Experimental testing of joints for seismic design of lightweight structures. Part 2: Bolted joints in straps

An experimental testing campaign on tensile bolted joints between straps is reported. Two dominant failure modes are identified: (1) tilting, bearing and tearing of the sheets (TS) and (2) tilting, bearing and net-section failure (NSF). The analysis in terms of ductility and strength shows that bolted connections are less adequate than screwed connections (reported in Part 1 of this paper) for the seismic design of X-braced shear walls in lightweight structures. NSF joints are more ductile than TS joints in the sense that they undergo larger displacements before failure. However, if washers are not used, both types of connections fail before energy dissipation through yielding of the diagonal straps can occur. Some design recommendations to improve the seismic performance of bolted joints, including the use of washers, are given. The accuracy of Eurocode 3 formulas to predict the ultimate load is also analyzed.     

Seismic behavior experimental study of frame joints with special-shaped column and dispersed steel bar beam

To overcome the problem that steel bars are put too close at a flame joint with special-shaped beam and column, mechanical performance of three groups of six RC flame joints with special-shaped (L, T and+) column and dispersed-steel bars-beam on the top floor under cyclic loads were studied. Experimental comparison was conducted between special-shaped (L, T and+) column and normal beams. The cracking load, yielding load, ultimate bearing capacity, failure patterns, and hysteretic properties at joint core area were investigated. The seismic behaviors of the joints with different proportions of dispersed-steel-bar beams were analyzed. The results of experimental analysis indicate that the mechanical and seismic behaviors of frame joints with T-shaped and+-shaped column are nearly not changed when suitable proportion steel bars are dispersed to flange plane. Stiffness degeneration of flame joint with L-shaped column is rather serious due to concrete damage stiffness. Theoretical result indicates that distributing area of the dispersed steel-bar beams in the flange plate should be strictly controlled to avoid anchor destroy.     

Cyclic loading tests and shear strength of steel reinforced recycled concrete beam–column inner joints

To study the seismic behavior and shear strength of steel reinforced recycled concrete (SRRC) beam–column inner joints, four 1:2.5 scaled specimens with different replacement percentage of recycled coarse aggregates were fabricated and tested under cyclic lateral loadings. The failure modes of SRRC joints were observed, and the various mechanical indexes of SRRC joints, including hysteresis loops, envelope curves, load carrying capacity, ductility, energy dissipation capacity, and stiffness degradation, were analyzed. The results indicate that the main failure mode of the SRRC joints is the shearing diagonal compression in the core zone of joint. The seismic behavior of the SRRC inner joints degrade only slightly compared with the ordinary steel reinforced concrete inner joints. Based on the test and analysis results, a modified design method is proposed to calculate the nominal shear strength of SRRC inner joints.     

十字形钢管混凝土柱框架中节点抗震性能试验研究

以十字形截面钢管混凝土异形柱-钢梁框架中柱节点为研究对象,按1∶2比例设计了4个弱节点和强节点模型,通过施加恒定轴压比的竖向荷载和低周反复水平荷载,对节点模型进行了加载破坏试验。试验结果表明:弱节点试件破坏形态为节点核心区剪切破坏,随轴压比增大,试件受剪承载力提高,但其延性性能降低;强节点试件破坏形态为梁端受弯破坏,破坏前经历了较大的塑性变形,延性系数达到了5.65。由此可见,合理地设计钢管混凝土异形柱-钢梁框架中节点,可保证其延性破坏,实现"强柱弱梁,节点更强"的设计原则,满足抗震性能要求。     

型钢混凝土异形柱框架节点抗震性能试验研究

为研究型钢混凝土(SRC)异形柱框架节点的破坏特征和抗震性能,进行了9个中间层边节点、4个角节点和4个中节点的低周反复荷载试验。观察了各类型节点的受力过程及破坏形态,并分析了试件的荷载-位移滞回曲线、承载能力、层间位移角和延性以及耗能能力等力学特性。结果表明:SRC异形柱框架节点的典型破坏形态是节点核心区剪切斜压破坏和梁端弯剪破坏;滞回曲线饱满,层间位移角延性系数及位移延性系数介于1.80~5.63,弹塑性极限层间位移角约为1/67~1/28,等效粘滞阻尼系数介于0.150~0.294,破坏时节点核心区的剪切角约为0.03~0.04。并给出了节点设计建议。     

方钢管混凝土柱与钢梁框架节点的抗震性能试验研究

为验证方钢管混凝土柱与工形钢梁框架节点的破坏特征和抗震性能,本文进行了A、B两组共6个足尺节点试件的低周反复循环加载试验,其中A组三个试件梁端采用栓-焊连接;B组三个试件梁端为全对接焊接。试验结果表明:6个试件的层间位移延性系数μ≈2.28～3.86,弹性极限层间位移角y≈0.001～0.014,弹塑性极限层间位移角u≈0.0297～0.0424,节点梁柱的相对极限塑性转角θu≈0.0163～0.0343rad,能量耗散系数E≈2.029～2.494;A、B两类节点均有良好的抗震性能,在相同轴压比下A类节点的延性较B类略好一些,而耗能能力B类节点却略大一些,但二者相差不大,均满足结构抗震设计的要求。文章还分析了节点域的剪切变形,给出了改造节点设计的几点建议。     

Q690高强钢外伸端板加劲螺栓连接节点抗震性能试验研究

为研究高强钢外伸端板加劲螺栓连接节点的抗震性能和设计方法,基于EC3规范组件法和同步塑性设计理念,设计了3种不同屈服机制的Q690高强钢外伸端板加劲螺栓连接节点,通过循环加载试验研究了节点的破坏模式、刚度和承载力、耗能能力以及应变分布规律等,进一步验证了节点能力设计计算模型的有效性.研究结果表明:高强钢外伸端板加劲螺栓...     

钢筋混凝土框架夹心节点抗震性能试验研究

钢筋混凝土框架结构中通常柱混凝土强度高于梁的混凝土强度,当节点与梁用较低强度混凝土同时浇筑时,便形成钢筋混凝土框架夹心节点。通过11个钢筋混凝土框架夹心节点（包括平面中节点2个,平面端节点2个,改进型平面节点4个,空间中节点、空间端节点、空间角节点各1个）及3个用于对比分析的传统空间节点（空间中节点、空间端节点、空间角节点各1个）的拟静力试验,结合之前完成的7个平面夹心节点试验及6组平面夹心节点与传统节点的抗震性能对比,对钢筋混凝土框架夹心节点的抗震性能进行研究,包括开裂损伤过程、失效模式、位移延性、变形性能、受压承载力、受剪承载力、滞回耗能、梁筋粘结锚固性能等。研究表明：虽然核心区混凝土强度降低对试件抗震性能有一定不利影响,但通常不会改变框架节点的破坏模式,满足剪压比、轴压比、梁柱混凝土强度比、核心区配筋量条件下的夹心节点,其抗震性能大多可以满足结构设计的需求,或采取加插短筋、增设斜筋等加强措施后可以满足。     

配置500 MPa纵筋钢筋混凝土框架顶层端节点抗震性能试验研究

按照《混凝土结构设计规范》（GB 50010—2010）设计了6个配置500 MPa 纵筋的钢筋混凝土框架顶层端节点,并进行了低周反复加载抗震性能试验,验证了规范规定的抗震措施对配置500 MPa 钢筋的顶层端节点的有效性,分析了配置500 MPa 级钢筋的顶层端节点的受力特点、节点区的破坏形态以及节点的综合抗震性能,并与受力条件基本相同的配置 HRB335级纵筋节点的受力性能进行了对比,对采用不同延性指标评价配置不同强度钢筋节点的延性性能差异进行了讨论。     

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。     

钢板攻丝高强螺栓连接钢框架节点力学性能试验研究

对采用钢板攻丝高强螺栓连接的钢框架节点分别进行了高强螺栓拉伸及剪切试验、钢柱法兰连接节点静力及拟静力试验、梁柱半刚性连接静力试验。基于试验数据对节点连接的承载能力、失效模式以及刚度特征等关键问题进行了分析。研究结果表明:由自攻螺纹钢板及高强螺栓构成的连接形式具有良好的抗拉、抗剪性能,以螺杆断裂为最终破坏模式;钢柱法兰连接中法兰板无明显滑移及翘曲,高强螺栓没有拔出或断裂,试件表现出较好的延性和承载能力;梁柱连接表现出典型半刚性特征,桁架梁先于节点域发生破坏,破坏特征为桁架弦杆屈服及斜腹杆屈曲,节点连接符合"强节点、弱构件"的抗震设计原则。     

Seismic behavior experimental study of frame joints with special-shaped column and dispersed steel bar beam

To overcome the problem that steel bars are put too close at a flame joint with special-shaped beam and column, mechanical performance of three groups of six RC flame joints with special-shaped (L, T and +) column and dispersed-steel bars-beam on the top floor under cyclic loads were studied. Experimental comparison was conducted between special-shaped (L, T and +) column and normal beams. The cracking load, yielding load, ultimate bearing capacity, failure patterns, and hysteretic properties at joint core area were investigated. The seismic behaviors of the joints with different proportions of dispersed-steel-bar beams were analyzed. The results of experimental analysis indicate that the mechanical and seismic behaviors of frame joints with T-shaped and +-shaped column are nearly not changed when suitable proportion steel bars are dispersed to flange plane. Stiffness degeneration of flame joint with L-shaped column is rather serious due to concrete damage stiffness. Theoretical result indicates that distributing area of the dispersed steel-bar beams in the flange plate should be strictly controlled to avoid anchor destroy.     

T形钢管混凝土柱-工字钢梁框架顶层边节点抗震性能试验研究

选择T形截面钢管混凝土异形柱-工字钢梁框架顶层边节点为研究对象,按1∶2的缩尺比例设计并制作3个“弱节点”模型和1个“强节点”模型,通过施加恒定轴压比的竖向荷载和低周往复水平荷载,对节点模型进行加载破坏试验,观察节点模型的受力过程和破坏形态,得到水平荷载-柱端位移滞回曲线和骨架曲线,分析节点荷载特征值、延性、耗能以及刚度退化等。试验结果和分析表明：弱节点试件破坏形态主要为节点核心区在剪压复合应力作用下的剪切破坏,随轴压比增大,试件受剪承载力提高,但其延性和耗能能力有所下降;强节点试件破坏形态为钢梁的局部屈曲破坏,节点区基本完好,滞回曲线饱满,延性系数为3.89;合理地设计钢管混凝土异形柱-钢梁框架边节点,可满足抗震延性要求,实现“强柱弱梁,节点更强”的抗震设计目标。     

钢筋混凝土框架节点破坏模式影响因素分析及分化参数研究

钢筋混凝土框架节点受力情况复杂,破坏形式多样,已有的节点抗震设计理论及规范中没有给出明确的节点破坏模式分化的界定方式。选取了典型的足尺框架节点,分析了不同弯矩调幅、混凝土抗压强度、轴压比及剪跨比影响下节点的抗震性能,并在此基础上提出了节点破坏模式分化参数的设计计算方法,进一步明确了节点破坏模式分化的影响因素,为实现节点基于性能的抗震设计提供了理论基础。     

不同连梁节点构造的联肢钢板剪力墙结构抗震性能试验研究

为研究不同连梁节点构造时联肢钢板剪力墙结构的抗震性能,制作了3个缩尺比例为1∶3的联肢钢板剪力墙试件。试件中连梁与柱的连接分别采用隔板贯通式焊接节点、穿芯螺栓节点和悬臂梁段-端板节点,竖向边缘构件采用方钢管混凝土柱。对3个试件进行了拟静力试验,得到了联肢钢板剪力墙的滞回曲线、骨架曲线、特征荷载和位移等指标,分析了结构的延性、耗能能力、承载力及刚度退化等性能。结果表明,各试件位移延性系数均大于5.37,等效黏滞阻尼系数均大于0.211,刚度和承载力退化稳定,承载力退化系数均大于0.91。连梁节点的差异导致各试件的屈服顺序均不相同,采用穿芯螺栓连梁节点的试件,连梁先发生剪切屈服,耗能能力最优;采用悬臂梁段-端板连梁节点的试件,连梁与剪力墙板几乎同时屈服,耗能能力次之;采用焊接连梁节点的试件,连梁因节点焊缝断裂而破坏,试件初始刚度较高,承载力与耗能能力低于其他试件。总体上,各试件的剪力墙板与连梁均发生了较严重的破坏,实现了多道抗震设防的设计目标。     

圆形截面组合柱-钢梁框架节点反复加载性能试验研究

本文以北京LG大厦塔楼为工程背景,采用6个大尺寸试件,对钢梁和钢骨混凝土圆柱组成的框架节点进行了低周反复加载试验。试件包括按“弱梁强柱强节点”设计和“强梁强柱弱节点”设计两种情况。前者发生梁铰型破坏,节点核心区始终基本完好,试件承载力由梁端承载力控制,延性和耗能均满足要求。后者虽发生节点核心区破坏,但其性能明显好于钢筋混凝土框架节点,能满足抗震基本要求;当轴压比从0.16提高到0.32时,节点核心区强度有所提高;在节点附设柱面承压板(FBP板)可提高承载力、延性和耗能能力。在钢骨上焊接栓钉的构造措施可避免粘结破坏。     

震损钢筋混凝土框架节点修复后抗震性能试验研究

针对已震损的钢筋混凝土框架节点加固后的抗震性能,进行了8个带楼板的三维框架节点的预震损、加固和低周反复荷载破坏试验。试验研究了玄武岩纤维和外包钢套两种加固方法,不同的预震损程度,灌缝等因素对加固效果的影响。对加固节点的滞回曲线、骨架曲线、延性系数、承载力及刚度退化等参数的分析可知：玄武岩纤维加固提高节点的承载力作用有限,但提高抗震性能效果明显;外包钢套法在提高节点承载力、刚度及抗震性能各方面均有显著的效果。加固后节点由“弱柱强梁”转变成了“强柱弱梁”的破坏形式。试验表明,通过加固,节点恢复并超过了受损前的抗震性能,说明此类加固方法是合理、有效的。     

不等高H形钢梁-钢管再生块体混凝土柱异型节点抗震性能试验研究

为了研究左右不等高H形钢梁-钢管再生块体混凝土柱异型节点的抗震性能,对2个该类节点试件进行了往复加载试验,考察了再生块体混凝土取代率对节点抗震性能的影响,得到了节点的破坏形式,并建立了节点有限元分析模型,对其抗震性能进行了参数分析。结果表明：在圆钢管混凝土柱异型节点中使用再生块体混凝土,与不使用再生块体混凝土节点相比,其抗震性能差异很小;对于左右不等高H形钢梁-圆钢管混凝土柱异型节点,在加载过程中,上部节点域的应变大于下部节点域的,最终会导致上部节点域发生剪切破坏;在设计时,应以上部节点域作为节点抗剪设计的控制区域;对于合理设计的钢管壁厚,可以避免发生节点区钢管壁剪切破坏。     

型钢混凝土十形柱及其节点抗震性能演变、传递机制及设计理念

为研究型钢混凝土十形柱与型钢混凝土十形柱框架节点在抗震性能方面的演变规律,通过13个型钢混凝土十形柱及其框架节点的反复荷载试验,揭示了型钢混凝土十形柱、十形柱平面节点、十形柱空间节点的震损机理及性能差异,深入分析了配钢形式、加载方向、剪跨比以及轴压比等关键参数对此类构件抗震性能的影响;考虑荷载加载方向对双向受剪性能的影响,提出了型钢混凝土十形柱及其节点的受剪承载力统一预测模型;采用OpenSEEs零长单元并引入荷载加载角对弯曲型破坏的型钢混凝土十形柱双向压弯承载力进行了全过程受力性能模拟并证实其可行性。结果表明：型钢混凝土十形柱及其节点由平面受力转变至空间受力时,其受剪承载力和耗能能力也随之提高;十形柱的位移延性系数最大,而平面节点的位移延性系数最小。试验轴压比在0.5范围内时,提高轴压比有利于构件和节点受剪承载力及耗能能力的增长;试验轴压比小于0.3时,随着轴压比的增大,十形柱及其节点的延性随之提高,而试验轴压比大于0.3时则随之降低。型钢混凝土十形柱及其框架节点的弹性及弹塑性层间变形能力均大于规范规定的要求。基于综合性能研究成果,给出了型钢混凝土十形柱合理配钢形式的设计建议、轴压比控制原理、最不利地震作用验算方向等结构设计理念。