偏心支撑高层建筑的地震反应

偏心支撑高层建筑的地震反应美国旧金山的Ｅｍ～大楼（ＥＭＢ）是１９７９年按照１９７６年的美国统一建筑规范要求设计的。在１９８９年１０月间日的７．１级ＷＰｒｉｅｔａ地震中，距ＥＭＢ约１００ｍ的Ｅｍｂａｒｃｅｄｅｒｏ超速干道遭到严重的破坏（１９９１年夷为平...     

高层偏心支撑钢框架弹塑性地震反应分析

偏心支撑框架与纯框架相比,有更大的抗侧移刚度及极限承载力,与中心支撑框架相比,可有效地降低地震作用.国内外学者对偏心支撑性能做了较多研究,但实际工程中鲜有应用,我国现有钢结构建筑大多为中心支撑框架或纯框架,结合一工程实例,对高层偏心支撑钢框架进行弹塑性时程分析和抗震性能研究.     

偏心支撑钢框架拟动力地震反应试验研究

本文介绍了一榀偏心支撑钢框架在El Centro(1940 NS）波作用下的拟动力试验，研究了按照一定要求设计的偏心支撑钢框架的地震作用下的性能。     

单斜杆型偏心支撑钢框架的地震反应分析

偏心支撑结构弹性阶段刚度大,塑性阶段耗能能力强,是适用于高烈度地震区的一种有效的抗侧力结构体系。采用梁单元与壳单元相结合的非线性有限元模型,对单斜杆型偏心支撑钢框架进行弹塑性时程分析,研究耗能梁段的长度、腹板高厚比和加劲肋间距的变化对单斜杆型偏心支撑钢框架结构抗震性能的影响,提出了相应的抗震设计建议。     

高层建筑偏心支撑钢框架减轻地震响应分析

本文首先分析了偏心支撑钢框架中的关键构件－耗能连梁的弹塑性性能,提出了一种简化的屈服模型,并在此基础上编制一种新型的弹塑性时程分析程序。利用所编制的程序对两个典型算例进行了弹塑性时程分析,并对算例中偏心支撑框架和中心支撑框架两种结构的地震响应进行了比较。其结果表明,偏心支撑框架结构的地震响应要明显小于中心支撑框架结构的地震响应。     

偏心支撑钢框架的设计

简述了偏心支撑钢框架结构的工作原理及特点,介绍了偏心支撑钢框架的设计计算方法,其中重点介绍了各杆件的内力计算：耗能梁段设计、非耗能梁段设计、支撑设计和框架柱设计,为工程设计人员提供了指导。     

偏心支撑钢框架在循环荷载作用下非线性有限元分析

偏心支撑是高层钢结构中一种有效的抗震耗能的结构形式 ,针对这种结构形式 ,对变形大、进入塑性的耗能梁段采用退化曲壳单元 ,其余部分采用梁单元的非线性有限元分析模型 ,以此来分析偏心支撑钢框架在循环荷载作用下的耗能性能 ,并编制了相应的计算程序。算例分析表明 ,此计算模型精确、高效     

不同高宽比3/4支撑与交叉支撑结构效率研究

3/4支撑是指支撑交点位于支撑节间高度h的3/4处的支撑。基于等效水平集中荷载,以顶点位移最小化为设计目标进行拓扑优化得到的3/4支撑,其荷载边界条件与实际工程中常见的跨层支撑有一定区别,设计时需要判断其差异性。层间位移角和顶点位移作为不同设计目标的差异亦不能忽略。对高宽比2～12有限元模型进行参数化分析,结果表明:总体来看,高宽比越大则3/4支撑的抗侧效率越高,有可能超过交叉支撑;随支撑截面加大或柱截面减小,3/4支撑的抗侧效率会逐渐提高;弯曲变形的比例越高,则3/4支撑越有效;3/4支撑角度的突变会导致层刚度的突变和层间位移角不均匀,内筒的存在有助于缓解此问题;3/4支撑的扭转刚度稍差于交叉支撑,对于平面不规则的结构需要关注其差异。     

偏心支撑框架设计新进展

介绍了美国新标准对偏心支撑框架设计的修订,并对我国抗震规范和有关规程对偏心支撑框架的修订作了说明。与过去的规定相比,新规定对构件的内力增大系数有明显降低。说明了降低的原因,并介绍了偏心支撑框架构件和连接设计的有关要求和应考虑的问题,可供设计人员参考。     

框架—偏心支撑结构的抗震分析

运用有限元分析软件SAP2000对一个10层的框架结构进行建模,得到两种不同的方案模型,并对这两种方案分别进行双向水平地震作用下的时程分析,通过对结构动力特性结果进行分析,得出偏心支撑抗震性能方面优于中心支撑。     

Seismic eccentrically braced frames

This paper provides an overview of the behavior and design of seismic-resistant eccentrically braced frames (EBFs). Basic characteristics of EBFs are first discussed. The important effects of link length on the performance of EBFs are reviewed. The capacity design concept for EGFs is then addressed. The paper addresses several design issues that appear to have been inadequately considered either in current practice or in the emerging seismic code provisions. Some important observations are provided from pseudodynamic tests of large EBFs and experimental studies of EBF subassemblages with link-to-box column connections conducted recently. Future research needs are discussed.     

Recent research on eccentrically braced frames

Recent research developments on eccentrically braced steel frames for seismic design are reviewed. The emphasis is placed on the design of links, which are short sections of beams between columns and braces, and similar elements at eccentric joints. The review includes some highlights of the latest experiments with one-third scale models employing different eccentric bracing schemes, an updated classification of links, and special design requirements for different types of links. Some results are given on recent cyclic tests of full-size links.     

Seismic behaviour of eccentrically braced frames

In the past, the analysis of the seismic behaviour of eccentrically braced frames designed in fulfilment of capacity design principles has highlighted the significant role of the link overstrength factor. The link overstrength factor is, however, unable to explain many seismic responses because it is defined on the basis of the sole elastic behaviour of structures. To achieve thorough comprehension of the seismic behaviour of eccentrically braced systems, a new parameter, called damage distribution capacity factor, is defined here. The proposed parameter is calculated on the basis of the inelastic structural behaviour and is intended to evaluate the effect of premature yielding of links on the ability of structures to develop significant inelastic behaviour of all links prior to link failure. The paper discusses the distribution of the damage distribution capacity factor in eccentrically braced structures designed in accordance with capacity design principles and the influence of this parameter on the seismic response of structures. Finally, an analytical relation is defined between overstrength factor of links, damage distribution capacity factor and plastic rotation of links to obtain quantitative evaluation of the structural damage of eccentrically braced structures upon first failure of links.     

Design overstrength of steel eccentrically braced frames

The paper reports an analytical study on the design overstrength of steel eccentrically braced frames (EBFs). The study aimed at examining the influence of geometrical factors and seismic hazard on the design overstrength of EBFs. Pursuant to this goal a computer program which facilitates EBF designs was developed. The algorithm of the program adopts the lightest uniform frame design and library of link-beam-brace sub-assemblages concepts. The design output from the program was compared with published solutions and the results indicate that the algorithm developed as a part of this study is capable of providing lighter framing solutions. A parametric study was conducted using the developed computer program. The results indicate that the frames considered in this study have on average higher overstrength values when compared with the codified value even without considering potential increases due to material overstrength and strain hardening. The design overstrength was found to be influenced primarily by the link length to bay width ratio and the bay width, and secondarily by the building height and seismic hazard level.     

Fundamental periods of steel eccentrically braced frames

This paper describes formulation of a hand method that can be used to estimate the computed fundamental periods of vibration of building structures in general and steel eccentrically braced frames (EBFs) in particular. The developed method uses the Rayleigh's method as a basis and utilizes the roof drift ratio (RD_R) under seismic forces as a parameter. To obtain RD_R, more than 4000 EBFs were designed by considering the seismic hazard, number of stories, braced bay width and link length to bay width ratio as prime variables. A model was developed to estimate RD_R, which depends on the rigid plastic deformation mechanism for a typical EBF. The method was verified using design data produced as a part of this work as well as data published in literature. The verifications indicate that the proposed formulation is capable of providing acceptable estimates of the computed period. When compared with existing empirical period–height relationships, the proposed formulation offers closer estimates with reduced scatter. The method was further refined to derive new period–height relationships for two different seismicity regions. The accuracy of the relationship for high seismic regions was verified using measured periods of EBF buildings. Copyright © 2014 John Wiley & Sons, Ltd.     

Evaluation of hysteretic behavior of eccentrically braced frames with zipper-strut upgrade

This paper describes the seismic behavior of Eccentrically Braced Frames (EBF) upgraded using zipper-struts which connect the mid-point of shear links in all stories.The numerical modeling of the zipper-strut-equipped model is conducted using finite-element method software under cyclic load, with the goal of evaluating the behavior of shear links. The interaction of shear links and zipper-struts is also studied. Furthermore, the prototypes are subjected to nonlinear static (Pushover) analysis in two configurations; one with moment-resisting connections and one with pinned connections. Finally, the increase of ductility coefficient for the prototypes with zipper-strut is studied. The prototypes are also subjected to time-history analysis using scaled earthquake records, with the purpose of studying the energy parameters of the models.The unbalanced shear force is distributed among all stories due to the added continuity among shear links. This results in the extension of structural displacement capacity according to acceptance criteria. Moreover, a noticeable delay occurs until shear links experience enough rotation to meet Collapse Prevention acceptance criteria. By imposing acceleration on the structure and conducting time history analysis, it is observed that the zipper-strut-equipped system shows a stronger tendency to form shear links, leading to greater dissipation capacity in plastic zone.     

Assessment of eccentrically braced frames strength against progressive collapse

One of the most important and effective factors of structural strength against the risk of progressive collapse is the type of lateral load bearing system of a building. In this research, strength of dual steel moment frames equipped with a variety of eccentric bracings against progressive collapse was evaluated by using nonlinear static alternate path method. 6-floored building samples were designed with steel frame using a dual steel moment system together with 3 different types of bracing, including inverted eccentrically V-shaped bracing (chevron bracing), eccentrically V-shaped bracing and eccentrically X-shaped bracing, each with two different kinds of arrangement of bracings in the structural plan, in form of alternate and neighbor. The effects of sudden removal of columns on different floors of these buildings were examined. These studies showed that dual steel moment frames equipped with eccentric bracings generally exhibited desirable strength against progressive collapse. A change in the type of bracing resulted in significant changes in the system capacity in the progressive collapse. Among the different types of braces assessed, chevron type eccentrically brace showed higher strength against progressive collapse. Also, that alternate arrangement of bracings in structure plan demonstrated better performance than neighboring arrangement.     

两种偏心支撑钢框架受力性能对比分析

建立了空间Y型与K型偏心支撑钢框架有限元模型,对两种模型框架进行了单向加载和循环加载试验,对比分析了两种空间偏心支撑框架的屈服强度、极限承载力、侧向刚度、延性和耗能能力等方面受力性能的差异,为工程设计提供参考。     

Experimental investigation of link-to-column connections in eccentrically braced frames

The design of link-to-column connections in seismic-resistant eccentrically braced frames remains a largely unresolved problem. In order to address this problem, twenty-four large-scale specimens were tested under cyclic loading. The test parameters included the connection detail, link length, link section, and cyclic loading protocol. The test results suggest that link-to-column connections are susceptible to fracture at the link flange welds, regardless of the link length. A large number of specimens failed prematurely, before meeting the plastic link rotation requirement in US code provisions. However, two promising link-to-column connection details were developed as an outcome of this research. The new connection details include a detail using all-around fillet welds between the link and the column flange, and a reinforced connection detail that welds a pair of stiffeners in the first link web panel next to the column, parallel to the link web. Test specimens using either of these two details were able to exceed the plastic link rotation requirement.     

Performance of intermediate and long links in eccentrically braced frames

Recent researches about the performance of eccentrically braced frames have shown that some of the intermediate-length links do not meet the requirements of AISC2005. Further investigations on the current AISC 2005 provisions and also assessing the effect of involved parameters on the behavior of this type of links have been carried out in this research. Moreover, to cover the shortages of previous researches conducted on the performance of long links compared to short ones, some flexural links are also put into the study. By analyzing the links made of European-standard rolled shape sections, validity of the provisions for these types of links, which fewer investigations about them are available, is also examined. The Finite element analysis employing 3D solid elements is implemented to model a total of 68 links. Results of the study imply some design suggestions for these types of links. Also, the slenderness ratio of the web as well as the specification of the stiffeners is discerned as important parameters impacting on the performance of the intermediate links.