高层屈曲约束钢板墙-混凝土框架结构抗震性能研究

为研究高层屈曲约束钢板墙-混凝土框架结构的抗震性能,分别设计了一个10层钢筋混凝土框架结构和屈曲约束钢板墙-混凝土框架结构模型,进行了地震作用下动力非线性分析。结果表明：屈曲约束钢板墙可显著减小高层钢筋混凝土框架结构在地震作用下的层间位移,同时在罕遇地震作用下框架中塑性铰的数量也有大幅减少,表现出良好的抗震性能。在此基础上,综合规范对框架结构和框架-抗震墙结构抗震等级和柱轴压比限值的规定,并结合屈曲约束钢板墙-混凝土框架结构的受力特点,提出了高层屈曲约束钢板墙-混凝土框架结构的抗震设计建议。建议屈曲约束钢板墙的边缘构件按框架结构确定抗震等级和柱的轴压比限值,其他框架部分根据其承担的地震倾覆力矩比例大小,按框架结构或框架-抗震墙结构确定抗震等级和柱的轴压比限值。     

近场强震作用下上海地区百米高层建筑地震动反应分析

首先,依据汶川地震中不同震中距基岩地震波记录,选取假设上海近场发生M8.0级强震时的基岩地震波.然后,对上海某百米高层建筑场地进行深覆盖土层地震反应分析,获得该场地在近场强震时的地表波.最后,以此百米高层建筑为例,分析该结构在此地表波作用下的地震动反应特点,从而评估近场强震对上海高层建筑的影响.分析结果表明:结构在双向地震动作用下的反应与单向地震动作用下的反应有明显不同.其中,地震动垂直分量对结构顶层节点竖向反应放大作用显著;地震动水平分量对结构顶层节点三个方向反应都有放大效应;地震动水平分量对结构层间位移角起决定性作用;地震动水平分量对结构底层角柱内力的影响大于地震动垂直分量对其的影响.     

Reliability assessment of structure subjected to horizontal-vertical random earthquake excitations

Statistical analysis of the response spectra due to both horizontal and vertical ground excitations is conducted. A method is presented for generating a uniform hazard response spectrum making use of the seismic hazard curve expressing annual probability of exceedance as a function of peak ground acceleration (PGA), a set of normalized mean response spectra, and a coefficient-of-variation function for the random normalized spectral values in terms of period T. The response spectra of the system are calculated by considering both horizontal and vertical excitations simultaneously. Comparison on the uniform hazard response spectrum for case of single input (horizontal excitation only) and for case of multiple inputs (horizontal and vertical excitations) are made. It is important to note that the effect of load ratio (Mg /P_cr) as well as the PGA ratio between horizontal and vertical ground accelerations are two important parameters in the analysis of structural systems subjected to both horizontal and vertical ground motions.     

Seismic behavior of strengthened square reinforced concrete columns under combined loadings

Abstract

This paper presents an experimental study examining the seismic behavior of square reinforced concrete (RC) columns subjected to combined loadings. In this study, nine full-scale square RC columns were made with the same structural properties. Five of them were strengthened with high-performance ferrocement laminate and bonded steel plates in order to investigate the effects of strengthening on the seismic behavior of RC columns under combined loadings. Finally, the failure mode, hysteretic load-displacement response, bearing capacity, energy dissipation, ductility and plastic hinge characteristics were recorded and analyzed. The results show that combined loadings reduced the bearing capacity and changed the failure modes and deformation characteristics. Strengthened RC columns had significantly improved bearing capacity and different failure modes under the same combined loadings in contrast to the non-strengthened RC columns. The vertical eccentricity had little effect on the mechanical properties of columns, while the horizontal eccentricity significantly weakened the mechanical properties of columns. The mechanical properties of uniaxial compression-bending-shear-torsion columns were the worst. The tri-linear model calculation parameters under different failure modes and combined loadings were fixed and validated by experimental results.     

Seismic design and performance analysis of buckling‐restrained braced RC frame structures

Due to the stable hysteretic behavior, buckling‐restrained braces (BRBs) have been increasingly adopted in reinforced concrete (RC) frame structures to develop a dual structural system (BRB‐RCF). This study proposed an alternative strength‐based design approach that decomposes the dual BRB‐RCF system into two independent RC frame and BRB system using the BRB‐carrying story shear ratio. The design of RC frame is performed in an integrated manner by considering the BRB postyielding force demands. Three RC frames with five, 10, and 15 stories were employed as prototype structures, and seven story shear ratios ranging from 0.1 to 0.7 were used to generate a total of 21 structural modes. The material usage, maximum axial compression ratio of columns, and elastic interstory drift ratio were compared for different story shear ratios. Nonlinear dynamic analysis of the BRB‐RCFs subjected to 12 ground motions were carried out. The seismic response including the maximum interstory drift ratio, hysteretic energy dissipation ratio, and actual BRB‐carrying story shear ratio were systematically assessed for different design story shear ratios. Based on the considerations of material usage and seismic performance, it is suggested that the design BRB‐carrying story shear ratio should be in the range of 0.3 to 0.5.     

Fiber element modeling for seismic performance of bridge columns made of concrete-filled FRP tubes

Concrete-filled fiber reinforced polymer (FRP) tubes (CFFT) are an alternative to reinforced concrete, providing for rapid construction with comparable strengths and higher ductility. Despite encouraging test data, it is not clear as to whether traditional analytical tools may be used for prediction of structural performance of CFFT, especially in seismic applications. This paper reports on modeling of CFFT either as cast-in-place reinforced or precast post-tensioned column in conjunction with a reinforced concrete (RC) footing. The model is verified against two earlier experimental programs at the member-level and subassembly-level. The model was then used to conduct a parametric study of different column configurations under a constant axial load and a reversed cyclic lateral load. Moreover, seismic performance of a typical CFFT column is compared with its RC counterpart under three different ground acceleration records. The study shows that seismic analysis of CFFT columns is possible using available analytical tools for conventional RC columns. Also, CFFT columns demonstrate superior performance over their RC counterparts in response to wide-ranging ground acceleration records. Fiber architecture of the FRP tube could be optimized for strength and ductility. Internal steel reinforcement and a minimum thickness of FRP tube are deemed necessary to provide adequate ductility and system integrity in seismic applications.     

变轴力下钢筋混凝土柱的抗震性能分析

准确预测地震作用下钢筋混凝土(RC)柱的受力特性,对评估混凝土结构的抗震性能具有重要意义。地震作用下,混凝土结构中的RC柱除承受水平荷载外,还由于地震作用引起的倾覆力矩影响承受变轴力作用。因此,往复荷载下RC柱受力及变形特性的研究应该考虑变轴力的影响。首先通过恒轴力和变轴力下RC柱滞回性能的模拟,验证了本研究基于纤维模型程序开发的数值分析模型的准确性。然后,利用该数值模型和分析程序,对一RC柱进行了不同变轴力模式下滞回性能的分析研究。分析结果表明,轴力的变化对RC柱的滞回性能有很大影响。由于非耦合型变轴力变化过程的随机性,为便于变轴力下RC柱的抗震性能分析和试验研究,提出了等代定轴力的概念及其确定方法。     

细长钢筋混凝土柱在地震荷载作用下的P-Δ效应

基于分层截面方法,对细长钢筋混凝土柱的P-Δ效应进行了研究。为了对钢筋混凝土柱的周期性行为进行有效分析(这种周期性行为可以根据外加轴向力的大小表现出荷载-位移关系曲线的改变),采用了分层截面方法,并且还采用程序在钢筋的应力-应变关系曲线中考虑了粘结滑移作用[Kwak HG,Kim JK.Implementation of bond-slipeffect in analyses of RC frames under cyclic loadsusing layered section method.Engineering Struc-tures2006,28(12):1715-27]。为了检验这种方法的有效性,以及确定在钢筋混凝土细长柱的综合反应中各种作用的重要性,采用了非线性动力分析方法对60组水平和竖向地震作用下位于常用范围内的长细和稳定度参数的构件进行分析。基于得到的大量分析结果,评估了轴向力、P-Δ效应和竖向地震力对结构反应的影响以及它们的相应贡献。此外,通过与精确的非线性动力分析中得到的结果相比较,评估了在钢筋混凝土结构的抗震设计中采用能力需求曲线的适用性。     

钢-聚丙烯混杂纤维混凝土柱抗震性能试验研究

考虑纤维种类、轴压比、剪跨比、配筋率等因素,设计制作22根钢-聚丙烯混杂纤维混凝土框架柱试件,通过低周反复荷载试验研究柱的抗震性能。基于实测的荷载-位移滞回曲线、骨架曲线及破坏形态,探讨纤维种类等因素对试件耗能能力和延性的影响规律,建立钢-聚丙烯混杂纤维混凝土柱位移延性系数计算公式。结果表明,钢-聚丙烯混杂纤维在增强柱耗能能力方面优于钢纤维或聚丙烯纤维,并随轴压比的增大,其发挥作用越明显;剪跨比、纵筋配筋率和配箍率对混杂纤维混凝土柱耗能能力和延性的影响与普通混凝土柱类似,随其增大而提高。     

Probabilistic seismic demand analysis of a slender RC shear wall considering soil-structure interaction effects

Reinforced concrete shear walls are often used to resist the lateral loads imposed by earthquakes. Accurate evaluation of the seismic demands on shear walls requires adequate considerations of the nonlinear behavior of structural and foundation elements, the interaction between them, and the uncertainty and variability associated with earthquake ground motions. This paper presents a comprehensive probabilistic seismic demand analysis of a typical mid-rise slender shear wall in western US with a flexible foundation and evaluates the significance of soil-structure interaction (SSI) effects on their damage probability. Utilizing realistic numerical models for the shear wall and its foundation, the nonlinear time history analyses were conducted with a large number of recorded ground motions. Response quantities such as maximum inter-story drift ratio, base shear, foundation displacement and rotation are monitored and related to the intensity measure of ground motions (i.e. the inelastic spectral displacement S_di) for the cases with and without considering the SSI effects. Subsequently, the fragility functions of the shear wall are derived and the impact of SSI effects is investigated. It is found that the SSI generally reduces the damage probability of the shear wall, especially when soil nonlinearity is taken into account. The sensitivity of various seismic demands to soil parameters is also discussed. Under strong ground shakings, SSI effects on the maximum inter-story drift are most sensitive to the friction angle of the soil. It is suggested that the damages in foundation and surrounding soil should also be considered in order to systematically evaluate the SSI effects on damage probability of shear wall buildings.     

广州西塔结构抗震设计

广州西塔地下4层(局部5层),地面以上103层,主塔楼高432m,采用巨型钢管混凝土柱斜交网格外筒+钢筋混凝土内筒的筒中筒结构。斜交网格筒侧向刚度、抗扭刚度大,以斜柱轴力抵抗水平荷载引起的结构楼层水平剪力和倾覆力矩,充分发挥了高强钢管混凝土柱的优势,是超高层建筑的优良结构形式。介绍西塔结构的抗震设计,以概念设计和简单演算论证了结构的抗震安全性。由于结构构件承载力及刚度需求为风荷载组合所控制,相对于地震作用而言,结构的超强系数大,易于达到比现行建筑结构抗震设计要求更高的抗震性能目标。结合西塔的具体情况,讨论了西塔结构抗震等级的设定问题,指出有必要循R-μ-T关系改进关于结构抗震等级的规定。     

One-dimensional wave equation analyses for pile responses subjected to seismic horizontal ground motions

This paper presents a numerical one-dimensional wave equation analysis technique for piles and pile groups subjected to seismic horizontal ground motions in liquefiable zones. The so-called Earthquake Wave Equation Analysis for Piles (EQWEAP) procedure is introduced for piles subjected to horizontal earthquake excitations. Disregarding the effects of kinematic soil–pile interaction, the seismic responses of piles can be obtained by approximating the free-field ground response analysis, the ultimate earth pressure model, and the ground displacement profiles. The nonlinearities of the concrete piles were modeled using the approximate tri-linear moment–curvature relationships. A case study and application concerns were presented. Although the analysis is in one dimension, it is found to be effective and able to provide a rapid estimation in foundation design when seismic pile behaviors are of interest. The advantages of this analysis are the time efficiency of the seismic design of pile foundations and the relative simplicity of the analysis. In addition, it suggests alternative modeling for the dynamic analysis adopting the commonly known static models and/or methods.     

Enhancement of seismic performance of reinforced concrete columns with buckling-restrained reinforcement

Reinforced concrete (RC) columns with light confinement prevalent in developing countries exhibit low ductility with brittle shear failure, especially when buckling of longitudinal rebars takes place. This study applies the buckling restraining concept widely used in seismic resistant steel structures to reinforcing bars. Two RC columns 270 mm×300 mm in cross section with a height of 1200 mm and minimum (non-seismic) transverse reinforcement were tested under cyclic lateral loading. Buckling-restrained reinforcement was provided over the critical zone. The buckling-restraining casing effectively prevented buckling of slender vertical bars under a substantially high axial load level, resulting in a more ductile mode of failure with the evident formation of plastic hinge at the base of the column. Prior to gravity load collapse, the drift capacities and the degraded concrete shear capacities of the specimens were significantly increased compared to their counterparts without casings.     

柱失效方程中荷载相关特性对承载力抗震设计可靠度的影响

以竖向荷载和水平地震作用组合下的钢筋混凝土柱和钢柱为对象,研究了失效方程中荷载相关特性对柱承载力抗震可靠性的影响。根据现行《混凝土结构设计规范》和《钢结构设计规范》分析了不同柱弯矩轴力相关曲线的特性。结合多个框架结构实例,对比了柱失效方程中荷载相关曲线与规范考虑情形的异同。实例分析表明:水平地震和竖向荷载组合作用下,小偏压RC柱和工字型钢柱的荷载相关曲线与规范考虑的情形较为符合,均近似为负相关的直线;水平地震和竖向荷载组合作用下,大偏压RC柱的荷载相关曲线则与规范考虑的情形有较大出入,存在明显的正相关段部分。在此基础上,考虑失效方程复杂特性,依据已有的荷载和抗力变量概率模型,采用Monte Carlo法分析了水平地震和竖向荷载组合作用下柱的可靠性。结果表明:钢柱和小偏压RC柱的承载力抗震可靠度随轴压力荷载效应比值的变化幅度较小,与规范模式计算结果较接近;大偏压RC柱的承载力抗震可靠度随轴压力荷载效应比值的变化会有较大幅度波动,与规范模式计算结果差异较大;当轴压力荷载效应比值为负时,大偏压RC柱的承载力抗震可靠度会低于规范计算值较多,现行柱可靠性设计方法会偏于不安全。     

钢筋混凝土柱弯剪破坏恢复力模型骨架曲线

为研究弯剪破坏柱的抗震性能,进行了不同设计参数的24根钢筋混凝土（RC）柱的拟静力试验,分析了剪跨比、轴压比及配箍率（箍筋间距）对柱破坏模式及其抗震性能的影响,给出了确定弯剪破坏柱开裂、屈服和破坏时对应荷载及位移的计算方法,并提出了建立弯剪破坏柱恢复力模型骨架曲线的简化方法。研究结果表明：发生弯剪破坏的柱,其变形在2Δy～4Δy前弯曲作用明显,滞回曲线饱满,但之后由于抗剪能力不足会突然丧失承载力;利用弯剪破坏柱的3个特征点（开裂点、屈服点、剪切破坏点）建立其恢复力模型骨架曲线的方法,简化了RC柱的受力分析,可用于计算地震作用下弯剪破坏RC柱的荷载-变形全曲线。建立的恢复力模型骨架曲线与试验曲线吻合较好。     

碳纤维加固混凝土柱设计计算方法探讨

本文结合国内外碳纤维加固混凝土柱的试验研究成果以及我国现行的建筑设计规范对碳纤维加固混凝土柱的轴向承载力和抗震加固等设计计算方法进行了探讨 ,并给出了相应的计算算例 ,以便工程设计人员参考     

钢管约束钢筋混凝土柱与型钢混凝土柱滞回性能试验研究

进行了3组共6个框架柱的滞回性能试验研究,3组试件分别为钢筋混凝土柱(RC柱)、型钢混凝土柱(SRC柱)与钢管约束钢筋混凝土柱(STRC柱);每组2个试件,包括1个剪跨比λ=3.0的中长柱和1个剪跨比λ=1.5的超短柱。3组试件的截面尺寸、柱子长度和轴力相同,且SRC柱与STRC柱的用钢量相同。试验结果表明,RC与SRC超短柱的变形能力不满足现行抗震规范要求。SRC柱的受弯承载力高于STRC柱,但其变形能力、延性和耗能能力低于STRC柱。STRC短柱中,外包钢管不能有效提高短柱的受剪承载力,但外包钢管对核心混凝土的约束作用有效提高了短柱的延性和变形能力。根据试验结果,建议了STRC超短柱的受剪承载力计算方法,可为工程实践提供参考。     

CFRP加固高强混凝土方柱的延性性能试验分析与计算

为了研究碳纤维增强复合材料(CFRP)加固高强混凝土方柱的抗震性能,对13个高强混凝土方柱进行低周反复荷载试验,研究了试件破坏形态、滞回特性、骨架曲线、耗能能力和延性等抗震性能,探讨了轴压比、剪跨比、CFRP加固量对高强混凝土方柱延性性能的影响,给出了计算CFRP布有效约束系数和位移延性系数的公式。结果表明:随着轴压比增大、剪跨比减小,试件耗能能力和延性降低;横向包裹CFRP布可以显著改善高强混凝土方柱耗能能力和延性;与未加固试件相比,横向包裹CFRP布对轴压比较大或剪跨比较小试件的延性提高效果更为显著;随着加固量的增加,试件的耗能能力和延性增大,但增加幅度逐渐降低。     

新型模块化自保温混凝土剪力墙抗震性能试验研究

为研究新型模块化装配式自保温混凝土剪力墙在不同轴压比作用下的抗震性能,设计并制作了4组共12个混凝土剪力墙试件,所有试件均为配筋相同的一字型剪力墙,两端设置暗柱,包括1组实心现浇对比剪力墙试件,1组预制空心后填实剪力墙试件和2组新型自保温预制混凝土剪力墙试件,对其进行低周反复加载试验。采用ABAQUS有限元软件建立自保温混凝土剪力墙精细化有限元分析模型。试验结果表明,在3种设计轴压比下,自保温预制剪力墙的平均屈服荷载和平均峰值荷载均与预制实心剪力墙近乎相等;自保温预制剪力墙的延性系数和累积耗能均低于预制实心剪力墙;自保温预制剪力墙的刚度退化规律与预制实心剪力墙相近。在三种设计轴压比下,当顶点水平位移在±20mm以内时,在相同顶点水平位移下自保温预制剪力墙和预制实心剪力墙的耗能系数接近;当顶点水平位移大于±20mm时,在相同顶点水平位移下自保温预制剪力墙的耗能系数略大于预制实心剪力墙。自保温预制剪力墙试件峰值荷载的数值模拟结果与试验结果的误差在5%以内,满足工程精度要求。     

考虑防屈曲支撑影响的钢筋混凝土框架柱设计方法

针对防屈曲支撑 混凝土框架(RC-BRBF)体系中防屈曲支撑（BRB）对相连柱产生附加变轴力影响,提出了RC框架柱设计方法。该方法首先通过等价轴压比指标获得RC柱设计轴压比限值,保证了一级、二级以及三、四级框架柱极限侧移水平分别达到2.7%、2.4%以及2.1%;然后通过体系延性水平获得柱位移延性指标,保证其延性性能。研究表明,RC柱设计轴压比限值与等价设计轴压比水平、构件受等效重力与地震作用的轴力标准值之比有关;改进后的设计方法能够有效考虑BRB对相连柱附加变轴力影响,并保证了变轴压比下柱的极限侧移水平。算例分析结果表明,该方法通过优化柱截面提高了体系经济性,同时保证体系满足“三水准”设防目标,RC柱设计轴压比限值的设定是合理的。