Seismic Behavior of Diaphragm-Through Connections of Concrete-Filled Square Steel Tubular Columns and H-Shaped Steel Beams

Based on the introductions of a type of diaphragm-through connection between concrete-filled square steel tubular columns (CFSSTCs) and H-shaped steel beams,a finite element model of the connection is developed and used to investigate the seismic behavior of the connection.The results of the finite element model are validated by a set of cyclic loading tests.The cyclic loading tests and the finite element analyses indicate that the failure mode of the suggested connections is plastic hinge at the beam with inelastic rotation angle exceeding 0.04 rad.The suggested connections have sufficient strength,plastic deformation and energy dissipation capacity to be used in composite moment frames as beam-to-column rigid connections.

Seismic performance of interior precast concrete beam-column connections with T-section steel inserts under cyclic loading

An experimental investigation was conducted to study the performance of precast beam-column concrete connections using T-section steel inserts into the concrete beam and joint core,under reversed cyclic loading.Six 2/3-scale interior beam-column subassemblies,one monolithic concrete specimen and five precast concrete specimens were tested.One precast specimen was a simple connection for a gravity load resistant design.Other precast specimens were developed with different attributes to improve their seismic performance.The test results showed that the performance of the monolithic specimen M1 represented ductile seismic behavior.Failure of columns and joints could be prevented,and the failure of the frame occurred at the flexural plastic hinge formation at the beam ends,close to the column faces.For the precast specimens,the splitting crack along the longitudinal lapped splice was a major failure.The precast P5 specimen with double steel T-section inserts showed better seismic performance compared to the other precast models.However,the dowel bars connected to the steel inserts were too short to develop a bond.The design of the precast concrete beams with lap splice is needed for longer lap lengths and should be done at the beam mid span or at the low flexural stress region.

Numerical stress analysis of crack at welded beam-to-column connection

In the past, brittle fracture of steel structure was reported rarely under earthquake. However, recent earthquakes, especially Northridge Earthquake (USA) and Hyogoken Nanbu earthquake (Japan), astonished engineers in the field of construction. The experience from recent earthquakes of USA and Japan shows that brittle fracture of welded steel structure always starts from high stress zone with welded crack [1～5] . As backing bar for grooved weld on beam flange exists, artificial crack is formed because of lack of fusion at the root of flange weld. In this paper stress distribution of connection is computed with FEM, and stress concentration at the root of flange weld is also analyzed. Stress intensity factors (SIFs), K I, at the root of flange weld are computed in the method of fracture mechanics. The computation shows that stress intensity factor on bottom flange weld is obviously higher than that on top flange weld. It is proved by the fact that brittle fracture is liable to start at the root of bottom flange weld on actual earthquake [1,4] . Finally measures are brought forward to avoid fracture of weld structure against earthquake.

Numerical Modeling on Seismic Performance of Castellated Composite Beam⁃Reinforced Concrete Column Connection

The hybrid structure consisting of castellated composite beam and compound spiral hoop reinforced concrete column take full advantages of steel and concrete material.To popularize the structural form in real conditions,a beam⁃through⁃type beam⁃column connection is proposed.Two 1/2⁃scaled connection specimens were tested and three⁃dimensional finite element models of the beam⁃column connection were set up.The longitudinal reinforcements,concrete beam,and column were simulated by link and solid elements,respectively.The influences of the parameters such as expansion ratio,location of web opening,and original height of steel beam were studied.The results show that connections possessed high initial rigidity.The expansion ratio of steel beam showed more important influence on the connection’s ultimate bearing capacity.For the connection models with steel beam expansion ratio of 1.4,the maximum increment of the ultimate bearing capacity of the connection could reach 28%.In order to prevent the local buckling failure of steel beam from occurring near web opening,the expansion ratio of steel beam should not be greater than 1.3.

Experimental study on full-scale steel beam-to-column moment connections

Ten full-scale steel beam-to-column moment connections used in moment-resisting frames （MRFs） were tested to study the failure process, failure mode, strength and plastic rotation capacity. The specimens include one traditional welded flange-bolted web connection, one traditional fully welded connection, four beam flange strengthened connections, three beam flange weakened connections, and one through-diaphragm connection. The test results show that the connections with flange cover plates or with partly cut beam flanges satisfy the beam plastic rotation demand for ductile MRFs. From the measured stress profiles along the beam flange and beam web depth, the mechanics of brittle fracture at the end of the beam is discussed. Design recommendations for steel beam-to-column moment connections are proposed.

Monotonic and Cyclic Pushover Tests of Wood Beam-Column Connections:Ancient Chinese Tenon Joint vs Typical and Simplified US Connections

Wood beam-column frame is a popular structural system in United States and in ancient China. Chinese wood beam-column frame structures showed better seismic resistance properties than the US ones.The tenon joint is one of the reasons.This study performed monotonic and cyclic pushover tests to understand the behavior of Chinese tenon joints versus the behavior of the commonly used US wood beam-column connections. The test results indicate that the typical US wood beam-column connection is very strong under monotonic loads.The ancient Chinese tenon joint has the best behavior under cyclic loads.

部分包覆钢-混凝土组合梁柱节点抗震性能试验研究

为研究不同连接构造的部分包覆钢-混凝土组合梁柱节点(PEC梁柱节点)的抗震性能,对2个PEC梁柱节点试件进行了拟静力加载试验,研究了低周往复荷载作用下PEC梁柱节点试件的破坏现象、滞回曲线、骨架曲线、延性、耗能能力和刚度退化等抗震性能。结果表明:强轴连接PEC梁柱节点的滞回曲线呈梭形和弓形,在达到极限承载力后仍能保持一定的延性和耗能能力;弱轴连接PEC梁柱节点牛腿与梁间的焊缝处发生破坏,未展现出预期的耗能能力,PEC梁仍在弹塑性状态,没有达到极限状态;PEC梁柱节点核心区混凝土替换为加劲肋板后,试件仍具有较好的承载力、延性和耗能能力,刚度退化规律无明显变化,且强轴连接节点与弱轴连接节点刚度变化规律基本一致;PEC柱牛腿设计过短会导致焊缝连接处断裂,试件延性和耗能能力得不到发挥,剩余刚度较大。

模块化钢结构梁柱子结构抗连续倒塌性能研究

模块化钢结构作为一种高度预制的装配式建筑,具有工业化程度高、绿色节能环保等优点。但是,由于模块化钢结构体系超静定次数较低,其在极端荷载工况下的抗连续倒塌性能应予以特别关注。模块化钢结构梁柱子结构作为主要的传力路径,具有多梁多柱等有别于传统框架梁柱子结构的特点,需对其抗连续倒塌性能开展研究工作。该文针对采用螺栓-角件连接节点的模块化钢结构梁柱子结构进行Pushdown试验及数值模拟,分析了在双柱失效、单柱失效工况下试件的破坏模式和抗连续倒塌机理。结果表明,梁柱子结构在两种工况下的受力机理不同:在双柱失效工况下,梁柱子结构抗力主要由梁机制提供,加载后期抗力提供方式体现出一定的悬链线机制,并随水平连接板厚度的增加而增强;在单柱失效工况下,子结构抗力主要由模块间水平连接抗剪能力提供,由梁机制及悬链线机制提供的抗力较小。

基于转动摩擦铰阻尼器的干式装配梁-柱节点抗震性能试验

基于转动摩擦铰阻尼器(RFHD),提出了转动摩擦耗能干式装配梁-柱节点(DRFDBJ)。为了验证DRFDBJ结构对于实现预期力学性能的可行性和合理性,以施加在摩擦片表面的螺栓预紧力(P_(c))为变量,开展了2个工况下的DRFDBJ试件低周往复拟静力试验研究。结果表明:DRFDBJ结构的力学性能主要由RFHD提供并控制,试验中节点呈现了稳定的承载力和理想的变形、耗能能力,并实现了预期的损伤集中;2个不同P_(c)水准下节点承载力的试验值与理论值误差不超过5%,通过调整P_(c)可实现节点承载力的调控,为DRFDBJ结构承载力的可调控提供了支撑。

钢管混凝土柱-钢梁外加强环螺栓连接节点抗震性能有限元分析

为深入研究钢管混凝土柱-钢梁外加强环螺栓连接节点的抗震性能,建立了螺栓连接节点的精细化三维实体有限元模型。在对已有试验成果进行验证分析的基础上,研究加劲肋、螺栓连接数量对节点塑性耗能分配机制的影响。结果表明:当钢材本构后期考虑韧性损伤后,有限元计算结果与已有拟静力试验结果更吻合;CFST-1节点(梁高300 mm,有螺栓垫板)耗能能力最优,但仅达到相应焊接节点的一半;与CFST-1节点相比,CFST-3节点(梁高300 mm,无螺栓垫板)及CFST-2节点(梁高250 mm,有螺栓垫板)的总耗能更低;各螺栓节点的塑性耗能分配机制主要依靠梁耗能,而相应的加强环焊接节点主要依靠梁与加强环耗能;当螺栓节点采用环板加劲肋、4排螺栓以及腹板加劲肋构造优化后,刚度、承载力、延性与相应焊接节点一致,总塑性耗能达到刚接节点的79.1%,基本达到刚接节点的抗震水平。

功能可恢复RCS混合框架结构研究进展

钢筋混凝土柱-钢梁(RCS)混合框架结构以其结合了混凝土优异的抗压性能及钢材优异的抗弯性能而受到广泛关注,而可恢复功能结构以其震后快速恢复使用功能的能力,也成为地震工程界研究的新热点。功能可恢复RCS混合框架结构可以在弯矩较大的梁端和柱脚部位设置可更换构件,实现结构的功能可恢复能力。文中简述了近年来功能可恢复RCS混合框架结构研究进展,重点关注各类型功能可恢复钢梁、功能可恢复摇摆柱脚的构造研究,介绍了功能可恢复RCS混合框架结构性能分析研究进展。最后,对功能可恢复RCS混合框架结构仍需深入研究的问题进行了展望。

蜂窝梁H型柱绕弱轴向端板连接节点抗震性能研究

目的 提出一种蜂窝梁H型柱绕弱轴向端板连接节点,探究节点抗震性能及不同因素对其影响规律,为相关设计提供借鉴。方法 理论分析蜂窝梁H型柱绕弱轴向端板连接节点传力机制,建立并验证蜂窝梁H型柱绕弱轴向端板连接节点ABAQUS模型,研究端板厚度、开孔率对节点初始转动刚度、承载能力、耗能能力、延性、刚度退化及破坏形式影响规律。结果 蜂窝梁H型柱绕弱轴向端板连接节点弯矩最终由柱腹板与正向端板抗弯、柱翼缘与侧向端板抗剪承担;剪力最终由高强摩擦型螺栓连接面间摩擦力承担;端板厚度及开孔率越大,节点耗能进入蜂窝梁耗能阶段越早,连接刚度足够时节点抗震性能主要取决于蜂窝梁。结论 提出了蜂窝梁H型柱绕弱轴向端板连接节点弯矩路径传递分配系数计算方法,建议节点端板厚度应大于1倍柱翼缘厚度,开孔率取值为60%~65%。

带非对称摩擦连接的RCS梁柱节点抗震性能与构造参数研究

基于非对称摩擦连接(AFC)的耗能特点,提出了一种新型的钢筋混凝土柱-钢梁(RCS)梁柱节点,对3组采用AFC连接的RCS梁柱节点进行往复加载试验,考虑了螺栓预紧力、摩擦垫片材料等构造因素对节点抗震性能的影响.结果表明:3组带摩擦连接RCS试件均为梁铰机制破坏,满足“强节点,弱构件”的抗震设计要求;3组试件的滞回曲线具有明显的双平台耗能,滞回曲线饱满稳定,有利于实现两阶抗震设防目标;耐磨钢材料与黄铜材料的两组试件的承载力相近,滞回曲线特征相似,都具有良好的耗能能力;随着螺栓预紧力的增加,试件获得的承载力、刚度也随之大,耗能能力得到了提升,在实际应用中,可通过合理控制预紧力来满足预期所需的滑移荷载与耗能能力.

装配式混凝土梁柱节点连接形式研究进展

装配式混凝土结构的发展是建筑行业转型升级路上的重要一环,而梁柱节点是装配式框架体系的关键部分。预制梁、柱的连接根据是否二次浇筑混凝土可分为湿式连接和干式连接。以连接形式为切入点,对国内外装配式混凝土梁柱节点的研究现状进行归纳,重点介绍节点连接形式研究的最新进展,提出未来研究方向以及可能存在的问题。

不同构造下的钢管混凝土柱-钢梁节点抗震性能研究

与普通节点不同,钢管混凝土柱-钢梁节点在地震作用下更容易发生破坏,为了提高钢管混凝土柱与钢梁连接节点的抗震性能,进行了不同构造下的钢管混凝土柱-钢梁节点抗震性能研究。以预埋锚杆构造的两种钢管混凝土柱-钢梁节点和钢梁穿透式构造的钢管混凝土柱-钢梁节点为研究对象,在梁体中部设置了横向支承,采用层间位移角控制周期性荷载,当地震荷载不同时,测试了3种构造钢管混凝土柱-钢梁连接节点的抗震性能。结果表明,钢梁穿透式构造的钢管混凝土柱-钢梁节点对地震具有较高的承载能力,弱化伸缩梁端节点的构造方法符合抗震设计要求,通过端板的屈曲可以消散大部分能量,具有强大的耗能能力。

湿式连接装配式混凝土梁柱子结构连续倒塌的精细数值分析

为研究湿式连接预制装配式混凝土梁柱子结构的抗连续倒塌性能,采用LS-DYNA有限元软件对前期工作中的三个试件建立了精细化有限元模型。混凝土采用实体单元和CSCM材料模型模拟,钢筋采用梁单元和分段线性塑性材料模型模拟。在梁柱节点区1.5倍梁高范围内考虑钢筋和混凝土的粘结滑移,利用LS-DYNA提供的单元失效功能模拟钢筋断裂和混凝土开裂。机械套筒连接模拟时考虑钢筋尺寸缩减,锚固板模拟按等面积法在梁柱节点建模内并利用关键字*CBIS定义接触防止穿透。数值模拟所得的承载力与试验之间的误差不超过15%,各试件的受力行为和破坏模式与试验一致。

局部高性能装配式混凝土框架梁柱节点抗震性能

采用一种新型的钢筋滞回模型对一种钢绞线锚入式装配混凝土框架梁柱节点进行计算,计算结果与试验结果吻合良好。在此基础上,采用该模型对新型装配式RPC/RC组合框架梁柱节点的滞回曲线、耗能能力、刚度退化、位移延性进行分析,通过分析发现,节点区浇筑RPC并设置摩擦阻尼器的节点PC3极限承载能力较PC2的提升了26.3%,PC1和PC4的极限承载能力相差不大。由于在加载初期,摩擦阻尼器没有完全参与工作,4个节点的耗能能力基本相当,但是随着位移荷载继续施加,摩擦阻尼器完全参与工作后,设置摩擦阻尼器节点PC1和PC3耗能能力明显强于PC2和PC4节点,总体来看,设置摩擦阻尼对节点承载能力和耗能能力是有利的。在上述分析的基础之上,对PC3节点进行参数化分析,通过改变阻尼器摩擦系数和节点区箍筋间距,以得出不同参数变化对节点力学性能的影响。

斜撑对方钢管柱-桁架梁节点抗震性能影响试验

为实现施工现场绿色、高效率、高精度的模块化装配式钢结构建筑的建造,分别提出基于柱座式的带斜撑和不带斜撑的装配式方钢管柱-桁架梁节点。共设计4个十字形足尺试件,并对其进行滞回加载试验。分别考察梁破坏和斜撑破坏模态下试件的抗震性能,探究两种破坏模态产生的原因。评估斜撑对节点极限承载力、延性、刚度以及能量耗散能力等抗震性能的影响,分析两种破坏模态下节点的传力机制,并结合破坏模态和受力特性分别给出带斜撑和不带斜撑节点的设计建议。结果表明:不设置斜撑的试件表现出良好的塑性变形和能量耗散能力等抗震性能;斜撑的设置不仅有效地将塑性铰由桁架梁转移到斜撑端部,而且大幅度地提高节点的承载力和刚度,但在斜撑破坏前桁架梁塑性变形能力受限。整个加载过程中,4个试件的柱座与桁架梁之间的连接未出现破坏,且柱子与柱座之间的法兰板未出现明显的滑移现象,该柱座式连接可靠。

标准化Z字形钢结构梁柱连接节点转动刚度研究

为研究标准化Z字形钢结构梁柱连接节点的转动刚度,对翼缘焊接和搭接两种形式的Z字形钢结构梁柱连接节点进行了单调和往复循环加载试验及有限元分析。研究了不同连接节点设计强度对Z字形钢结构梁柱连接节点转动刚度和循环刚度退化等力学性能的影响。结果表明,翼缘焊接和搭接两种形式的Z字形钢结构梁柱连接节点均具有良好的延性和滞回性能。翼缘焊接Z形节点转动刚度表现为刚性连接,翼缘搭接Z字形钢结构节点转动刚度表现为铰接。对于翼缘焊接Z字形钢结构梁柱连接节点,其转动刚度和循环刚度退化程度受焊缝连接强度影响显著。较小的强度设计倍数(0.2~0.4)时节点破坏模式为焊缝率先发生破坏,其节点转动性能表现为半刚性。较大节点强度设计倍数(0.7~1.1)时节点破坏模式转变为构件率先发生破坏,节点表现为刚性连接且其循环刚度退化程度(转角小于0.02 rad条件下)明显小于强度设计倍数较小的Z字形钢结构节点循环刚度退化程度。总体上看,可通过改变节点强度设计倍数来调节其转动刚度。

新型外包钢板-自攻螺钉连接胶合竹梁柱节点转动性能

针对胶合竹材不易预开槽和预开孔以及节点转动时竹材易发生横纹劈裂的问题,研究了新型外包钢板-自攻螺钉连接节点的转动性能。对T形外包钢板-自攻螺钉连接节点和双L形外包钢板-自攻螺钉连接节点共5个试件进行了单调加载试验,分析了节点的破坏模式、初始刚度、极限承载力、变形能力和延性系数。试验发现,T形外包钢板-自攻螺钉连接节点相较双L形外包钢板-自攻螺钉连接节点,各项受力性能参数均较优。布置直径小但数量多的自攻螺钉时,节点(T8×8-M)的破坏表现为钢板和自攻螺钉的受拉断裂以及与胶合竹柱连接的自攻螺钉受拉断裂,布置直径较大但数量少的自攻螺钉时,节点(T6×10-M)的破坏则表现为竹材的横纹劈裂和自攻螺钉的剪切破坏。横纹方向采用自攻螺丝加强,可改善节点的受力性能,对T形外包钢板-自攻螺钉连接节点改善更明显。现行《工程竹结构设计标准》(T/CECS 1101—2022)提供的节点设计方法偏于安全地预测胶合竹自攻螺钉连接梁柱节点的抗弯承载力。