二重钢管防屈曲耗能支撑的有限元分析

设计了12组41种二重钢管防屈曲耗能支撑试件,应用有限元软件ABAQUS对其进行了有限元分析,研究了径厚比、约束比、长细比和边界条件对支撑性能的影响.分析结果表明:二重钢管防屈曲耗能支撑的径厚比取值不大于24、约束比的取值不小于3时,支撑的滞回曲线饱满、稳定;当支撑的长细比增加时,可以通过提高约束比来避免支撑发生整体屈...     

铝管约束轻型防屈曲支撑的实验研究

针对传统的混凝土灌浆型和全钢型防屈曲支撑质量较大,无法适用于大跨空间结构等轻型建筑的问题,本文提出一种铝管约束轻型防屈曲支撑的设计方法。在核心钢管和约束管间设置不同宽度的间隙并对部分核心钢管进行开孔,通过拉压往复试验,研究了间隙和开孔对试件性能的影响,得到构件的相关恢复力特征,并分析了试件相关参数对耗能特性的影响。结果表明,本文设计的轻型防屈曲约束支撑,滞回曲线饱满,耗能效果良好;核心钢管宜开孔且支撑间隙应设置在1 mm左右,以减轻试件端部压力并简化施工工艺。     

间隙与支座类型对开孔三重钢管防屈曲耗能支撑性能的影响

利用ABAQUS有限元分析软件对开孔三重钢管防屈曲耗能支撑进行拉压循环荷载作用下的滞回性能、支撑的承载力及核心管的应力和变形进行模拟分析,研究了核心管与内外约束管之间的间隙和支撑的支座类型对支撑性能的影响。研究结果表明:当间隙为0 mm时,防屈曲耗能支撑在加载过程中出现套箍效应和整体屈曲现象;当间隙为1~2 mm时,加载过程中不出现套箍效应和屈曲现象;当间隙大于3 mm时,三钢管出现明显的弯曲,建议支撑的间隙控制在1~2 mm之间;当支座类型为铰接时,支撑还没屈服就已经屈曲;当支座类型为半刚接时,加载到38 mm时支撑发生屈曲;当支座类型为刚接时,支撑在加载的过程中不出现屈曲现象,在设计的过程中按铰接考虑是偏于安全的。     

钢铅组合防屈曲支撑的滞回性能与参数研究

为简化防屈曲支撑的加工工艺,提高防屈曲支撑的初始刚度和在小变形下的耗能能力,基于现有防屈曲支撑在截面形式与构造方式上的特点,提出了一种新型钢铅组合防屈曲支撑并进行了构造设计。通过有限元数值模拟,分析了钢铅组合防屈曲支撑的耗能特性与效果,建立了恢复力简化模型,并根据理想弹塑性材料本构关系推导出滞回规则。通过对不同设计参数的理论分析和数值模拟,分析了钢铅屈服力比、铅剪切面长宽比、核心段宽厚比和耗能段长度等参数对防屈曲支撑滞回性能的影响。研究结果表明,钢铅组合防屈曲支撑能够提供较大的抗侧刚度,耗能效果良好,加工工艺简单,适合工程应用。     

新型防屈曲耗能支撑的设计、试验及其减震性能研究

设计制作了一种新型全钢、装配式的防屈曲耗能支撑(BRB),给出了主要的理论计算公式,采用有限元方法对其工作过程和机理进行数值模拟并进行了足尺实验研究,最后,将这种装置安装到框架结构,基于非线性动力时程分析评估其减震性能.研究结果表明了简化计算和有限元分析在产品初步设计中的有效性;防屈曲耗能支撑明显减小了结构动力响应,提...     

端部加强型双重钢管防屈曲支撑试验研究

为了研究端部加强型双重钢管防屈曲支撑的力学性能,检验间隙及约束比变化对支撑性能的影响,设计并制作了6个防屈曲支撑试件,通过低周循环加载静力试验,研究了力-位移滞回曲线、恢复力模型、割线刚度变化规律、粘滞等效阻尼比、耗能系数等滞回性能,并比较研究了间隙及约束比变化对防屈曲支撑性能的影响.研究表明:端部加强型双重钢管防屈曲支撑性能稳定,延性较高,具有良好的耗能性能和抗低周疲劳特性,其恢复力特性可以采用双线性模型进行描述;间隙应控制在合理的范围内,大于2mm或为0mm时均不利于内核钢管材料强度的发挥,影响支撑的耗能及延性;随着约束比的增大,耗能能力增强,但增加的幅度变小,在满足约束比限值情况下,约束比的变化对支撑的性能不产生明显的影响.     

防屈曲支撑的研究现状及关键理论问题

防屈曲支撑(BRB)是一种兼具普通支撑和金属阻尼器双重功能的支撑形式,但是必须在通过合理构造以及合理设计方法对各种可能出现的屈曲破坏形态进行有效约束的前提下,防屈曲支撑才能够充当阻尼器的功能。从轴力传递的角度来说,防屈曲支撑中的支撑内芯与约束构件之间是分工的,但从侧向变形约束的角度来说,上述两者又是共同工作的,正是这种相互作用使得此类支撑的工作机理、力学性能以及设计方法均不同于普通支撑,其中的关键理论问题主要表现在支撑内芯与约束构件的相互接触作用、构件稳定性设计方法以及框架与BRB的相互作用等问题上。本文主要针对防屈曲支撑的关键理论问题介绍其研究进展,并指出了有待进一步研究的问题。     

基于OpenSees的防屈曲支撑加固钢筋混凝土框架数值模拟

提出了一种既有钢筋混凝土框架结构的抗震加固方法,该法采用防屈曲支撑提高框架结构体系的水平承载力和耗能能力,利用外包钢进一步提高柱子的抗弯和抗剪承载力。采用开源有限元程序OpenSees,分别建立空钢筋混凝土框架和防屈曲支撑加固钢筋混凝土框架的分析模型,对2榀钢筋混凝土框架的抗震性能进行模拟。防屈曲支撑采用了弹塑性桁架单元模型,加固框架柱混凝土考虑了外包钢的约束作用。将分析结果与拟静力试验结果进行比较,以检验分析模型的准确性,以及研究防屈曲支撑和外包钢对混凝土框架抗震性能的影响。分析结果表明,数值模拟与试验结果吻合较好,验证了基于OpenSees建立的数值模型的准确性;外包钢有效改善了框架柱的抗弯承载力和变形能力;防屈曲支撑显著提高了加固框架体系的水平刚度、水平承载力和耗能能力。     

变厚度钢板内芯防屈曲支撑试验研究

提出了一种变厚度钢板内芯防屈曲支撑（VTBRB）。设计了2个足尺变厚度钢板内芯防屈曲支撑试件,其中:1个试件在变厚度内芯端部设置加劲肋;另1个试件采用无肋式变厚度内芯。通过拟静力试验分析了2种内芯构造形式对变厚度钢板内芯防屈曲支撑的滞回性能、失效模式、受压承载力调整系数和累计塑性变形等的影响。研究表明:2个变厚度钢板内芯防屈曲支撑均表现较好的抗震耗能特性,其受压承载力调整系数均满足相关规范的限值要求。设置加劲肋可以减少变厚度内芯端部无粘结材料的磨损,并可以有效提高变厚度内芯防屈曲支撑的低周疲劳性能。     

带防屈曲支撑的钢管混凝土框架抗震性能参数分析

设置防屈曲支撑的钢管混凝土框架是一种新型钢管混凝土减震结构。采用有限元软件Opensees对设置防屈曲支撑的单层单跨钢管混凝土减震框架进行数值模拟,研究了框架梁柱线刚度比、防屈曲支撑初始刚度以及钢管混凝土柱轴压比等设计参数对该减震结构抗震性能的影响。研究结果表明：1数值模拟和试验结果吻合较好,验证了有限元模型的正确性;2梁柱线刚度比在0.1~0.3之间变化时,钢管混凝土减震框架的抗震性能较好;3BRB耗能支撑的初始刚度K1在40~80kN/mm变化时,减震框架的耗能减震效应较明显;4在合理的钢管混凝土柱轴压比范围内,当轴压比较大时,在钢管混凝土框架中设置防屈曲支撑能明显地提高结构的耗能能力和改善结构的强度退化现象。     

Ductility demands on buckling-restrained braced frames under earthquake loading

Accurate estimates of ductility demands on buckling-restrained braced frames (BRBFs) are crucial to performance-based design of BRBFs. An analytical study on the seismic behavior of BRBFs has been conducted at the ATLSS Center, Lehigh University to prepare for an upcoming experimental program. The analysis program DRAIN-2DX was used to model a one-bay, four-story prototype BRBF including material and geometric nonlinearities. The bucklingrestrained brace (BRB) model incorporates both isotropic and kinematic hardening. Nonlinear static pushover and timehistory analyses were performed on the prototype BRBF. Performance objectives for the BRBs were defined and uscd to evaluate thc time-history analysis results. Particular emphasis was placed on global ductility demands and ductility demands oa the BRBs. These demands were compared with anticipated ductility capacities. The analysis results, along with results from similar previous studics, are used to evaluate the BRBF design provisions that have been recommended for codification in the United States. Thc results show that BRB maximum ductility demands can be as high as 20 to 25. These demands significantly exceed those anticipated by the BRBF recommended provisions. Results from the static pushover and timehistory analyses are used to demonstrate why the ductility demands exceed those anticipated by the recommended provisions.The BRB qualification testing protocol contained in the BRBF recommended provisions is shown to be inadequate because it requires only a maximum ductility demand of at most 7.5. Modifications to the testing protocol are recommended.     

建筑抗震构件中屈曲约束支撑结构研究新进展

详细介绍了近年来中国学者在屈曲约束支撑研究方面取得的研究成果，着重讨论了屈曲约束支撑构件（核心单元、约束机构、无黏结构造层）和整体抗震性能以及设计方法的研究现状。结果表明：屈曲约束支撑以其良好的耗能性能具有很好的发展潜力，屈曲约束支撑的适用范围不断拓展，结构形式更趋多样化，设计方法不断优化。     

Critical limit states in seismic buckling‐restrained brace and connection designs

A welded end‐slot buckling‐restrained brace (WES‐BRB) has been developed at the Taiwan National Center for Research on Earthquake Engineering (NCREE). A steel frame equipped with a WES‐BRB can offer a cost‐effective solution to meet interstory drift and earthquake‐resistant design requirements for seismic steel buildings. According to the WES‐BRB and connection design procedure proposed by NCREE, there are seven key elements of a buckling‐restrained braced frame (BRBF) design that require design checking. In order to assist an engineer with the design of the WES‐BRB members and connections, an innovative cloud service named Brace on Demand has been constructed at NCREE. In this study, using 581 BRBF design examples, the effectiveness of the proposed design procedures to meet all design checks is demonstrated. It is found that the most critical limit states for an initial design are joint region buckling, gusset plate buckling, and gusset‐to‐beam and gusset‐to‐column interface strength. Accordingly, the causes of improper designs and associated strategies for improving the initial designs are discussed in this paper. Recommendations on initial selections including the BRB joint size and gusset plate thickness are given. The paper provides the detailed road map for engineers to develop the spreadsheet for BRB and connection designs. Copyright © 2014 John Wiley & Sons, Ltd.     

Pseudo‐dynamic test of a full‐scale CFT/BRB frame—Part II: Seismic performance of buckling‐restrained braces and connections

This paper is Part II of a two‐part paper describing a full‐scale 3‐story 3‐bay concrete‐filled tube (CFT)/buckling‐restrained braced frame (BRBF) specimen tested using psuedo‐dynamic testing procedures. The first paper described the specimen design, experiment, and simulation, whereas this paper focuses on the experimental responses of BRBs and BRB‐to‐gusset connections. This paper first evaluates the design of the gusset connections and the effects of the added edge stiffeners in improving the seismic performance of gusset connections. Test results suggest that an effective length factor of 2.0 should be considered for the design of the gusset plate without edge stiffeners. Tests also confirm that the cumulative plastic deformation (CPD) capacity of the BRBs adopted in the CFT/BRBF was lower than that found in typical component tests. The tests performed suggest that the reduction in the BRB CPD capacities observed in this full‐scale frame specimen could be due to the significant rotational demands imposed on the BRB‐to‐gusset joints. A simple method of computing such rotational demands from the frame inter‐story drift response demand is proposed. This paper also discusses other key experimental responses of the BRBs, such as effective stiffness, energy dissipation, and ductility demands. Copyright © 2008 John Wiley & Sons, Ltd.     

Effect of non‐moment braced frame seismic deformations on buckling‐restrained brace end connection behavior: Theoretical analysis and subassemblage tests

In‐plane buckling‐restrained brace (BRB) end rotation induced by frame action is a commonly observed phenomenon in buckling‐restrained braced frames (BRBFs). However, its effect on BRB end connection behavior has not yet been clear. In this study, four BRB end deformation modes for quick determination of end rotational demand are proposed for non‐moment BRBF considering different BRB arrangements, installing story of BRBs, and boundary condition of corner gussets connected with column base. Key factors affecting BRB end rotation and flexural moments are examined theoretically by parametric analysis. Subassemblage tests of seven BRB specimens under horizontal cyclic loading were conducted by adopting two loading frames to impose the expected BRB end deformations. It shows that BRB end rotation subjected BRB ends to significant flexural moments, leading to premature yielding of BRB ends or even tendency of end zone buckling. The deformation modes, the flexural rigidity of BRB ends, and the initial geometric imperfections of BRBs were found to have significant influence on BRB end connection behavior. The triggering moment induced by BRB end rotation was the main contributor to end flexural moment. However, the moment amplification effect induced by flexure of BRB end zones became prominent especially for small flexural rigidity of BRB ends. Implications and future research needs for design of BRB end connections are provided finally based on the theoretical and experimental results. Copyright © 2015 John Wiley & Sons, Ltd.     

Development of a ten-element hybrid simulation platform and an adjustable yielding brace for performance evaluation of multi-story braced frames subjected to earthquakes

This paper presents a ten-element hybrid (experimental-numerical) simulation platform, referred to as UT10, which was developed for running hybrid simulations of braced frames with up to ten large-capacity physical brace specimens. This paper presents the details of the development of different components of UT10 and an adjustable yielding brace (AYB) specimen, which was designed to perform hybrid simulations with UT10. As the first application of UT10, a five-story buckling-restrained braced frame and a special concentrically braced frame (BRBF and SCBF) were designed and tested with AYB specimens and buckling specimens representing the braces. Cyclic tests of the AYB, one- and three-element hybrid simulations of the BRBF, and four-element hybrid simulations of the SCBF inside the UT10 confirmed the functionality of UT10 for running hybrid simulations on multiple specimens. The tests also indicated that AYB was capable of producing a stable hysteretic response with characteristics similar to BRBs. Comparison of the results of the hybrid simulations of the BRBF and SCBF with their fully numerical models showed that the modeling inaccuracies of the yielding braces could potentially affect the global response of the multi-story braced frames further emphasizing the need for experimental calibration or hybrid simulation for achieving more accurate response predictions. UT10 provides a simple and reconfigurable platform that can be used to achieve a realistic understanding of the seismic response of multi-story frames with yielding braces, distinguish their modeling limitations, and improve different modeling techniques available for their seismic response prediction.