压构件受力性能研究

将圆锥形中空夹层钢管混凝土用于风电塔筒或输电塔架时,为满足在塔筒内设置设备等需求而将该类构件空心部分加大。为研究该类构件的偏压受力性能,进行了12个大空心率下的圆锥形中空夹层钢管混凝土偏心受压构件的试验研究,主要试验参数为荷载偏心率和长细比。利用ABAQUS软件建立有限元分析模型,对圆锥形中空夹层钢管混凝土偏心受压构件的典型破坏模态和荷载-变形关系曲线进行模拟,所得计算结果与试验结果基本吻合。通过典型算例分析了受力过程中钢管和混凝土各自所承担的荷载和纵向应力分布情况,同时分析了内、外钢管与混凝土之间相互作用力的变化情况。结果表明：偏心率和长细比对圆锥形中空夹层钢管混凝土偏心受压构件承载力及刚度有显著影响;该类构件力学行为与等截面圆中空夹层钢管混凝土偏心受压构件类似,锥度的存在使破坏位置从等截面柱的中部上移到锥形柱的3/4柱高处(柱顶处),因此在设计大空心率圆锥形中空夹层钢管混凝土偏压(压弯)构件时应考虑柱头处加强。同时,对该类构件压弯承载力计算方法给出了建议。     

圆锥形中空夹层钢管混凝土压弯构件抗震性能

选取合理的材料本构模型和混凝土损伤指标,通过ABAQUS软件建立圆锥形中空夹层钢管混凝土构件数值模型,并采用现有试验数据进行模型验证。在此基础上建立典型算例,分析典型算例的抗震性能指标,同时描述构件的破坏模态。对轴压比、空心率和长细比这3个对圆锥形中空夹层钢管混凝土抗震性能指标影响较为显著的参数进行分析,探究3个参数对滞回曲线极限承载力、延性系数和耗能能力的影响规律。比较圆锥形中空夹层钢管混凝土与不同截面尺寸的等截面圆中空夹层钢管混凝土抗震性能的差别,探究圆锥形中空夹层钢管混凝土与何种截面尺寸的圆中空夹层钢管混凝土可以实现抗震性能上的等效。结果表明:在一定范围内,轴压比和长细比的增大使得构件的耗能性能变差,空心率的增大使得构件的耗能性能变好,但需明确各参数的限值; 截面面积减小使得构件的承载力降低、耗能性能变差; 圆锥形中空夹层钢管混凝土的抗震性能与距其底部1/4高度处截面大小的圆中空夹层钢管混凝土等效。     

中空夹层钢管混凝土柱在长期荷载作用下的力学性能研究

基于美国混凝土协会ACI 209(1992)提供的混凝土徐变和收缩模型,对长期荷载作用下中空夹层钢管混凝土柱的变形和承载力进行计算。分析加荷龄期、持荷时间、长期荷载比、名义含钢率、钢材屈服强度、内钢管厚度、混凝土强度、空心率、长细比和荷载偏心率等参数对中空夹层钢管混凝土柱变形特性和承载力的影响。最后,在系统分析各影响因素的基础上,提出长期荷载作用对中空夹层钢管混凝土柱承载力影响系数的计算方法。     

八边形中空夹层钢管混凝土偏心受压柱的试验研究

以长细比和偏心率为变化参数,对4个八边形中空夹层钢管混凝土偏心受压构件进行试验研究。通过对试验现象和试验结果的详细分析,总结出此类构件的一些力学特点,并与相同条件下的圆中空夹层钢管混凝土、方中空夹层钢管混凝土进行比较,发现其承载能力比方形截面柱高,比圆形截面柱稍低。其承载力影响因素主要有构件的轴压性能、抗弯性以及偏心率。在分析试验结果和利用数值分析的基础上,提出压弯构件承载力验算公式,与试验结果吻合良好。     

钢管初应力对中空夹层钢管混凝土轴压与抗弯力学性能影响的研究

采用数值方法计算考虑钢管初应力影响时的中空夹层钢管混凝土构件荷载-变形关系曲线,在此基础上,分析初应力系数、截面含钢率、材料强度和空心率等因素的影响规律,最后给出考虑钢管初应力影响时中空夹层钢管混凝土抗弯刚度影响系数的实用验算方法。     

钢管高强混凝土偏压柱性能与承载能力的研究

本文介绍了两种长细比、五种偏心率共12个钢管高强混凝土偏压柱试件(f_()cu=88.5MPa)的试验研究工作。研究表明,具有较高套箍指标的钢管高强混凝土偏压柱的性能与普通钢管混凝土相似,但当偏心率大于1时钢管高强混凝土的承载能力衰减得较快。为了充分利用高强混凝土的强度,应控制钢管高强混凝土柱子的偏心率小于1,这样普通钢管混凝土承载能力偏心率影响折减系数φ_e的计算公式也适用于钢管高强混凝土偏压柱。     

Nonlinear Buckling Analysis of H-Type Honeycombed Composite Column with Rectangular Concrete-Filled Steel Tube Flanges

This paper was concerned with the nonlinear analysis on the overall stability of H-type honeycombed composite column with rectangular concrete-filled steel tube flanges (STHCC). The nonlinear analysis was performed using ABAQUS, a commercially available finite element (FE) program. Nonlinear buckling analysis was carried out by inducing the first buckling mode shape of the hinged column to the model as the initial imperfection with imperfection amplitude value of L/1000 and importing the simplified constitutive model of steel and nonlinear constitutive model of concrete considering hoop effect. Close agreement was shown between the experimental results of 17 concrete-filled steel tube (CFST) specimens and 4 I-beams with top flanges of rectangular concrete-filled steel tube (CFSFB) specimens conducted by former researchers and the predicted results, verifying the correctness of the method of FE analysis. Then, the FE models of 30 STHCC columns were established to investigate the influences of the concrete strength grade, the nominal slenderness ratio, the hoop coefficient and the flange width on the nonlinear stability capacity of SHTCC column. It was found that the hoop coefficient and the nominal slenderness ratio affected the nonlinear stability capacity more significantly. Based on the results of parameter analysis, a formula was proposed to predict the nonlinear stability capacity of STHCC column which laid the foundation of the application of STHCC column in practical engineering.     

中空夹层方钢管再生混凝土柱火灾后剩余承载力

为研究中空夹层方钢管再生混凝土柱火灾后剩余力学性能,运用有限元分析软件ABAQUS建立了ISO 834标准火灾作用后中空夹层方钢管再生混凝土柱的有限元模型,分析了截面温度场和应力场的变化规律。在此基础上分析了混凝土强度、钢材强度、计算长度、受火时间、空心率、混凝土取代率、偏心率等参数对构件火灾后剩余力学性能的影响;结合大量计算结果给出了中空夹层方钢管再生混凝土柱火灾后剩余承载力简化计算公式。结果表明:构件的火灾后剩余承载力随钢材强度和混凝土强度的增加而增加;构件火灾后剩余承载力随计算长度和受火时间的增加,总体呈降低趋势,当受火时间超过60 min时,构件火灾后剩余承载力急剧降低;空心率和混凝土取代率对构件火灾后剩余承载力影响较小,构件火灾后剩余承载力随空心率的增加而降低,随混凝土取代率的增加先增加后降低;构件火灾后剩余承载力随偏心率的增加而降低;所提公式计算精度良好,可为中空夹层方钢管再生混凝土柱抗火设计提供参考。     

Behavior of biaxially-loaded rectangular concrete-filled steel tubular slender beam-columns with preload effects

In composite construction, rectangular hollow steel tubular slender beam-columns are subjected to preloads arising from construction loads and permanent loads of the upper floors before infilling of the wet concrete. The behavior of biaxially loaded thin-walled rectangular concrete-filled steel tubular (CFST) slender beam-columns with preloads on the steel tubes has not been studied experimentally and numerically. In this paper, a fiber element model developed for CFST slender beam-columns with preload effects is briefly described and verified by existing experimental results of uniaxially loaded CFST columns with preload effects. The fiber element model is used to investigate the behavior of biaxially loaded rectangular CFST slender beam-columns accounting for the effects of preloads and local buckling. Parameters examined include local buckling, preload ratio, loading angle, depth-to-thickness ratio, column slenderness, loading eccentricity and steel yield strength. The results obtained indicate that the preloads on the steel tubes significantly reduce the stiffness and strength of CFST slender beam-columns with a maximum strength reduction of more than 15.8%. Based on the parametric studies, a design model is proposed for axially loaded rectangular CFST columns with preload effects. The fiber element and design models proposed allow for the structural designer to efficiently analyze and design CFST slender beam-columns subjected to preloads from the upper floors of a high-rise composite building during construction.     

圆中空夹层钢管混凝土柱力学性能研究

分别进行了十四个轴心受压构件和十二个偏心受压构件的试验研究 ,二种构件的试验参数分别为钢管径厚比和空心率 ,构件长细比和偏心率。在确定组成圆中空夹层钢管混凝土的钢材和核心混凝土应力 -应变关系模型的基础上 ,利用数值解法对圆中空夹层钢管混凝土轴压和压弯构件的荷载 -变形关系进行了全过程分析 ,分析结果与试验结果吻合良好。最后在参数分析的基础上 ,提供了圆中空夹层钢管混凝土轴压和压弯构件承载力实用验算方法。     

局部加载下中空夹层钢管混凝土的试验研究

对局部受压下的中空夹层钢管混凝土进行试验研究。分别对含内外两层钢管的14个圆形构件和15个方形试件进行试验,试验参数包含:空心率、顶端板厚度、局压面积比。结果表明:局部受压下中空夹层钢管混凝土呈现延性。各试验参数对局部受压中空夹层钢管混凝土短柱的性能和破坏模型有很大影响。最后,提出分析局部受压下中空夹层钢管混凝土承载力的简化计算模型。     

四肢钢管混凝土格构柱极限承载力试验研究

进行共计22根四肢钢管混凝土格构柱的极限承载力试验,试验参数为长细比和偏心率。介绍试验过程和试件的破坏形态,对试件的荷载-挠度曲线、极限承载力及组成构件的受力等进行了分析。试验结果表明,格构柱的柱肢以受压为主,缀管受力较小且处于弹性阶段。近载侧柱肢在试件进入非线性后紧箍效应开始发生作用且不断增大。格构柱破坏时有较明显的面内弯曲,属整体破坏。随着长细比和偏心率的增大,构件整体侧向挠度增大、极限承载力降低。长细比和偏心率对极限承载力的影响基本上是独立的,格构柱总体承载力的折减系数可采用分离的偏心率折减系数和长细比折减系数相乘来计算。研究结果表明,偏心率折减系数可采用与单圆管钢管混凝土偏压柱相似的公式计算;长细比折减系数计算中,换算长细比可应采用简化的放大系数法。     

Tests on stub stainless steel-concrete-carbon steel double-skin tubular (DST) columns

A new type of composite member, a stainless steel-concrete-carbon steel double-skin tubular (DST) column, is introduced in this paper. This composite member is expected to combine the advantages of all three types of materials, and have additional advantages of esthetics and resistance to corrosion that outer stainless steel offers. A series of tests are performed to investigate the performance of the composite column, and a total of 80 specimens were tested. The main parameters of the tests are the sectional type (circular, square, round-end rectangular and elliptical), the column type (straight, inclined and tapered), and the hollow ratio of the composite section (from 0.5 to 0.75). The results show that all types of columns behaved in a ductile manner, and the mechanical behavior is similar to those columns with double carbon steel tubes. A simplified model for the prediction of the stainless steel-concrete-carbon steel double-skin tubular (DST) columns cross-sectional strengths is suggested as well.     

High strength thin-walled rectangular concrete-filled steel tubular slender beam-columns,Part II: Behavior

Experimental and numerical research on full-scale high strength thin-walled rectangular steel slender tubes filled with high strength concrete has not been reported in the literature. In a companion paper, a new numerical model was presented that simulates the nonlinear inelastic behavior of uniaxially loaded high strength thin-walled rectangular concrete-filled steel tubular (CFST) slender beam-columns with local buckling effects. The progressive local and post-local buckling of thin steel tube walls under stress gradients was incorporated in the numerical model. This paper presents the verification of the numerical model developed and its applications to the investigation into the fundamental behavior of high strength thin-walled CFST slender beam-columns. Experimental ultimate strengths and load-deflection responses of CFST slender beam-columns tested by independent researchers are used to verify the accuracy of the numerical model. The verified numerical model is then utilized to investigate the effects of local buckling, column slenderness ratio, depth-to-thickness ratio, loading eccentricity ratio, concrete compressive strengths and steel yield strengths on the behavior of high strength thin-walled CFST slender beam-columns. It is demonstrated that the numerical model is accurate and efficient for determining the behavior of high strength thin-walled CFST slender beam-columns with local buckling effects. Numerical results presented in this study are useful for the development of composite design codes for high strength thin-walled rectangular CFST slender beam-columns.     

圆锥形中空夹层钢管混凝土轴压短柱受力机理分析

为了研究圆锥形中空夹层钢管混凝土轴压短柱的受力机理,通过有限元软件ABAQUS建立了该类构件的力学模型,并与已有试验数据进行对比,验证了模型的合理性。分析了典型构件的受力全过程荷载-应变关系曲线、钢管与混凝土之间的相互作用力、破坏模态和荷载分配; 同时分析了空心率、锥度、钢管径厚比和混凝土强度等参数对相互作用力的影响。结果表明:典型构件荷载-应变关系曲线可分为弹性段、弹塑性段、下降段和稳定段4个阶段; 构件破坏是由外钢管向外鼓曲所导致的,破坏截面约在0.8H(H为构件高度)柱高处; 锥度和空心率的改变对构件破坏截面位置影响较大,随着锥度和空心率的增大,破坏截面位置逐渐向柱顶靠近; 影响外钢管与混凝土之间相互作用力的主要因素有空心率、锥度、外钢管径厚比、外钢管屈服强度和混凝土强度; 影响内钢管与混凝土之间相互作用力的主要因素有空心率、锥度和外钢管屈服强度; 内钢管径厚比与内钢管屈服强度对混凝土与内、外钢管之间的相互作用力影响较小,可不作为主要参数进行分析。     

Numerical analysis of slender elliptical concrete filled columns under axial compression

This paper presents a non-linear finite element model (FEM) used to predict the behaviour of slender concrete filled steel tubular (CFST) columns with elliptical hollow sections subjected to axial compression. The accuracy of the FEM was validated by comparing the numerical prediction against experimental observation of eighteen elliptical CFST columns which carefully chosen to represent typical sectional sizes and member slenderness. The adaptability to apply the current design rules provided in Eurocode 4 for circular and rectangular CFST columns to elliptical CFST columns were discussed. A parametric study is carried out with various section sizes, lengths and concrete strength in order to cover a wider range of member cross-sections and slenderness which is currently used in practices to examine the important structural behaviour and design parameters, such as column imperfection, non-dimension slenderness and buckling reduction factor, etc. It is concluded that the design rules given in Eurocode 4 for circular and rectangular CFST columns may be adopted to calculate the axial buckling load of elliptical CFST columns although using the imperfection of length/300 specified in the Eurocode 4 might be over-conservative for elliptical CFST columns with lower non-dimensional slenderness.