铝合金芯板防屈曲耗能支撑滞回性能研究

为开发轻质高效的结构耗能阻尼器并将其应用于空间结构振动控制,利用国产铝合金作为防屈曲耗能支撑的核芯材料,并对研制的6个支撑试件进行了拟静力试验。按照稳定理论设计的试件在试验中未发生整体失稳,铝芯板与约束钢管间预留一定间隙并填充锂基润滑脂以消除套箍效应和减小界面摩擦。试验结果显示：支撑在受拉和受压时都能屈服而不屈曲,铝芯板应变强化现象明显,滞回曲线稳定饱满,有较高的耗能能力,其拉压峰值不均匀系数不超过1.3。基于Chaboche钢材循环塑性本构模型,通过试验数据对相关铝材模型参数进行了标定,并将其应用于防屈曲支撑的有限元分析,计算结果与试验曲线吻合良好,相关模型参数能够进一步应用于结构抗震弹塑性分析。     

一字形全钢防屈曲支撑耗能性能试验研究

对一种新型防屈曲支撑进行性能试验研究。该种防屈曲支撑（以下称一字形全钢防屈曲支撑）的内核为一字形钢板,外约束单元为双腹板工字形钢,中间用薄橡胶作为无黏结材料。通过对8个一字形全钢防屈曲支撑试件进行轴向循环往复加载试验,研究了防屈曲支撑的耗能性能以及不同芯材特性、支撑长度对其耗能性能的影响。结果表明：一字形全钢防屈曲支撑的构造合理,所有试件的滞回曲线稳定饱满;芯材特性和支撑长度对于该种防屈曲支撑的耗能性能均有较大影响;以SLY225为芯材的防屈曲支撑,其耗能性能、低周疲劳性能与塑性变形能力均明显优于以SN490B为芯材的防屈曲支撑;SLY225能提供45%以上的附加有效阻尼比;增加支撑长度,防屈曲支撑的塑性变形能力与低周疲劳性能均有所下降。     

Ductility capacity models for buckling-restrained braces

Buckling-restrained braces (BRBs), which are braces that do not buckle in compression, have recently become popular for use in the primary lateral-force-resisting systems of structures located in high seismic regions of the United States. Although testing has shown that BRBs possess high ductility capacity, no generally accepted method yet exists to predict the cumulative plastic ductility capacity of a BRB. This research developed ductility capacity models for BRBs using a statistical framework and the results of past experimental studies. The primary outcome of the research is a model with sufficient accuracy for predicting BRB failure in engineering applications.     

State of the art of buckling-restrained braces in Asia

This paper presents a summary of buckling-restrained braces (BRBs). BRBs show the same load-deformation behavior in both compression and tension and higher energy absorption capacity with easy adjustability of both stiffness and strength. Research and developments of various types of BRBs with different configurations in Asia, especially in Japan, are introduced. Analyses and experiments are illustrated to show the conditions necessary for restraining steel braces from buckling. Some key issues of BRB configurations, such as gap and debonding processing between core braces and encasing members, contraction allowance in BRBs and necessary clearances between restraining panels and surrounding frames, BRB projection stiffening approaches to prevent it from buckling, are also described. Based on initial deflections of core braces, both stiffness and strength requirements of encasing member to prevent buckling of core brace are given. Applications for both new high-rise steel buildings and the seismic retrofit of existing buildings show good prospects of using BRBs.     

不同构造钢板装配式屈曲约束支撑性能试验研究

设计5个钢板装配式屈曲约束支撑（Buckling-Restrained Brace, BRB）试件,对其进行低周反复试验,研究无黏结材料、约束比和加载制度等对其力学性能的影响。结果表明：无黏结材料能有效减小外约束单元与核心单元之间的摩擦力,设置无黏结材料的屈曲约束支撑滞回曲线对称、饱满,耗能性能稳定,有较强的抗疲劳能力;设置无黏结材料钢板装配式屈曲约束支撑等效黏滞阻尼比曲线呈现两阶段双线性的特征;约束比小于1的钢板装配式屈曲约束支撑发生整体屈曲失稳;先压后拉和先拉后压的加载方式对屈曲约束支撑滞回性能基本没有影响;基于屈曲约束支撑先于主体结构屈服和不发生因塑性能力不足而提前破坏的设计原则,工程设计中建议屈曲约束支撑延性系数μmax＞13,累积塑性变形CPD＞1200。     

Experimental optimization studies on steel core lengths in buckling restrained braces

Concentric braced frames are commonly used in steel structures to withstand lateral forces. However, brace hysteretic behavior is asymmetric in tension and compression. These frames typically exhibit substantial strength deterioration when loaded in compression. Consequently, the concept of Buckling Restrained Brace (BRB) has been introduced to overcome this deficiency.The length of a BRB steel core could have a significant effect on its overall behavior since it directly influences the energy dissipation of the member. Furthermore, BRB could be effectively utilized as a damper to dissipate seismic input energy, particularly when used as a fuse within the brace in a frame. Modified BRBs with shorter lengths may be called damper BRBs, because they function as if a typical damper is utilized along any brace member. These damper BRBs are fabricated and tested in this study both experimentally and analytically. Useful insights into local retrofitting of core plates and connections are also provided.     

Experimental investigation on buckling‐restrained braces using mortar‐filled steel tubes with steel lining channels

A new type of buckling‐restrained braces (BRBs) using mortar‐filled steel tubes with steel lining channels is proposed to reduce the frictional force between the core member and the restraining member. After covering the core plate with the unbonding material, steel lining channels are set on the surface along the longitudinal direction, thus transforming the contact property between the core plate and the restraining member from steel–mortar interface to steel–steel interface. First, comparative cyclic tests are conducted on two new BRBs with steel lining channels and one conventional BRB. All the specimens exhibit stable hysteretic performance without visible global or local instability prior to failure. It is confirmed that the steel lining channels can improve the interface evenness between the core plate and the restraining member, reduce the compression strength adjustment factor, and improve the low‐cycle fatigue behavior and energy dissipation capacity of the BRB. Furthermore, the analytical model for the local stability of the restraining tube is proposed when the core plate buckles about the strong axis, and the corresponding practical design criteria are provided. The influence of various core plate layouts on the local stability of the restraining tube is finally investigated.     

Effect of filler material on local and global behaviour of buckling‐restrained braces

The nonlinear response of buildings has attracted a tremendous amount of attention in recent years. Braces, as lateral force‐resisting elements of a structure, are designed to not only react in the elastic region, but also to exhibit nonlinear response beyond the elastic limit. However, buckling in compression drastically degrades the performance of braces under earthquake loading. Buckling restrained braces (BRBs) have been evolved into very effective systems for severe seismic applications. They prevent buckling in compression through the encasing of core steel into a steel tube and confining infill concrete. The effect of infill material is investigated in this research through the use of experimental tests. Filler material may be concrete, grout or mortar, as well as granular material such as compacted aggregate. Moreover, lightweight concrete or lean concrete may be utilized as filler to reduce the overall structural weight. Furthermore, the need for unbonding material may not arise when sand and gravel mixture is used. Nevertheless, the strength of the aggregate should be such that no buckling or strength deterioration is observed. Parametric studies on BRB characteristics are carried out in this research. Results of cyclic loading tests are then provided for individual cases to characterize the effect of response parameters of BRB assemblages. Copyright © 2009 John Wiley & Sons, Ltd.     

Tests of hysteretic behavior for unbonded steel plate brace encased in reinforced concrete panel

Quasi-static tests for ten pieces of the unbonded steel plate brace encased in reinforced concrete panel, which is referred to as the panel buckling-restrained brace (panel BRB), have been carried out. The effects of some constructional details, such as unbonded material, clearance between the panel and the brace, configuration of the steel bar and the edge reinforcement, effective width of the panel, etc., on the hysteretic behavior of the panel BRBs are examined. The results indicate that the panel BRBs with evener unbonded materials, smaller clearance and additional steel bars and ties along the encased braces exhibit better ductility and energy dissipation capacity than the others. The brace under compression appears to exhibit small amplitude flexural buckling with multiple waves, and its ultimate axial force exceeds its yield load capacity significantly due to strain hardening and frictional action. All specimens of panel BRB exhibit a stable performance under the quasi-static loading until local failure of the panel occurs by either flexure or punching shear. The results also reveal that, with the same construction details mentioned above, the hysteretic behavior of the specimens with the effective width panel almost matches that of the specimens with normal weight concrete panel, however, the former kind of panel BRB would be advantageous in the aseismic performance of the buildings because of its lighter weight.     

防屈曲支撑对芯板局部屈曲的约束条件

防屈曲支撑广泛应用于地震区的支撑构件中,该支撑设计中较为关键的极限状态控制是预防其弯曲屈曲。然而,当钢管的壁厚相对于芯板的横截面尺寸小到一定程度时,芯板局部屈曲的约束条件相对于防屈曲支撑的稳定和强度便显得非常关键了。利用了具有各种不同形状的管状约束对防屈曲支撑进行了往复加载试验和数值分析,以研究这种约束的局部屈曲对防屈曲支撑强度和延性的影响。     

Local buckling restraint condition for core plates in buckling restrained braces

Buckling Restrained Braces (BRBs) are commonly used as bracing elements in seismic zones. A key limit state governing BRB design is to prevent flexural buckling. However, when the wall thickness of the steel tube restrainer is relatively small compared to the cross-section of the core plate, the restraint conditions against the local buckling of the core plate can be critical for the stability and strength of the BRB. In this study, cyclic loading tests and numerical analyses of BRBs were carried out using various tube restrainer configurations to investigate the influence of local buckling of the restrainer on BRB strength and ductility.     

双管式挫屈束制(屈曲约束)支撑之耐震行为与应用

挫屈束制(屈曲约束)支撑一般是由十字型或一字型钢板构成之核心单元加上钢管混凝土构成之束制(约束)单元所组成。由于单核心断面之挫屈束制支撑在与构架接合时每一端需使用八片续接板及两套的螺栓，造成接合部分较长且易发生挫屈(屈曲)，为了改善此种挫屈束制支撑与接合，相关研究已发展出以双T型核心配双钢管或双钢板核心配双钢管而组成之双钢管型挫屈束制支撑构件，并已成功地在台大完成一系列之试验，本研究进一步针对大尺寸之单层挫屈束制支撑构架进行试验。研究目的包括：(1)探讨支撑具不同核心长度比例构架之试验与解析行为；(2)研究挫屈束制支撑核心应变与楼层侧位移角之关系；(3)提供含挫屈束制支撑构架之分析与设计建议。由i组V型双钢板双钢管挫屈束制支撑构架之试验显示，支撑核心之极限应变可利用楼层的最大侧位移角需求，以简单的几何关系及支撑核心长度与工作点间长度之比值计算而得，试验结果亦显示，在构架产生最大侧位移角时支撑之核心拉应变会大于相邻支撑之核心压应变，显示两相邻支撑之轴拉力与轴压力在试体巾有互相平衡之趋势，而不会发生最大轴压力显著大于最大轴拉力的现象。     

轻质组装墙板内置钢板支撑滞回性能试验研究

为改善墙板内置钢板支撑的延性,避免钢筋混凝土墙板局部冲切破坏,便于检修内置支撑和减小墙板自重,提出了轻质组装墙板。通过对6个组装墙板内置钢板支撑的试验研究,考察了支撑和墙板的厚度、支撑与墙板间的间隙等构造对支撑滞回性能的影响。试验表明,轻质组装墙板内置Q235钢板支撑具有良好的延性和耗能能力。总体上,墙板内置支撑破坏前骨架曲线呈双折线,支撑屈服后因钢材应变硬化以及支撑和墙板间摩擦等因素,支撑的承载力随侧移的增加而增大。达最大侧移角约1/25时,受拉承载力调整系数范围为1.36～1.61。侧移角在1/25以内时,受压承载力调整系数均小于13,支撑的轴向累积非弹性变形能力远大于200,均满足美国ANSI/AISC 341 16的要求。试件最终因内置支撑受拉断裂而破坏,破坏前滞回曲线饱满稳定。组装墙板保持完好,可重复利用。支撑与墙板间留置适宜间隙后,受压支撑在墙板孔壁内仅发生微幅多波弯曲变形,避免了墙板局部破坏。当仅考虑支撑附件的主钢管和开孔钢板简化计算墙板绕钢板支撑弱轴的欧拉临界力,墙板的欧拉临界力与内置支撑的最大轴向受压承载力之比(约束比)达1.15~2.42,墙板内置支撑不发生受压整体失稳。     

Compressive behavior of central gusset plate connections for a buckling-restrained braced frame

Buckling-restrained braced frames (BRBFs) are used as lateral-load resisting systems in seismic design. The braces in BRBFs are connected to beams and columns by gusset plate connections, and can yield in both tension and compression instead of buckling. Although tests of buckling-restrained braces (BRBs) have demonstrated their ability to withstand significant inelastic axial deformation, large-scale BRBF tests have exhibited central gusset plate buckling before BRBs develop the ultimate compressive strength. To extend and better understand the experimental work, this paper presents an analytical study of the compressive behavior for BRBF central gusset plate connections using the finite element computer program ABAQUS. A model of a previously tested BRBF is conducted to predict experimental buckling load of the central gusset plate and verify the accuracy of a simple model of a central gusset plate connection including a beam and part of the BRB. The out-of-plane deformation of the central gusset plate resembles the buckled shape of a gusset plate with low bending rigidity provided by the BRB end. The experimental buckling load of the central gusset plate cannot be predicted based on the AISC-LRFD approach with an effective column length factor of 1.2. Therefore, a parametric study on the compressive strength of BRBF central gusset plate connections is conducted with various gusset plate dimensions and free-edge stiffeners. An inelastic plate buckling equation together with coefficient charts is proposed to predict ultimate load. For gusset plates with sufficient free-edge stiffener rigidity, the yield load can be developed and increased to the post-yield strength level. A required free-edge stiffener size is also recommended for BRBF central gusset plates to develop compressive yield load.     

防屈曲耗能钢支撑的试验研究

结合自行设计的外包钢筋混凝土防屈曲耗能钢支撑的工程应用项目,完成了7个防屈曲耗能钢支撑和3个普通钢支撑的反复单轴受压和反复拉压试验,比较了两种支撑的受力性能差别。试验研究表明,所设计的防屈曲耗能钢支撑,能使核心钢支撑材料的拉、压强度得到充分发挥;核心钢支撑截面屈服前未发生失稳破坏,达到了防屈曲的目的;核心钢支撑与混凝土之间的无粘结构造措施达到预期要求,且在反复拉压受力下的低周疲劳性能满足工程要求。根据试验结果,提出了防屈曲耗能钢支撑的端部构造措施。     

脱层材料与槽接式挫屈束制支撑的性能研究

挫屈束制支撑耐震性能优劣与否与脱层材料性能有密切关系,首先提出了一种估算脱层不完全因子的方法,利用4组分别使用不同脱层材料的挫屈束制支撑进行构件试验;研究结果表明以黏性橡胶作为脱层材料具有可靠性、经济性与优良的施工性。特别介绍了地震工程研究中心近期所研发的槽接式挫屈束制支撑,并通过3组实尺寸构件试验验证了其耐震性能;测试构件包含一组长度为12.5m,最大抗压强度超过16800kN,核心消能段应变量达3.5%的构件。试验结果表明,新研发的槽接式挫屈束制支撑经济效益极高,迟滞消能行为良好稳定,具有优良的耐震性能,各组试体于试验停止前所累积的总非线性变形量皆超过400倍斜撑屈曲位移量;研究亦显示,非线性结构分析软件PISA3D可准确预测其受力与变形反应。     

某小学教学楼的屈曲约束支撑抗震加固设计

屈曲约束耗能支撑在拉、压两种受力状态下都能达到屈服,是一种集抗侧力和耗能为一体的耗能减震构件。结合学校加固工程特点和支撑受力性能,应用屈曲约束耗能支撑在某平面严重不规则的教学楼中进行加固设计,通过反应谱以及非线性时程分析方法,比较研究采用支撑加固前后教学楼相关信息。结果显示,小震作用下支撑可很好地调整原有结构抗扭和抗侧刚度,大震作用下支撑能有效消耗地震能量,提高结构承载力,加固效果明显。     

新型全钢防屈曲支撑的拟静力滞回性能试验

为减少传统防屈曲支撑(BRB)的十字形支撑内芯在焊接后所产生的残余弯曲变形,提出一种新型全角钢式防屈曲支撑(ABRB)。该支撑的内芯由4个等边角钢通过屈服段无焊接技术组合而成,约束构件则由两个等边角钢沿纵向焊接组合而成。对4个ABRB试件进行拟静力滞回性能试验,重点考察支撑边界条件,支撑端部转动约束构造、内芯外伸段构造以及加力长度等因素对其滞回性能的影响。试验前首先对试件内芯的初始弯曲进行测量,结果表明,绝大多数试件内芯屈服段的相对初始弯曲均有效控制在1/1000以内。拟静力试验结果表明,当支撑端部边界条件为固接时,ABRB的延性及耗能发展最为充分;当支撑两端为铰接且支撑端部无转动约束时则较容易发生内芯外伸段的局部压弯破坏,且当加力长度增加时,局部压弯破坏则越早发生,但该破坏模式可通过在铰接ABRB两端设置转动约束构件的构造予以避免。对试件的抗震性能分析表明,构造合理的ABRB表现出较好的延性以及十分稳定的累积滞回耗能特性,因此ABRB可作为有效的耗能减震装置应用于工程结构中。最后提出进一步改进的建议以及有待深入研究的问题,为此类支撑性能的进一步完善奠定基础。     

屈曲约束支撑装配式混凝土框架结构抗震性能试验研究

消能减震技术能有效地提高装配式混凝土结构的整体抗震性能,改善其破坏模式。然而,目前对屈曲约束支撑装配式混凝土框架结构尚缺乏试验研究。为了获悉屈曲约束支撑装配式混凝土框架的抗震性能和破坏机理,文章进行3榀屈曲约束支撑装配式混凝土框架和1榀现浇混凝土框架的低周反复荷载试验。研究了地震作用下采用整体式和暗牛腿式预制混凝土梁柱节点的屈曲约束支撑装配式混凝土框架抗震性能,观察和记录试验现象和破坏特征,对各试件的滞回曲线、刚度退化、耗能能力、骨架曲线和延性系数等进行对比分析。试验结果表明：屈曲约束支撑装配式混凝土框架具有良好的耗能能力和延性,能量耗散系数E=1.464?1.759,延性系数?=3.02~3.61,屈曲约束支撑可以有效地提高装配式混凝土框架的抗震性能,改善其失效模式;研发的支撑与梁柱连接节点的连接构造可以有效地实现屈曲约束支撑与装配式混凝土框架在地震作用下的协同受力。文中研究成果将为屈曲约束支撑在多高层装配式混凝土结构中的设计和应用提供科学依据。     

屈曲约束支撑体系的应用与研究进展(Ⅰ)

屈曲约束支撑框架体系(BRBF)是新近发明并逐渐得到应用的一种抗震框架体系。因为屈曲约束支撑(BRB)在受拉和受压时都可屈服而不屈曲,因此克服了传统支撑体系的缺点。本文分两部分,第一部分主要介绍其基本原理和各组成部分的概况、BRBF的特点,还简要介绍了该体系在各国家和地区应用和研究的进展情况。