既有RC框架结构BRB加固方案对比研究

为比较附加防屈曲支撑框架和附加摇摆防屈曲支撑框架加固既有RC框架结构后的抗震性能,通过PERFORM 3D软件对两种加固方案下的一幢美国加州20世纪70年代14层RC框架结构进行建模,采用基于性能的抗震设计方法对加固结构进行静力弹塑性分析和动力弹塑性时程分析,比较了两种加固方案下结构层间位移角、层间剪力、防屈曲支撑框架层间剪力比以及结构底柱轴力的不同动力响应。分析结果表明,采用附加摇摆防屈曲支撑框架加固既有RC框架结构更为可行,研究为既有RC框架结构抗震加固提供参考和指导。     

厦门新机场结构耗能减震设计研究北大核心CSCD

结合厦门新机场航站楼指廊工程,研究在复杂框架结构中,通过采用防屈曲支撑减震设计方案来满足结构的抗震性能目标的方法。介绍了本工程的结构体系特点、采用防屈曲支撑的必要性以及防屈曲支撑框架的设计方法。防屈曲支撑框架结构的设计包括构件设计和防屈曲支撑框架结构整体抗震性能分析两大部分内容。作为消能减震构件,防屈曲支撑既能在弹性阶段为主体结构提供抗侧刚度,又能在中震、大震阶段通过自身的滞回耗能为主体结构提供附加阻尼比,减小地震能量。从小震、中震和大震三个阶段,深入分析了防屈曲支撑框架的抗震性能,验证了防屈曲支撑在复杂框架结构中良好的减震效果。     

基于能量平衡的梁柱刚接防屈曲支撑钢框架设计方法

针对梁柱刚接的防屈曲支撑钢框架,根据能量平衡的概念提出基于能量的抗震设计方法,使结构在罕遇地震作用下满足给定的目标位移。设计方法以钢框架与防屈曲支撑在目标位移下耗散的能量之和等于地震输入能量为准则进行能量分配。地震输入能量以原钢框架的地震输入能量为基准,计入结构周期和延性变化的影响进行调整后得到,并以结构在位移幅值下循环1周耗能作为总耗能。建立防屈曲支撑的耗能需求曲线和目标位移下的耗能能力曲线,求得防屈曲支撑的截面面积。应用此方法设计3跨5层的防屈曲支撑钢框架结构,采用ANSYS软件建立有限元模型,对所设计的钢框架结构进行罕遇地震作用下的时程分析,结果表明：应用此方法设计的梁柱刚接防屈曲支撑框架在地震作用下最大层间位移角与给定的设计目标较为一致,所设计的结构安全可靠。     

防屈曲支撑框架与普通支撑框架的抗震性能比较

利用有限元软件ABAQUS6.5对普通中心支撑框架结构、采用低屈服点钢材的防屈曲中心支撑框架结构模型进行了大震时程分析。发现采用低屈服点钢材的防屈曲支撑,不仅解决了支撑杆件的失稳问题,而且明显减小了结构位移等响应,优势明显。     

防屈曲支撑钢框架结构中被撑柱抗震设计探讨

通过3个算例,对采用人字形和V字形的无粘结内藏钢板支撑剪力墙(即人字形和V字形防屈曲支撑)的防屈曲支撑钢框架结构的抗震性能进行分析。重点考察大震下,支撑的轴力分布和对被撑柱所受轴力的影响。分析表明,采用结构在一阶振型下的支撑轴力分布来设计被撑柱的做法,适用于多层的防屈曲支撑钢框架结构;而对于高层的防屈曲支撑钢框架结构,高振型影响较显著,上述设计方法对被撑柱的设计较保守,有必要考虑高振型参与下的支撑轴力分布来设计被撑柱。     

用附加防屈曲支撑钢筋混凝土框架加固既有钢筋混凝土框架抗震性能试验研究

利用附加防屈曲支撑（BRB）钢筋混凝土框架对既有钢筋混凝土框架结构进行减震加固。设计3榀钢筋混凝土框架,其中2榀为附加设置BRB加固框架的钢筋混凝土框架,另外1榀为纯钢筋混凝土框架以作对比。通过低周反复加载试验,验证所设计的外贴防屈曲支撑钢筋混凝土框架加固既有钢筋混凝土框架的可行性。分析既有及外贴钢筋混凝土框架的开裂、荷载 侧移滞回曲线、骨架曲线、荷载 防屈曲支撑变形曲线,以及等效黏滞阻尼比和等效刚度等特性。结果表明：所设计的附加钢筋混凝土框架、预埋件、连接构造受力可靠,附加设置BRB的钢筋混凝土加固框架具有良好的减震耗能能力;水平荷载-侧移滞回曲线圆润饱满;防屈曲支撑在小层间位移角下可屈服耗能,大位移下不失效,耗能稳定;附加框架能够显著增加既有钢筋混凝土框架结构的阻尼,有效降低地震反应,改善既有框架结构抗震性能。     

基于构件损伤的屈曲约束支撑钢框架结构地震倒塌易损性分析

构件参与结构抗震的贡献不同,传统结构地震易损性评价指标不能反映此特点,亦不能准确合理评价结构在地震作用下的抗倒塌能力。地震作用下,防屈曲支撑钢框架结构各构件参与抗震方式不同,防屈曲支撑通过轴向变形耗散地震能量,梁端通过弯曲变形耗散地震能量,框架柱通过适当变形保证结构不失稳倒塌。为此,针对防屈曲支撑钢框架整体结构提出基于构件损伤的易损性分析评价指标和方法。通过定义结构极限状态,对比基于不同评价指标的防屈曲支撑框架结构地震易损性分析结果。结果显示:基于单一评价指标的评价方法不能准确评价结构抗倒塌能力,防屈曲支撑钢框架结构虽然由于防屈曲支撑的优越变形能力使得结构耗能能力提升,但梁端仍可能发生破坏。     

基于抗震韧性的功能可恢复防屈曲支撑-框架结构设计方法研究

为解决大震后传统防屈曲支撑-框架结构残余位移较大和修复难度大、成本高等问题，基于抗震韧性的思想，对传统防屈曲支撑-框架结构进行优化设计，提出功能可恢复防屈曲支撑-框架结构体系的设计方法，提升建筑的抗震能力和震后可修复性。以实际工程为例，采用传统防屈曲支撑-框架结构和基于抗震韧性的功能可恢复防屈曲支撑-框架结构对其进行抗震设计，对比分析了两种方案的结构抗震性能和抗倒塌易损性。结果表明：大震下传统防屈曲支撑-框架结构最大残余位移角为1/15,超过《建筑抗震韧性评价标准》(GB/T 38591—2020)中建议的可修复范围限值1/200;功能可恢复防屈曲支撑-框架结构最大残余位移角为1/207,处于可修复范围，且倒塌概率远低于10%,具有良好的抗倒塌能力。功能可恢复防屈曲支撑-框架结构体系对于实现建筑震后快速修复或继续使用具有良好的可行性。     

防屈曲耗能支撑在铰接混凝土框架抗震加固中的应用

在我国部分地区还存在有铰接混凝土框架结构,这种结构体系在设计时未进行抗震设计,如继续使用,应进行抗震加固以使其满足抗震要求。防屈曲耗能支撑克服了普通钢支撑失稳的缺点,具有明确的屈服位移和屈服力,在多遇地震下可保持弹性状态,为结构提供刚度和抗震承载力。在设防烈度地震和罕遇地震下,防屈曲耗能支撑将屈服耗能,从而为结构提供耗能能力。结合防屈曲耗能支撑的特点,提出在铰接混凝土框架结构中的抗震加固方法,并结合实际工程实例,研究加固后结构的耗能能力。     

装配式防屈曲支撑构件及框架设计理论

防屈曲构件作为一种性能优越的消能减震构件,在很多国家得到广泛应用。一种新型的装配式防屈曲支撑构件,解决了传统防屈曲支撑由混凝土外围约束构件所导致的加工精度控制困难及湿作业等诸多问题,而且现场组装更加快捷。提出了多种创新型的装配式防屈曲支撑构件形式,其外围约束构件多采用常用型钢或钢板组合而成,外围多个约束构件之间通过螺栓连接并形成捆绑作用。这种装配式防屈曲支撑的设计除了满足一般防屈曲支撑构件的约束比限值要求外,还要对外围约束构件间的"捆绑作用"进行计算以设计螺栓连接,保证多个外围约束构件满足变形协调而作为一个整体构件参与工作。还对一种由防屈曲支撑衍生出的屈曲延迟性构件的计算方法进行了介绍,其在加固改造工程中有很大应用空间。最后对防屈曲支撑框架的抗震性能与设计理论进行了探讨,并对未来研究工作进行了展望。     

支撑屈服后屈曲约束支撑框架损伤集中效应分析

屈曲约束支撑(BRB)屈服后刚度较低,某一层或几层BRB率先屈服会造成屈曲约束支撑框架(BRBF)进入弹塑性阶段后不同楼层间刚度的突变,框架弯矩会重分布,进而影响框架的损伤机制。为此,提出框架基于柱端弯矩比的强柱弱梁计算公式,公式表明：当框架节点下部与上部柱端弯矩同号相等时,柱梁承载力比需求最小为1;当弯矩反向相等时,需求则为无穷大;通过分析楼层间BRB刚度比对两层BRBF弯矩分布的影响,说明BRBF中某层支撑屈服会导致该层节点下部与上部柱端弯矩比发生较大的改变,节点上部柱端弯矩甚至反向增大;综上,支撑屈服后BRBF易出现层间柱铰机制。最后,通过算例验证提出的强柱弱梁计算公式和BRBF弯矩分布规律,同时表明：当BRB-框架刚度比较大或者框架柱梁承载力比较小时,BRBF损伤集中效应较为明显。     

Evaluation of buckling-restrained braced frame seismic performance considering reserve strength

Buckling-restrained braced frame (BRBF) systems are used extensively for resisting lateral forces in high seismic regions of the United States. Numerical and large-scale experimental studies of BRBFs have shown predictable seismic performance with robust ductility and energy dissipation capacity. However, the low post-yield stiffness of buckling-restrained braces (BRBs) may cause BRBFs to exhibit large maximum and residual drifts and allow the formation of soft stories. Thus, reserve strength provided by other elements in the lateral-force-resisting system is critical to improving seismic performance of BRBFs. This reserve strength can be provided in two primary ways: (1) moment-resisting connections within the BRBF and (2) a steel special moment-resisting frame (SMRF) in parallel with the BRBF to create a dual system configuration. These two approaches to providing reserve strength can be used together or separately, leading to a variety of potential system configurations. In addition, special attention must be given to the connections within the BRBF since moment-resisting connections have been observed experimentally to limit drift capacity due to undesirable connection-related failure modes. This paper presents nonlinear dynamic analysis results and evaluates performance of BRBF and BRBF-SMRF systems using moment-resisting and non-moment-resisting beam-column connections within the BRBF. Reserve strength is shown to play a critical role in seismic behavior and performance of BRBFs.     

Seismic performance of stiffness-based designed buckling-restrained braced frame and special moment-resisting frame dual systems

Conventional procedure for designing dual systems, proposed in seismic regulations, encompasses some limitations such as not putting a required minimum stiffness value for the secondary system. This research investigates the stiffness limit value required for the secondary system for designing buckling-restrained braced frame (BRBF) and special moment-resisting frame (SMRF) dual systems. Non-linear static and time history analyses were carried out on the sample dual structures with different heights and different relative stiffness ratios of the primary system to the secondary system. A stiffness-based designing approach is employed to ensure that the designed system comprises the predefined relative stiffness ratios. It is demonstrated that the suitable stiffness combination ratio is gained when the BRBF and SMRF subsystems have 65% and 35% of the total stiffness, respectively. Implementation of the suitable relative stiffness ratio in the dual systems designed according to the presented approach, leads to a uniform plasticity profile in the height of structures.     

Seismic performance of buckling-restrained braced frames with varying beam-column connections

The effect of beam-column connections and brace configurations on the overall seismic response of a medium-rise bucklingrestrained braced frame (BRBF) is analytically evaluated in the present study. Two types of brace configurations (chevron and Double-X) and a combination of the moment-resisting and the non-moment-resisting beam-column connections are considered. A total of five design cases are studied for a seven-story BRBF in which a constant value of response reduction (R) factor equal to 8 is considered in the design. Nonlinear dynamic analyses are carried out for all study frames for an ensemble of forty ground motions representing the DBE and MCE hazard levels. Fragility curves are developed for all study frames considering the interstory drift ratio and residual drift ratio as the damage parameters. Results showed that a higher value of response reduction factor should be adopted in the design of BRBFs for both pinned and rigid beam-column connections. Further, in order to achieve the desired seismic performance of BRBFs, Double-X brace configurations and rigid beam-column connections at the alternate story levels should be used.     

A quick method for estimating the lateral stiffness of building systems

This paper presents a quick method for estimating the lateral stiffness of building structures, including regular and irregular moment frames, braced frames as well as frames with shear walls, which can be used for preliminary analysis and especially final check purposes. The method can be utilized for the calculation of the building displacement at different levels under lateral loads, the contribution of various lateral resisting systems to carrying the lateral loads, and finally the natural frequencies of the system. The basic idea of the method is based on some facts about the lateral deformation and stiffness of building structures, which make it possible to consider an equivalent single‐bay single‐story frame module for every story of the real multi‐bay multi‐story frame. This leads to a 3‐diagonal or banded stiffness matrix in most cases. Even in the cases resulting in a full stiffness matrix the proposed method does not require solving a system of simultaneous equations for obtaining the lateral displacements. Several numerical examples show the higher efficiency and precision of the proposed method in comparison with the Kan method. The use of the main concepts of the proposed method for preliminary design purposes is also possible as a secondary application. Copyright © 1999 John Wiley & Sons, Ltd.     

钢管混凝土柱-钢梁平面框架抗震性能的试验研究

为了探讨钢管混凝土柱-钢梁平面框架的抗震性能,本文进行了12个框架试件在恒定轴力和水平反复荷载作用下的试验研究,主要考察了柱截面形状(圆形、方形)、含钢率(圆形:α=0.06,0.103;方形:α=0.125,0.126)、柱轴压比(圆形:n=0.06~0.60;方形:n=0.04~0.60)、梁柱线刚度比(圆形:i=0.36~0.58;方形:i=0.34~0.62)等参数对其力学性能的影响。试验结果表明:钢管混凝土柱-钢梁框架滞回曲线较为饱满,强度和刚度退化不明显;柱轴压比和含钢率对框架的承载力和抗震性能影响较大,随着轴压比的增大,框架的水平极限承载力下降,位移延性和耗能能力降低,而含钢率影响规律则相反;圆形截面柱框架抗震性能整体上优于方形截面柱框架。按照《钢管混凝土结构技术规程》(DBJ13—51—2003)设计的钢管混凝土框架能够满足结构抗震设计要求。     

水平地震作用下转换层上、下结构侧向刚度比对框支剪力墙结构抗震性能的影响

针对不同的转换层上、下结构侧向刚度比γ,采用有限元软件ANSYS对转换层设在第1层的14层框支剪力墙结构在水平地震作用下的抗震性能进行了计算分析。研究了水平地震作用下转换层上、下结构侧向刚度比对框支剪力墙结构抗震性能的影响,并对加强落地剪力墙和减少转换层上部剪力墙对框支剪力墙结构抗震性能的影响进行了比较分析。     

Storey-based stability of unbraced steel frames at elevated temperature

The evaluation of the lateral stability of steel frames subject to elevated temperatures is different from that at ambient temperature. This is because the degradation of the Young's Modulus of steel associated with elevated temperature will lead to the loss of column lateral stiffness. In this study, the lateral stability of unbraced steel frames subjected to elevated temperature is investigated based on the concept of storey based buckling. First, to simulate a steel column exposed to the elevated temperature, an analytical model was proposed to examine the effects of axial loading, elevated temperature, and thermal boundary restraints on the lateral stiffness of steel columns in unbraced frames. Then, a method of evaluating the stability capacity of unbraced steel frames at elevated temperature is proposed. Numerical examples are presented to demonstrate the evaluation procedure of the proposed method and investigate the frame stability subjected to different scenarios of frame members exposed to the elevated temperature. The validity of the proposed method is verified by the numerical analysis with the use of finite element analysis.     

无支撑钢框架在高温下的楼层稳定性

受高温影响的钢框架的侧向稳定性与其在环境温度下的稳定性不同。这是由于高温下钢框架的弹性模量的降级将导致柱的横向刚度也跟着减少。在楼层屈曲理论的基础上调查无支撑钢框架在高温下的横向稳定性。首先,模拟一个钢柱暴露于高温之下,提出一个分析模型来测试无支撑框架中的轴向载荷、高温以及受热边界限制的钢管的横向刚度所带来的影响。之后,提出一个评估无支撑钢框架在高温下的稳定承载力的方法。数值实例用于展示所提出的方法的评估过程,并且研究不同场景中框架构架暴露于高温时框架结构的稳定性。使用有限元分析对所提出方法进行了数值分析,验证了该方法的有效性。     

框支和梁支组合墙体的抗侧承载力及刚度

位于框架梁上和由纵向梁承托的横向组合墙体,由于梁的变形而使墙体的抗侧承载力及刚度均有不同程度的降低,这对底层框剪和底层大开间上部小开间组合墙体房屋的抗震性能将带来影响。本文研究了这些二、三层横向组合墙体的强度和刚度变化情况,并分析了其中的主要影响因素。