Seismic behaviour of beam-to-column partial-strength joints for steel-concrete composite frames

The paper presents a large experimental campaign carried out on ten steel-concrete composite beam-to-column sub-assemblages employing monotonic and cyclic loading test protocols. Structural members (beams, columns and slabs) were defined through the design of a full-scale 3D prototype frame subjected to PSD testing campaign; main design hypothesis was to dissipate seismic energy in the joints designed as partial-strength. Testing programme on beam-to-column sub-assemblages was executed in order to assess seismic performance varying structural details at beam-to-column connection level and material qualities. Different mechanical connecting systems between concrete slab and column, two end-plate configurations, weak and strong column web panel, two steel qualities and different concrete strengths.The analysis of sub-assemblages performance was realized in two steps: a first step in which the joints behaviour was assessed, characterizing response at local level (e.g. moment-rotation curves); a second step in which the response was assessed at global level (e.g. force-displacement curves). The structural behaviour (i.e. resistance, plastic deformation and stiffness) was evaluated at three stages-identified as initial, service and maximum load-in order to monitor the evolution of sub-assemblage response increasing solicitation level. Moreover, seismic behaviour of specimens-in terms of dissipated energy, ductility, over-strength and equivalent viscous damping-was also executed. Comparison between experimental results was made in order to identify those parameter suitable for improved and reliable seismic behaviour of steel-concrete composite partial-strength joints.     

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。     

Dynamic response of composite frames with different shear connection degree

The influence of partial composite action between concrete slab and steel beam and of partial-strength connections on the seismic response of composite frames is evaluated. To this end, experimental tests were carried out at the Laboratory of the National Technical University of Athens. The specimens, one-story one-bay moment-resisting frames with steel–concrete composite beams, were tested under base acceleration on the shaking table. Experimental results demonstrated that for different degrees of partial interaction between the slab and the beam the response of the specimens varied significantly. Specimens with intermediate and low shear connection degree showed the most favourable performance, in terms of ductile behavior and energy dissipation. The slip between the slab and the beam interface contributed to the energy dissipated by the system and the ductility demands decreased on other parts like the beam ends and the joints. Then, finite element models simulating the behavior of the tested specimens were developed and, after validation, extended parametric studies were carried out. The main objective is to investigate the influence of the partial interaction and the employment of partially restrained beam-to-column joints on the dissipative capacities of composite frames under strong ground motions. Numerical results confirmed the experimental conclusions and revealed that the use of intermediate and low shear connection degrees with partial-strength joints results in an advantageous seismic design.     

Seismic behavior of steel beam and reinforced concrete column connections

This paper aims to investigate the seismic behavior of steel beam to reinforced concrete column connections with or without the floor slab, acting as a proof test for a three-story-three-bay reinforced concrete column and steel beam (RCS) in-plane frame tested at the National Center for Research on Earthquake Engineering (NCREE), Taiwan, by the Taiwan-USA international research cooperation group. In total, six cruciform RCS joint sub-assemblages were constructed and tested. Parameters considered included composite effects of the slab and beam, the tie configuration in the panel zone, effects of the cross-beam, and the loading protocol. Force-deformation behavior was also simulated by a nonlinear analysis program, DRAIN-2DX, with consideration of composite effects of the beam and slab as well as shear distortion in the panel zone. Test results showed that all specimens performed in a ductile manner with plastic hinges formed in the beam ends near the column face. It was found that the ultimate strength of the composite beam was increased by 27% on average, compared with that of the steel beam without the slab.     

装配式异形柱节点抗震性能试验研究

为了研究新型装配式异形柱节点的抗震性能,更好地推广新节点应用于实际工程,设计制作并进行了2组异形柱节点的拟静力试验。通过观察4个试件的裂缝开展破坏过程,分析每个试件位移、刚度、强度和耗能等抗震指标。结果表明:装配边柱节点与现浇节点的破坏过程和类型基本一致,而两个中柱节点的破坏过程及类型有明显区别;纵筋采用直螺纹套筒和灌浆套筒连接均能够有效传递双向应力,实现钢筋与混凝土的有效传力;叠合板滑移影响装配节点承载力;装配节点的刚度比现浇节点稍低,但因较早屈服,破损位移相近,延性变形优于现浇节点,能够满足基于性能设计的框架结构层间位移角限值2%(生命安全(LS)性能)要求。     

锚固对梁柱端板连接半刚性组合边节点力学性能影响的试验研究

为了研究混凝土翼板外伸锚固的梁柱端板连接半刚性组合边节点力学性能,设计了3个足尺试件,其中两个混凝土翼板外伸150mm,厚度分别为140mm和200mm;另外一个为混凝土翼板未外伸的对比试件。采用柱顶水平位移控制低周循环加载试验,分析了锚固对该半刚性组合边节点力学性能的影响。结果表明,混凝土翼板外伸锚固(尤其是外伸锚固部分加厚)能够提高该半刚性组合边节点的稳定性及其抗震能力。因此,在实际施工中,应该尽可能锚固。     

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.     

胶合木-混凝土组合梁与木柱组合体抗震性能试验研究

木-混凝土组合楼盖已经得到了广泛的应用,但在木结构节点设计中一般均忽略混凝土楼板对节点受力性能的影响。为研究混凝土楼板的组合作用和混凝土板内纵向钢筋配筋率对胶合木-混凝土组合节点抗震性能的影响,对3个胶合木-混凝土组合梁与木柱组合体和1个胶合木梁柱组合体试件进行了低周反复加载试验,研究了试件变形特征与破坏模式、荷载-位移滞回曲线、骨架曲线及组合梁界面相对滑移等的变化规律,探讨了试件承载力、刚度退化及耗能能力等抗震性能指标,并对比分析了纯木与带有混凝土楼板的试件的抗震性能。研究结果表明,胶合木梁与混凝土板的组合作用能显著提高试件的承载力和耗能能力等,且混凝土板对节点的约束作用可以有效抑制其刚度退化;在一定范围内,混凝土板配筋率越大,其对节点的约束作用越大,对刚度退化的抑制作用也越强,从而可有效提高试件的抗震性能。     

短肢墙无粘结预应力楼盖结构顶层端节点抗震性能试验研究

本文通过两个由短肢墙、无粘结预应力现浇板和梁组成的空间组合体结构模型的低周反复加载试验,对采取两种不同构造方案共计4个顶层端节点的受力性能、传力机理以及进入节点区梁、墙肢钢筋的实测应变分布进行了分析研究。研究结果表明,短肢墙顶层端节点上部钢筋的粘结环境很差,梁端受弯屈服后,随着反复荷载作用,充分受力的负弯矩梁筋极易在节点顶部发生粘结退化甚至粘结失效,这种梁筋粘结明显退化和失效将对组合体的整体抗震性能带来较大的不利影响;短肢墙顶层端节点的传力机理不同于普遍框架柱节点,桁架机构是这类节点的主导传力机构;在试验研究的基础上,对短肢墙顶层端节点的构造措施提出了设计建议。     

对钢-混凝土组合连接件的试验分析

对6个全尺寸梁柱节点进行试验研究。钢构件由一个焊接在梁端,与柱翼缘以螺栓连接的钢板组成。所有6个构件的梁截面和混凝土板的尺寸都是统一的。使用了三种类型的柱：光管钢筋柱、部分外包型钢筋柱、全部外包钢筋柱。另外的变量包括楼板中的钢筋面积,柱网中的加劲肋。将从试验中得到的弯矩-转角曲线与分析模型中预测的曲线进行对比。     

木-混凝土梁柱组合节点的受力性能试验研究与理论分析

为探索木-混凝土组合梁在框架结构中运用的可行性,借鉴钢结构顶底翼缘角钢连接,提出了角钢混合连接木-混凝土梁柱组合节点形式,并就其受力性能展开了试验与理论研究.试验中共设计了3个节点试件,即木梁-木柱节点、木-混凝土组合梁与木柱组合节点和木-混凝土组合梁与钢柱组合节点,并对其进行低周反复荷载试验.结果表明:提出的角钢混合...     

Seismic-induced fire resistance of composite welded beam-to-column joints with concrete-filled tubes

Major earthquakes in urban areas have often been followed by significant fires that cause extensive damage to property. Therefore, a seismic-induced fire is a scenario that should be addressed properly in performance-based engineering. In this paper, numerical and experimental results of welded steel-concrete composite full-strength beam-to-column joints under post-earthquake fires are described. This was part of a European project aimed at developing fundamental data and prequalification design guidelines of ductile and fire-resistant composite beam-to-column joints with concrete-filled tubes. In detail, seismic and fire analyses were used to design moment-resisting frames endowed with the proposed joint typology. A total of six specimens were designed and subjected to both monotonic and cyclic lateral loads. The specimens were subassemblages of beam-to-column joints, and performed well. Since the scope of the project was to promote joint typologies able to survive a seismic-induced fire, some specimens were pre-damaged before being subjected to fire loadings by imposing monotonic loads equivalent to damage levels induced by seismic loadings. Thus, after fire testing, valuable information about the performance of the proposed joint typology was obtained, and the adequacy of the concurrent seismic and fire design was demonstrated.     

楼板对钢筋混凝土柱-钢梁空间组合体抗震性能影响研究

楼板在地震作用下对钢筋混凝土柱-钢梁组合体抗震性能的影响是建立地震作用下节点计算模型的基础,也是准确评价组合结构体系抗震性能的关键问题之一。为此,完成了3个钢筋混凝土柱-钢梁(RCS)空间组合体试件在考虑不同楼板宽度情况下的抗震性能试验,分析整个受力过程中楼板受力性态对组合构件受力特征、破坏模式等抗震性能的影响。各试验模型在加载过程中均产生梁铰破坏,并表现出较好的延性和耗能能力,最终因节点区钢梁屈曲、扁钢箍开裂和柱端混凝土压碎而丧失承载力。分析表明,楼板裂缝以横向裂缝为主,随着楼板宽度增加,次生斜裂缝增多,板底混凝土压碎区域增大;混凝土楼板与钢梁组合体对节点核心区的约束作用较明显地改善了空间组合体受力性能。对楼板混凝土和板内纵筋在受力过程中的应变进行分析,结果表明,随着楼板宽度的增加,楼板对RCS空间组合体刚度、承载力的贡献值有限。对现浇板受拉有效翼缘宽度进行分析,结果表明考虑钢-混凝土组合梁翼缘有效宽度对梁端受弯承载力、惯性矩影响较大。     

钢筋混凝土框架边节点现浇板受拉有效翼缘宽度研究

现浇板参与受力会影响甚至改变钢筋混凝土框架节点的破坏模式,其对结构抗震性能的影响可通过计算有效翼缘宽度来反映。通过3个钢筋混凝土梁-柱-板边节点试件的低周反复荷载试验,对带现浇板的边节点破坏形态、滞回曲线以及现浇板纵向钢筋应变等进行了分析。研究结果表明：由于现浇板参与受力,增大了框架梁端弯矩,使得钢筋混凝土梁-柱-板边节点的下柱顶部发生破坏,未能实现“强柱弱梁”预期破坏机制;现浇板纵筋应变随层间侧移角增加而增大,在相同层间位移角下,板筋应变值随距梁侧距离的增大而减小。为进一步对钢筋混凝土梁-柱-板边节点的受力机理进行研究,以力学模型为基础建立了现浇板受拉有效翼缘宽度计算方法,根据建议公式对8组钢筋混凝土梁-柱-板边节点现浇板的有效翼缘宽度进行分析,计算结果与试验结果吻合较好,建议的计算方法有效解决了设计规范中经验公式计算结果离散性大的问题。     

设置垫板的梁柱T形件连接节点抗震性能试验研究

针对传统钢结构梁柱连接在地震中易脆性破坏,改进连接震后不易修复等问题,提出设置垫板的梁柱T形件连接构造措施。设计、制作3个不同形式的梁柱T形件连接试件,分别为未设置混凝土板的连接节点、设置混凝土板的连接节点和未设置混凝土板的传统梁柱T形件连接节点,对其进行往复荷载作用下的拟静力试验,研究试件的抗弯刚度、承载力、延性、滞回性能、耗能能力、破坏模式等。此外,更换梁下部翼缘处已破坏的T形件进行修复,并对修复后的试件进行拟静力试验。结果表明：设置垫板的T形件连接节点在往复荷载作用下具有稳定的滞回性能和良好的耗能能力;破坏试件的梁、柱均不发生屈服,转动中心位于梁端上部翼缘附近,能够保证在地震作用下梁端上部翼缘连接部位不发生破坏,并能够保护梁上混凝土楼板不发生较大的损坏;混凝土楼板的存在会提高节点正弯矩下的初始刚度和承载力,并使弯曲中性轴上移;更换梁下部翼缘处已破坏的T形件进行修复,修复后试件的滞回性能与原试件无明显差异。     

中空夹层钢管混凝土柱与钢-混凝土组合梁节点抗震性能试验研究

以中空夹层钢管混凝土柱与带钢筋混凝土楼板的钢-混凝土组合梁采用高强螺栓及T形钢连接件构成的组合节点的抗震性能为研究对象,对6个十字形组合节点以梁端反对称加载的形式进行拟静力试验。试验中以柱轴压比、加劲肋、T形钢连接件尺寸、楼板厚度和楼板配筋率等为变化参数,研究该组合节点的破坏特征、滞回性能、抗剪性能、承载力衰减、刚度退化规律、耗能特性以及应变变化等力学性能。研究结果表明：柱内置钢管在增加柱受压承载力的同时可以有效增加节点核心区受剪能力,改善了节点整体受力性能;增大楼板配筋率(当1%≤ρ≤ρmax时)和减小柱轴压比(当n≤0.3时)能增强节点总耗能能力,但会降低节点延性且对节点承载力无明显提高作用;T形钢翼缘厚度和设置加劲肋对节点抗震性能影响较大。     

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。     

螺栓连接钢-混凝土组合结构的开发

1994年的Northridge地震和1996年的Kobe地震带给人们的最为惨痛的教训之一就是现代钢结构焊接抗弯节点的开裂和脆性破坏。由此引发的研究所获得的成果导致了设计方法的改进。研究表明．为了改善地震多发地区刚性框架房屋的设计和施工,可以采用钢一混组合抗弯框架体系。由于钢筋混凝土的存在和组合抗弯框架刚度高的特点,内置有型钢的组合节点的变形需求比起纯钢抗弯框架节点来要小得多。而且组合梁一柱节点有着更为顺畅的传力机制和较小的应力集中。因此,组合刚框架的开发可为结构设计和施工提供了许多新的优良的结构体系。为了在保证优良的抗震性能的同时改善可施工性,本文作者设想了几种创新性的组合节点构造．并将对这几种节点构造展开研究。本文描述了作者提出的设计方法以及对试件的分析结果。     

外伸式端板连接蜂窝钢梁-混凝土柱组合节点抗震性能试验研究

通过7个1∶2比例外伸式端板连接蜂窝钢梁-混凝土柱组合节点的低周反复加载试验,研究不同螺栓数目、直径及排列方式的外伸式端板连接蜂窝钢梁-混凝土柱组合节点在各受力阶段的抗震性能和合理的节点构造形式。基于试验数据,分析了节点在反复荷载作用下的破坏形态、滞回曲线、骨架曲线、刚度退化、延性和耗能性能等。试验结果表明：试件的破坏形态和变形与螺栓数目、直径及排列方式有关,外伸端板螺栓连接中螺栓数目多、直径大的节点连接形式的承载力高,抗震性能较好;8个端板螺栓4行2列的排列形式为最合理的抗震节点形式;外伸端板螺栓数量为8个时的延性和耗能性能都能满足抗震的要求。