钢筋混凝土框架柱的延性设计

从延性破坏的概念出发，给出了对钢筋混凝土框架结构延性的理解，介绍了作为结构主要竖向受力构件的框架柱的破坏形态，分析了影响框架柱延性的主要因素，并结合分析所得的影响因素提出在实际工程设计中提高框架柱延性、进而提高结构抗震能力的一些建议。     

新型钢筋混凝土延性框架的非线性全过程分析

鉴于钢筋混凝土框架结构的实际受力特性,本文提出了容许框架柱下端出现塑性铰的新型延性框架结构.在进行非线性全过程分析时,根据试验所得柱铰的M-θ曲线,提出了多分量杆单元模型,并考虑了剪切变形和刚性域的影响以及N-△效应的作用.试验钢筋混凝土框架结构的计算结果表明,计算与试验曲线符合较好.与普通框架的对比计算证实,新型延性框架具有良好的延性和抗震性能.本文还给出了延性框架的设计建议.     

钢管混凝土框架结构抗震性能的试验研究

按照现行规范的有关规定设计制作了一榀两跨 3层钢梁 圆钢管混凝土柱的钢管混凝土框架结构模型 ,并通过施加恒定竖向荷载和低周反复水平荷载 ,对模型框架进行了抗震性能试验研究。结果表明 ,基于现行规范所设计的钢管混凝土框架在地震时能形成梁铰破坏机制 ,框架的变形能力、承载能力、延性、耗能能力等受力性能均满足延性框架的抗震要求 ,且模型框架的有效延性系数达到了 7 5 4,远大于一般延性框架延性系数应不小于 4 0的要求。由此可以得出结论 ,钢管混凝土框架结构的抗震性能优于钢筋混凝土框架结构和钢框架结构 ,可在我国中高层住宅建筑中推广应用     

钢筋混凝土框架柱的延性设计

从延性破坏的概念出发,给出了对钢筋混凝土框架结构延性的理解,介绍了作为结构主要竖向受力构件的框架柱的破坏形态,分析了影响框架柱延性的主要因素,并结合分析所得的影响因素提出在实际工程设计中提高框架柱延性、进而提高结构抗震能力的一些建议,为同类工程设计提供参考。     

延性节点钢框架结构的抗震性能分析

为简化延性耗能节点钢框架结构的数值计算,利用延性耗能节点简化理论模型分别对6层、12层的翼缘削弱型节点钢框架和盖板加强型节点钢框架进行简化,并对框架简化模型和实际框架模型进行模态分析;提取框架结构的前3阶基本周期并计算阻尼比,并对框架结构简化模型和实际模型开展El Centro波和Taft波2种地震波下的动力时程分析,将框架简化模型计算得到的框架基本周期、柱顶位移和柱底剪力时程曲线与实际框架模型的数值计算结果进行对比。结果表明:整体上框架简化模型和实际框架模型的数值计算结果吻合较好,翼缘削弱型节点框架简化模型计算的框架基本周期比实际模型计算值稍小,相对误差在8.5%以内,而盖板加强型节点框架简化模型计算的框架基本周期比实际模型计算值稍大,相对误差在4.0%以内;柱顶位移和柱底剪力时程曲线吻合较好。延性节点简化理论模型用于框架结构动力计算具有极高的计算精度,可有效分析延性节点钢框架结构的抗震性能。     

低周反复荷载下新型组合框架结构受力性能的试验

按照现行规范的有关规定设计制作了1榀2跨单层新型外包钢-混凝土组合梁-普通钢混凝土柱的组合框架结构模型，并通过施加恒定竖向荷载和低周反复水平荷载，对模型框架进行了抗震性能试验研究。分析了新型组合框架滞回性能、变形能力、承载能力、延性、耗能能力、刚度退化等受力性能。试验表明，新型组合框架结构具有良好的抗震能力。     

对斜支撑结构于抗震设计中作用的探讨

单个结构单元的非线性分析说明，在异型柱框架中添加了人字形支撑后，结构的抗扭刚度和抗扭承载力有显著提高，延性也有所提高。通过对异型柱框架结构和矩形柱结构进行地震作用下的对比分析，说明异型柱框架的抗扭性能要远低于等惯性矩的矩形框架结构，添加斜支撑对提高异型柱框架抗震性能有显著作用。本文采用有限元程序Ansys和SAP，对异型柱框架结构和异型柱加斜支撑结构进行了空间受力分析，并建议在刚心与质心不一致的异型柱框架结构中，适当使用斜支撑结构以便提高结构抗扭性能。     

双肢冷弯C型钢支撑框架抗震性能试验研究

双肢冷弯薄壁C型钢框架是一种新型的钢框架结构。对两榀3层单跨双肢冷弯薄壁C型钢框架进行拟静力试验,以是否设置交叉支撑作为设计参数,研究支撑对该类钢框架抗震性能的影响。通过对两榀框架结构的试验破坏现象、滞回曲线和骨架曲线的分析,得到了两榀框架结构的破坏模式和各项抗震性能指标,总结了交叉支撑对框架传力机制及抗震性能的影响。结果表明,该类钢框架结构的破坏模式符合"强柱弱梁"的抗震设计要求,具有良好的延性和耗能能力,承载力退化稳定;增设交叉支撑后,框架结构的承载力和刚度明显提高,框架侧移明显减小,但延性和耗能能力有所降低;通过对支撑及框架的受力分析结合试验结论提出该类框架结构支撑的设计建议。     

装配式中空夹层钢管混凝土组合框架混合动力试验研究

为研究中空夹层钢管混凝土组合框架的抗震性能，设计了一个3跨10层的中空夹层钢管混凝土组合框架结构，利用OpenSEES建立了该结构的混合动力模型，以中跨底部两层框架为试验子结构，采用混合试验方法开展了装配式中空夹层钢管混凝土组合框架拟动力试验研究。根据试验结果，验证了混合动力模型的准确性，获得了组合框架在地震作用下的破坏模式和动力响应，分析了中空夹层混凝土柱和组合节点的受力性能，揭示了组合框架的整体抗震性能。结果表明：中空夹层钢管混凝土组合框架破坏模式包括节点端板鼓曲、梁下翼缘屈曲、楼板混凝土压溃和柱钢管鼓曲；在罕遇地震作用下整体结构未出现明显的破坏现象，框架整体呈现出良好延性；由于结构中部荷载较大，中柱比边柱更早进入屈服阶段，而组合节点能够通过自身转动产生的塑性变形耗散大部分地震能量，避免梁端出现塑性铰并减小传递给柱端的弯矩，进而改善柱端受力，提高组合框架的整体抗震性能。     

填充节能复合墙板钢框架结构的抗震性能

为了获悉节能复合墙板与H形钢框架在地震作用下的受力性能与破坏机理,进行了8榀足尺填充节能复合墙板钢框架结构的低周反复荷载试验。详细分析了破坏模式、滞回曲线、骨架曲线、延性、耗能能力等。利用ABAQUS程序建立了填充节能复合墙板钢框架结构的有限元分析模型,进行了结构非线性全过程受力分析;该模型考虑了材料本构关系模型和复杂接触模型。试验结果验证了有限元分析的准确性。研究表明,填充节能复合墙板钢框架结构有良好的抗震性能和延性;墙板连接方式和墙板厚度是影响结构承载力和刚度的主要因素;建立的有限元模型可以用于填充节能复合墙板钢框架结构的数值分析;采用的螺栓连接方式较好地实现了节能复合墙板与钢框架在地震作用下的协同工作。     

Comparative study of special and ordinary braced frames

The collapse probability of ductile and non‐ductile concentrically braced frames was investigated using nonlinear dynamic response analysis. Two buildings with three and nine stories located in Boston and Los Angeles, respectively, were designed and subjected to ground motions from the areas. In Boston area, three‐story and nine‐story buildings were designed as ordinary concentrically braced frame with response modification reduction factor R equal to 3 1/4 to be considered as non‐ductile structural systems; comparatively, in Los Angeles area, three‐story and nine‐story buildings were designed as special concentrically braced frame with response modification reduction factor R equal to 6 to be considered as ductile structural systems. In order to evaluate the performance of ductile and non‐ductile concentrically braced frames in moderate and severe seismic regions, ATC‐63 would be used as reference to assess the seismic behaviors. Evaluation approach recommended by ATC‐63 was adopted, and hundreds of nonlinear dynamic analyses were performed. Through alternating the scale factors of designated ground motions, median of structural collapse intensity was presented for each structure. By observing the results of statistical performance assessment, the seismic performance of the systems was evaluated, and some observations are made based on the study. Copyright © 2012 John Wiley & Sons, Ltd.     

Progressive collapse resisting capacity of braced frames

In this study, the progressive collapse potential of braced frames was investigated using nonlinear static and dynamic analyses. Eight different bracing types were considered and their performances were compared with those of a special moment‐resisting frame designed with the same design load. According to the pushdown analysis results, most braced frames designed per current design codes satisfied the design guidelines for progressive collapse initiated by loss of a first story interior column; however, most model structures showed brittle failure mode caused by buckling of braces and columns. Among the braced frames considered, the inverted‐V type braced frames showed superior ductile behaviour during progressive collapse. The nonlinear dynamic analysis results showed that all the braced structures remained in stable condition after sudden removal of a column, and their deflections were less than that of the moment‐resisting frame. Copyright © 2009 John Wiley & Sons, Ltd.     

Performance evaluation of special and intermediate moment‐resisting reinforced concrete frames using pushover and incremental dynamic analysis

In this study, the seismic performance of special and intermediate moment‐resisting reinforced concrete frames are evaluated through nonlinear static and dynamic analysis. According to experimental studies, one of the most important parameters affecting the behavior of special and intermediate ductile reinforced concrete frames is the transverse reinforcement ratio. In this paper, constitutive law of material for concrete under the influence of various transverse reinforcement ratios have been derived using Mander et al. model, and 20 ground‐motion accelerograms have been utilized for dynamic analysis. Additionally, the results of pushover and incremental dynamic analysis were compared in order to evaluate seismic performance of the selected high‐rise structures. Results reveal that both types of reinforced concrete frames with beam‐hinge type failure mechanisms have ductile behavior. Special moment frames have higher ductility because of early entry into nonlinear range resulting in higher plastic rotations, which result in greater lateral displacements. Due to the differences in behavior of intermediate and special ductility frames, confinement has an important role in the ductile behavior of structures. Copyright © 2011 John Wiley & Sons, Ltd.     

Reliability analysis of frame structures with brittle components

A review is provided of the recent developments in the reliability analysis of ductile (elastic-plastic) systems and of the stable configuration approach of structural system reliability analysis. These are combined to obtain a methodology for evaluating the reliability of frames that have primarily ductile components but also a few brittle components. The methodology is applied to two frame structures.     

Seismic performance of R/C plane frames irregular in elevation

The paper addresses multistorey reinforced concrete (R/C) frame buildings, irregular in elevation. Two ten-storey two-dimensional plane frames with two and four large setbacks in the upper floors respectively, as well as a third one, regular in elevation, have been designed to the provisions of the 2004 Eurocode 8 (EC8) for the high (DCH) and medium (DCM) ductility classes, and the same peak ground acceleration (PGA) and material characteristics. All frames have been subjected to both inelastic static pushover analysis and inelastic dynamic time-history analysis for selected input motions. The assessment of the seismic performance is based on both global and local criteria. It is concluded that the effect of the ductility class on the cost of buildings is negligible, while the seismic performance of all irregular frames appears to be equally satisfactory, not inferior to (and in some cases superior than) that of the regular ones, even for motions twice as strong as the design earthquake. As expected, DCM frames are found to be stronger and less ductile than the corresponding DCH ones. The overstrength of the irregular frames is found to be similar to that of the regular ones, while DCH frames are found to dispose higher overstrength than DCM ones. Pushover analysis seems to underestimate the response quantities in the upper floors of the irregular frames.     

钢筋混凝土框架的抗震性能

纯框架被分类为典型的韧性、名义韧性和GLD(重力荷载设计)。根据侧向抗力、层间位移的分布和构件屈服的次序,可对这些结构的抗震性能进行评估。在研究中,对一个典型的5层框架按照(a)韧性;(b)名义韧性;(c)GLD;(d)改进的GLD方法进行设计,采用非线性时间序列分析和推覆分析,提出了混凝土框架抗震评估的分析方法。通过有效的试验结果验证了分析模型。采用分析模型评估了5层框架的抗震性能。可推断出,在所考虑的地震荷载下,韧性和名义韧性的框架性能良好,而GLD结构的抗震性能不令人满意。损坏的GLD框架被加固后,抗震性能有所提高。     

Displacement-restraint bracing for seismic retrofit of steel moment frames

This paper presents a seismic retrofit method using wire rope (cable) bracing for steel moment-resisting frames. The retrofitted frame using the proposed bracing system exhibits ductile behavior and maintains seismic energy dissipation capacity to the same extent as the original bare frame. The bracing member does not act for small and medium vibration amplitudes. For large vibration amplitudes, the bracing member acts and restrains unacceptably large story drift. This retrofit method prevents an increase in the column compression force resulting from the brace action. Cyclic loading test results of the portal frames reveal fundamental characteristics of the proposed bracing system. Seismic response analyses are also conducted for the three-story moment-resisting frames. The effectiveness of the retrofit method is discussed in light of these test and analysis results.     

基于拟力法的框架结构静力弹塑性分析

针对拟力法仅在刚性连接钢框架中应用的现状,根据钢筋混凝土框架以及半刚性连接钢框架的受力特点,并基于拟力法的基本假定与思路,得出了钢筋混凝土结构中塑性铰和半刚性连接钢框架中连接的弯矩-相对转角关系,从而推导并获得了拟力法在框架结构静力弹塑性分析中的通用公式。通过与有限元理论计算结果的比较,表明基于拟力法的框架结构静力弹塑性分析方法在应用于各类框架结构时都有着较高的精度,从而为将基于拟力法的动力弹塑性分析包括地震能量分析拓展到钢筋混凝土框架结构以及半刚性连接钢框架结构中奠定了基础。     

Seismic design, performance, and behavior of composite-moment frames with steel beam-to-concrete filled tube column connections

Concrete filled steel tube (CFT) columns have been widely used in composite-moment frames (C-MFs) both in non-seismic and in high seismic zones. The objective of this research is to develop a design methodology of such moment resisting frame structures designed with CFT columns in achieving ductile behavior and high strength. These composite-moment frames mostly constructed around the perimeter of the building provide the enough stiffness to withstand the lateral displacement due to wind or seismic loads. In this research, three sets of prototype composite frame models were designed on the basis of the proposed design examples as 3-, 9-, and 20-story post-Northridge SAC buildings with composite-special moment frame (C-SMF) systems designed for the western US area. The exact moment-rotational behavior of steel beam-to-CFT column connections including the strength degradation was simulated using the 2D joint model with the rigid boundary element. Nonlinear pushover analyses were conducted on the numerical frame models so as to evaluate the over-strength, inelastic deformation, and P-Delta effect for the entire structure. The statistical investigation was introduced to nonlinear dynamic analyses under 40 SAC ground motions corresponding to a seismic hazard level of 2% probability of exceedence in 50 years in order to efficiently examine seismic performance and behavior of entire composite frame structures. All frame models meet the allowable limit for safe designs. In addition, the entire frame design becomes conservative as the number of stories increases. The distribution of interstory drift ratios (ISDRs) as well as the over-strength ratio also demonstrates this conservative design of low to high-rise CMF structures.