Seismic Behaviour of Beam-Column Joints of Precast and Partial Steel Reinforced Concrete

A beam-column joint of precast and partial steel reinforced concrete( PPSRC) is proposed for precast reinforced concrete frames. The PPSRC consists of partial steel and reinforced concrete. The partial steel is located in the core joint region and the connections between concrete members. This paper presents an experimental study of a series of PPSRC specimens. These specimens are tested under low cyclic loading.Experimental results demonstrate that the bearing capacity of the PPSRC specimens is 3 times that of the ordinary reinforced concrete( RC) beam-column joints. The strength and stiffness degradation rates are slower compared with that of the RC beam-column joints. In addition,the strength of the core joint region and the connections is higher than other parts of the PPSRC specimens. Beam failure occurs firstly for the PPSRC specimens,followed by column failure and connections failure. The failure of the core joint region occurs finally.Test results show that the seismic performance of the PPSRC is better than that of the ordinary RC beam-column joints.

Study on Strengthening of RC Beam Column Joint Using Hybrid FRP Composites

Beam-Column joints are critical zones in reinforced concrete structures which are most vulnerable to earthquake forces. Hence strengthening beam-column joint is vital to save the structure and its inhabitants in case of seismic forces. Numerous retrofitting works using fibre reinforced polymer (FRP) composites are being undertaken worldwide. This work aims to investigate the effectiveness of strengthening beam-column joints using natural and artificial fibres. In this study, basalt (natural fibres) as monolithic composite (BFRP) and as hybrid composite along with glass (artificial fibres) were used for strengthening of beam-column joints. Totally six specimens were prepared and tested under monotonic loading. Specimen details used were: two control specimen, two specimens for monolithic wrapping and remaining two specimens for hybrid wrapping. The test results were compared with control and rehabilitated specimens. The performance of the treated joints was studied using the following parameters: initial and ultimate cracking loads, energy absorption, deflection ductility and stiffness at ultimate. From the test results, it was found that the hybrid combination of Basalt and Glass FRPs were found to be more effective in the treatment of beam-column joints. The strong column weak beam concept was achieved by failure in beam portion which helped in preventing the catastrophic failure of the entire structure.

Seismic performance of steel reinforced ultra high-strength concrete composite frame joints

To investigate the seismic performance of a composite frame comprised of steel reinforced ultra high-strength concrete （SRUHSC） columns and steel reinforced concrete （SRC） beams, six interior frame joint specimens were designed and tested under low cyclically lateral load. The effects of the axial load ratio and volumetric stirrup ratio were studied on the characteristics of the frame joint performance including crack pattern, failure mode, ductility, energy dissipation capacity, strength degradation and rigidity degradation. It was found that all joint specimens behaved in a ductile manner with flexural-shear failure in the joint core region while plastic hinges appeared at the beam ends. The ductility and energy absorption capacity of joints increased as the axial load ratio decreased and the volumetric stirIup ratio increased. The displacement ductility coefficient and equivalent damping coefficient of the joints fell between the corresponding coefficients of the steel reinforced concrete （SRC） frame joint and RC frame joint. The axial load ratio and volumetric stirrup ratio have less influence on the strength degradation and more influence on the stiffness degradation. The stiffness of the joint degrades more significantly for a low volumetric stirrup ratio and high axial load ratio. The characteristics obtained from the SRUHSC composite frame joint specimens with better seismic performance may be a useful reference in future engineering applications.

Static behavior of semi-rigid thin-walled steel-concrete composite beam-to-column joints with bolted partial-depth flush end plate:experimental study

A new type of semi-rigid thin-walled steel-concrete composite beam-to-column joint has been proposed in this paper.Five semi-rigid composite beam-to-column joint specimens subjected to hogging moments under monotonic loading were tested to study the static behavior of this new type of joint.The main variable parameters for the five joint specimens were the longitudinal reinforcement ratio and the joint type.The experimental results designated that the magnitude of extension of the longitudinal reinforcement is the most important factor that influenced the moment-rotation characteristic of the new type of joint.The concrete slabs could resist 3.8%-19.1% of the total shear load applied to the cross-sections near the beam-to-column connection.The edge stiffened elements,such as the flange of the lipped I-section thin-walled steel beam,were capable of having considerable inelastic deformation capacity although they had comparatively large width-to-thickness ratios.The shear failure of the concrete cantilever edge strip must be taken into account in practical design because it has significant influence on the anchorage of the longitudinal reinforcement in the new type of external joints.

基于CTM和Beam-Column Joint Element的梁柱节点核心区抗剪仿真

为研究基于CTM和Beam-Column Joint Element单元的钢筋混凝土梁柱节点核心区抗震仿真计算,本文先分析了CTM的计算原理和局限性,并对原计算模型进行调整;之后通过试验数据验证了调整前后模型的正确性,并通过参数分析得出调整前后CTM在不同参数下核心区抗剪强度的变化规律;最后通过对比理论计算与试验下核心区抗剪强度变化规律,证明调整后模型更为准确。

Rapid Repair of Earthquake Damaged RC Interior Beam-wide Column Joints and Beam-wall Joints Using FRP Composites

This paper studies the seismic performance of FRP-strengthened RC interior non-seismically detailed beam-wide columns and beam-wall joints after limited seismic damage.Four eccentric and concentric beam-wide column joints and two beam-wall joints,initially damaged in a previous study,were repaired and tested under constant axial loads(0.1fc′Ag and 0.35fc′Ag) and lateral cyclic loading.The rapid repair technique developed,aimed to restore the original strength and to provide minimum drift capacity.The repair schemes were characterized by the use of:(a) epoxy injections and polymer modified cementitious mortar to seal the cracks and replace spalled concrete;and(b) glass(GFRP) and carbon(CFRP) sheets to enhance the joint performance.The FRP sheets were effectively prevented against possible debonding through the use of fiber anchors.Comparison between responses of specimens before and after repair clearly indicated reasonable restoration in strength,drift capacity,stiffness and cumulative energy dissipation capacity.All specimens failed with delamination of FRP sheets at beam-column joint interfaces.The rapid repair technique developed in this study is recommended for mass upgrading or repair of earthquake damaged beam-column joints.

装配式局部活性粉末混凝土梁柱节点恢复力模型

为了验证所提出的装配式局部活性粉末混凝土框架梁柱节点的抗震性能,对4个足尺节点进行了低周反复荷载试验,在试验的基础之上,针对节点的连接特点,提出了强度和变形计算方法,构建了平顶的三折线骨架曲线理论模型.通过理论计算得到试验滞回曲线各阶段曲线刚度值,并拟合得到试件在低周往复荷载作用下各级加载、卸载刚度与加载位移角的关系,进而根据滞回规则建立恢复力模型.计算结果表明:通过理论计算所建立的三折线骨架曲线和滞回曲线与试验结果均吻合较好,能够较好地反映该类连接节点在各阶段的受力特点,为弹塑性分析和抗震设计提供理论依据.

方钢管混凝土柱穿入式组合节点耗能机制

开展了4个翼缘削弱的钢管混凝土柱穿入式组合节点抗震性能与三维实体有限元精细化模型分析。在混凝土三轴塑性损伤和钢材混合强化模型基础上,进一步引入钢材的韧性损伤模型,探讨了钢梁削弱程度对节点抗震性能与破坏形式的影响规律,结果显示引入钢材韧性损伤的有限元模型分析结果与试验结果更加吻合,且钢梁削弱程度降低了该节点的刚度、承载力和耗能。随后对不同钢梁尺寸和柱端拉筋强构造下的组合节点进行了承载力、刚度和塑性耗能分配与失效机制的影响规律分析,分析结果表明:穿入式节点分别在梁-柱抗弯承载力比介于1.66~2.11、梁-柱线刚度比介于1.90~1.96、梁-柱截面刚度比介于1.16~1.21时,将由梁耗能向柱耗能转变;柱端拉筋强构造技术后,由于拉筋直接约束混凝土,大幅度提升了柱端抗弯承载力和耗能能力,组合节点在高轴压比时仍维持梁端失效破坏模式;根据《建筑抗震设计规范》,梁-柱抗弯承载力比取值小于1时为强柱弱梁,这对穿入式组合节点强柱弱梁的定义较为保守。

往复荷载作用后钢管混凝土柱-组合梁节点耐火性能数值分析

为研究钢管混凝土柱-组合梁节点在往复荷载作用后的耐火性能,利用有限元软件ABAQUS建立了该节点的有限元分析模型,并与已有试验结果进行对比验证。在此基础上,分析了往复荷载作用后塑性损伤和残余变形对组合梁节点火灾下的应力和变形的影响,以及不同损伤程度、荷载作用水平和防火保护层厚度对节点耐火极限和破坏模态的影响。结果表明:地震预损伤对节点的耐火极限有不利影响,且随损伤程度的增加,耐火极限下降明显;重度损伤下节点的耐火极限与无损伤节点相比降低了23.5%;重度损伤的节点在火灾作用下形成塑性铰,且产生较大的耗能损伤,轻度和中度损伤下未形成明显塑性铰,耐火极限分别仅下降1.0%和3.6%;对于以梁损伤作为预损伤模式的节点,梁荷载比和防火保护层厚度是影响有地震预损伤节点耐火极限的主要因素;随柱荷载比的增大,耐火极限呈降低趋势,但整体影响不大。

新型钢管混凝土梁柱节点力学性能试验研究

为研究内加强环式圆钢管混凝土柱与矩形钢管混凝土梁这种新型连接节点的力学性能,设计了缩尺钢管混凝土梁柱节点试件,开展了相同梁柱节点试件的静力加载试验和低周往复加载试验。通过研究该节点试件的破坏模式、荷载-位移曲线以及拟静力加载试验的骨架曲线、核心区剪切变形等,分析了节点试件的承载能力、延性和耗能能力,全面考察了同一梁柱节点在静力加载和低周往复加载两种工况下的受力性能和破坏模式。结果表明:钢管混凝土梁柱节点试件核心区强度较强,破坏模式主要为梁端破坏,低周往复加载试验时试件梁柱连接处附近的梁端钢板发生拉裂破坏和钢板鼓曲,静力加载试验时试件梁端焊缝发生拉裂破坏;试件延性较好,加载过程中经历了弹性、弹塑性和塑性发展阶段。最后提出了该类钢管混凝土梁柱节点核心区的抗剪强度计算公式。

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。

预应力混凝土梁-型钢混凝土柱框架节点抗震性能试验研究

预应力混凝土框架结构具有较好的抗裂性能和较高的承载能力,但在实际工程中,裂缝控制要求较为严格,容易出现预应力混凝土框架梁端配筋过多,进而导致梁端承载力过剩,难以实现“强柱弱梁”的抗震设计原则。针对这一问题,提出3种不同连接形式的预应力混凝土梁-型钢混凝土柱节点,通过6个预应力混凝土梁-型钢混凝土柱框架节点试件的低周反复加载试验,研究抗裂等级(影响梁预应力筋数量)、梁柱节点形式对节点破坏形态、滞回曲线、延性、刚度退化等影响规律。研究结果表明:3种不同连接形式的6个试件均发生了“梁端弯剪破坏”,而节点和柱破坏轻微,预应力混凝土框架节点通过使用型钢混凝土柱实现了“强柱弱梁”的抗震设计目标,试件延性和耗能能力较好;二级抗裂的节点试件强度退化、割线刚度退化较三级抗裂更快,抗震性能稍差;三种形式的节点中,形式2节点的强度退化、刚度退化较慢,抗震性能较好,且施工方便。

考虑尺寸效应的RC梁-柱节点抗剪承载力计算方法研究

依据《混凝土结构设计规范》(GB 50010—2010)设计的RC梁-柱节点,其抗剪承载力安全储备随节点尺寸增大而显著降低,这主要是因为节点名义抗剪强度的尺寸效应。首先,基于不同因素对节点名义抗剪强度及其尺寸效应行为的影响规律分析,建立了综合考虑节点配箍率、轴压比及混凝土强度影响的RC梁-柱节点名义抗剪强度尺寸效应公式。然后,通过引入尺寸效应系数,提出了针对《混凝土结构设计规范》(GB 50010—2010)中RC梁-柱节点抗剪承载力计算公式的修正建议。与相关试验数据对比分析表明:基于修正公式设计RC梁-柱节点的抗剪承载力可有效改善大尺寸节点的安全储备。

开槽侧板加强型连接梁柱节点子结构抗连续倒塌性能研究

为了优化侧板加强型节点的抗连续倒塌性能,提出了一种开槽侧板加强型梁柱连接节点形式。通过静力加载试验,得到了新型节点子结构的破坏模式、竖向抗力发展机制、应变分布、延性水平和动力承载力等。试验结果表明:钢梁翼缘在盖板附近首先开裂并向腹板外排螺栓中部延伸贯穿,导致竖向承载力快速下降为峰值荷载的20%左右。相比传统侧板加强型和圆弧扩盖板型梁柱节点,新型节点的峰值承载力分别提高了62.1%和19.6%,塑性弦转角分别提高了203.6%和25.8%。通过有限元分析得到了试件的断裂路径发展过程,进一步地通过参数化分析发现:扩大过焊孔构造对改善峰值后塑性弦转角及残余强度提升无明显作用;随着螺栓群远离钢梁翼缘起始断裂位置,最小残余强度比不断增大,但峰值后塑性弦转角呈先增大后减小的趋势;当螺栓群内移45mm时,峰值后塑性弦转角及最小残余强度比分别达到0.149rad和0.88,提高了38.2%和200.8%。

钢管混凝土柱-钢梁连接节点形式与研究进展

钢管混凝土结构体系中,梁柱节点的受力状态复杂,是结构体系中的关键连接部位,对结构的承载力、刚度以及稳定性能均有重要影响。对国内外钢管混凝土柱-钢梁连接节点的相关研究进行了全面的综述,总结了内加强型连接节点、外加强型连接节点、贯通式连接节点、螺栓连接节点等各类钢管混凝土柱-钢梁连接节点形式的特点和已有研究,从承载力、刚度、破坏模式、抗震性能、设计方法等方面对各类连接节点的优势和存在的问题进行了分析和归纳。旨在为钢管混凝土柱-钢梁连接节点的相关研究提供参考,促进钢管混凝土柱结构体系的研究和工程应用。

混凝土梁柱节点带锚固板钢筋锚固性能试验研究

为研究混凝土梁柱节点带锚固板钢筋锚固性能,共设计33个满足现行规范构造要求的拟梁柱节点试件,通过静载试验分析混凝土强度、锚固长度、锚固板尺寸、箍筋间距等参数对带锚固板钢筋锚固承载力的影响;通过拟合试验数据得到带锚固板钢筋锚固力经验公式,提出带锚固板钢筋锚固长度设计建议,并基于试验数据库对建议公式以及中国规范公式进行了统计分析。结果表明:混凝土强度、钢筋锚固长度和锚固板面积对带锚固板钢筋锚固承载力有较大的影响,而承载力对箍筋间距不是很敏感;锚固板分担的锚固力占总锚固力的70%以上,中国规范对锚固板分担占比的规定偏小,对锚固长度的规定偏于不安全;建议现浇框架中间层梁柱角节点带锚固板钢筋的锚固长度调整为0.45 l_(ab)(l_(ab)为中国规范的基本锚固长度),中间层梁柱边节点的锚固长度可不作调整。

高强螺栓工字钢连接混凝土梁柱节点的抗震性能研究

目的提出一种以高强螺栓工字钢连接混凝土梁柱节点的连接方法,研究该节点抗震性能,为工程设计提供依据。方法采用ABAQUS有限元软件模拟节点的受力过程,研究后浇混凝土强度、节点区长度、工字钢翼缘厚度等参数对节点抗震性能的影响。结果与现浇结构相比,新型节点承载能力更高,其屈服荷载和峰值荷载相较于现浇试件的屈服荷载和峰值荷载分别提升2.08倍和2.64倍;提高后浇混凝土强度等级、增加节点区的长度对承载能力影响较小;提高工字钢翼缘厚度、工字钢屈服强度,节点的承载能力提高较明显。结论采用高强螺栓工字钢连接混凝土梁柱节点的连接结构满足承载力要求,且工字钢翼缘厚度、工字钢屈服强度对结构的承载能力影响较大。

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。

预应力混凝土梁-型钢混凝土柱新型框架节点受剪承载力计算方法

梁柱节点受剪承载力计算是混凝土框架结构节点抗震设计的关键点之一,由于节点剪力传递机理与构造的复杂性,目前尚未形成完善的节点受剪承载力计算理论。该文阐述了预应力混凝土梁-型钢混凝土柱新型框架节点的受力机理,并基于桁架模型和斜压杆模型,提出了一种同时考虑预应力筋与型钢贡献的节点受剪承载力计算方法。开展了新型节点受力性能拟静力试验,分别选取了梁端破坏与节点剪切破坏两种破坏形式的节点试验数据,对所建立的新型节点受剪承载力计算方法进行了验证评估,结果表明,该文提出的预应力混凝土梁-型钢混凝土柱框架节点承载力计算方法具有较好的精度。

钢管混凝土扁柱-钢梁节点抗震性能有限元分析

为避免钢框架结构中梁柱节点凸出墙体,文章提出一种钢管混凝土扁柱与钢梁节点,采用ABAQUS有限元模拟软件建立4个不同连接位置的钢管混凝土扁柱-钢梁节点的有限元模型,分析节点在低周往复荷载下的破坏模式和抗震性能;结果表明,所提出的节点构造可以实现梁柱刚性连接,所有节点均发生梁铰破坏,抗震性能和耗能能力良好。进一步研究轴压比、竖向隔板厚度和连接构造对节点抗震性能的影响规律,结果表明:随着轴压比的提高,柱端峰值承载力随之下降;减小柱内竖向内隔板的厚度会导致柱端承载力的降低;将盖板连接改为竖向加劲肋连接后,能有效缓解节点处柱壁的应力集中现象。