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.     

Seismic behavior and modeling of high-strength composite concrete-filled steel tube (CFT) beam–columns

The behavior of square concrete-filled steel tube (CFT) beam–columns made from high-strength materials was investigated experimentally. The effects of the width-to-thickness ratio, yield stress of the steel tube and the axial load level on the stiffness, strength and ductility of high-strength CFT beam–columns were studied. Sixteen three-quarter scale CFT specimens, which included eight monotonic beam–column specimens and eight cyclic beam–column specimens, were tested. The experimental results indicate that cyclic loading does not have a significant influence on the stiffness or strength of CFT beam–columns. However, it causes a more rapid decrease of the post-peak moment resistance. The moment capacity of high-strength CFT beam–columns can be predicted with reasonable accuracy using the American Concrete Institute (ACI) code provisions for composite columns.Fiber-based models were developed for the CFT beam–column specimens. The uniaxial stress–strain curves for the fibers were derived from three-dimensional nonlinear finite element analyses of the CFTs. The results from the fiber analyses of the monotonic and cyclic beam–column specimens compare favorably with the experimental results.     

复式钢管混凝土柱与H形钢梁连接节点抗震性能试验研究

借鉴方钢管混凝土柱-钢梁外肋环板节点形式,将非梁柱连接面的柱两侧外肋环板改为竖贴于柱侧的竖向肋板并伸出与梁翼缘焊接,同时设置锚固腹板,形成复式钢管混凝土柱与H形钢梁连接节点。通过7个梁柱组合体试件的低周反复荷载试验,分析各试件的破坏过程及特征,并对试件的滞回性能、承载力、延性、耗能能力和承载力及刚度退化等抗震性能进行研究。研究结果表明：节点的破坏形态基本相同,梁端先屈曲,形成塑性铰;锚固腹板可有效提高节点的承载力和变形能力;竖向肋板外伸长度可提高试件的初始刚度,使梁端塑性铰外移,有效保护节点核心区;试件的滞回曲线呈明显的梭形,具有良好的承载力、延性及耗能能力;试件在整个加载过程中刚度退化现象明显,承载力退化很小,可应用于抗震设防地区。     

后张无黏结预应力干式连接梁柱节点抗震性能试验研究

为研究后张无黏结预应力干式装配梁柱节点在低周往复荷载作用下的抗震性能,对其进行了拟静力试验研究。试验中设计了2个常规现浇梁柱节点和4个装配式梁柱节点,包含中节点和边节点。对比分析了现浇节点和装配节点滞回性能、刚度、承载能力以及变形能力差异。试验结果表明：试验中设计的后张无黏结预应力装配式梁柱节点试件在初始刚度、承载能力、变形能力以及损伤控制等方面均优于传统的现浇节点试件,耗能能力略低;进一步研究了后穿耗能钢筋无黏结段位置对装配节点性能的影响,认为后穿耗能钢筋无黏结段设置在柱外时,装配节点呈现更高的耗能能力和变形能力;装配式节点预应力钢绞线在1/20大位移角下仍能保持弹性,梁柱接触面基本无摩擦滑移,该类装配式节点具有良好的整体性和安全性。     

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。     

宽肢组合异形柱-钢梁节点抗震性能试验研究

为研究适用于高层钢结构住宅体系的组合异形柱框架结构的翼缘加强型节点的抗震性能,设计了两种不同构造形式的足尺节点试件,即格构式宽肢组合异形柱节点和实腹式宽肢组合异形柱节点,并进行拟静力试验,研究了该类节点的破坏形态、滞回性能、承载能力、梁端转角、延性及耗能能力。试验结果表明：2个节点最终均在加强件端部发生了翼缘开裂而破坏;节点的受弯承载力是梁端全截面塑性承载力的1.10~1.13倍;钢梁转角是梁端总转角的主要组成部分,节点区转角只占梁端总转角的1.0%~1.8%,柱变形转角占9.2%~13.0%;节点的位移延性系数约为2.33~2.38,黏滞阻尼系数约为0.264~0.267。此外,2个节点的承载能力基本相当,格构式宽肢组合异形柱节点的抗震性能指标相对实腹式宽肢组合异形柱节点较好;但与传统翼缘加强型节点相比,其延性和耗能能力略有降低。     

钢梁与SRC柱之梁柱接头耐震试验

相对于传统SRC梁接SRC柱的梁柱接头而言,本研究采用钢梁接SRC柱之接头型式,尝试利用SRC柱在劲度与抗压强度之优点,并避开SRC梁在施工上的不便,初步进行了两组大尺寸试体之反复载重试验,以探讨此种型式接头之耐震行为。实验结果显示,由于两组试体之钢梁与钢柱之弯矩强度比并未满足强柱弱梁的规定(但SRC柱整体之抗弯强度仍大于钢梁之强度),因此其反复载重位移曲线并不如满足强柱弱梁的纯钢构接头饱满,而在非弹性阶段出现较明显劲度衰减的现象;但由于SRC柱接头区的混凝土对钢柱提供了良好的围束,使得试体极限强度仍可稳定发展,且两支试体之最大层间变位角均超过5％弧度     

矩形钢管混凝土柱-H型钢梁节点抗震性能试验研究及有限元分析

以天津泰达广场CBD工程A、B区超高层项目为背景,进行了不同连接方法的6个足尺矩形钢管混凝土柱-H型钢梁节点试件拟静力试验,分析了试件的破坏特征、承载力、延性、耗能能力、刚度退化、强度退化等性能。结果表明：在保证焊接及安装质量的前提下不同连接方法节点均具有较高的承载力及良好的抗震性能;在梁翼缘两侧焊接加强板有利于节点承载力的提高,矩形钢管中填充混凝土有利于减小节点核心区的剪切变形,提高节点的强度及刚度。利用ANSYS 10.0软件对试件在循环荷载作用下的滞回性能进行非线性模拟计算,并将理论分析结果与试验结果进行对比。对比结果表明,非线性有限元分析得出荷载-位移曲线与试验结果吻合较好,矩形钢管混凝土柱-H型钢梁节点均具有良好的耗能能力。     

设分配梁与内环板传力构造的巨型钢管混凝土柱抗震性能试验研究

针对7个按1∶5缩尺的设置分配梁加内环板传力构造的巨型钢管混凝土柱试件进行拟静力试验研究,考察了轴压比、长细比、管壁宽厚比及纵向T形加劲肋等因素对此类构件抗震新能的影响。研究结果表明,管壁宽厚比大于60的试件,在达到极限荷载之前（约为极限荷载的63%）发生管壁局部屈曲,延性较差;设置T形加劲肋可有效减小管壁宽厚比,提高管壁局部屈曲强度,改善试件的延性性能及耗能能力;试件位移延性系数随轴压比和试件长细比的增大而降低,刚度退化越明显;在低周反复荷载作用下,同时设置分配梁与内环板传力构造的钢管混凝土柱试件破坏时的位移角超过了规范规定的弹塑性层间位移角限值,满足抗震设计要求,且钢管与核心混凝土变形协调,相应的截面属性和压弯承载力可按平截面假定计算。     

方钢管钢骨混凝土柱与钢梁端板螺栓连接节点抗震性能试验研究

为研究方钢管钢骨混凝土柱与钢梁端板螺栓连接节点的抗震性能,进行了5个节点拟静力试验研究,分析了端板厚度、螺栓直径、混凝土强度和轴压比等因素对承载力、弯矩-转角曲线、耗能能力、承载力衰退、刚度退化、延性以及破坏模式的影响。研究结果表明：方钢管钢骨混凝土柱与钢梁端板螺栓连接节点均属于半刚性节点,初始转动刚度随着端板厚度和螺栓直径增大而提高,但节点的极限转动能力随着端板厚度的增大而减小;当承载力由端板或钢梁控制时,其具有良好的转动和耗能能力;试件承载力退化系数在0.8～1.0之间,变化幅度不大,刚度退化相比荷载退化严重;设计中应避免高强螺栓发生脆性破坏。     

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.     

Foundation connections for circular concrete-filled tubes

Concrete filled steel tubes (CFTs) promote economical and rapid construction. They offer increased strength and stiffness relative to structural steel and reinforced concrete. The steel tube serves as formwork and reinforcement to the concrete fill, thereby reducing the labor requirements. CFT components encourage the optimal behavior of each material (concrete and steel) while providing a symbiotic relationship between the two to mitigate undesirable failure modes. The fill increases the compressive strength and stiffness, delays and restrains local buckling of the tube, and enhances ductility and resistance if composite action is achieved.Both rectangular and circular CFT have been employed, but circular CFT provide better performance, because they provide increased confinement of the concrete and composite action. A missing component for circular CFT construction is reliable and ductile connections. The research described herein that investigated and develops design procedures for simple and economical connections of circular CFT piers or columns to reinforced concrete foundations, pile caps and wide cap beams (bridge construction) is presented and evaluated. The connection requires no dowels or internal reinforcement connecting the tube to the footing or cap beam. Experiments and analytical studies evaluate the inelastic seismic performance and establish design criteria for the connection. The seismic performance of a CFT column and connection assembly is compared to a conventional reinforced concrete column. The research shows that the proposed connection develops the full capacity of the composite column. The assembly provides excellent ductility and inelastic deformation capacity under seismic loading while mitigating damage even at larger drift demands.     

L形钢管混凝土柱-H型钢梁全螺栓装配节点抗震性能研究

为同时实现梁柱之间和柱柱之间装配,提出一种适用于多高层钢结构的异形钢管混凝土柱与H型钢梁的全螺栓连接节点.上柱、下柱、L形件与H型钢梁4个模块在工厂制作完成,在施工现场通过螺栓进行装配,可实现梁与柱、柱与柱之间的快速连接.通过改变盖板螺栓数量、加劲肋种类设计了4个节点,对其进行了拟静力试验与有限元分析,获得了节点的滞回...     

法兰连接L形钢管混凝土柱-H型钢梁全螺栓节点抗震性能研究

为降低多高层钢结构的梁柱间的装配难度,提出了法兰连接L形钢管混凝土柱-H型钢梁全螺栓装配节点,包括梁与柱连接和柱与柱连接,梁与柱现场全螺栓连接,柱与柱现场法兰连接。为研究连接件形式及加劲肋对该种节点抗震性能的影响,以改变连接件形式、加劲构造为主要变化参数,设计了4个该类型节点,通过低周反复加载试验和有限元分析获得了节点的破坏模式、滞回曲线、耗能能力和性能指标。研究结果表明：4个节点的滞回曲线均呈梭形,具有良好的耗能能力;节点正负方向的塑性转角超过0.05 rad,满足抗震规范要求;L形连接件与T形连接件均有足够的刚度传递荷载,4个节点的破坏模式、耗能能力与滞回曲线形状较为接近;连接件与梁翼缘之间的滑移提高了节点的延性、耗能能力与转动能力。     

圆形钢管混凝土柱的基础连接件

钢管混凝土柱促进了经济且快速的建设方式。两者的组合增大了结构钢和混凝土的强度和刚度,使用钢管作为模板和核心混凝土的约束减少了工作量。钢管混凝土柱为混凝土和钢材提供了一个共生关系来缓和其不良的失效模式,激发了各种材料的最优性能(混凝土和钢材)。综合作用下,混凝土抗压强度和刚度增大,延缓和抑制了钢管的局部屈曲,并提升其延展性和抗力。矩形钢管混凝土柱与圆形钢管混凝土柱都被应用于实际建设生产中,但由于圆形钢管混凝土柱可以提供更强的混凝土约束和综合作用而拥有更好的性能。对于圆形钢管混凝土柱来说,其缺少可靠的、有延展性的连接件。对这方面的研究调查进行介绍,包括关于圆形钢管混凝土柱柱脚或钢筋混凝土地基柱的简便经济的连接件的开发设计过程,并介绍和评价了桥梁结构中的桩帽与宽桩梁。这种连接件不需要销子和内在的加固就能将钢管与基脚或桩梁相连接。试验分析研究和评估了这种连接件的非弹性抗震性能,并确立了设计标准。将1个装配这种连接件的钢管混凝土柱的抗震性能与传统的钢筋混凝土柱相比较。结果显示,此种连接件进一步增强了组合柱的承载力。这种形式在地震荷载下能提供极佳的延展性和非弹性变形能力,甚至在大侧移情况下也能减轻损害。     

现浇柱叠合梁框架节点抗震性能试验研究

以一幢六层现浇柱叠合梁框架实际工程为背景,按照强柱弱梁、强节点弱构件等原则进行设计,取4个不同位置的现浇柱叠合梁框架节点进行低周反复荷载下的足尺模型试验,对现浇柱叠合梁框架节点的破坏形态、滞回曲线、位移延性、刚度退化、耗能能力、预制梁与预制板之间和预制板与现浇板之间的滑移等进行了较系统的研究。结果表明:4个现浇柱叠合梁框架节点均实现了强柱弱梁、强节点弱构件的设计目标,破坏形态均为梁端受弯破坏形式,节点核心区仅有少量细小裂缝;边节点、中节点和平节点的初裂位置为梁中新旧混凝土界面处,而角节点的初裂发生在柱上;与其他2个节点相比,中节点和边节点的滞回曲线饱满;中节点、边节点和平节点的位移延性高于角节点;4个节点的刚度退化规律基本一致。研究成果可为现浇柱叠合梁框架在地震区的推广应用提供技术依据和基础数据。     

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。     

Hysteresis behavior of concrete filled square steel tube column-to-beam partially restrained composite connections

This study presents the development of an improved detail for a Concrete Filled Steel Tube (CFT) square column-to-beam partially restrained composite connection (PR-CC) and the evaluation of its hysteresis behavior under cyclic loading. The detail of the connection was designed to prevent brittle failure at the bottom of the connection due to the composite effect and to simplify its fabrication process. The suggested connection is a welded type of bottom beam flange connection and the existing PR-CC is a bolted type with a seat-angle. To evaluate their hysteresis behavior, specimens were fabricated at full scale and tested under cyclic loading. Results revealed that the suggested type fractured at the welding zone without a drop in capacity due to the anchors inside the steel tube, and reached over 0.04 radian of the plastic rotational angle. The stiffness of the suggested type was about 10% greater than the existing type because the bolted connection allowed more deformation than the welded connection. Both connections were classified as Semi-rigid connections by stiffness analysis according to Eurocode3. The suggested type can be classified as a partially restrained connection overall under cyclic loading because it reached more than 0.03 rad of an inelastic rotation angle 80% capacity of the maximum moment capacity. This type was evaluated to exhibit equal or more ductility than the existing type. As a result, it is concluded that the welded bottom beam flange connection type can be used in practice for the CFT column-beam connection instead of the existing bolt connection using a seat-angle.     

Cyclic testing of steel column-tree moment connections with weakened beam splices

Traditionally, the beam splice assemblies of column-tree connections are designed according to the full-strength design principle. Actually, the beam splice is set up at a certain distance from the column face, thus the plastic moment capacity of the beam splice does not need to be greater than the plastic moment capacity of the beam. This paper experimentally presents the effects of the weakened beam splice on the seismic performance of column-tree steel moment connections. Cyclic tests of two column-tree connection specimens with weakened beam splices and one specimen following the full-strength design principle were conducted to verify their inelastic behavior and failure modes. The test results showed that the moment resisting capacity of the column-tree connection specimens with weakened beam splices did not obviously decrease. Also, their energy dissipation capacity was better than that of the specimen following the full-strength design principle.     

削切钢盖板梁柱接头设计与耐震行为

本研究的目的为提出新式的梁柱接头以避免在工地现场进行梁柱接头全渗透焊接,同时亦控制塑性变形发生在一简单、可修复的装置(削切盖板)而非钢梁。削切盖板(RFP)以焊接或栓接方式固定于钢管混凝土(CFT)柱,以螺栓或填角焊与梁翼板接合,四组全尺寸削切盖板梁柱接头试体试验结果显示:(1)削切盖板梁柱接头在反复载重作用下均可超越0.04弧度的位移角,而使梁的塑性弯矩强度得以发挥;(2)塑性变形发生在削切盖板而非钢梁上,进而避免钢梁的挫屈;(3)利用有限元素分析程序ABAQUS可预测试体接头的反复载重行为,并证明削切盖板梁柱接头的弹性挠曲劲度与盖板梁柱接头相似,满足刚性接头的劲度要求;(4)削切盖板的非弹性挫屈强度可藉由本研究提出的非线性回归分析模型预测。