八边形中空夹层钢管混凝土轴压短柱力学性能的研究

在总结圆中空夹层钢管混凝土和方中空夹层钢管混凝土柱受力性能与工程应用优缺点的基础上,提出采用八边形中空夹层钢管混凝土结构的合理性。对八边形中空夹层钢管混凝土轴压短柱力学性能进行试验分析,得到构件各组成部分的荷载-应变关系曲线和极限承载力值,由试验现象与试验结果发现八边形截面中空夹层钢管混凝土柱的承载能力比方形截面柱承载能力高,比圆形截面柱承载能力稍低,且与八边形直边与斜边之比相关。为拓展此类构件应用的几何尺寸范围,在确定材料合理的应力-应变关系模型后,采用有限元方法进一步分析此类构件的力学性能,由此得到的荷载-应变关系曲线以及构件承载力与试验结果能较好地吻合。通过对影响构件承载能力各主要参数的分析,利用试验与数值模拟结果,提出轴压条件下八边形中空夹层钢管混凝土短柱极限承载力的计算公式,供工程设计人员参考。     

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。     

中空钢管混凝土轴压短柱有限元分析与验证

为了研究中空钢管混凝土(HCFST)短柱的轴压性能,本文采用有限元软件ABAQUS对5根已有中空钢管混凝土短柱轴压试验进行数值模拟分析。通过选择合理的材料本构模型,建立该类短柱的有限元模型,获得轴压短柱的荷载-位移全过程曲线,与已有的试验结果进行对比,二者吻合良好。验证了本文有限元建模方法的合理性和可实施性,为中空钢管混凝土短柱在实际工程中的推广应用提供技术支撑。     

钢管混凝土柱与组合梁端板连接的非线性有限元分析

为了研究钢管混凝土组合框架梁柱半刚性连接的受力性能与破坏形式,本文采用ABAQUS软件建立了钢管混凝土柱与钢-混凝土组合梁端板连接的非线性有限元模型。该模型考虑了材料非线性、几何非线性和复杂接触问题,确定了钢管核心混凝土和楼板混凝土的本构关系模型、各组件的复杂接触关系。研究了组合节点的柱端水平荷载-水平位移关系曲线和破坏形式,并用试验结果验证了计算结果的准确性。进行了大量的参数分析,获得了在正、负弯矩作用下影响组合节点极限承载力和初始刚度的主要参数。研究结果表明:所建立的钢管混凝土柱与钢-混凝土组合梁端板连接的有限元模型具有较好的准确性,可以为半刚性钢管混凝土组合框架的理论研究提供参考依据。     

实腹式双钢管异强混凝土组合短柱轴压承载力研究

为研究实腹式双钢管异强混凝土(CFDST)组合短柱的轴压性能,以长细比(λ)、核心混凝土和夹层混凝土抗压强度(f_cki,f_cko)、内外钢管厚度(t_i,t_o)、直径(D_i,D_o)及抗拉强度(f_yki,f_yko)为主要参数,共设计21根CFDST组合短柱。基于钢材简化的双线性本构模型和考虑约束效应的核心、夹层混凝土非线性本构模型,采用ABAQUS软件对18根双钢管混凝土组合短柱试件进行了数值仿真,获得短柱竖向荷载-位移关系曲线。通过与已有的试验数据对比,验证了材料本构模型和有限元建模的合理性。基于此对CFDST组合短柱进行扩展参数分析,考察了不同参数对该类短柱轴压承载力的影响规律,获得此类构件的受力机理、应力分布规律及破坏形态。结果表明,随f_cki,t_o,D_o和f_cko的增大,CFDST组合短柱的轴压承载力均会显著提高。而随λ的...     

方钢管混凝土轴压短柱力学性能非线性有限元分析

在以往有关研究成果的基础上,选取具有代表性的轴压方钢管混凝土结构试验,利用通用有限元软件ABAQUS建立有限元模型,对方钢管混凝土轴压短柱的受力性能进行计算分析。分析受力过程中钢管混凝土柱的破坏模态;计算方钢管混凝土轴压短柱荷载-变形关系曲线;分析含钢率、套箍系数对极限承载力和荷载-变形关系曲线的影响规律。并将计算分析结果与试验结果相比较,验证了建立的模型可以模拟方钢管混凝土柱的极限承载力和破坏全过程。文中的研究成果可为其他研究提供相关参考。     

中空夹层钢管再生混凝土短柱受压性能分析

为了研究震后建筑废弃物再生混凝土材料及其钢管短柱的力学性能,以混凝土的再生骨料取代率为主要参数,分别进行了10个圆中空和10个方中空夹层钢管再生混凝土短柱的轴压试验研究,比较了试件的荷载变形曲线和极限承载力关系.结果表明：随着再生骨料取代率的增大,试件的极限承载力逐渐降低,100%再生骨料取代率的圆中空试件和方中空试件比原生骨料试件的极限承载力分别下降16%和10%.在确定试件钢材和核心再生混凝土的应力应变模型的基础之上,利用数值计算方法对中空夹层钢管再生混凝土的荷载应变全过程关系进行了分析,理论计算结果与试验结果吻合较好.建立了中空夹层钢管再生混凝土轴压试件极限承载力的实用验算方法.     

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。     

基于微平面模型的钢管混凝土柱承载力有限元模拟

钢管混凝土是在钢管中填充混凝土而形成的一种组合结构材料,该结构中的钢管与混凝土协同工作,优势互补,大幅提高了其极限承载能力,极大改善了构件的延性和塑性性能,故广泛应用于高层建筑、桥梁和地下空间等结构工程领域.在钢管混凝土的有限元模拟中,混凝土的材料模型极大地影响了构件承载力的计算和分析结果.尝试采用混凝土微平面本构模型,运用通用有限元分析软件,编写了混凝土微平面模型的用户材料子程序,分析钢管混凝土构件的受压承载力性能,并在已有试验的基础上进行了比较和分析.     

简析混凝土非线性分析中的本构关系

对混凝土非线性分析中本构关系的研究现状作了介绍与评述,并对线弹性类、非线弹性类及基于弹塑性理论的混凝土模型进行了分析,最后对其今后的发展趋势进行了展望,为其进一步的研究分析奠定了基础。     

Behavior of concrete-filled double skin steel tubular columns with octagon section under axial compression

Based on some conclusions of two kinds of concrete-filled double skin steel tube (CFDSST) members with circular or square sections, a new kind of CFDSST with octagonal section, where the outer tube has an octagonal section and the inner tube has a circular section, is proposed in this paper. Behaviors of the CFDSST members with octagon section subjected to axial compression are investigated, and some curves of load-strain of steel tubes and confined concrete and the bearing capacity of members are obtained. It is indicated that the bearing capacity of the columns with octagonal section is larger than that with square section and is smaller than that with circular section, and the bearing capacity of members is related to the ratio of the straight side to the bevelled one. Based on the proper stress-strain relationship, a couple of numerical analyses are made using the finite element software named ANSYS. Finally, a simplified formula is proposed in the paper, and the numerical results agree well with the experimental results and the mathematical solutions. The results are valuable for engineers. __________ Translated from China Civil Engineering Journal, 2007, 40(2): 33–38 [译自: 土木工程学报]     

Behavior of concrete-filled double skin steel tubular columns with octagon section under axial compression

Based on some conclusions of two kinds of concrete-filled double skin steel tube (CFDSST) members with circular or square sections, a new kind of CFDSST with octagonal section, where the outer tube has an octagonal section and the inner tube has a circular section, is proposed in this paper. Behaviors of the CFDSST members with octagon section subjected to axial compression are investigated, and some curves of load-strain of steel tubes and confined concrete and the bearing capacity of members are obtained. It is indicated that the bearing capacity of the columns with octagonal section is larger than that with square section and is smaller than that with circular section, and the bearing capacity of members is related to the ratio of the straight side to the bevelled one. Based on the proper stress-strain relationship, a couple of numerical analyses are made using the finite element software named ANSYS. Finally, a simplified formula is proposed in the paper, and the numerical results agree well with the experimental results and the mathematical solutions. The results are valuable for engineers.     

钢管自密实混凝土短柱的有限元分析

钢管自密实混凝土在工程结构中得到了广泛的应用.通过理论分析,建立了轴心受压钢管自密实混凝土短柱的承载力计算公式.并借助有限元分析软件ANSYS,考虑了钢管与混凝土两种材料本构关系的非线性,对轴心受压钢管自密实混凝土短柱进行了大量的非线性有限元分析,建立了钢管自密实混凝土短柱在轴心压力作用下的非线性有限元计算模型.通过数值模拟,对提出的轴心受压钢管自密实混凝土短柱的承载力计算公式得出的结果进行了验证,发现计算结果与有限元分析结果吻合良好.     

Fire performance of stiffened concrete filled double skin steel tubular columns

A major deficiency of the concrete-filled double skin steel tube (CFDST) columns in fire exposure is the inadequate steel-concrete interface bonding leading to separating concrete and steel surfaces at elevated temperatures and triggering buckling failure of the columns. To improve interface interaction as well as postpone overall buckling, it is proposed in this study to use longitudinal steel stiffeners in CFDST columns. Different patterns of stiffeners including six, four and two number of stiffeners embedded in the interior or exterior surfaces of the inner or outer tubes are considered in the analysis. A sequentially-coupled thermal-stress analysis procedure is conducted to evaluate the effects of different patterns of stiffeners on the fire performance of these columns. One of the novelties of the current study is the incorporation of the confinement effects of both inner and outer tubes on the compressive strength of concrete at elevated temperatures which gives a realistic prediction of the fire resistance behavior of the CFDST columns. From the results, it is found that among the different patterns studied, stiffeners embedded in the exterior surface of the inner tubes or interior surface of the outer tubes enhancing steel-concrete interface interaction have a determinant role in much-improving fire endurance of the columns. With increase in the load ratio fire resistance of the specimens decreases drastically. The stiffeners strength and concrete strength have minimal effect on the fire performance of the stiffened CFDST columns. The conclusions, drawn from this study, can in turn, lead to the suggestion of some guidelines for the design of CFDST columns.     

Experimental and computational study of concrete filled steel tubular columns under axial loads

The paper presents an experimental and computational study on the behaviour of circular concentrically loaded concrete filled steel tube columns till failure. Eighty-one specimens were tested to investigate the effect of diameter and D/t ratio of a steel tube on the load carrying capacity of the concrete filled tubular columns. The effect of the grade of concrete and volume of flyash in concrete was also investigated. The effect of these parameters on the confinement of the concrete core was also studied. Diameter to wall thickness ratio between 25<D/t<39, and the length to tube diameter ratio of 3<L/D<8 was investigated. Strength results of Concrete Filled Tubular columns were compared with the corresponding findings of the available literature. Also a nonlinear finite element model was developed to study the load carrying mechanism of CFTs using the Finite Element code ANSYS. This model was validated by comparison of the experimental and computational results of load-deformation curves and their corresponding modes of collapse. From the experimental and computational study it was found that for both modes of collapse of concrete filled tubular columns at a given deflection the load carrying capacity decreases with the increase in % volume of flyash up to 20% but it again increases at 25% flyash volume in concrete.     

圆钢管混凝土结构非线性有限元分析

基于合理的钢管混凝土拉、压材料数值本构模型,采用U.L.列式单元增量平衡方程,引入分层梁单元材料非线性分析理论,通过调整截面形心应变和曲率,使梁端内外力平衡,完善了分层单元法,编制了相应的非线性有限元程序,并对已有钢管混凝土结构面内受力,如钢管混凝土偏压柱、不等端弯矩钢管混凝土偏压柱、钢管混凝土压弯构件和钢管混凝土模型拱肋等试验资料进行双重非线性有限元分析。结果表明:几组钢管混凝土模型拱和钢管混凝土压弯构件的荷载-变形曲线和极限承载力与试验结果最接近,验证了本文方法与程序的可靠性,通过与其他学者计算结果相比,表明本文方法具有较高的计算精度。     

有初应力的钢管混凝土格构柱轴压试验研究

为了研究初应力对钢管混凝土格构柱受力性能的影响,进行了有初应力的钢管混凝土格构柱的轴压试验研究,对初应力的施加方式、荷载 位移全过程曲线、柱肢套箍效应等进行分析。研究结果表明：初应力的存在会使钢管混凝土格构柱弹塑性阶段提前出现,试件的组合刚度下降、局部屈曲明显;同时,初应力影响组合材料的泊松比发展历程,使得套箍作用出现推迟,从而影响套箍作用的充分发挥,并最终降低试件的承载力。初应力对缀管受力性能的影响不大,缀管的受力处于弹性工作阶段。     

钢管超高强石渣混凝土轴压短柱静力性能试验研究

通过14个钢管超高强石渣混凝土短柱试件的轴压试验,考察其破坏形态,分析混凝土强度、试件的直径、径厚比等参数对其力学特性的影响。试验结果表明:以较低的水泥消耗量配制的超高强石渣混凝土填充至钢管内,钢管与核心混凝土界面密实,没有脱空的现象;在试验参数范围内,试件的套箍指标和混凝土强度是影响其静力特性的主要因素,试件的峰值荷载、低谷荷载及二次峰值荷载与核心混凝土的名义承载力(f_cA_c)之比基本与套箍指标成线性关系,但变化规律有别;试件的荷载-轴向平均应变曲线可以分为四个阶段,即弹性阶段、弹塑性阶段、荷载下降阶段和荷载回升阶段;套箍指标较小时,弹塑性段较短,下降段陡峭,峰值荷载后荷载下降幅值较大;套箍指标较大时,弹塑性上升段和荷载下降变形曲线较平缓,峰值荷载后荷载下降幅值较小;所有试件都呈剪切型的破坏特征,有较高的残余承载力和良好的延性;最后,给出了经回归分析得到与试验结果比较吻合的钢管超高强石渣混凝土短柱轴心受压承载力的计算公式。     

Fire performance of self-consolidating concrete filled double skin steel tubular columns: Experiments

An investigation into the fire performance of self-consolidating concrete (SCC) filled double skin tubular columns (CFDST) during the standard fire test is reported. Six full size SCC filled CFDST columns were designed for the fire tests. Detail failure modes of overall specimens and each component in the columns as well as temperatures, deformation and fire endurance were presented. Fire performance of the CFDST columns were studied through analysis of the limiting temperature of the outer tube, composite action between steel and concrete and effect of a number of parameters on the fire endurance. It showed that the limiting temperature in the CFDST columns is significantly higher than that in concrete filled steel tubular (CFST) columns or critical temperature in steel structural components. Strong evidence was found to prove the existence of composite action between steel and concrete in the CFDST columns during fire exposure. Effect of a number of parameters on the fire endurance of the composite columns was identified. Investigation into the fire performance of the columns also reveals possible solutions to improve the fire resistance of CFDST members.