钢管混凝土柱-钢梁节点在具有冷却过程的模拟火灾中的性能分析

对3个带有钢筋混凝土楼板的钢管混凝土柱与钢梁的节点进行了试验,这些节点承受组合荷载、同时具有加热和冷却的火荷载的共同作用。试验参数包括加热时间和防火材料厚度。测量了节点在加热、冷却和灾后的温度和变形。采用有限元模型模拟了节点在组合荷载和火灾下的反应。通过试验结果证实了有限元模型的有效性。随后采用有限元模型分析加热和冷却过程各自引起的节点温度变化。另外,给出此类节点在组合荷载和加热冷却火荷载作用下的弯矩-转角关系。     

Seismic performance of CFST column to steel beam joint with RC slab: Experiments

The objective of this research is to investigate the seismic behaviour of the composite joint consisting of circular concrete filled steel tubular (CFST) column and steel beam with reinforced concrete (RC) slab. Six specimens, including four interior and two exterior joints, were tested under constant axially compressive load on the top of the columns and cyclic loads at the ends of the beams. The main experimental parameters were the type of the joint, the axial load level on the CFST column and the section configuration of the beam. Several indexes that could reflect the seismic behaviour of the composite joint, such as the ductility, the strength degradation, and the energy dissipation capacity were analyzed. It was found that the composite joints exhibited favorable seismic performance.     

Seismic performance of CFST column to steel beam joints with RC slab: Analysis

This paper presents a finite element analysis (FEA) model for the concrete-filled steel tubular (CFST) column to steel beam joint with a reinforced concrete (RC) slab under cyclic loading. The feasibility of the FEA model is verified by a set of experimental results presented in the companion paper as well as available test data from other researchers. Stress analysis is conducted by using this FEA model to investigate the failure mode and mechanism of the composite joint. Parametric studies are then carried out to study the influence of the following parameters for the composite joint: material strength, the thickness of RC slab, the slenderness ratio and steel ratio of the column, the dimension of the diaphragm and the axial load level of the CFST column.     

Post-fire behaviour of concrete-filled steel tubular column to axially and rotationally restrained steel beam joint

This paper presents a numerical investigation on the post-fire behaviour of concrete filled steel tubular (CFST) column to restrained steel beam joint. An entire loading and fire phase, including ambient loading, heating with constant loads, cooling with constant loads and post-fire loading, was employed in the numerical analysis, and a finite element analysis (FEA) model was built to simulate the behaviour of CFST column to axially and rotationally restrained steel beam joints with external diaphragm connections under the entire loading and fire phase. For validation, the proposed modelling method was used to predict the test results of CFST columns and joints in fire and post-fire. The comparison demonstrates that the accuracy of the proposed FEA model is acceptable. Afterwards, the FEA model was used to analyse the mechanics characteristics of CFST column to restrained steel beam joints in the entire loading and fire phase. Based on the numerical analysis, the joint moment versus relative rotation angle relationship in the entire loading and fire phase was addressed, and the residual joint strength index and stiffness index were defined to evaluate the post-fire performance of joints. Finally, simplified calculating formulas were proposed to calculate the two indexes, which provide a simply and feasible method to evaluate the post-fire performance of external diaphragm joints in the CFST column - steel beam framed structure.     

钢管混凝土柱、钢筋混凝土板、钢梁连接节点的抗震性能:节点模型

基于已有试验和数值计算结果,研究了钢管混凝土柱(CFST)和钢梁的复合节点模型。采用参数研究法利用有限元分析方法(FEA)分析了节点连接处的弹性剪切刚度和剪切变形,给出了复合节点连接处包含弹性剪切刚度、剪切强度、剪切变形和滞后准则的迟滞模型。该迟滞模型用于整合基于纤维的节点宏单元,节点宏单元通过有限元方法和试验结果得到证实。研究了CFST节点和宏单元框架的整体和局部性能。该模型计算精确,建模方法适当,能够用于大尺寸和复杂组合结构的抗震性能分析。     

Concrete-filled circular steel tubes subjected to local bearing force: Finite element analysis

This paper presents a finite element analysis (FEA) of circular concrete filled steel tubular (CFST) members under local bearing forces applied either perpendicularly to the member or at an angle of 45°. The established FEA modeling was verified by the experimental results that have been published in an international journal. The FEA modeling was then used to perform analysis on the typical failure modes and full-range load-deformation relations of CFST subjected to local bearing forces. Finally, simplified formulae for calculating the strength of CFST under local bearing forces was presented. Practical guidance was also given to avoid premature local buckling of brace member and premature fracture of chord member.     

Investigation on square concrete filled double-skin steel tube (CFDST) subjected to local bearing force: Experiments

Experimental studies on the behaviour of concrete filled double-skin steel tube (CFDST) subjected to local bearing forces are presented in this paper. Sixteen specimens were prepared and tested with the included angle between bearing member (BM) and compression member of 45° and 90°, whilst both the inner and outer steel tubes of the CFDST specimens are square hollow sections (SHS). The main parameters in the tests were: 1) outside width ratio between BM and compression member: from 0.4 to 0.6; 2) hollow ratio of CFDST: from 0 to 0.6; 3) wall thickness of outer steel tube: 3.05 mm and 3.95 mm; and 4) cross-section of BM: solid and hollow. The failure pattern, load versus deformation curve, bearing capacity and corresponding deformation at bearing capacity of the tested specimens are presented and analyzed. The experimental results show that, while subjected to local bearing forces, CFDST specimens have a high bearing capacity and a good deformation-resistant ability. The calculated bearing capacities of CFDST under local bearing forces using the proposed formulae in the paper are evaluated by comparison with the experimental results.     

钢管混凝土柱与钢梁组合节点的抗震试验

研究了由带钢筋混凝土板的钢管混凝土柱与钢梁组成的组合节点的抗震性能。进行了4个内部节点和2个外部节点的试验,柱顶承受恒定轴力,梁端承受循环荷载。主要参数有:节点形式,柱顶轴力大小及梁截面构造形式。对能反映组合节点韧性、强度退化、耗能能力等抗震性能的几个指标进行分析,结果证明组合节点的抗震性能非常好。     

Flexural performance of rectangular CFST members

This paper presents a finite element analysis (FEA) modeling to study the flexural performance of rectangular concrete filled steel tubular (CFST) members with compact, non-compact or slender element sections. Seventy test results are used to verify the FEA modeling. Generally good agreements were achieved in the ultimate bending capacity and the curvilinear trends of the moment versus mid-span deflection relations of the composite member between the experimental results and the FEA results. The FEA modeling is then used to investigate the residual failure patterns of the core concrete, the typical residual deformations of outer steel tube and the stress and strain distributions across the composite section in the whole loading procedure. Analysis results show that interaction of steel and concrete in the composite beam offers stress redistribution in steel and concrete which makes the rectangular CFST beam have high flexural capacity and ductility. Finally, the reliability analysis method is used to calibrate the existing design formulae on composite beam in EC4 (2004), AISC (2010) and DBJ/T13-51-2010 (2010). It was found that all the design formulae achieved adequate reliability index.     

考虑受火全过程的高温作用后型钢混凝土柱力学性能研究及有限元分析

进行了高温作用后型钢混凝土柱力学性能试验,在试验的基础上建立了高温作用后型钢混凝土柱力学性能的数值模拟方法。通过在ABAQUS平台上开发子程序建立了升降温作用下型钢混凝土柱温度场的计算模型,通过选择合适的材料本构关系以及在ABAQUS平台上开发自定义场变量子程序,在考虑升温、降温以及高温作用后不同阶段材料本构关系的基础上,提出了高温作用后型钢混凝土柱力学性能分析的计算模型,实现了高温作用后型钢混凝土柱力学性能的计算模拟。计算结果与试验结果的对比表明,二者吻合较好,提出的方法合理可行。     

Behaviour of flush end plate joints to concrete-filled steel tubular columns

This paper presents the results of an experimental program for bolted moment connection joints of circular or square concrete filled steel tubular (CFST) columns, and H-shaped steel beams using high-strength blind bolts. In order to investigate the static performance and failure modes of the blind bolted connection, an experimental program was conducted involving four sub-assemblages of cruciform beam-to-column joints subjected to monotonic loading. Moment-rotation relationships of the tested connections were obtained and their performance was evaluated in terms of their stiffness, moment capacities and ductility. The test parameters varied were the column section type and the thickness of the end plate. The results showed that the proposed blind bolted connection, which behaves in a semi-rigid and partial strength manner according to the EC3 specification, displays reasonable strength and stiffness. The rotation capacity of this type of connection to square or circular CFST columns exceeds 70 mrad and this satisfies the ductility requirements for earthquake-resistance in most aseismic regions. The blind bolted connection is shown to be a reliable and effective solution for moment-resisting composite frame structures.     

Concrete-filled double skin steel tubular (CFDST) columns subjected to long-term sustained loading

This paper carried out a series of tests on concrete-filled double skin steel tubes (CFDST) columns under long-term sustained loading condition. The test process included two stages, i.e. long-term service test and ultimate strength test. Numerical models on analysis of the CFDST column under long-term sustained loading were presented. A comparison of results calculated using these models showed generally good agreement with the test results. Additionally, a detailed analysis was performed to analyse the long-term behaviour of CFDST columns. Finally, simplified formula for calculating the ultimate strength of CFDST columns subjected to long-term sustained loading was proposed.     

型钢混凝土梁与钢管混凝土柱节点加强环研究

探讨了型钢混凝土梁与钢管混凝土柱节点的外加强环板受力特性，基于既有的试验结果和理论计算，分析了加强环板的应变分布规律，研究了环板宽度对节点的承载力和刚度的影响，并通过建立承载力—变形双控原则来确定外加强环板尺寸的计算公式。     

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.     

Performance and calculations of concrete filled steel tubes (CFST) under axial tension

This paper reports the behavior of concrete filled steel tubes (CFST) under axial tension. A total of 18 specimens were tested. The main parameters were steel ratio, concrete type and bond or unbonded between the steel tube and its core concrete. A finite element model (FEM) was developed to perform mechanism analysis and parametric studies for CFST under axial tension. It was found that the tensile strength of steel tube can be increased due to the existence of the core concrete in CFST. Finally, a simplified formula that can predict the tensile strength was proposed.     

芯钢管连接的钢管混凝土半连通边节点试验研究

提出一种芯钢管连接的钢管混凝土半连通边节点形式。该种节点在有梁的3个方向间断外钢管,设置芯钢管补偿间断外钢管对节点的削弱。在无梁一侧保持钢管混凝土柱的外钢管连通,梁中纵筋在节点直通,梁、柱、节点的混凝土一次整浇。通过模型试验,研究节点的破坏过程、破坏形态、梁和局部连通钢管的作用及试件各组成部分的荷载-应变关系。使用ANSYS程序对模型试件进行分析,试验结果和数值计算结果吻合良好,均证实了新型节点具有良好的强度和刚度,节点承载力大于所连接梁、柱的承载力。试件破坏时,节点芯钢管还具有较大的承载潜力。局部连通的钢管对节点混凝土有一定保护作用且有利于施工中上下钢管的对中。     

Behaviour of concrete filled steel tubular (CFST) stub columns under eccentric partial compression

This paper investigates the behaviour of concrete filled steel tubular (CFST) stub columns subjected to eccentric partial compression. Twenty-eight specimens were tested and presented. The main parameters in test program include: (1) section type: circular, square and rectangular; (2) load eccentricity ratio (including uniaxial and biaxial loading): from 0 to 0.4; and (3) shape of the loading bearing plate (BP): circular, square, strip and rectangular. The test results indicated that, similar to the corresponding fully loaded CFST stub columns under eccentric loading, CFST stub columns under eccentric partial compression have generally reasonable bearing capacity and favorable ductility. A finite element analysis (FEA) model for CFST stub columns under eccentric partial compression is developed and the predicted performances are validated through measured results. The FEA model is then used to investigate the mechanisms of such composite columns further.     

Research on seismic behavior of cruciform special-shaped CFST column to H-section steel beam joint

为了研究十字形钢管混凝土柱-H形钢梁框架中节点的抗震性能和破坏机理，进行了6个缩尺比为1∶2的节点拟静力试验。观察节点的损伤过程及破坏模式，分析柱端荷载-位移滞回曲线、节点核心区剪力-剪切变形曲线、层间位移角组成、耗能能力及应力分布。采用ABAQUS软件建立钢管混凝土异形柱-H形钢梁框架节点的有限元分析模型，分析结果与试验结果吻合良好，并对节点核心区受剪承载力和节点刚度进行参数分析。研究结果表明：节点的滞回曲线饱满，延性系数介于2.63～4.45之间，等效黏滞阻尼系数介于0.202～0.241之间，节点域的变形和耗能能力较强；建立的有限元分析模型可用于模拟节点的抗震性能，有限元参数分析结果表明增加节点区钢管厚度可以明显提高核心区受剪承载力，增加竖向肋板尺寸可以有效提高节点刚度。为保证竖向肋板节点达到刚性节点要求，建议柱钢板宽厚比不大于30；竖向肋板翼缘外高度、翼缘内高度以及竖向肋板与梁翼缘连接长度分别不应小于梁翼缘宽度的30%、15%和150%；竖向肋板厚度不应小于梁翼缘厚度。     

十字形钢管混凝土柱-H形钢梁框架节点抗震性能研究

为了研究十字形钢管混凝土柱-H形钢梁框架中节点的抗震性能和破坏机理,进行了6个缩尺比为1∶2的节点拟静力试验。观察节点的损伤过程及破坏模式,分析柱端荷载-位移滞回曲线、节点核心区剪力-剪切变形曲线、层间位移角组成、耗能能力及应力分布。采用ABAQUS软件建立钢管混凝土异形柱-H形钢梁框架节点的有限元分析模型,分析结果与试验结果吻合良好,并对节点核心区受剪承载力和节点刚度进行参数分析。研究结果表明：节点的滞回曲线饱满,延性系数介于2.63～4.45之间,等效黏滞阻尼系数介于0.202～0.241之间,节点域的变形和耗能能力较强;建立的有限元分析模型可用于模拟节点的抗震性能,有限元参数分析结果表明增加节点区钢管厚度可以明显提高核心区受剪承载力,增加竖向肋板尺寸可以有效提高节点刚度。为保证竖向肋板节点达到刚性节点要求,建议柱钢板宽厚比不大于30;竖向肋板翼缘外高度、翼缘内高度以及竖向肋板与梁翼缘连接长度分别不应小于梁翼缘宽度的30%、15%和150%;竖向肋板厚度不应小于梁翼缘厚度。     

Experimental behaviour of steel reduced beam section to concrete-filled circular hollow section column connections

In this paper, five specimens of connections of reduced beam section (RBS) steel beam to concrete-filled steel tubular (CFST) circular hollow section (CHS) column using an external ring were tested. The experiments considered the hysteretic behaviour under combined constant axial load and cyclic lateral load. For comparison, three specimens of a weak-column without an RBS configuration steel beam to CFST column connection were tested under the same conditions. The axial load level of the CFST column, width of connection stiffening ring and RBS configuration were considered as the experimental parameters of their seismic behaviour. It was found that the lateral load (P) versus lateral deformation (Δ) hysteresis curves exhibited no obvious strength deterioration and stiffness degradation. The energy dissipation of the RBS connections is significantly improved when compared with weak-column connections. The concrete filled CHS columns failed as a weak-column connection and their energy dissipation capacity was reduced. It can be concluded that the RBS connections exhibit good seismic performance.