Experimental and numerical analyses of blind bolted moment-resisting composite joints to CFST columns with RC slab

In this paper, experimental and numerical analyses were conducted to investigate the structural properties and failure modes of the blind bolted flush or extended end plate joints between concrete-filled steel tubular (CFST) columns and composite beams. The experimental program and the main results of the tests were elaborated. Four full-scale subassemblages beam-tocolumn exterior joints to hot-rolled and cold-formed CFST columns were tested. The failure modes and moment-rotation relation curves of the joints were evaluated. The test results showed that all specimens exhibited favorable strength and stiffness, and larger deformation capacities. Meanwhile, finite element analysis (FEA) modeling of the specimens was built and analyzed. The results obtained from the FEA modeling were satisfactory agreement with the experimental tests results. Then, an extensive parametric study was conducted to investigate the influence of various parameters on the moment capacity and rotation stiffness of composite joints under positive or negative moment. The experimental studies and numerical analyses can improve the design of the typed joints to be used in moment-resisting composite frames.     

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

Based on the previous experimental and numerical investigations presented in Han and Li (2010)and Li and Han (2011), this paper studies the joint model for the composite joint consisted of circular concrete filled steel tubular (CFST) column and steel beam with external diaphragm. The elastic shear stiffness and the shear deformation of the joint panel zone are investigated by parametric study using the finite element analysis (FEA) model. A hysteretic model incorporating the shear stiffness, shear strength, shear deformation and the hysteretic rules is proposed for the panel zone of the composite joint. This hysteretic model is then integrated in a fiber-based joint macro element. The joint macro element is validated by both FEA and experimental results. The overall and the local behavior of CFST joints and frame with macro elements are investigated. The proposed model is featured with a favorable accuracy and amenable modeling method, and could be applied to simulate the seismic behavior of large-scale and complex composite structural systems.     

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。     

Performance of CFTST column to steel beam joints with blind bolts under cyclic loading

The objective of this research is to investigate the seismic performance of the composite joint consisting of square concrete filled thin-walled steel tubular (CFTST) column and steel beam with end plate and blind bolts. The cold-formed square tube in each CFTST column connection was fabricated by seam welding together four pieces of lipped angle with nominal wall thickness 1.5 mm or 3 mm. Four exterior joint specimens were tested under axially compressive load on the top of the columns and cyclic loads on the beam tip. The experimental parameters in the study were the thickness of the steel tube and the type of end plate. The seismic response of the blind bolted moment joints to CFTST columns was analyzed and evaluated in terms of the hysteretic behavior, failure modes, stiffness and strength degradation, ductility, and energy dissipation capacities of the joints. To improve the tension behavior of the blind bolted moment connections to the thin tube wall, the anchorage action of reinforcing rebar welded to the bolts with concrete-filled steel tubes was also investigated to consider the effect of cyclic loading. The experimental and analytical results indicated that when the end plate thickness is not less than 3 mm, the flush or extended end plate joints to CFTST columns exhibited large hysteretic loops and excellent seismic performance, such as ductility and energy dissipation capacity. The proposed innovative blind bolted joint was verified as a reliable and effective solution applied in mid- and low-rise buildings through properly design and detailing.     

半刚性连接梁柱组合节点低周反复荷载试验研究

为研究半刚性连接梁柱组合节点的抗震性能,开展了1个纯钢框架梁柱中节点、2个组合框架梁柱中节点的低周反复荷载试验。梁柱采用平齐式高强螺栓端板连接,试验采用柱顶加载模式。对试件的试验现象、变形、应变和耗能能力等进行了分析和比较。试验结果表明,组合节点相对于纯钢节点而言,由于负弯矩作用下钢筋的抗拉作用和正弯矩作用下混凝土板的抗压作用,其受弯承载力和转动刚度均有较大程度地提高;连接弯矩-转角关系的滞回曲线饱满、稳定,具有良好的耗能能力;平端板连接梁柱组合节点在反复荷载作用下具有较高的承载力和良好的延性,抗震性能良好。     

矩形钢管混凝土柱与钢梁半刚性节点的抗震性能试验研究

本文进行了两种矩形钢管混凝土柱与钢梁半刚性连接节点———加劲端板(SEP)连接节点与双T板(DST)连接节点在柱端低周反复荷载作用下的拟静力试验,目的在于了解这两类节点在不同轴压比下的滞回性能、强度与刚度退化、延性与破坏机制。并与常规焊接翼缘板(WFP)连接节点作了比较。结果表明:不同轴压比对节点转动有一定的影响,加劲端板(SEP)连接节点与双T板(DST)连接节点具有良好的转动延性与耗能能力。     

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.     

Experimental investigation of the influence of steel joints upon the flexural capacity of precast concrete columns

In previous studies, the authors have shown that successful modular construction depends on using the correct types of joint connections. In this experimental study, steel beam–column joint connections were shown to be very efficient in facilitating the construction of modular frames while ensuring sufficient flexural moment capacity at the joints to resist lateral loads. This research also included an investigation of the behavior, the crack pattern, and the flexural moment capacity of concrete columns with hybrid composite joints by means of structural experiments on three specimens. Three column specimens were subjected to cyclic loading under displacement control using an oil jack. The influence of including steel sections at the beam–column joint upon the flexural moment capacity of the column was studied, and the use of concrete–steel hybrid composite joints was found to increase the flexural structural performance of the concrete columns. The flexural moment capacity in the maximum load limit state of a concrete column with steel joints was 43.2% greater than that of a conventional reinforced concrete column without steel joints. The steel section in the joint was found to greatly contribute to the flexural moment capacity and to the modular construction technologies.     

加强环式钢管混凝土柱-钢梁节点的刚性研究

借助ANSYS软件建立实体模型来分析加强环式钢管混凝土柱节点的性能;制作了6个比例1:3的节点模型进行试验,研究节点在不同钢梁尺寸下的受力变形性能和半刚性特性,并利用试验结果对有限元模型的适用性进行了校核,得到与实际相符的有限元模型;然后在此模型基础上,对三种形式的加强环节点进行刚度分析比较,确定计算模型。分析表明,加强环式钢管混凝土柱节点在梁端荷载作用下,之间存在着相对转动;加强环形式对节点刚度有一定影响,整环节点的刚度要比部分环节点刚度大,部分环节点的刚度可按其相对的整环节点刚度的89%进行折减;在所有影响节点刚度的参数中,梁的截面高度影响最大,而梁腹板厚度几乎没有影响;最后确定的该节点的M-θ模型,可以在设计时参考使用。     

Experimental investigation of dry mechanical beam–column joints for precast concrete based frames

This paper proposes dry mechanical beam–column joints for fully restrained moment connections of concrete components. This novel joint can be used for reinforced concrete precast frames and steel–concrete composite precast frames. The new dry mechanical joint consists of extended steel plates with bolts designed to transfer tension and compression forces, providing fully restrained moment connections at the beam–column joint. The extended end plate with bolts introduced for column‐beam joint assembly was originally used in the steel moment frame, as introduced in AISC 358. This study developed similar but unique mechanical joint details for concrete frames in order to provide fully restrained moment connections for both steel–concrete composite precast frames and reinforced concrete precast frames. Experimental and analytical investigations were performed to verify the structural behavior of fully restrained moment connections for concrete components in order to identify the parameters that influence the structural behavior of dry mechanical moment concrete connections. These connections are expected to be used in modular offsite construction for buildings and heavy industrial plants. Copyright © 2016 John Wiley & Sons, Ltd.     

高轴压比下复式钢管混凝土柱 钢梁连接节点抗震性能试验

为了研究高轴压比下复式钢管混凝土柱 钢梁连接节点的抗震性能,按照现行规范设计了3个强柱弱梁型复式钢管混凝土外环板节点试件,进行了低周往复加载试验,研究其在高轴压比下的破坏形态、承载能力、变形能力以及耗能能力等。结果表明:增加水平环板的宽度可以有效提高节点的延性;锚固腹板加肋可以增加梁柱连接节点的初始刚度,增强节点的整体性,从而提高节点的承载能力和耗能能力;节点试件的破坏表现为钢梁翼缘首先发生屈服,随着水平荷载加大,试件同时出现梁端塑性铰和柱端塑性铰的破坏形态,锚固腹板加肋和水平环板加宽的试件在加载后期出现明显的柱端压弯破坏,各节点核心区应力较小,基本处于弹性阶段,因此高轴压比下复式钢管混凝土柱 钢梁连接节点可实现强节点要求,但不能满足“强柱弱梁”的抗震设防要求。     

广府古建筑木结构箍头榫节点抗震性能研究

为研究广府古建筑木结构中广泛采用的箍头榫节点的抗震性能，以梁截面高度、柱直径、梁榫宽和柱顶轴压力为研究参数，设计制作了8个缩尺节点试件进行低周反复荷载试验，得到了不同研究参数下箍头榫节点试件的破坏形态、滞回曲线、骨架曲线、延性、承载力退化、刚度退化及能量耗散能力等。研究表明：各箍头榫节点试件转角达到0.1rad时，仍可维持稳定的承载状态，其承载力退化不明显，具有较好的承载性能以及良好的延性。试件的破坏形态包括柱内侧梁榫顶部(或底部)顺纹拉裂破坏、柱外侧梁榫竖向劈裂破坏和水平劈裂破坏；各节点的弯矩-转角滞回曲线均呈反Z形，且有明显的“捏缩”现象；在试验设计参数范围内，节点的转动刚度、极限弯矩和耗能能力均随着梁截面高度和柱直径的增大而增大，并随着梁榫宽的增大呈现出先增大后减小的趋势，一定范围内改变柱顶轴压力对试件抗震性能影响不大。采用有限元软件ABAQUS建立了箍头榫节点模型，并与试验进行了对比验证，结果表明该模型可较好地模拟反复荷载作用下的节点滞回性能。通过参数分析进一步研究了不同参数下箍头榫节点的弯矩-转角曲线，结果表明节点的屈服弯矩和极限弯矩基本与梁截面高度、柱直径大小呈线性正相关关系。     

Experimental study and numerical analysis of a composite truss joint

This paper presents a model test and numerical finite element analysis (FEA) on the mechanical behavior of a composite joint in a truss cable-stayed bridge. The model test with the scale of 1:2.5 for the truss joint was conduct to fully understand the safety and serviceability. In the experiment, stress distribution, crack resistance ability and shear resistance of headed studs were carefully measured to investigate the mechanical performance, force transmission of the joint part. The maximum strain of the steel plate and concrete chord remained in the linear elastic region until 1.7 times the design load, which means there is a significant safety margin for such composites. On the basis of the experimental results of composite truss joints, three-dimensional finite element models are established. The results of the finite element analysis are in good agreement with those of the tests in terms of strength and stiffness. It is also expected that the results presented in this paper would be useful as references for the further research and the design of composite truss bridges and composite joints.     

法兰连接钢管混凝土柱-钢梁外加强环节点受力性能研究

钢管混凝土柱-钢梁混合结构是工程常用的结构形式.为了有效减小钢管混凝土结构在施工现场的焊接工作量,提高钢管混凝土柱-钢梁节点的安装效率,提出了一种基于法兰连接和外加强环的钢管混凝土柱-钢梁连接装配方法,其特点是采用高强螺栓、刚性法兰盘、外加强环板在同一位置实现了钢管混凝土柱-柱连接、钢管混凝土柱-钢梁连接.对采用该方法...     

榫卯连接组合框架节点受力性能试验及理论分析

为了探索榫卯节点在钢-混凝土组合结构中应用的可行性,提出了一种钢混组合装配式节点——榫卯连接组合框架节点,设计并制作了2个足尺的榫卯连接节点,对其进行梁端单调静载试验,并采用ABAQUS软件进行有限元模拟分析,探讨了梁内钢筋面积的变化对节点破坏模式、承载能力、刚度、弯矩-转角关系等特征的影响。试验结果表明,该节点具有较好的承载能力和延性,梁内钢筋面积的增加使得节点的刚度、正弯矩区承载力有一定的提高,但对节点负弯矩区承载能力影响不大。节点的破坏模式主要为柱壁鼓曲变形、组合梁翼缘楼板受拉断裂。有限元模拟结果与试验结果吻合较好,验证了有限元模型的有效性。最后对该类节点受剪机制进行了分析,结果表明节点核心区受剪承载力主要由钢管、槽钢腹板及核心区混凝土斜压杆组成,并采用叠加方法推导了该类节点核心区的受剪承载力计算式。     

Experimental and Analytical Behavior of Square CFDST Column Blind Bolted to Steel Beam Connections

In recent years, steel or composite beam-column connections adopting blind fasteners have drawn increasing praise due to the rapid development of assembled steel structures. However, limited researches have paid attention to the experimental and analytical behavior of concrete filled double-skin steel tube (CFDST) column blind bolted joints. For investigating the structural performance and seismic behavior of this type of connection, cyclic tests on blind bolted joints to square CFDST columns were carried out to explore the effects of column hollow ratio and end plate type. Finite element analytical modelling of the semi-rigid joint was performed considering complex contact interactions and material models. Good agreement between the test and analytical results was observed in terms of the failure modes and the hysteretic behavior. Substantial parametric analyses were conducted on typical CFDST column connections to observe the influence of parameters including strength of steel tube, column hollow ratio and bolt pretension force. Furthermore, certain constructional measures commonly employed in engineering practice were also discussed. It was concluded that the CFDST column blind bolted to the steel beam joint has favorable seismic behavior and is feasible for application in high-intensity earthquake regions.

     

Experimental and numerical study on cyclic behaviour of steel beam-to-column joints

Ten specimens are tested to investigate the cyclic behavior of beam-to-column joints of steel frames with joint panels. The performances of the joints with respect to strength, rigidity, and hysteretic performance are examined. Three different load-carrying mechanisms can be identified. Panel resistance ratio (R _p ) is presented for predicting the buckling patterns. The validity ofR _p is confirmed through the present experimental results. On the basis of the experimental results of steel beam-to-column moment joints, 3-D nonlinear finite element models are established to analyze the mechanical properties of these connections. The load-displacement curves of the finite element analysis are in good agreement with those of the tests in terms of strength and unloading stiffness. A shear lag phenomenon was captured in the beam flanges by not only experimental results but also numerical analysis. Parametric studies are conducted on the connections under monotonic loading to investigate the influences of connection dimension, resistance ratio on the connection behavior. It was found that the failure modes are influenced by the resistance ratio, while the thickness of joint panels resulting in large effects on the strength and stiffness under shear failure mode.     

预制装配式混合框架屈曲约束狗骨式节点抗震性能试验研究

为充分发挥装配式混凝土结构施工便捷的特性及钢结构中狗骨式钢梁的抗震性能优势,提出了预制装配式混合框架屈曲约束狗骨式节点。该混合框架节点由预制钢筋混凝土柱和预制钢-混凝土混合梁通过高强螺栓连接而成,其中混合梁由屈曲约束狗骨式钢梁段与混凝土梁段采用高强螺栓连接。完成了2个框架中节点及2个框架边节点的低周往复加载试验。通过对节点的破坏形态、滞回曲线、骨架曲线、耗能能力及变形能力、承载力及刚度退化的研究,对节点类型及梁内是否布置预应力筋对该节点抗震性能的影响进行了分析。研究结果表明：该节点的拼装方式采用全螺栓连接,施工便捷;节点的破坏主要集中于钢梁段,达到了塑性铰外移的目的;节点梁内布置预应力筋能明显提高混凝土梁段的抗裂性能及节点整体抗震能力;提出了该节点中梁端受弯承载力计算方法,试验值与计算值吻合较好。     

双钢管混凝土柱与钢筋混凝土间环梁节点抗震性能研究

介绍了新型节点——在双钢管混凝土柱(CFTSTs)与钢筋混凝土梁(RC)之间使用间断套管的环梁节点。由于该节点处外钢管被打断,因此RC梁中纵向钢筋在连接区域能够连续。依靠连续钢筋传递弯矩和剪力;连接区内箍筋起到了限制作用,柱外侧的八角形环梁使受压区得到改善,补偿了外钢管不连续所引起组合柱刚度的减小。在循环荷载下对4个梁-柱组合试样进行试验,研究节点的抗震性能,包括:加载变形性能、典型破坏模式、应力应变分布、能量耗散能力。试验结果显示,节点的抗震性能较好,能够达到抗震设计准则中"强柱弱梁"和"强节点弱构件"的要求。采用有限元模型对相关参数进行分析。