Behaviour of concrete-filled double skin rectangular steel tubular beam-columns

Double skin composite columns are formed from two steel skins filled with concrete in between. This new form of hybrid column has the potential to be used in many domains such as high-rise bridge piers and large diameter columns in high-rise buildings, etc. This paper describes a series of tests carried out on concrete-filled double skin steel tubular (CFDST) stub columns, beams and beam-columns. Both outer and inner tubes are cold-formed rectangular hollow sections (RHS). The failure modes, and load-deformation behaviour of CFDST specimens are compared with those of conventional concrete-filled steel tubular members and empty double skin tubular members. A theoretical model is developed in this paper for the CFDST stub columns, beams and beam-columns. Reasonably good agreement is observed between the predicted and tested curves. Simplified models are derived to predict the load-carrying capacities of the composite members.     

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。     

中空夹层钢管混凝土短柱的性能分析

对外管为方形中空截面或者圆形中空截面,内管为圆形中空截面的夹层钢管混凝土短柱的抗压性能进行了有限元分析。通过与一系列由不同研究者进行的试验数据进行对比,以证实有限元建模的有效性。归纳了平均应力与纵向应变的典型曲线、混凝土应力曲线、混凝土和钢管的交互曲线以及空心率对CFDST短柱性能的影响。对影响复合柱截面性能的重要参数也进行了分析。     

Analytical behaviour of concrete-filled double skin steel tubular (CFDST) stub columns

This paper reports a finite element analysis of the compressive behaviour of CFDST stub columns with SHS (square hollow section) or CHS (circular hollow section) outer tube and CHS inner tube. A set of test data reported by different researchers were used to verify the FE modelling. Typical curves of average stress versus longitudinal strain, stress distributions of concrete, interaction of concrete and steel tubes, as well as effects of hollow ratio on the behaviour of CFDST stub columns, were presented. The influences of important parameters that determine sectional capacities of the composite columns were investigated.     

夹层钢管混凝土梁-柱在循环荷载作用下的性能分析

夹层钢管混凝土(CFDST)在桥梁和建筑的建设中具有很大的潜能。轴力和循环加载的弯曲荷载作用下,弯矩曲率曲线(M-(?)),柱侧向荷载-侧移曲线(P-Δ)模型的研究信息非常有限。建立了一个力学模型,用于分析轴向恒荷载和循环加载的弯曲荷载作用下的CFDST梁-柱。预测的组合梁柱的循环反应性能与试验结果一致。基于这个理论模型,对组合梁柱有关弯矩曲率曲线(M-(?)),侧向荷载-侧移曲线(P-Δ)的性能进行了参数分析。最后,提出了计算弯矩曲率曲线(M-(?)),侧向荷载-侧移曲线(P-Δ)的简化模型。     

方中空夹层钢管混凝土纯弯力学性能研究

以空心率为变化参数 ,进行了 5个纯弯构件的试验研究 ,考察了方中空夹层钢管混凝土在纯弯状态下的力学性能。然后在确定钢和混凝土应力 -应变关系模型的基础上 ,采用数值方法对方中空夹层钢管混凝土纯弯构件进行理论分析 ,分析结果和试验结果吻合较好。最后提供了构件抗弯承载力和抗弯刚度的简化计算公式 ,可供有关工程实践参考。     

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。     

Analytical behaviour of concrete-filled double skin steel tubular (CFDST) beam-columns under cyclic loading

Concrete-filled double skin steel tubes (CFDST) have a great potential to be used in the construction of bridges and buildings. Limited information is available on the models for the moment (M) versus curvature (φ) response, and the lateral load (P) versus lateral displacement (Δ) relationship of these columns subjected to axial load and cyclically increasing flexural loading. A mechanics model is developed in this paper for CFDST beam-columns subjected to constant axial load and cyclically increasing flexural loading. The predicted cyclic responses for the composite columns are in good agreement with test results. Based on the theoretical model, parametric analysis was performed on the behaviours of moment (M) versus curvature (φ) response and lateral load (P) versus lateral displacement (Δ) relationship for the composite columns. Finally, simplified models for the moment (M) versus curvature (φ) response, and the lateral load (P) versus lateral displacement (Δ) relationship were suggested.     

锥形中空钢管混凝土(CFDST)短柱的性能

目前,虽然锥形中空钢管混凝土(CFDST)柱被用于中国的输电塔中,但是关于这类输电塔中构件性能的信息仍很缺乏。因此,本文对锥形CFDST短柱的轴压性能进行研究。研究的参数包括锥角和截面尺寸。通过建立有限元模型分析锥形构件的性能。结果表明,钢管和夹层混凝土不受锥角影响,能够很好地协同工作。锥形CFDST短柱的失效模式与直线型的类似,失效出现在最小截面附近。通过应力分析讨论锥形构件的约束效应。最后,给出用于计算锥形CFDST短柱极限强度的建议公式。     

Behaviour of tapered concrete-filled double skin steel tubular (CFDST) stub columns

Recently, tapered concrete-filled double skin steel tubular (CFDST) columns have been applied in electricity transmission towers in China. However, there is still lack of information on the behaviour of such kind of members. This paper thus carried out the investigation on axially loaded tapered CFDST stub columns. The parameters included the tapered angle and the sectional profile. A finite element analysis (FEA) model was developed to predict the behaviour of the tapered member as well. The results showed that the steel tubes and the sandwiched concrete could work together well despite the tapered angle. The failure mode of the tapered CFDST stub column was similar to that of the straight one, and the failure occurred near the smallest section. The confinement effect of the tapered member was discussed by using the stress analysis. Finally, formulas were suggested for the calculation on the ultimate strength of the tapered CFDST stub column.     

Testing of self-consolidating concrete-filled double skin tubular stub columns exposed to fire

A concrete-filled double skin tube (CFDST) is an innovative steel and concrete composite construction with the potential to be used as columns in high-rise buildings. Self-consolidating concrete (SCC) can offer convenience for construction and ensure the construction quality of CFDST columns. There is very limited knowledge about the fire performance of CFDST columns, which is a key issue in the application to high-rise buildings. This paper reports an experimental investigation into the fire behaviour of CFDST stub columns filled with SCC and fibre reinforced SCC. The study aims to obtain thermal and structural responses of the stub columns through standard fire testing. Details are given in terms of the failure mode, temperature distribution, critical or limiting temperature and fire resistance. It was found that the added fibre does not affect the temperature distribution whereas the increased concrete thickness and outer tube perimeter reduces the temperature in CFDST specimens. The added steel fibre increases the fire resistance of CFDST stub columns especially for load levels less than 0.6. The critical or limiting temperature for CFDST sections was found to be higher than for CFST (concrete-filled steel tube) or unfilled tubes.     

圆中空夹层钢管混凝土纯弯力学性能研究

以空心率为变化参数,对5个纯弯构件进行试验研究,同时考察圆中空夹层钢管混凝土在纯弯状态下的力学性能。在确定了钢材和混凝土应力-应变关系模型的基础上,利用数值方法对圆中空夹层钢管混凝土纯弯构件进行分析,分析结果和试验结果吻合较好。最后在参数分析的基础上,提出构件抗弯承载力的简化计算公式。     

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。     

Tests and calculations for hollow structural steel (HSS) stub columns filled with self-consolidating concrete (SCC)

The behaviour of self-consolidating concrete (SCC) filled hollow structural steel (HSS) stub columns subjected to an axial load was investigated experimentally. A total of 50 specimens were tested. The main parameters varied in the tests are: (1) sectional types: circular and square; (2) steel yielding strength: from 282 to 404 MPa; and (3) tube diameter or width to wall thickness ratio (D/t or B/t): from 30 to 134.A mechanics model is developed in this paper for concrete-filled HSS stub columns. A unified theory is described whereby a confinement factor (ξ) is introduced to describe the composite action of the steel tube and the filled concrete. The predicted load versus deformation relationship was in good agreement with test results. The theoretical model was used to investigate the influence of important parameters that determine the ultimate strength of the composite columns. The parametric and experimental studies provide information for the development of formulae for the calculation of the ultimate strength and the axial load versus axial strain curves of the composite columns. Comparisons are made with predicted stub column strengths using the existing codes, such as ACI-1999, AISC-LRFD-1999, AIJ-1997, BS5400-1979 and EC4-1994.     

大空心率圆锥形中空夹层钢管混凝土压弯构件滞回性能研究

为研究大空心率圆锥形中空夹层钢管混凝土压弯构件的滞回性能,对10个圆锥形中空夹层钢管混凝土压弯试件(8个往复加载和2个单调加载试件)进行试验研究。考察空心率(0.6和0.8)和轴压比(0、0.2、0.4和0.6)对试件的破坏模态、P-Δ关系曲线和滞回性能的影响,并建立数值模型对单调加载的压弯试件的受力机理进行分析,最后讨论了圆锥形中空夹层钢管混凝土压弯构件侧向承载力简化计算方法。研究结果表明,两种空心率试件的破坏形态基本一致,表现为试件下部不同程度的局部破坏;往复压弯试件的P-Δ曲线较为饱满,表现出较好的滞回性能。空心率从0.6增加到0.8对试件的侧向承载力和延性影响较小,两种空心率下的峰值荷载平均相差约3%。随着轴压比增加,试件的极限荷载降低,延性逐渐变差。往复加载试件的强度退化不明显,空心率为0.8的试件刚度退化更显著。试件的平均位移延性系数为3.56,平均黏滞阻尼系数为0.322,表现出较好的耗能能力。当空心率为从0.6增加到0.8,试件的黏滞阻尼系数平均提高15%。     

Analytical behavior of frames with steel beams to concrete-filled steel tubular column

This paper reports the mechanism of composite frames with steel beams connected to concrete-filled square hollow section (SHS) columns. Detailed analysis was carried out on longitudinal stress in steel beams, axial stress distribution in concrete, and concrete stress along the column height and at the connection panel. Parametric studies were conducted to investigate the influence of axial load level, beam-to-column linear stiffness ratio on the structural behavior of composite frames. Simplified hysteretic lateral load (P) versus lateral displacement (Δ) models are proposed for such composite frames.     

钢管再生混凝土构件荷载-变形关系的理论分析

在确定钢材与核心再生混凝土本构关系模型的基础上,采用数值方法对钢管再生混凝土轴心受压、纯弯曲和压弯构件的荷载-变形全过程关系曲线进行模拟,对此类构件的力学性能进行研究,理论分析结果与试验结果非常吻合。最后在参数分析结果的基础上,提出钢管再生混凝土压弯构件承载力的简化计算公式。     

Analysis of axially loaded concrete filled circular hollow double steel tubular columns exposed to fire

A series of new unified design formulas for calculating the temperature field and fire resistance under axial compressive loading of a circular solid or hollow concrete filled double steel tubular (CFDST) short and slender columns exposed to fire are presented in this paper. The results of the experiments are firstly derived from exploring the fundamental behavior of the CFSDT slender columns under the ISO 834 standard fire and temperature distributions. Failure modes and axial deformation versus time curves are also obtained and discussed. It was realized that a solid or slender CFDST column has different temperature fields, stronger limiting temperature and better fire resistance, as compared to columns filled with plain concrete. Also, the load ratio and steel ratio have no evident difference between the results of the solid and hollow CFDST columns. A three-dimensional finite element analysis (FEA) model is developed to calculate the temperature field of CFDST columns. After calibration of the FE model, the influences of important parameters on the temperature field of the composite columns are investigated and a unified formula for calculating average temperatures of the columns’ cross-section is obtained. Combining the average temperature with the “Unified theory” under axial compression, a simplified design method is put forward, which provides a unified formulation for both the plain CFST and CFDST columns relating to the axial bearing capacity at room and elevated temperature. The proposed formulas are calibrated through comparisons with fire tests on the columns, and it was found that the method produces safe results on average.     

钢管再生混凝土构件受力机理研究

在确定钢管与核心再生混凝土本构关系模型的基础上,采用有限元法对钢管再生混凝土轴压短柱、纯弯构件和压弯构件的破坏模态和荷载-变形关系曲线进行全过程分析,揭示出受力过程中钢管与核心再生混凝土截面应力分布规律及钢管与核心再生混凝土之间的相互作用,较为深入地认识了静力荷载作用下钢管再生混凝土构件的工作机理。     

带端板圆锥形中空夹层钢管混凝土短柱轴向局压力学性能研究

利用有限元分析软件ABAQUS对带端板圆锥形中空夹层钢管混凝土短柱局压力学性能进行有限元分析和相应的试验研究,所得的荷载-位移全过程曲线及短柱破坏形态吻合较好。在此基础上对其受力全过程中上端板、内外钢管及混凝土应力分布情况进行了分析,同时给出了内外钢管与夹层混凝土之间的相互作用,并对锥度、材料强度、空心率、局压面积比、端板刚度等参数对局压时短柱极限承载力及荷载-位移曲线的影响进行了比较。