内置角钢改进夹心节点抗震性能研究与抗剪承载力计算

梁柱采用不同强度混凝土的节点核心区通常采用同柱等强的高强度混凝土浇筑（传统节点）,而采用同梁等强的低强度混凝土浇筑（夹心节点）可简化施工过程,但同时降低了节点的抗震性能。为研究内置角钢改进夹心节点的可行性,通过一个空间夹心节点和一个内置角钢空间夹心节点试件进行双向等幅低周往复试验研究,对比分析了破坏模式、延性、耗能、刚度、应变和抗剪承载力等方面的差异。结果表明:采取改进和不采取改进措施节点破坏模式均以梁端屈服后的节点破坏为主,但采取改进措施的试件延性和抗剪承载力明显提高,耗能能力、刚度退化和变形能力有一定改善,表明改进措施改善了节点的抗震性能。最后在此基础上,给出了与该文和其他文献试验结果吻合较好的采取或者不采取改进措施夹心节点抗剪承载力计算公式。     

环口板加强后T型管节点落锤抗冲击试验研究

针对管节点抗冲击性能比较差的特点,工程常采用在主管和支管相贯区域焊接环口板的方法进行加强。本文以环口板加强和未加强的T型管节点为研究对象,进行落锤抗冲击比较试验研究。通过比较两类管节点的破坏模态和变形发展规律,并分析其冲击力、位移和应变时程曲线以及荷载-位移关系曲线,揭示环口板加强后管节点的抗冲击工作机理和冲击过程中的能量转换规律。研究成果可为正确评估该类管节点抗冲击性能和制定合理加固方法提供可靠的试验数据和设计建议。     

内置加劲环K型管节点抗冲击性能研究

为揭示内置加劲环K型钢管节点在冲击荷载作用下的抗冲击工作机理,采用高性能落锤冲击试验机进行了4个内置加劲环和1个未加强K型管节点的抗冲击性能试验,得到节点的破坏模态并分析了冲击力时程曲线。建立内置加劲环K型管节点有限元数值分析模型,与试验结果对比验证模型可靠性。分析加劲环几何参数对节点冲击性能指标的影响和冲击能量的耗散机理。研究结果表明:内置加劲环可以增强节点的刚度和强度,加劲环宽度和厚度的增加均使K型管节点抵抗冲击荷载的能力有所提高,且加劲环厚度增大对提高节点抗冲击性能的效果要强于宽度;加劲环先于主管耗能,随着加劲环耗能能力达到峰值,主管开始逐步耗能并成为主要耗能构件;设置加劲环可增大K型管节点的耗能能力,加劲环宽度、厚度越大,节点的耗能量越大,主管的耗能量越少。基于K型管节点在静力荷载作用下的承载力计算公式,通过数值模拟分析得出带有加劲环节点的动力放大系数R,提出内置加劲环K型管节点抗冲击承载力计算公式,并验证公式的有效性。     

空心球节点加肋板的实验应力分析

网架结构中球节点的静力实验研究国内几家曾做过大量工作，提出经验计算公式，但对空心球加单肋板，对提高承载能力，降低应力水平的有关报导较少，本文重点研究了直径为５００ｍｍ壁厚为２０ｍｍ的加肋板与不加肋板两种球，在拉，压受力状态下的应力变化规律，同时对肋板上的应力变化进行了测试，利用电测应力分析的方法进行了实验研究与分析，实验模型，采用首都机场四机位工程所用球节点。     

板柱-剪力墙结构抗震的弹塑性时程分析及失效模拟

罕遇地震作用下,板柱节点主要有弯曲破坏和冲切破坏两种破坏形态,而板柱节点发生冲切破坏后,板传递弯矩的能力迅速降低。模拟板柱节点冲切破坏的滞回曲线,在IDARC程序的基础上增加了考虑冲切破坏的恢复力模型,从而采用了弹塑性时程分析方法对板柱-剪力墙结构进行抗震性能分析。对比分析了板柱-剪力墙结构顶层有梁和顶层无梁两种情况下抗震性能的差异,前者相对于后者而言,并没有显示出很大的优势。     

含屈曲约束连接件的钢框架节点抗震性能研究EI北大核心CSCD

基于屈曲约束和损伤控制的思想,提出了一种含屈曲约束连接件的钢框架节点,连接件的一对核心板传递翼缘轴力并平衡梁端弯矩,对核心板设置了由约束板、填充板和梁外伸翼缘组成的屈曲约束系统。对有无设置约束板的两个试件进行了低周往复荷载试验,分析了节点的滞回曲线、骨架曲线、能量耗散和应变分布,考察了约束板对节点滞回性能的影响;采用有限元软件ABAQUS对该节点进行了数值模拟,研究了核心板螺栓和厚度对该节点滞回性能的影响。结果表明:提出的节点可以达到预期的屈曲约束和损伤控制机制,即核心板率先屈服耗能,约束板可防止核心板发生过大的面外屈曲,主体梁柱保持弹性,节点具有稳定的滞回性能和较大的变形能力;核心板上螺栓预紧力决定了核心板是否会滑移,进而影响滞回曲线的饱满程度,核心板厚度主要影响节点刚度、承载力和损伤分布。最后,理论推导了节点的承载力和变形计算公式,给出了节点理论骨架曲线。     

不同连接方式对钢梁钢柱节点抗爆性能的影响

研究爆炸荷载作用下钢梁钢柱节点的动力学性能,对有效预防整体结构的连续性倒塌具有重要意义。先利用有限元分析软件ANASYS/LS-DYNA对爆炸荷载作用下的钢梁进行数值模拟,并与Amr的实验结果进行对比以验证模型和所用材料参数的合理性;然后研究采用不同连接方式(狗骨式连接和端板螺栓式连接)对钢框架梁、柱节点抗爆性能的影响。研究表明:与端板螺栓式连接相比,在相同爆炸荷载作用下,狗骨式连接时节点的最大应力较小,梁跨中节点的最大挠度最大。由于狗骨式连接在梁的上、下翼缘处进行了一定的削弱处理,使得较长的梁段能同时进入塑性阶段,可有效保护节点。在相同爆炸荷载作用下,端板螺栓式连接时,节点的承载能力和抗塑性变形能力要优于狗骨式连接。     

不同连接方式对钢梁钢柱节点抗爆性能的影响

研究爆炸荷载作用下钢梁钢柱节点的动力学性能,对有效预防整体结构的连续性倒塌具有重要意义。先利用有限元分析软件ANASYS/LS-DYNA对爆炸荷载作用下的钢梁进行数值模拟,并与Amr的实验结果进行对比以验证模型和所用材料参数的合理性;然后研究采用不同连接方式(狗骨式连接和端板螺栓式连接)对钢框架梁、柱节点抗爆性能的影响。研究表明:与端板螺栓式连接相比,在相同爆炸荷载作用下,狗骨式连接时节点的最大应力较小,梁跨中节点的最大挠度最大。由于狗骨式连接在梁的上、下翼缘处进行了一定的削弱处理,使得较长的梁段能同时进入塑性阶段,可有效保护节点。在相同爆炸荷载作用下,端板螺栓式连接时,节点的承载能力和抗塑性变形能力要优于狗骨式连接。     

钢管混凝土格构柱-组合箱梁节点抗震性能试验研究

为验证巨型组合结构体系中钢管混凝土格构柱-组合箱梁节点的破坏特征和抗震性能,进行了节点核心区连接分别为单肢斜撑、交叉斜撑和横隔板三种不同连接构造形式的节点低周反复循环加载试验。分析了各节点形式的荷载-位移滞回曲线和骨架曲线及评价节点抗震性能的主要参数(承载力、延性、刚度退化规律、耗能指数和等效粘滞系数等)。同时,利用ABAQUS对各节点进行了有限元数值计算,并与试验结果进行对比分析进一步对组合节点进行了研究。结果表明:试验与有限元数值计算结果吻合良好,验证了理论分析的正确性;三种不同连接构造形式的节点试件正向具有良好的位移延性,但反向位移延性不及正向,随着节点连接方式的加强,节点的屈服位移逐渐减小,延性增大,节点承载能力逐渐增大。横隔板连接形式节点相对另两种连接构造耗能能力较好,改善了节点的抗震性能。     

钢管混凝土板柱结构点受冲切承载力的研究

本文通过理论分析和试验研究，探讨了钢管混凝土板柱节点的受力性能，对板节点受冲切承载力以及节点的延性进行了分析，并提出了在平衡弯矩和平衡弯矩作用下受冲切承载力计算公式和节点的设计方法及相及相应的构造措施。     

位移放大型转动摩擦阻尼器增强榫卯节点抗震性能试验研究

古建木构中的榫卯节点属于典型的弱连接,地震作用时常常早于构件产生损坏,是预防性加固的关键节点。为提升榫卯节点的抗震性能,提出并设计了一种位移放大型转动摩擦阻尼器。通过对1组未设置阻尼器和3组设置阻尼器的足尺单向直榫节点进行了拟静力试验,得到并对比分析了加固和未加固节点的破坏状态、弯矩-转角关系、骨架曲线、强度退化曲线、刚度退化曲线以及耗能能力,分析了阻尼器的位移放大效应和拔榫抑制能力。结果表明:相对于未加固节点,设置摩擦型阻尼器节点的抗弯承载力最高提升了2.3倍;摩擦阻尼器具有显著的位移放大作用,其最大转动角度为榫卯节点转角的4.5倍;在不显著提升节点刚度的同时大幅度提高了榫卯节点的滞回耗能能力,且提高程度随螺栓预拉应变的增大而增大,最大可提升3.9倍;所研发阻尼器可有效抑制节点拔榫量,且抑制作用随螺栓预拉应变的增大而显著提高。研究结果可为古建木构的科学加固提供技术借鉴。     

不同界面处理方法的自密实混凝土加固框架节点抗震性能试验研究

通过5个自密实混凝土加固框架中节点和1个整浇的对比框架节点进行二次受力下自密实混凝土框架节点的拟静力试验,研究不同界面处理对自密实混凝土加固节点抗震性能的影响。5个加固试件的界面分别采用了凿毛法、刻槽法、凿毛加刻槽法以及凿毛加植筋法等4种方法进行处理。通过对试件破坏过程、新老钢筋应变、荷载位移滞回曲线等试验结果的分析得到:4种界面处理方法均能使自密实混凝土与老混凝土具有较好的协同工作性能,而采用凿毛法与刻槽法相结合或凿毛法与植筋法相结合的加固节点其极限承载力、极限位移、位移延性系数等较单独采用凿毛处理或刻槽处理的效果明显提高,而极限承载力已接近整浇对比试件。     

Bond Analysis of Timber Structures Strengthened with FRP Systems

Abstract: This study focuses on the adhesion analysis of glued joints between Norway Spruce and Carbon fibre reinforced polymer (CFRP) regarding timber reinforcement. An experimental programme was carried out on two different test series to evaluate the behaviour of timber‐CFRP bonded joints. ‘Pull‐Off’ tests were achieved to evaluate the strength of the adhesion connection between materials. Two strengthening techniques [externally bonded reinforcement (EBR), near‐surface mounted (NSM)] and several composite systems (laminate, sheets and textile) were analysed. Through ‘Four Point Bending’ tests, the adhesion behaviour of timber‐CFRP joints along the fibres direction was evaluated. Three trials were performed on models strengthened with different criteria (one EBR and two NSM series), each with three different bonding lengths. The maximum anchor strength of the composite, the effective bonding length between the materials, the medium shear strength developed along the interface and the maximum composite strain for the EBR and NSM reinforcements were obtained. The experimental results were compared with equivalent values from concrete‐CFRP joints found in literature. Furthermore, the theoretical model proposed in Fib Bulletin 14 was calibrated to predict the maximum anchor strength of the composite according to its bonding length. Finally, some recommendations are proposed for the design of timber structures reinforced with CFRP systems.     

Strength and ductility of FRP web-bonded RC beams for the assessment of retrofitted beam–column joints

It is generally accepted that beam–column joints are critical elements of reinforced concrete (RC) buildings subjected to lateral loads, and that they may require specific design treatment following the accepted design philosophy of the strong-columnweak-beam. In earthquake-prone regions, the joints must be designed to allow the dissipation of large amounts of energy into the neighbouring elements without a significant loss of strength and ductility. The frames are often designed carefully based on the strong-column–weak-beam concept and their joints detailed accordingly. Sometimes, though, the detailing is inadequate (example, RC joints designed to earlier codes have insufficient lateral resistance). Web-bonded FRP (fibre reinforced plastic) is one of the few possible strengthening methods that can be used when an inadequately detailed joint is damaged causing severe degradation of the joint’s structural strength. In this paper, the results of some tests on FRP strengthened specimens are presented. The results show that the method is effective and capable of restoring or even upgrading the strength of the system. In addition, using the basic principles of equilibrium and compatibility, an analytical model is presented that simplifies the analysis and design of this strengthening scheme. Based on the model, a range of design graphs are presented for selection of the type and the amount of FRP required upgrading an existing joint to a specified moment capacity and curvature ductility.     

GFRP管-灌浆料修复锈蚀钢管节点受压性能研究

圆钢管焊接节点应用广泛,长期服役后的腐蚀退化问题严重影响其安全性和剩余寿命。为研究GFRP管-灌浆料修复锈蚀钢管节点的效果,对6组未锈蚀、锈蚀未修复和GFRP管-灌浆料修复的锈蚀圆钢管T形节点开展了支管轴压力静载试验。试验结果表明：主管锈蚀导致的约10%重量损失会使节点承载力降低近20%;GFRP管-灌浆料有效地约束了锈蚀主管的侧向外凸变形,使节点的控制破坏模式由主管塑性化转变为主管冲剪,从而使锈蚀节点的受压承载力和初始刚度分别提升约100%和50%,且均高于未锈蚀的对比试件。基于验证的精细化有限元模型,进一步参数分析表明,支主管直径比、GFRP管厚度以及修复主管截面空心率是影响修复节点受压性能的关键参数,主管修复长度和灌浆料强度的影响较小;优化修复构造,可使主管重量损失28%的锈蚀节点承载力提升至锈蚀前的1.5倍以上。最后,基于修复节点承载力达到1.2倍未锈节点的目标,提出了适用于不同节点锈蚀率的修复建议,可为长期服役后锈蚀钢管结构的修复与性能提升提供参考。     

新型误差可调弦支穹顶模型加载试验研究

弦支穹顶结构是一种由上层网壳结构和下层索杆体系复合而成的结构体系,上层网壳节点的初始安装偏差是影响结构受力性能的重要因素之一。为此,提出了多向误差可调节点的概念,容许与节点相连的网格杆件在水平方向、竖直方向和杆件轴线方向进行空间三维多向调整,进而能够调节节点空间几何位置。设计了一种针对弦支穹顶结构的多向误差可调节点,并对其进行了分级加载试验,结果表明该节点受力在加载过程中始终处于弹性范围以内,验证了其安全性和可靠性。然后,制作了一跨度为3m的节点误差可调弦支穹顶模型,提出了误差可调节点的安装调节流程,分别对节点位置误差未调整和调整的结构进行了静力加载试验,试验结果表明:误差调整后的结构试验位移值比未调整的小,误差调整后的结构杆件轴力分布较合理,且荷载-位移曲线和荷载-轴力曲线都具有较好的线性关系,结构的受力性能得到了改善。     

屈曲约束支撑钢筋混凝土框架结构干式柔性梁柱节点的试验研究

建议了一种由受弯框架与采用梁柱柔性节点的屈曲约束支撑框架并联组成的装配式混凝土双重抗侧力体系,设计并完成了4个装配式梁柱节点试件和1个现浇节点试件的往复加载试验。研究了混凝土楼板、螺栓孔形式等因素对该柔性节点受力性能和破坏模态的影响,并与现浇试件进行了对比。试验结果表明:混凝土楼板对柔性节点刚度及承载力有很大的影响,在设计时不可忽略;螺栓孔形式在结构位移较小时对节点的受力性能没有影响,但当结构位移较大时会影响节点的破坏模式;与现浇节点相比,装配式柔性节点具有很大的变形能力。     

支主管夹角对X形圆钢管节点平面外受弯性能影响

应用于单层网壳结构的X形圆钢管相贯节点往往具有支主管平面内非正交、平面外夹角的几何特征。为了研究支主管平面内、平面外夹角对节点平面外受弯性能的影响,进行了支主管平面内夹角不同的两个X形节点试件的平面外受弯滞回性能试验、以及理论研究和有限元分析。研究结果表明:两个节点均表现出较好的抗震性能和变形能力,节点主要依赖主管管壁的塑性变形以及开裂后裂缝扩展来耗能;支主管平面内夹角较小时,节点域主管管壁的塑性发展更加缓慢、均匀,节点具有更高的承载力和抗震性能;支主管平面外夹角导致节点平面外抗弯弹性刚度和反向抗弯承载力降低、但增强了节点的正向抗弯承载力。     

Diffusion bonding of ferritic oxide dispersion strengthened alloys to austenitic superalloys

The superior high temperature mechanical strength and oxidation resistance of ferritic oxide dispersion strengthened (ODS) tubular alloys are compromised by the difficulties encountered in joining. Conventional fusion welding techniques generate a weld fusion zone which is devoid of the mechanical strength exhibited by the base material. Therefore, more sophisticated solid state joining techniques, such as diffusion bonding, must be employed when joining ODS materials. This paper describes a series of solid state diffusion bonding experiments carried out between two tubular ferritic ODS alloys and two high temperature austenitic alloys. Careful control of bonding conditions produced pressure retaining joints between one of the tubular ODS alloys and both austenitic alloys. The successful joint design was incorporated into the manufacture of a tubular creep component, which enabled a series of internally pressurized creep tests to be carried out. The microstructure developed at the bond interface of each of the four separate material couples is described and the high temperature performance of the pressure retaining joints is discussed.     

Behavior and performance of RC T-section deep beams externally strengthened in shear with CFRP sheets

A series of experimental tests were carried out to investigate the behavior and performance of reinforced concrete (RC) T-section deep beams strengthened in shear with CFRP sheets. Key variables evaluated in this study were strengthening length, fiber direction combination of CFRP sheets, and an anchorage using U-wrapped CFRP sheets. A total of 14 RC T-section deep beams were designed to be deficient in shear with a shear span-to-effective depth ratio (a/d) of 1.22. Crack patterns and behavior of the tested deep beams were observed during four-point loading tests. Except the CS-FL-HP specimen, almost all strengthened deep beams showed a shear–compression failure due to partial delamination of the CFRP sheets. From the load–displacement (p–u) curves, the effects of key variables on the shear performance of the strengthened deep beams were addressed. It was concluded from the test results that the key variables of strengthening length, fiber direction combination, and anchorage have significant influence on the shear performance of strengthened deep beams. In addition, a series of comparative studies between the present experimental data and theoretical results in accordance with the commonly applied design codes were made to evaluate the shear strength of a control beam and deep beams strengthened with CFRP sheets.