Use of steel bracing in reinforced concrete frames

In this paper the use of steel bracing in concrete-framed structures is investigated. The investigation is carried out through a series of tests conducted on a number of model frames. The object of the tests was to determine the degree of effectiveness of different diagonal bracing arrangements to increase the in-plane shear strength of the concrete frame and to observe the relative behaviour of tension and compression braces. The important question of the proper connections between the steel braces and the concrete frame is also considered. The test results indicate a considerable increase in the in-plane strength of the frame due to steel bracing. As an overall conclusion it is noted that, with proper connection between the brace and the frame, the steel bracing could be a viable alternative or supplement to shear walls in concrete framed buildings in seismic areas.     

Behavior and design of reinforced concrete frames retrofitted with steel bracing against progressive collapse

Steel bracing is able to improve progressive collapse resistance of reinforced concrete (RC) frames, but the bracing design is typically based on seismic retrofitting or lateral stability. There is no approach for design of steel bracing against progressive collapse. To this end, a retrofitting approach with steel braces is proposed based on analysis of macro finite element (FE) models with fiber beam elements. The FE models were initially validated through the experimental results of a braced frame and then used to investigate the effects of pertinent parameters on the progressive collapse resistance of planar frames. The results suggest the braces should be placed at the top story. Thereafter, macro FE models are built to investigate the dynamic responses of the three‐dimensional prototype RC frames under different column removal scenarios (CRS) and show the necessity of retrofitting. Accordingly, the design approach of steel bracing is proposed with incremental dynamic analysis (IDA) and assuming independent contribution of braces and frames to resistance. Finally, the fragility analysis of the frames under a corner‐penultimate‐exterior CRS is conducted through IDA and Monte Carlo simulation, and the results confirm the validity of the proposed design approach for retrofitting RC frames.     

Design and seismic response of tall chevron panel buckling‐restrained braced steel frames

The numerical analysis of the seismic performance for tall chevron panel buckling‐restrained braced steel frames (PBRBFs) under small and strong earthquake excitations has been carried out to investigate a capacity design procedure for chevron PBRBFs and to examine the effects of axial strength distribution of braces along the height of buildings, vertical supports of braces for the braced beams and the overstrength of braces on the seismic response of PBRBFs. It revealed that the chevron braces that remained elastic can actually provide the vertical supports for the braced beams. Under severe earthquake excitations, the vertical supports deteriorated greatly after braces yielding. The PBRBFs designed by omitting vertical supports of braces for the braced beams and considering the overstrength of braces exhibited superior performance with smaller plastic deformations for braced beams and reduction in ductility demands for panel buckling‐restrained braces (PBRBs) as compared with the others. The distribution of yielding for PBRBs in 10‐story buildings verified that the participation from the higher modes is not very remarkable and that the capacity design based on the first‐mode response can be considered for multistory PBRBFs. Moreover, on the basis of the analysis results of the 30‐story PBRBF, the participation of the higher modes should be taken into account for high‐rise PBRBFs. Copyright © 2011 John Wiley & Sons, Ltd.     

翼缘削弱的型钢混凝土框架抗震性能研究

为了研究翼缘削弱的型钢混凝土框架的抗震性能,对一榀两跨三层型钢混凝土框架模型进行了低周反复荷载试验。框架模型按"强柱弱梁"原则设计,且对节点核心区附近梁端工字形型钢的上、下翼缘采取狗骨式削弱,并适当增加最大削弱部位纵向钢筋的配筋率。通过对框架模型顶层施加低周反复水平荷载,观察了框架模型的破坏过程,测得框架模型的荷载-位移滞回曲线和骨架曲线以及各阶段的荷载和位移值,并分析了框架模型的延性、耗能、强度降低、刚度退化以及破坏机制。试验结果表明:框架模型的承载能力、变形能力和耗能能力高,延性大(延性系数大于7),满足延性框架的抗震要求。进一步分析了翼缘削弱在型钢混凝土框架中的具体作用。分析结果表明:翼缘削弱不仅能将塑性铰从梁端根部转移到翼缘削弱部位,从而降低节点核心区所受的剪力以及梁柱连接焊缝的应力,而且有利于框架形成梁铰耗能机构,从而提高框架的整体耗能能力。翼缘削弱能有效提高型钢混凝土框架的抗震性能,可在型钢混凝土     

预应力及非预应力型钢混凝土框架受力及抗震性能试验研究

进行了两榀预应力型钢混凝土框架和非预应力型钢混凝土框架在竖向荷载及水平低周反复荷载作用下受力与抗震性能试验研究,研究结果表明：在型钢混凝土梁中采用预应力,可以有效地控制结构裂缝宽度,改善结构的正常使用性能;梁中施加预应力没有明显改变型钢混凝土结构优良的抗震性能,预应力型钢混凝土框架低周反复加载滞回曲线饱满,抗震性能优良;在型钢混凝土梁中施加预应力,可以充分发挥型钢与混凝土等材料各自的优势。在试验研究的基础上,提出了预应力型钢混凝土框架和型钢混凝土框架的三线型恢复力模型,并利用该恢复力模型进行了预应力型钢混凝土框架和型钢混凝土框架在低周反复荷载作用下的滞回性能分析,分析结果与试验结果吻合良好。     

不同支撑形式的型钢混凝土剪力墙抗震性能试验研究

型钢混凝土剪力墙具有强度高、刚度大、稳定性好等优点,广泛应用在高层建筑中。为研究不同支撑形式对型钢混凝土剪力墙抗震性能的影响,进行了3个1/3缩尺的型钢混凝土剪力墙(型钢支撑布置形式分别为X型、AC1型和AC2型)和1个普通混凝土剪力墙对比试件在低周反复荷载作用下的试验研究,得到了其破坏过程的变化规律和破坏模式,分析了不同型钢支撑类型对剪力墙抗剪承载能力、裂缝开展、刚度、延性及耗能的影响规律。试验研究表明:型钢支撑对剪力墙的承载能力、刚度、延性及耗能性能均有较大幅度提高。试验研究表明:AC1型、AC2型和X型型钢支撑的剪力墙极限承载能力较普通混凝土剪力墙分别提升了71.9%、64.6%和49.4%,其延性系数分别提高了19.3%、5.0%和14.5%;型钢混凝土剪力墙的刚度退化速率与普通混凝土剪力墙相比更加缓慢,而且中后期刚度明显优于普通混凝土剪力墙;型钢混凝土剪力墙的塑性区范围较普通混凝土显著增加,试验获得的滞回曲线也更加饱满。     

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。     

钢纤维局部增强高强混凝土框架边节点抗震性能试验研究

通过3个钢纤维局部增强框架边节点的低周反复加载试验,探讨了柱端轴压比对钢纤维高强混凝土框架边节点抗震性能的影响.结果表明:随着柱端轴压比的增加,其对节点核心区混凝土的约束作用逐渐增大,减缓了抗剪承载力和刚度的退化,限制了节点核心区剪切变形,提高了节点核心区的抗剪承载力、延性和耗能能力.     

钢筋混凝土抗震框架节点受力机理及轴压比影响的试验研究

通过19个剪压比水平和轴压比水平不同的接近足尺的钢筋混凝土框架中间层中间节点梁柱组合体的低周反复加载试验,对节点的传力机理以及轴压比对节点抗震性能的影响规律进行了分析研究,取得了以下结果:(1)随着轴压比的增加,梁筋在节点内的粘结滑移量明显减小。节点的作用剪力较大时,梁筋的粘结退化加剧;(2)通过对节点内不同受力阶段箍筋应变的量测,明确了平行受力方向箍肢除承受桁架机构的拉力外,还与垂直受力方向的箍肢一起对节点核心区双向交替斜向受压混凝土发挥重要约束作用;(3)节点作用剪力在中等以上作用水平时,轴压比的增大对节点抗震抗剪的延性起不利作用。     

Comparison of nonlinear behavior of steel moment frames accompanied with RC shear walls or steel bracings

In this paper, the seismic behavior of dual structural systems in forms of steel moment‐resisting frames accompanied with reinforced concrete shear walls and steel moment‐resisting frames accompanied with concentrically braced frames, have been studied. The nonlinear behavior of the mentioned structural systems has been evaluated as, in earthquakes, structures usually enter into an inelastic behavior stage and, hence, the applied energy to the structures will be dissipated. As a result, some parameters such as ductility factor of structure (μ), over‐strength factor (R_s) and response modification factor (R) for the mentioned structures have been under assessment. To achieve these objectives, 30‐story buildings containing such structural systems were used to perform the pushover analyses having different load patterns. Analytical results show that the steel moment‐resisting frames accompanied with reinforced concrete shear walls system has higher ductility and response modification factor than the other one, and so, it is observed to achieve suitable seismic performance; using the first system can have more advantages than the second one. Copyright © 2011 John Wiley & Sons, Ltd.     

型钢混凝土—钢筋混凝土结构地震反应时程分析

指出型钢混凝土组合结构以较低的造价实现了优越的结构性能,在我国具有广阔的应用前景,研究了该类结构在地震反应过程中各个时刻位移、加速度等情况,结果表明,型钢混凝土组合结构具有良好的抗震性能。     

粘钢加固混凝土梁抗弯强度的理论研究

用Fortran语言编制了梁截面弯矩一曲率关系的分析程序,梁单元采用分布柔度单元,材料采用成熟的本构模型,非线性分析的计算结果与试验结果进行了比较,验证了非线性分析模型的合理性,采用这一计算程序对比分析了混凝土梁加固前、后承载力的变化,提供了粘钢加固后梁的承载力变化的定量指标,可供工程设计参考。     

青岛万邦中心型钢混凝土柱-钢梁-钢斜撑节点抗震性能试验研究

青岛万邦中心1#楼高度232.4m,采用钢-混凝土混合结构,体系为混合斜撑框架-核心筒结构。其中,型钢混凝土柱-钢梁-钢斜撑节点为本工程典型节点,受力复杂,对两个1∶4缩尺节点模型进行了试验研究。结果表明,节点核心区在低周往复试验下基本完好,未发生明显剪切破坏;通过对节点的承载力、延性、耗能能力、变形能力的分析评估表明,节点具有良好的承载能力、延性、耗能能力。     

浅谈现浇钢筋混凝土框架结构设计

介绍了现浇钢筋混凝土框架结构设计 ,从多层现浇钢筋混凝土框架结构的上部设计、多层框架房屋地基基础设计等方面进行了论述 ,指出框架结构体系在商场和办公楼中被广泛应用。     

附加减震钢框架的加固混凝土框架结构抗震性能试验研究

为提高既有混凝土框架抗震性能,在不显著增加既有结构构件受力的同时,在混凝土框架外部增设钢框架并设置屈曲约束支撑。设计并制作1榀纯混凝土框架和2榀设置附加减震钢框架的混凝土框架,通过低周往复加载试验,研究其开裂和破坏状态、滞回曲线、骨架曲线、刚度退化、等效阻尼比以及钢筋混凝土梁、附加钢框架的应变发展等。试验结果表明：增设附加减震框架后,结构破坏机制更加合理,屈曲约束支撑耗能性能稳定,加固后结构的滞回曲线饱满;采用外部附加钢框架加固钢筋混凝土框架,可提高既有混凝土框架结构的受剪承载能力至3倍以上,既有结构、外部附加钢框架和屈曲约束支撑可协同工作,在设防目标下可避免混凝土柱发生压剪脆性破坏;最后对附加减震框架改进连接构造设计提出了建议。     

钢纤维高性能混凝土框架节点的延性分析

根据试验对钢纤维混凝土框架梁柱节点的延性进行研究,分析了梁柱节点的破坏形态及节点抗剪强度和延性性能,基于试验结果提出了考虑钢纤维、混凝土、箍筋,共同作用的节点承载力计算方法。     

论述型钢混凝土在实际工程中的应用

介绍了在海口高烈度地区工业主厂房使用型钢混凝土组合结构的实际案例,通过结构分析计算,较为深入地探讨了采用型钢混凝土的原因,以及型钢混凝土结构的力学特点及优势,并针对在具体施工过程中遇到的问题和解决经验进行了详细的阐述。     

型钢混凝土梁-角钢混凝土柱框架抗震性能试验研究

完成两榀型钢混凝土梁-角钢混凝土柱框架水平低周反复荷载试验,考察这类框架的滞回特性、骨架曲线、刚度退化、耗能能力、残余变形、破坏形态等抗震性能,并采用OpenSees软件对两榀框架进行滞回模拟分析。考察柱长细比、轴压比、柱含钢率、梁内型钢截面抵抗矩、梁配筋率及预应力度等参数对框架骨架曲线的影响。研究结果表明,此类框架具有优良的抗震性能,为其在抗震区的推广使用提供了参考依据。     

型钢混凝土框架结构基于位移的抗震设计方法研究

根据型钢混凝土(SRC)框架结构的特点,将其性能划分为基本完好、轻微损坏、中等破坏和防止倒塌四个水平,并用层间位移角限值予以量化;将SRC多自由度体系转化为等效单自由度体系,导出了相应的等效参数,并根据其性能水平确定出结构的目标位移。在此基础上,提出SRC框架结构基于位移的设计步骤,并依此对结构进行承载力设计,用静力弹塑性分析方法对所设计的SRC规则框架结构进行推覆分析,校核结构的侧移形状与初始设计侧移曲线是否一致,在不满足变形需求时,用推覆至该性能水平时的侧移曲线作为修正后的侧移曲线重新计算。算例分析表明,文中方法简便实用、结果精确,能够实现SRC框架结构基于位移抗震设计的目的。     

型钢混凝土结构的抗震性能

指出型钢混凝土结构相对于混凝土结构和钢结构具有更好的耐久性、抗震性能等优点,是适于推广和应用的结构形式之一,重点介绍了型钢混凝土柱和型钢混凝土节点的力学性能,从而完善型钢混凝土结构的理论研究和抗震设计。