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1.
Christoph Mahrenholtz Pao‐Chun Lin An‐Chien Wu Keh‐Chyuan Tsai Shyh‐Jiann Hwang Ruei‐Yan Lin Muhammad Y. Bhayusukma 《地震工程与结构动力学》2015,44(1):59-78
Damage to buildings observed in recent earthquakes suggests that many old reinforced concrete structures may be vulnerable to the effects of severe earthquakes. One suitable seismic retrofit solution is the installation of steel braces to increase the strength and ductility of a building. Steel bracings have some compelling advantages such as their comparatively low weight, their suitability for prefabrication, and the possibility of openings for utilities, access, and light. The braces are typically connected to steel frames that are fixed to the concrete structure using post‐installed concrete anchors along the perimeter. However, these framed steel braces are not without some disadvantages such as heavier steel usage and greater difficulties during the installation. Therefore, braces without steel frames appear to be an attractive alternative. In this study, braces were connected to gussets furnished with anchor brackets, which were fixed by means of a few post‐installed concrete anchors. The clear structural system and the increased utilization of the anchors allowed the anchorage to be designed precisely and economically. The use of buckling‐restrained braces (BRBs) provides additional benefits in comparison with conventional braces. BRBs improve the energy dissipation efficiency and allow the limitation of the brace force to be taken up by the highly stressed anchorage. Cyclic loading tests were conducted to investigate the seismic performance of BRBs connected with post‐installed anchors used to retrofit reinforced concrete frames. The tests showed that the proposed design method is feasible and increases strength as well as ductility to an adequate seismic performance level. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
2.
This study explores seismic performance of steel frame buildings with SMA-based self-centering bracing systems using a probabilistic approach. The self-centering bracing system described in this study relies on superelastic response of large-diameter cables. The bracing systems is designed such that the SMA cables are always stressed in tension. A four-story steel frame building characterized until collapse in previous research is selected as a case-study building. The selected steel frame building is designed with SMA bracing systems considering various design parameters for SMA braces. Numerical models of these buildings are developed by taking into account the ultimate state of structural components and SMA braces as well as the effect of gravity frames on lateral load resistance. Nonlinear static analyses are conducted to assess the seismic characteristics of each frame and to examine the effect of SMA brace failure on the seismic load carrying capacity of SMA-braced frames. Incremental dynamic analyses (IDA) are performed to compute seismic response of the designed frames at various seismic intensity levels. The results of IDA are used to develop probabilistic seismic demand models for peak inter-story and residual inter-story drifts. Seismic demand hazard curves of peak and residual inter-story drifts are generated by convolving the ground motion hazard with the probabilistic seismic demand models. Results show that steel frames designed with SMA bracing systems provide considerably lower probability of reaching at a damage state level associated with residual drifts compared to a similarly designed steel moment resisting frame, especially for seismic events with high return periods. This indicates reduced risks for the demolition and collapse due to excessive residual drifts for SMA braced steel frames. 相似文献
3.
The paper presents a comparative study of an existing retrofit for a mid-rise steel building using additional stiff steel braced-frames against an alternate retrofit using ADAS (Added Damping and Stiffness) passive energy dissipation devices. The subject building, located near Alameda Park in downtown Mexico City, is a ten-storey office building that was built in the 1950s. The structure was damaged during the 1985 Michoacán Earthquake because of resonant response with the site. The building was later retrofitted using additional braced frames according to the seismic provisions of Mexico's 1987 Federal District Code. The retrofit scheme was planned to take the structure away from resonant responses and to inhibit structural damage. A proposed upgrade using ADAS energy dissipation devices was studied to compare energy dissipation against traditional stiffening using steel braces as retrofit options for mid-rise buildings in Mexico City's lake-bed zone. Different sets of analyses were carried out to compare both alternatives: (a) three-dimensional elastic analyses; (b) limit analyses and; (c) nonlinear dynamic analyses for postulated site ground motions for a Ms=8.1 earthquake. Initial costs of the retrofit schemes were also studied. The comparative studies suggest that a retrofit using ADAS devices would have a better dynamic performance than the one using steel braces. However, the steel bracing retrofit provides more strength and its initial cost of retrofit is less than that of the ADAS retrofit. © 1997 John Wiley & Sons, Ltd. 相似文献
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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。 相似文献
6.
Scientific research proposing any type of device/technique for seismic protection of buildings is generally based on numerical models that adopt simplifications to make possible extensive analyses. This means that important details of the inelastic response could be neglected. Following this consideration, regardless of the device/technique invented, before it could be put into practice, an experimental verification of the actual structural performance should be conducted by full-scale tests at building level. This issue is investigated in the paper considering seismic retrofit of reinforced concrete (RC) framed structures by buckling-restrained braces (BRBs) as technique to be validated, while hybrid test is selected as tool for experimental validation at building level. The analysed seismic upgrading technique consists in the insertion of BRBs into the RC frame. The upgrading intervention is designed by a method developed in previous studies. This technique responds to an important need of the society. Indeed, existing RC frames showed high vulnerability in occurrence of past earthquakes when they were not originally conceived to sustain horizontal forces. The hybrid test is selected among the available experimental techniques because it allows the experimentation on full-scale specimens with reasonable cost. In this study, a substructure hybrid test was conducted and the results are here presented to (a) evaluate the effectiveness of the design method of BRBs for seismic upgrading, (b) investigate the integration of BRBs in existing RC frame, and (c) show the potentiality of the substructure hybrid test for the experimental verification of innovative techniques for seismic protection of buildings. 相似文献
7.
为检验抗侧刚度比和支撑布置方式等因素对具有不同总层数的屈曲约束支撑钢框架的抗震性能影响,借助SAP2000软件,探讨6层、12层、18层屈曲约束支撑钢框架结构在抗侧刚度比分别为1、2、3、4、5共五种工况及倒V型和单斜向两种支撑布置方式下的抗震性能。结果表明,屈曲约束支撑钢框架结构基底剪力-顶点位移曲线呈典型的双线性特征;随抗侧刚度比的增大,结构的层间位移角总体上呈降低趋势,基底剪力及支撑轴力增大,顶点水平位移变小,框架所分担的剪力降低;倒V型布置支撑较单斜向布置具有略大的基底剪力、谱加速度,较小的顶点位移、层位移、层间剪力和框架剪力分担率。分析表明,总体上来看,倒V型布置较单斜向布置时支撑框架结构具有略优的抗震性能;抗侧刚度比较支撑布置方式对支撑框架结构抗震性能的影响更为显著。 相似文献
8.
Self-centering seismic retrofit scheme for reinforced concrete frame structures: SDOF system study 总被引：1，自引：1，他引：0
This paper presents the results of a parametric study of self-centering seismic retrofit schemes for reinforced concrete (RC) frame buildings. The self-centering retrofit system features flag-shaped hysteresis and minimal residual deformation. For comparison purpose,an alternate seismic retrofit scheme that uses a bilinear-hysteresis retrofit system such as buckling-restrained braces (BRB) is also considered in this paper. The parametric study was carried out in a single-degree-of-freedom (SDOF) system framework since a multi-story building structure may be idealized as an equivalent SDOF system and investigation of the performance of this equivalent SDOF system can provide insight into the seismic response of the multi-story building. A peak-oriented hysteresis model which can consider the strength and stiffness degradation is used to describe the hysteretic behavior of RC structures. The parametric study involves two key parameters -the strength ratio and elastic stiffness ratio between the seismic retrofit system and the original RC frame. An ensemble of 172 earthquake ground motion records scaled to the design basis earthquake in California with a probability of exceedance of 10% in 50 years was constructed for the simulation-based parametric study. The effectiveness of the two seismic retrofit schemes considered in this study is evaluated in terms of peak displacement ratio,peak acceleration ratio,energy dissipation demand ratio and residual displacement ratio between the SDOF systems with and without retrofit. It is found from this parametric study that RC structures retrofitted with the self-centering retrofit scheme (SCRS) can achieve a seismic performance level comparable to the bilinear-hysteresis retrofit scheme (BHRS) in terms of peak displacement and energy dissipation demand ratio while having negligible residual displacement after earthquake. 相似文献
9.
当前方法采用伸臂桁架加固建筑结构时,未考虑建筑结构的屈曲约束支撑力的影响,伸臂桁架与建筑结构的连接不牢固,导致其对建筑结构的抗震加固性能较差。故此,深入分析建筑结构的屈曲约束支撑对其抗震加固性能的影响,设计建筑结构抗震加固方案,利用高强螺栓节点经由连接钢板实现屈曲约束支撑与建筑结构的铰接固定。分别从支撑变形同建筑结构层间位移的关系、建筑结构支撑承载力、多遇地震影响下屈曲约束支撑框架的位移验算,以及罕遇地震影响下屈曲约束支撑的弹塑性位移验算方面,分析屈曲约束支撑对建筑结构抗震加固性能影响。经实验分析得出,建筑结构加入屈曲约束支撑后第一扭转周期同第一平动周期的比值降低0.14,X、Y两个方向的砌体墙同建筑结构的刚度比值降低6.9、8.0,最大顶点位移值降低15.4 mm、29.3 mm,抗震加固性能大大提高。 相似文献
10.
Esra Mete Güneyisi 《地震工程与结构动力学》2012,41(5):853-874
The present paper investigates the seismic reliability of the application of buckling restrained braces (BRBs) for seismic retrofitting of steel moment resisting framed buildings through fragility analysis. Samples of regular three‐storey and eight‐storey steel moment resisting frames were designed with lateral stiffness insufficient to comply with the code drift limitations imposed for steel moment resisting frame systems in earthquake‐prone regions. The frames were then retrofitted with concentrically chevron conventional braces and BRBs. To obtain robust estimators of the seismic reliability, a database including a wide range of natural earthquake ground motion records with markedly different characteristics was used in the fragility analysis. Nonlinear time history analyses were utilized to analyze the structures subjected to these earthquake records. The improvement of seismic reliability achieved through the use of conventional braces and BRBs was evaluated by comparing the fragility curves of the three‐storey and eight‐storey model frames before and after retrofits, considering the probabilities of four distinct damage states. Moreover, the feasibility of mitigating the seismic response of moment resisting steel structures by using conventional braces and BRBs was determined through seismic risk analysis. The results obtained indicate that both conventional braces and especially BRBs improve significantly the seismic behavior of the original building by increasing the median values of the structural fragility curves and reducing the probabilities of exceedance of each damage state. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
11.
《地震工程与工程振动(英文版)》2015,(1)
Recently, the structural fuse has become an important issue in the field of earthquake engineering. Due to the trilinearity of the pushover curve of buildings with metallic structural fuses, the mechanism of the structural fuse is investigated through the ductility equation of a single-degree-of-freedom system, and the corresponding damage-reduction spectrum is proposed to design and retrofit buildings. Furthermore, the controlling parameters, the stiffness ratio between the main frame and structural fuse and the ductility factor of the main frame, are parametrically studied, and it is shown that the structural fuse concept can be achieved by specific combinations of the controlling parameters based on the proposed damage-reduction spectrum. Finally, a design example and a retrofit example, variations of real engineering projects after the 2008 Wenchuan earthquake, are provided to demonstrate the effectiveness of the proposed design procedures using buckling restrained braces as the structural fuses. 相似文献
12.
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... 相似文献
13.
Buckling-restrained braces(BRBs)have recently become popular in the United States for use as primary members of seismic lateral-force-resisting systems.A BRB is a steel brace that does not buckle in compression but instead yields in both tension and compression.Although design guidelines for BRB applications have been developed,systematic procedures for assessing performance and quantifying reliability are still needed.This paper presents an analytical framework for assessing buckling-restrained braced f... 相似文献
14.
The paper illustrates a probabilistic methodology for assessing the vulnerability of existing reinforced concrete (RC) buildings with limited ductility capacity retrofitted by means of dissipative braces. The aim is to highlight the most important parameters controlling the capacity of these coupled systems and specific aspects concerning the response uncertainties. The proposed methodology is based on the use of local engineering demand parameters for monitoring the seismic response and on the development of component and system fragility curves before and after the retrofit. In the first part of the paper, the methodology is illustrated by highlighting its advantages with respect to the existing approaches. Then, its capability and effectiveness are tested by considering a benchmark two‐dimensional RC frame designed for gravity‐loads only. The frame is retrofitted by introducing elasto‐plastic dissipative braces designed for different levels of base shear capacity. The obtained results show the effectiveness of the methodology in describing the changes in the response and in the failure modalities before and after the retrofit, for different retrofit levels. Moreover, the retrofit effectiveness is evaluated by introducing proper synthetic parameters describing the fragility curves and by stressing the importance of employing local engineering demand parameters (EDPs) rather than global EDPs in the seismic risk evaluation of coupled systems consisting in low‐ductility RC frames and dissipative braces. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
15.
屈曲约束支撑的研究进展及其在结构抗震加固中的应用 总被引：5，自引：2，他引：5
本文首先介绍了屈曲约束支撑(BRB)的最新研究进展。屈曲约束支撑在承受拉力和压力的情况下,表现出相同的滞回性能和优良的耗能能力。文章介绍了近些年来发展和应用比较成熟的一些形式的屈曲约束支撑。对于近些年来这种支撑在一些主要抗震地区的应用进行了回顾。对于新建高层钢结构的大量应用案例和已有结构的抗震加固的应用表明,此种支撑的使用前景非常广阔。 相似文献
16.
The effectiveness of hysteretic passive devices to protect and mitigate the response of a structure under seismic loading is well established by both analytical and experimental research. Nevertheless, a systematic and well‐established methodology for the topological distribution and size of these devices in order to achieve a desired structural response performance does not exist. In this paper, a computational framework is proposed for the optimal distribution and design of yielding metallic buckling restrained braces (BRB) and/or friction dampers within steel moment‐resisting frames (MRF) for a given seismic environment. A Genetic Algorithm (GA) is used to solve the resulting discrete optimization problem. Specific examples involving two three‐story, four‐bay steel MRFs and a six‐story, three‐bay steel MRF retrofitted with yielding and/or friction braces are considered. The seismic environment consists of four synthetic ground motions representative of the west coast of the United States with 5% probability of exceedance in 50 years. Non‐linear time‐history analyses are employed to evaluate the potential designs. As a result of the evolutionary process, the optimal placement, strength and size of the dampers are obtained throughout the height of the steel MRF. Furthermore, the developed computational approach for seismic design based upon GAs provides an attractive procedure for design of MRFs with hysteretic passive dampers. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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K形高强钢组合偏心支撑(K-HSS-EBF)是指耗能连梁和支撑采用Q345钢,而框架梁、框架柱采用高强度钢(如Q460)。为研究其在罕遇地震作用下的抗震性能,在试验研究的基础上,采用直接基于位移的抗震设计方法设计了5层、8层和12层算例,分别进行静力推覆分析和动力弹塑性分析,研究高强钢组合偏心支撑钢框架在罕遇地震作用下层间侧移分布和破坏模式。研究结果表明:直接基于位移的抗震设计方法设计的算例在罕遇地震作用下,结构的层间侧移满足我国现行抗震规范的要求,结构呈理想的渐进式梁铰屈服机构,并证明该设计方法的合理性和可靠性。 相似文献
18.
Buckling restrained braces (BRBs) are very effective in dissipating energy through stable tension–compression hysteretic cycles and have been successfully experimented in the seismic protection of buildings. Their behavior has been studied extensively in the last decades and today the level of performance guaranteed by these devices and the technological constrains that have to be fulfilled to optimize their behavior are well known. Furthermore, several companies in the world have developed their own BRBs and are now producing them. In spite of this, many seismic codes (for instance, the EuroCode 8) do not stipulate provisions for the design and construction of earthquake‐resistant structures equipped with BRBs. This discourages the structural engineering community from using these devices and seriously limits their use in structural applications. In this paper a procedure for the seismic design of steel frames equipped with BRBs is proposed. Furthermore, the paper presents a numerical investigation aimed at validating this design procedure and proposing the value of the behavior factor q that should be used for this structural type. To this end, a set of frames with BRBs is first designed by means of several values of q. Then, the obtained frames are subjected to a set of accelerograms compatible with the elastic response spectrum considered in design. The seismic response of the frames is determined by nonlinear dynamic analysis and represented in terms of the ductility demand of BRBs and the internal force demand of nondissipative members (beams and columns). Finally, the largest value of q that leads to acceptable seismic performance of the analyzed frames is assumed as adequate. The value of q is given in the paper as a continuous function of the assumed ductility capacity of the BRBs. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
19.
耗能梁段作为偏心支撑结构的耗能元件,在大震作用下通过弹塑性变形吸收地震能量,保护主体结构处于弹性受力状态。现行规范基于强度的设计理论,为了保证耗能梁段进入塑性或破坏,梁柱构件需要进行放大内力设计,导致截面过大,而且基于强度的设计方法很难保证结构的整体破坏状态。目前,抗震设计越来越重视基于性能的设计思想,该方法能够评估结构的弹塑性反应。对于高强钢组合偏心支撑,其中耗能梁段和支撑采用Q345钢,框架梁柱采用Q460或者Q690高强度钢材,高强钢不仅带来良好的经济效益,而且能够推广高强钢在抗震设防区的应用。利用基于性能设计方法设计了4种不同形式的高强钢组合偏心支撑钢框架,包括K形、Y形、V形和D形,考虑4层、8层、12层和16层的影响。通过Pushover分析和非线性时程分析评估该结构的抗震性能,研究结果表明:4种形式的高强钢组合偏心支撑钢框架具有类似的抗震性能,在罕遇地震作用下,几乎所有耗能梁段均参与耗能,而且层间侧移与耗能梁段转角沿高度分布较为均匀。其中:D形偏心支撑具有最大的抗侧刚度,但延性较差,而Y形偏心支撑的抗侧刚度最弱,但延性最佳。 相似文献
20.
Hayato Asada Andrew D. Sen Tao Li Jeffrey W. Berman Dawn E. Lehman Charles W. Roeder 《地震工程与结构动力学》2020,49(15):1619-1639
Current seismic design requirements for special concentrically braced frames (SCBFs) in chevron configurations require that the beams supporting the braces be designed to resist the demands resulting from the simultaneous yielding of the tension brace and degraded, post-buckling strength of the compression brace. Recent research, including large-scale experiments and detailed finite-element analyses, has demonstrated that limited beam yielding is not detrimental to chevron braced frame behavior and actually increases the story drift at which the braces fracture. These findings have resulted in new expressions for computing beam demands in chevron SCBFs that reduce the demand in the tension brace to be equal to the expected compressive capacity at buckling of the compression brace. In turn, the resultant force on the beam is reduced as is the required size of the beam. Further study was undertaken to investigate the seismic performance of buildings with SCBFs, including chevron SCBFs with and without yielding beams and X-braced frames. Prototype three- and nine-story braced frames were designed using all three framing systems, that is, chevron, chevron with yielding beams, and X SCBFs, resulting in six building frames. The nonlinear dynamic response was studied for ground motions simulating two different seismic hazard levels. The results were used to characterize the seismic performance in terms of the probability of salient damage states including brace fracture, beam vertical deformation, and collapse. The results demonstrate that the seismic performance of chevron SCBFs with limited beam yielding performs as well as or better than the conventionally designed chevron and X SCBFs. 相似文献