Stiffened steel box columns. Part 1: Cyclic behaviour

This paper aims to study the cyclic inelastic behaviour of stiffened steel box columns failed by local and overall interaction instability under a constant compressive axial force and cyclic lateral loading. Such columns find broad application in steel bridge piers. The columns are of box sections with longitudinal stiffeners. In the analysis, a modified two‐surface plasticity model developed at Nagoya University is employed to model material non‐linearity. For comparison, analyses using classical isotropic‐ and kinematic‐hardening models are also carried out. Hysteretic curves and buckling modes obtained from analysis using the two‐surface model and classical models are compared with experimental results. Moreover, the progression of deformation from occurrence of local buckling to structural failure is discussed in detail. The comparisons show that the use of an accurate plasticity model is quite important in the prediction of both the cyclic inelastic behaviour and failure characteristic of steel box columns failed by coupled local and overall instability. It is found that the modified two‐surface model is a satisfactory model in predicting the cyclic hysteretic behaviour of both the thin‐ and thick‐walled steel box columns. Copyright © 2000 John Wiley & Sons, Ltd.     

钢管混凝土边框高强混凝土组合剪力墙抗震性能试验研究

钢管混凝土边框组合剪力墙是一种新型组合剪力墙。本文进行了2个1/4缩尺的高强混凝土剪力墙模型的低周反复荷载试验,模型1为普通钢筋混凝土剪力墙,模型2为钢管混凝土边框组合剪力墙。在试验研究基础上,对比分析它们的承载力、延性、刚度及其衰减过程、滞回特性、耗能能力及破坏特征,建立了组合剪力墙的承载力计算模型,计算结果与实测结果符合较好。研究表明,钢管混凝土边框高强混凝土组合剪力墙与普通剪力墙相比抗震性能显著提高。     

圆钢管混凝土边框内藏钢桁架剪力墙抗震性能试验研究

圆钢管混凝土边框内藏桁架剪力墙是一种新型组合剪力墙.为了解这种剪力墙的抗震性能,进行了 3个1/5缩尺试件的低周反复荷载试验.3个试件中,1个为圆钢管混凝土柱框架结构,1个为圆钢管混凝土边框-钢桁架结构,1个为圆钢管混凝土边框内藏钢桁架剪力墙.基于试验,对比分析了各试件的承载力、刚度及其退化过程、滞回特性、耗能能力及破...     

Seismic behavior and strength capacity of steel tube‐reinforced concrete composite columns

The steel tube‐reinforced concrete (ST‐RC) composite column is a novel type of composite column, which consists of a steel tube embedded in RC. In this paper, the seismic behavior of ST‐RC columns is examined through a series of experiments in which 10 one‐third scale column specimens were subjected to axial forces and lateral cyclic loading. The test variables include the axial force ratio applied to the columns and the amount of transverse reinforcement. All specimens failed in a flexural mode, showing stable hysteresis loops. Thanks to the steel tube and the high‐strength concrete it is filled with, the ST‐RC column specimens had approximately 30% lower axial force ratios and 22% higher maximum bending moments relative to the comparable RC columns when subjected to identical axial compressive loads. The amount of transverse reinforcement made only a small difference to the lateral load‐carrying capacity but significantly affected the deformation and energy dissipation capacity of the ST‐RC columns. The specimens that satisfied the requirements for transverse reinforcement adopted for medium ductile RC columns as specified by the Chinese Code for Seismic Design of Buildings (GB 50011‐2010) and EuroCode 8 achieved an ultimate drift ratio of around 0.03 and a displacement ductility ratio of approximately 5. The design formulas used to evaluate the strength capacity of the ST‐RC columns were developed on the basis of the superposition method. The predictions from the formulas showed good agreement with the test results, with errors no greater than 10%. Copyright © 2013 John Wiley & Sons, Ltd.     

高轴压比下钢管混凝土边框组合剪力墙抗震性能试验研究

钢管混凝土边框组合剪力墙是一种适用于高层及超高层建筑的新型组合剪力墙。轴压比是影响剪力墙抗震性能的一个主要因素,高层建筑底部轴压比较大。本文进行了1/4缩尺的1个普通钢筋混凝土剪力墙模型和1个钢管混凝土边框组合剪力墙模型在高轴压比下的低周反复荷载试验。在试验研究基础上,对比分析了剪力墙的承载力、延性、刚度及其衰减过程、滞回特性、耗能能力及破坏特征,建立了钢管混凝土边框组合剪力墙的承载力计算模型,计算结果与实测结果符合较好。研究表明:在高轴压比下钢管混凝土边框组合剪力墙与普通剪力墙相比抗震性能显著提高。     

Finite element analysis of damage and failure of reinforced concrete members under earthquake loading

This paper presents a three‐dimensional analysis framework, based on the explicit finite element method, for the simulation of reinforced concrete components under cyclic static and dynamic loading. A recently developed triaxial constitutive model for concrete is combined with a material model for reinforcing steel which can account for rupture due to low‐cycle fatigue. The reinforcing bars are represented with geometrically nonlinear beam elements to account for buckling of the reinforcement. The strain penetration effect is also accounted for in the models. The modeling scheme is used in a commercial finite element program and validated with the results of experimental static and dynamic tests on reinforced concrete columns and walls. The analyses are supplemented with a parametric study to investigate the impact of several modeling assumptions on the obtained results.     

Cyclic behavior of precast segmental concrete bridge columns with high performance or conventional steel reinforcing bars as energy dissipation bars

The cyclic behavior of precast segmental concrete bridge columns with high performance (HP) steel reinforcing bars and that with conventional steel reinforcing bars as energy dissipation (ED) bars were investigated. The HP steel reinforcing bars are characterized by higher strength, greater ductility, and superior corrosion resistance compared with the conventional steel reinforcing bars. Three large‐scale columns were tested. One was designed with the HP ED bars and two with the conventional ED bars. The HP ED bars were fully bonded to the concrete. The conventional ED bars were fully bonded to the concrete for one column, whereas unbonded for a length to delay fracture of the bars and to increase energy dissipation for the other column. Test results showed that the column with the HP ED bars had greater drift capacity, higher lateral strength, and larger energy dissipation than that with fully bonded conventional ED bars. The column with unbonded conventional ED bars achieved the same drift capacity and similar energy dissipation capacity as that with the HP ED bars. All the three columns showed good self‐centering capability with residual drifts not greater than 0.4% drift. An analytical model referred to as joint bar‐slip rotation method for pushover analysis of segmental columns with ED bars is proposed. The model calculates joint rotation from the slip of the ED bars from two sides of the joint. Good agreement was found between analytical predictions and the envelope responses of the three columns. Copyright © 2010 John Wiley & Sons, Ltd.     

核心型钢混凝土柱的轴压比限值试验研究

基于界限破坏时的内力平衡条件,推导了核心型钢混凝土柱轴压比限值的理论计算公式,计算分析了配钢率、混凝土强度等级、柱截面尺寸等因素对核心型钢混凝土柱轴压比限值的影响。进行了5个1/2比例模型柱试件的低周反复加载试验,验证了配置核心型钢对提高混凝土柱的抗震性能和轴压比限值的有效性。计算和试验结果表明,在混凝土柱中配置一定数量的核心型钢,可以有效提高轴压比限值。本文建议的方法可以较为合理地确定核心型钢混凝土柱的轴压比限值,供工程实践参考。     

钢管自应力混凝土柱抗震性能试验研究

本文通过对水平反复荷载作用下4根钢管自应力混凝土柱和2根普通钢管混凝土柱的抗震性能试验研究,分析了两种钢管混凝土的荷载-挠度(P-Δ)滞回曲线和骨架曲线特点,从而进一步阐述了轴压比、自应力大小和混凝土强度等因素对钢管混凝土抗震性能的影响。试验结果表明,影响柱抗震性能的最主要因素是轴压比和自应力。随着轴压比的增加,钢管自应力混凝土位移延性系数下降;而自应力的存在不仅提高了反复荷载作用下钢管混凝土的极限水平承载力,同时也使其延性系数得到显著的增加。     

型钢高强混凝土柱抗震性能的试验研究

通过14根型钢高强混凝土柱的低周反复加载试验，得到了型钢高强混凝土柱在压、弯、剪共同作用下的主要破坏形态，并探讨了剪跨比、配箍率、混凝土强度对型钢高强混凝土柱滞回曲线、耗能能力以及延性的影响。试验结果表明，型钢高强混凝土柱具有抵御二次地震作用的能力，其抗震性能优于钢筋混凝土柱。     

RC structures cyclic behavior simulation with a model integrating plasticity,damage, and bond‐slip

The behavior of reinforced concrete structures under severe demands, as strong ground motions, is highly complex; this is mainly due to the complexity of concrete behavior and to the strong interaction between concrete and steel, with several coupled failure modes. On the other hand, given the increasing awareness and concern on the worldwide seismic risk, new developments have arisen in earthquake engineering; nonetheless, some developments are mainly based on simple analytical tools that are widely used, given their moderate computational cost. This research aims to provide a solid basis for validation and calibration of such developments by using computationally efficient continuum mechanics‐based tools. Within this context, this paper presents a model for 3D simulation of cyclic behavior of RC structures. The model integrates a bond‐slip model developed by one of the authors and the damage variable evolution methodology for concrete damage plastic model developed by some authors. In the integrated model, a new technique is derived for efficient 3D analysis of bond‐slip of 2 or more crossing reinforcing bars in beam‐column joints, slabs, footings, pile caps, and other similar members. The analysis is performed by implementing the bond‐slip model in a user element subroutine of Abaqus and the damage variable evolution methodology in the original concrete damage plastic model in the package. Two laboratory experiments consisting of a column and a frame subjected to cyclic displacements up to failure are simulated with the proposed formulation.     

Composed analytical models for seismic assessment of reinforced concrete bridge columns

This paper presents general composed analytical models to predict the behavior of reinforced concrete (RC) bridge columns. The analytical models were developed in OpenSees to represent the common hysteretic behavior of RC bridge columns. The proposed composed models can accommodate flexure failure, flexure‐shear failure, and pure shear failure, which are observed in existing RC bridge piers. The accuracy of the models was verified using data from the static cyclic‐loading experiments of 16 single columns and one multi‐column bent and dynamical experiment from two pseudo‐dynamic tests. The results showed that the analytical models could simulate the nonlinear behavior until the post‐failure behavior, including the strength degradation, the buckling of the reinforcement, and the pinching effect. Therefore, a global view of the behavior of reinforcement concrete is prescribed as simply as possible from the academic perspective, and these models are expected to provide sufficient accuracy when applied in engineering practice. Copyright © 2014 John Wiley & Sons, Ltd.     

A new model for analyzing nonlinear torsion behavior of concrete filled steel tube columns with rectangular section

An experimental study on concrete filled steel tube columns with rectangular section subjected to compressionflexure-torsion combined action has been carried out. The failure modes and load-deformation hysteretic relations were obtained. Based on the principles of classical material mechanics, the relations between the torsion curvature of the section and the shear strain of the fiber on the section were established. Then the strain distribution on the rectangular section of concrete filled steel tube columns subjected to torsion was analyzed. The three-dimensional refined finite element model was also built, in order to make the precision verification. The matrix forms of the relation between the torsion curvature of the section and the shear strain of the fiber on the section were derived, and introduced into the fiber beam model considering nonlinear torsion effect on the section. The comparison between test results and calculation results showed that the fiber beam model considering nonlinear torsion effect had high modeling efficiency and solution precision for predicting the torsion behavior of concrete filled steel tube columns with rectangular sections, and was suitable for analyzing the dynamic response of various structures subjected to the combined cyclic load caused by the earthquake load.     

大跨度钢管混凝土拱桥抗震性能指标研究

高轴压比钢管混凝土墩柱的试验结果对钢管混凝土拱肋具有较大的借鉴意义。为明确大跨度钢管混凝土拱桥的抗震性能指标,研究了高轴比钢管混凝土构件的破坏过程及延性性能。以弯矩作为性能指标将高轴压比钢管混凝土构件的试验破坏过程分为轻微损伤、有限损伤与严重损伤3个阶段,结合钢管混凝土截面性能状态的数值分析,探讨了高轴压比钢管混凝土构件的破坏机理。结果表明:高轴压比钢管混凝土构件具有一定的可用延性;提出了以计算等效屈服弯矩作为抗震性能指标,适当利用延性和实现钢管混凝土拱桥的有限损伤抗震设计,并给出了与有限损伤相关的截面性能状态及参数。研究成果弥补了规范在此方面的不足,可供高烈度地震区大跨度钢管混凝土拱桥抗震设计时参考。     

Modeling RC column flexural failure modes under intensive seismic loading

The aim of this work is to model beam‐column behavior in a computationally effective manner, revealing reliably the overall response of reinforced concrete members subjected to intensive seismic loading. In this respect, plasticity and damage are considered in the predominant longitudinal direction, allowing for fiber finite element modeling, while in addition the effect of inelastic buckling of longitudinal rebars, which becomes essential at later stages of intensive cyclic loading, is incorporated. Α smooth plasticity‐damage model is developed for concrete, accounting for unilateral compressive and tensile behavior, nonlinear unloading and crack closure phenomena. This is used to address concrete core crushing and spalling, which triggers the inelastic buckling of longitudinal rebars. For this reason, a uniaxial local stress‐strain constitutive relation for steel rebars is developed, which is based on a combined nonlinear kinematic and isotropic hardening law. The proposed constitutive model is validated on the basis of existing experimental data and the formulation of the buckling model for a single rebar is developed. The cross section of rebar is discretized into fibers, each one following the derived stress‐strain uniaxial law. The buckling curve is determined analytically, while equilibrium is imposed at the deformed configuration. The proposed models for concrete and rebars are embedded into a properly adjusted fiber beam‐column element of reinforced concrete members and the proposed formulation is verified with existing experimental data under intensive cyclic loading.     

多腔扁钢管混凝土斜折柱抗震性能试验研究

大连国际会议中心结构幕墙柱中,采用了一种扁钢管混凝土斜折柱.文中结合该工程设计,进行了2个1/3缩尺的扁钢管混凝土斜折柱试件的低周反复荷载试验,1个试件为普通扁钢管混凝土斜折柱,1个试件为多腔扁钢管混凝土斜折柱.比较分析了两个试件的承载力、刚度、延性、滞回特性及破坏特征.研究表明:多腔扁钢管混凝土斜折柱与普通扁钢管混凝...     

钢管混凝土叠合柱边框内藏钢桁架核心筒抗震性能试验研究

为进一步改善混凝土核心简的抗震性能,本文提出了钢管混凝土叠合柱边框内藏钢桁架组合核心筒.进行了2个1/6缩尺的核心筒模型在低周反复荷载下的抗震性能试验研究,1个为钢管混凝土叠合柱边框毛组合核心筒,1个为钢管混凝土叠合柱边框内藏钢桁架组合核心筒.通过试验,对比分析了2个核心简的承载力、延性、刚度及其衰减、滞回特性、耗能能力及破坏特征,给出了钢管混凝土叠合柱边框内藏钢桁架组合核心筒的承载力计算模型,计算结果与实测值符合较好.研究表明,钢管混凝土叠合柱边框内藏钢桁架组合核心筒与钢管混凝土叠合柱边框组合核心筒相比,其抗震性能明显提高.     

钢管高强混凝土压弯构件滞回性能的研究

本文根据适用于三向周期受力的钢材本构关系模型,和适用于三向周期受力改进的混凝土本构关系的边界面模型,采用有限元法对钢管高强混凝土压弯构件的荷载－位移滞回曲线进行了理论分析,并进行了6个核心混凝土的强度为77N/mm2的钢管高强混凝土压弯构件滞回性能的试验研究。将理论分析和本试验研究及其他试验研究结果进行了对比,分析了荷载－位移滞回曲线的特点。     

往复荷载作用下锈蚀钢筋混凝土柱黏结滑移模型及数值模拟研究

为实现地震作用下锈蚀钢筋混凝土柱精细化数值模拟分析,基于已有研究成果建立往复荷载作用下锈蚀钢筋与混凝土间的黏结滑移本构模型:结合课题组前期试验结果,采用ABAQUS有限元分析软件对建立的黏结滑移本构模型进行有效性验证,通过对数值计算结果与试验结果之间误差分析,进一步对黏结滑移模型中的摩擦黏结应力系数和退化系数进行修正,最终建立更为合理的锈蚀钢筋与混凝土间黏结滑移本构模型。通过数值计算结果与试验结果的再次比较,验证修正后黏结滑移本构模型的有效性。结果表明:修正后的锈蚀钢筋与混凝土间黏结滑移模型可更好地反映往复荷载作用下锈蚀钢筋混凝土柱的滞回性能。该成果可为地震作用下锈蚀钢筋混凝土结构的数值分析计算提供理论参考。     

Failure simulation of shear‐critical RC columns with non‐ductile detailing under lateral load

Reinforced concrete columns with non‐ductile detailing typically exhibit a softening behavior characterized by severe degradation when subjected to cyclic lateral loads. Whether the response is brittle or ductile, shear failure occurs with an inclined through crack along which sliding occurs coupled with loss of horizontal and vertical load‐bearing capacity of the member. The rapid loss of resistance after the peak strength is reached is because of one or more of the following local failure mechanisms: brittle failure of poorly confined concrete; buckling of longitudinal reinforcing bars because of lack of adequate transverse reinforcement or following opening of stirrups after spalling of cover concrete; bond failure. In this study, a modeling strategy to build a detailed 3D finite element model capable of capturing all of the above‐mentioned local failure mechanisms is presented. In particular, a steel–concrete interface model for representing the interaction within the member between concrete core, cover and longitudinal and transverse reinforcement is proposed. Comparison with results of an experimental test of a shear‐sensitive column demonstrates the effectiveness of the simulation up to failure of the element. Copyright © 2016 John Wiley & Sons, Ltd.