新型外廊式钢筋混凝土框架结构抗震性能试验研究

为改善带填充墙外廊式框架结构的抗震性能,尝试将采用高阻尼砂浆阻尼层的阻尼填充墙和PVA-ECC材料应用于外廊式框架结构中。以5.12汶川地震中倒塌的漩口中学综合教学楼为原型,选取最具代表性的中间榀较大跨满布填充墙框架的底层,设计制作了2个缩尺比例为1/4的单层两不等跨试验模型,并进行了低周反复加载试验,得到了其裂缝发展情况、破坏形态、承载能力、滞回曲线、骨架曲线、位移延性、刚度退化以及耗能性能。结果表明:采用高阻尼砂浆阻尼层的阻尼填充墙较普通填充墙具有更强的变形能力,对主体框架变形约束更弱,能延缓主体框架的破坏;采用PVA-ECC柱的组合框架较普通混凝土框架具有更强的承载力、更高的延性、更好的刚度退化与耗能性能。     

钢筋混凝土框架抗震结构地震能量分布及耗散研究

基于能量平衡原理,对多层钢筋混凝土框架结构的地震输入能量的分布及耗散规律进行了研究。选用8条天然地震波和2条人工波,运用Perform-3D软件,对多层钢筋混凝土框架结构模型在7度罕遇地震作用下的弹塑性能量进行数值仿真计算。计算了钢混框架结构在不同地震波下的地震总输入能量、滞回耗能、阻尼耗能以及滞回耗能占总耗能的比例时程,分析了地震能量在各分量中的分布及分配规律;分析了阻尼比和延性比对地震输入能量的影响,确定了滞回耗能随阻尼比和延性比的变化规律;研究了钢筋混凝土框架结构梁柱构造和竖向侧移刚度变化对地震输入能及其分量的影响,确定了多层钢筋混凝土框架结构滞回耗能沿竖向的分布规律及沿横向在框架构件中的分配,研究了框架结构存在薄弱层情况下的滞回耗能的分布规律。揭示了多自由度钢筋混凝土框架结构地震输入能量及其分布规律,可为基于能量平衡原理的抗震设计理论在工程实际中的运用提供有益的参考。     

基于频响函数的高阻尼混凝土悬臂梁试验分析

本文对两根分别为普通C35混凝土悬臂梁及高阻尼混凝土悬臂梁进行了拟静力加载和锤击振动测试的交叉试验。基于结构频响函数,研究高阻尼混凝土悬臂梁基本频率与阻尼比随损伤的变化趋势;考察悬臂梁在不同损伤阶段的裂缝开展情况,建立悬臂梁弯曲动刚度与损伤之间的关系;通过各锤击点不同损伤阶段的频响函数,考察悬臂梁的动刚度退化情况。研究表明:随着控制位移的增加,两悬臂梁构件基本频率均逐渐减小,第一阶阻尼比则先增大后减小;高阻尼混凝土悬臂梁在屈服点后阻尼比显著高于普通混凝土;混凝土悬臂梁动力特性随损伤的关系与悬臂梁裂缝数量、裂缝宽度及塑性发展密切相关。     

CFRP加固半高填充墙短柱框架抗震性能试验研究

设置半高填充墙的钢筋混凝土框架结构在地震中极易发生短柱破坏,进而引起结构整体倒塌,为改善半高填充墙框架结构的抗震性能,制作了3组半高填充墙框架结构试验模型,采用不同方法对短柱外包(Carbon fiber reinforced polymer, CFRP)加固,分析了CFRP布条带加固模型和全包加固模型的延性系数、滞回曲线、骨架曲线、刚度退化、耗能能力及破坏模式。试验结果显示：CFRP加固将半高填充墙框架结构的薄弱环节从短柱转移到填充墙,在填充墙完全破坏后框架结构表现为强柱弱梁型的节点破坏,外包CFRP加固将半高填充墙框架短柱破坏的脆性破坏模式转变为强柱弱梁型的框架延性破坏模式;全包加固后结构的初始刚度有所提高,条带加固可以大大提高结构的耗能能力,2种加固方法都能提高结构的延性和抗震性能。     

钢筋混凝土框架结构阻尼性能的研究

阻尼比是一个重要的结构动力特性参数,它对结构的动力响应有重要影响。目前结构抗震计算通常取阻尼比为常数,这不能真实反映建筑物的阻尼机理,与阻尼比的实测结果也有很大的差距。本文以选取的混凝土框架现场脉动实测阻尼数据、混凝土框架模型振动台试验实测阻尼数据、由地震记录识别的混凝土框架阻尼数据及自行完成的混凝土悬臂试件自由振动实测阻尼数据为依据,对混凝土强度、实验方法、结构方位、结构自振频率和结构变形大小等对混凝土框架阻尼性能的影响进行了分析,在此基础上,统计得到了混凝土框架弹性阻尼比、弹塑性阻尼比与频率或变形相关的计算公式。通过与国内外已有公式的比较,论证了本文建立的阻尼比计算公式的合理性和有效性。     

基于OpenSees的防屈曲支撑加固钢筋混凝土框架数值模拟

提出了一种既有钢筋混凝土框架结构的抗震加固方法,该法采用防屈曲支撑提高框架结构体系的水平承载力和耗能能力,利用外包钢进一步提高柱子的抗弯和抗剪承载力。采用开源有限元程序OpenSees,分别建立空钢筋混凝土框架和防屈曲支撑加固钢筋混凝土框架的分析模型,对2榀钢筋混凝土框架的抗震性能进行模拟。防屈曲支撑采用了弹塑性桁架单元模型,加固框架柱混凝土考虑了外包钢的约束作用。将分析结果与拟静力试验结果进行比较,以检验分析模型的准确性,以及研究防屈曲支撑和外包钢对混凝土框架抗震性能的影响。分析结果表明,数值模拟与试验结果吻合较好,验证了基于OpenSees建立的数值模型的准确性;外包钢有效改善了框架柱的抗弯承载力和变形能力;防屈曲支撑显著提高了加固框架体系的水平刚度、水平承载力和耗能能力。     

纤维增强钢筋混凝土柱的抗震性能试验研究

纤维与胶粉的掺入可以改善混凝土材料的阻尼性能。本文首先利用自主开发的三点弯曲梁式大尺寸材料阻尼测试装置在频率(0.5~2.0Hz)条件下测定了4种不同配比纤维增强阻尼混凝土的损耗因子与储存模量,然后利用配制的纤维阻尼增强混凝土制作了4个框架柱,通过单轴滞回特性试验研究了在相同的轴压比、配筋率、配箍率、剪压比条件下,纤维增强阻尼混凝土与普通混凝土在非线性阶段阻尼性能、抗震性能及破坏特征的差异,得出纤维增强阻尼混凝土的骨架曲线和恢复力曲线的特征点。试验结果表明:在弹性范围内,纤维可以大幅提高素混凝土的阻尼性能,使素混凝土的损耗因子提高大约80%~200%,但是当构件进入非线性阶段以后,材料阻尼对普通混凝土阻尼性能影响很小。     

填充墙RC框架结构加固方法的研究现状及展望

综述了用于提高填充墙钢筋混凝土(RC)框架结构抗震性能和改善结构损伤模式的几类加固措施,从工艺、加固效果和破坏形式3个角度进行了分析。在建筑结构设计过程中,填充墙通常被视为一种典型的脆性非均质非结构构件,忽视了填充墙与RC框架之间的相互作用。地震调查报告表明,在结构遭受地震作用时,填充墙通常先于钢筋混凝土框架发生破坏,未经合理设计的填充墙RC框架结构将在地震作用下产生严重不良后果。试验结果和数值模拟分析结果证明,砌块的强度越低、砂浆的强度越高,结构的承载能力和刚度退化越慢、耗能能力越好。文中根据目前已有的建筑材料改性试验结果,从改性机理出发,分析了一系列有利于提高结构抗震性能的新型材料,并对结构的设计方案进行了探讨。     

基于弹塑性静力分析方法的一种摇摆式钢筋混凝土框架抗震性能研究

研究了一种摇摆式钢筋混凝土框架的抗震性能。首先建立了摇摆式钢筋混凝土框架结构的有限元模型并进行了试验验证;其次使用弹塑性静力分析方法评定无控及受控式摇摆钢筋混凝土框架结构的抗震性能;最后对比分析无控及受控摇摆式钢筋混凝土框架结构的抗震性能。结果表明设置阻尼器后的摇摆式钢筋混凝土框架的结构等效阻尼比大幅度提升,结构塑性变形耗能转变成阻尼器屈服耗能,结构位移响应得到了有效控制。     

结构阻尼与材料阻尼的关系

针对固体材料在弹性阶段的内阻尼,采用材料粘弹性本构关系,通过有限单元法建立了考虑剪切变形影响的杆单元阻尼矩阵,得到了材料拉压粘滞系数和剪切粘滞系数之间的关系。我们可以通过实验测试材料的损耗因子或粘滞阻尼系数(材料阻尼),像结构质量矩阵、刚度矩阵一样通过比较确切的计算得到弹性阶段结构内阻尼的阻尼矩阵(结构阻尼),而且此阻尼矩阵既基于材料阻尼实验测试,又便于数学处理,且物理意义明确。其次,本文分析了材料阻尼对结构阻尼比影响,得到了材料损耗因子与结构模态阻尼比间的关系,并通过10层钢筋混凝土剪切型框架结构进一步给出了具体的数值结果。     

Seismic performance of steel reinforced ultra high-strength concrete composite frame joints

To investigate the seismic performance of a composite frame comprised of steel reinforced ultra high-strength concrete (SRUHSC) columns and steel reinforced concrete (SRC) beams, six interior frame joint specimens were designed and tested under low cyclically lateral load. The effects of the axial load ratio and volumetric stirrup ratio were studied on the characteristics of the frame joint performance including crack pattern, failure mode, ductility, energy dissipation capacity, strength degradation and rigidity degradation. It was found that all joint specimens behaved in a ductile manner with flexural-shear failure in the joint core region while plastic hinges appeared at the beam ends. The ductility and energy absorption capacity of joints increased as the axial load ratio decreased and the volumetric stirrup ratio increased. The displacement ductility coefficient and equivalent damping coefficient of the joints fell between the corresponding coefficients of the steel reinforced concrete (SRC) frame joint and RC frame joint. The axial load ratio and volumetric stirrup ratio have less influence on the strength degradation and more influence on the stiffness degradation. The stiffness of the joint degrades more significantly for a low volumetric stirrup ratio and high axial load ratio. The characteristics obtained from the SRUHSC composite frame joint specimens with better seismic performance may be a useful reference in future engineering applications.     

Cyclic testing of a single bay reinforced concrete frames with various types of masonry infill

In this paper, a contribution of various types of masonry infill to the behaviour of reinforced concrete frames under lateral loads is presented. As a part of the bigger project, ten one‐bay, one‐storey reinforced concrete frames were designed according to the EC8, built in a scale 1:2.5, infilled with masonry and tested under constant vertical and cyclic lateral load. The masonry wall had various strength properties, namely, high strength hollow clay brick blocks, medium strength hollow clay brick blocks and low strength lightweight autoclaved aerated concrete blocks. There were no additional shear connectors between the masonry and frame. The results showed that the composite ‘framed wall’ structure had much higher stiffness, damping and initial strength than the bare frame structure. Masonry infill filled in the load capacity gap from very low (0.05%) to drifts when the frame took over (0.75%). The structures behaved as linear monolithic elements to drifts of 0.1%, reached the maximum lateral capacities at drift of 0.3%, maintained it to drifts of 0.75% and after that their behaviour depended on the frame. Masonry infill had severe damage at drift levels of about 0.75% but contributed to the overall system resistance to drifts of about 1%. At that drift level, the frame had only minor damage and was tested to drifts of about 2% without any loss of capacity. Improvement of the ‘infill provisions’ in the codes could be sought by taking into account the contribution of a common masonry that reduces expected damages by lowering the drift levels. Copyright © 2012 John Wiley & Sons, Ltd.     

新型框架结构弹塑性地震反应的等效线性化方法研究

等效线性化方法是计算结构弹塑性地震反应的实用方法.通过对几种等效线性化方法的比较分析,提出了基于FEMA440 （2005）计算等效刚度和等效阻尼比的等效线性化方法;分别采用静力弹塑性分析方法和等效线性化方法,分析了局部使用高性能纤维增强混凝土新型框架结构的弹塑性地震反应.结果表明,两种方法所得结构的地震反应均比较接近.因此,本文建议的等效线性化方法能够较好地预测新型框架结构的弹塑性地震反应.     

Masonry infill walls in reinforced concrete frames as a source of structural damping

This paper presents the results of an experimental study on the determination of damping characteristics of bare, masonry infilled, and carbon fiber reinforced polymer retrofitted infilled reinforced concrete (RC) frames. It is well known that the masonry infills are used as partitioning walls having significant effect on the damping characteristics of structures as well as contribution to the lateral stiffness and strength. The main portion of the input energy imparted to the structure during earthquakes is dissipated through hysteretic and damping energies. The equivalent damping definition is used to reflect various damping mechanisms globally. In this study, the equivalent damping ratio of carbon fiber reinforced polymer retrofitted infilled RC systems is quantified through a series of 1/3‐scaled, one‐bay, one‐story frames. Quasi‐static tests are carried out on eight specimens with two different loading patterns: one‐cycled and three‐cycled displacement histories and the pseudo‐dynamic tests performed on eight specimens for selected acceleration record scaled at three different PGA levels with two inertia mass conditions. The results of the experimental studies are evaluated in two phases: (i) equivalent damping is determined for experimentally obtained cycles from quasi‐static and pseudo‐dynamic tests; and (ii) an iterative procedure is developed on the basis of the energy balance formulation to determine the equivalent damping ratio. On the basis of the results of these evaluations, equivalent damping of levels of 5%, 12%, and 14% can be used for bare, infilled, and retrofitted infilled RC frames, respectively. Copyright © 2013 John Wiley & Sons, Ltd.     

An effective simplified model of composite compression struts for partially-restrained steel frame with reinforced concrete infill walls

To resolve the issue regarding inaccurate prediction of the hysteretic behavior by micro-based numerical analysis for partially-restrained(PR)steel frames with solid reinforced concrete(RC)infill walls,an innovative simplified model of composite compression struts is proposed on the basis of experimental observation on the cracking distribution,load transferring mechanism,and failure modes of RC infill walls filled in PR steel frame.The proposed composite compression struts model for the solid RC infill walls is composed ofαinclined struts and main diagonal struts.Theαinclined struts are used to reflect the part of the lateral force resisted by shear connectors along the frame-wall interface,while the main diagonal struts are introduced to take into account the rest of the lateral force transferred along the diagonal direction due to the complicated interaction between the steel frame and RC infill walls.This study derives appropriate formulas for the effective widths of theαinclined strut and main diagonal strut,respectively.An example of PR steel frame with RC infill walls simulating simulated by the composite inclined compression struts model is illustrated.The maximum lateral strength and the hysteresis curve shape obtained from the proposed composite strut model are in good agreement with those from the test results,and the backbone curve of a PR steel frame with RC infill walls can be predicted precisely when the inter-story drift is within 1%.This simplified model can also predict the structural stiffness and the equivalent viscous damping ratio well when the inter-story drift ratio exceeds 0.5%.     

Optimum strength ratio of hysteretic damper

This paper deals with steel moment frames combined with hysteretic dampers. Specifically, it examines the strength of dampers required to minimize damage to moment frames under earthquake loading. The important structural variables are the ratio of the dampers' shear strength to the maximum resistance, termed β in this study, and the relative stiffness between the damper and the main frame, termed k. The equivalent viscous damping ratio of the entire structural system is affected by the quantities β and k and the ductility ratio of the main frame. The optimum dampers' strength ratio (β_opt), which maximizes the equivalent viscous damping ratio, was formulated as a function of k, and it was found that β_opt is independent of the ductility ratio of the main frame. Earthquake response analysis confirmed that damage to the main frame can be significantly reduced by hysteretic dampers and minimized at the value of β_opt. © 1998 John Wiley & Sons, Ltd.     

附加或不附加粘滞阻尼墙的RC框架试验与分析

本文阐述了附加或不附加粘滞阻尼墙的2个相同的RC框架模型振动台试验和理论分析的情况.这2个钢筋混凝土框架模型为3层1跨两开间,几何相似关系大致为1：2.将阻尼墙附加到一个RC框架模型当中,先后对附加或不附加阻尼墙的2个相同的RC框架模型进行振动台试验.试验结果表明,阻尼墙有效减小了框架模型的地震反应.对耗能框架模型和普通框架模型进行了弹性和弹塑性时程分析,计算结果和试验结果吻合良好.改变阻尼墙的参数进行分析,结果表明选取合适的阻尼墙参数,才能达到最好的耗能减振效果;适当减小层间位移较小处的阻尼墙参数,对减振效果影响很小而又能节省投资.     

不同跨高比对多层钢框架内填混凝土深梁结构抗震性能影响

为了研究不同跨高比多层钢框架内填混凝土深梁结构的抗震性能,在钢框架内填混凝土深梁滞回性能试验的基础上,利用ABAQUS对六层纯钢框架（结构一）、钢框架内填跨高比为2混凝土深梁结构（结构二）和钢框架内填跨高比为0.75混凝土深梁结构（结构三）进行弹塑性时程分析。结果表明:内填混凝土深梁使结构整体刚度明显增大;在地震波的作用下,结构二的最大顶点位移降低可达58.3%,结构三的最大顶点位移降低可达89.3%,内填混凝土深梁,结构的抗侧移性能得到了极大改善,且随着深梁跨高比的减小而大幅度提升;结构二滞回曲线饱满,呈现纺锤形,混凝土深梁充分起到了第一道防线作用。经济合理的钢框架内填混凝土深梁结构具有一定的工程应用价值。     

Experimental tests on full‐scale RC unretrofitted frame and retrofitted with buckling‐restrained braces

The results of experimental tests carried out on reinforced concrete (RC) full‐scale 2‐storey 2‐bays framed buildings are presented. The unretrofitted frame was designed for gravity loads only and without seismic details; such frame was assumed as a benchmark system in this study. A similar RC frame was retrofitted with buckling‐restrained braces (BRBs). The earthquake structural performance of both prototypes was investigated experimentally using displacement‐controlled pushover static and cyclic lateral loads. Modal response properties of the prototypes were also determined before and after the occurrence of structural damage. The results of the dynamic response analyses were utilized to assess the existing design rules for the estimation of the elastic and inelastic period of vibrations. Similarly, the values of equivalent damping were compared with code‐base relationships. It was found that the existing formulations need major revisions when they are used to predict the structural response of as‐built RC framed buildings. The equivalent damping ratio ξ_eq was augmented by more than 50% when the BRBs was employed as bracing system. For the retrofitted frame, the overstrength Ω and the ductility µ are 1.6 and 4.1, respectively; the estimated R‐factor is 6.5. The use of BRBs is thus a viable means to enhance efficiently the lateral stiffness and strength, the energy absorption and dissipation capacity of the existing RC substandard frame buildings. The foundation systems and the existing members of the superstructure are generally not overstressed as the seismic demand imposed on them can be controlled by the axial stiffness and the yielding force of the BRBs. Copyright © 2011 John Wiley & Sons, Ltd.     

钢筋混凝土框架顶部钢结构加层的抗震性能分析

采用钢结构加层后,结构的整体质量、刚度、周期、阻尼比等都发生较大的变化。仅对加层部分结构进行计算分析是不安全的,应进行结构的整体分析。本文采用有限元软件ANSYS,对某4层钢筋混凝土框架结构办公楼顶部加2层纯钢框架的抗震性能进行分析,并在此基础上讨论了不同加层层数的整体框架模型、不同阻尼比ζ和有侧移及无侧移框架形式对结构整体抗震性能的影响分析。计算表明,由于加层后结构周期加长,整体框架的底层层剪力变化较小。