钢管混凝土柱在纯扭和压扭荷载下的抗震性能研究

为研究钢管混凝土的抗扭性能,完成8个钢管混凝土柱试件在纯扭和压扭荷载下的拟静力试验,变化截面形式、含钢率和轴力大小等参数。试验结果表明:钢管混凝土柱在往复扭矩荷载作用下的滞回曲线非常饱满,没有"捏拢"现象产生,卸载刚度几乎等于初始弹性刚度,试件的强度和刚度的损伤退化程度较低,具有较好的耗能能力。轴力较小时,轴力对钢管混凝土柱的抗扭承载力有提高作用,且延性较好;但轴力较大时,轴力将削弱钢管混凝土柱的抗扭承载力。在纯扭荷载作用下,钢管内的混凝土由于斜向开裂形成螺旋斜压杆,斜向压力的轴向分量由钢管的轴向拉力平衡,导致钢管存在拉应变。在纯扭和压扭荷载作用下,钢管剪应变与扭转角之间存在较好的线性关系。基于试验结果和已有文献研究成果,较为全面地分析钢管混凝土的抗扭机理,为进一步开发可考虑扭转作用的钢管混凝土杆系单元提供研究基础。     

圆锥形中空夹层钢管混凝土压扭构件力学性能分析

为了研究圆锥形中空夹层钢管混凝土在压扭复合受力下的力学性能,通过有限元软件ABAQUS建立了圆中空夹层钢管混凝土压扭构件的数值模拟模型,并与已有的试验结果进行对比,验证了模型的正确性.用同样建模方法对圆锥形中空夹层钢管混凝土压扭构件进行了数值分析,分析了该类构件在压扭复合作用下的扭矩-转角全过程关系曲线、各部件的承载力分配等,讨论了轴压比、空心率、锥度、混凝土强度及钢管强度对构件受力性能的影响规律.结果 表明:构件的扭矩-转角全过程曲线可以分为弹性、弹塑性、塑性强化三个阶段;加载过程中轴压比、混凝土强度、内钢管强度和空心率的变化对其极限扭矩的影响较小,锥度和外钢管强度的变化对该类构件抗扭承载力影响较大.本文所建议的抗扭承载力计算方法与数值模拟结果吻合良好.     

内配方钢管的钢管混凝土叠合柱轴压工作性能研究

为研究内配方钢管的钢管混凝土叠合柱轴压工作性能,基于合理的钢材和混凝土材料本构关系模型,采用有限元法对钢管混凝土叠合柱轴压荷载-变形关系曲线进行了计算。采用数值分析方法,对叠合柱轴压工作性能进行较为细致分析,包括轴压破坏模态、轴压荷载-变形全过程关系、应力发展规律以及钢管和混凝土之间的相互作用。研究方法和结论可为相关研究参考。     

考虑粘结作用及抗剪栓钉传力的巨型钢管混凝土柱共同工作性能分析

采用数值模拟手段对考虑粘结作用及抗剪栓钉传力的巨型钢管混凝土柱共同工作性能进行分析。首先介绍了ABAQUS程序中的材料本构模型、钢管、混凝土界面模型和抗剪栓钉简化本构模型。通过与相关文献试验结果进行对比,充分验证了本文理论模型的合理性与精确度。在此基础上,分别对只考虑粘结作用的巨型钢管混凝土柱和考虑粘结作用+抗剪栓钉的巨型钢管混凝土柱进行数值参数分析,主要考察巨型柱截面尺寸、管壁宽厚比、粘结强度、栓钉布置间距等对竖向荷载传递的影响。结果表明,粘结作用对混凝土共同工作性能的影响有限,单纯依靠粘结传力,钢管、混凝土两者不能够很好地共同工作;设置抗剪栓钉提高了巨型钢管混凝土柱共同工作性能。最后建议不应完全依赖粘结作用与抗剪栓钉传力,在设计时应通过设置足够的传力构造来保证巨型柱钢管、混凝土共同工作。     

轴压荷载下中空夹层钢管混凝土抗扭性能试验研究

以轴压比及截面尺寸为参数,对12个中空夹层钢管混凝土试件进行压-扭试验,并结合数值模型分析了扭转全过程截面剪应变开展及钢管与夹层混凝土相互作用力.结果表明:较小的轴向压力对极限抗扭承载力及扭转刚度均影响甚微,所有试件均表现出较好的延性.承载力受外钢管强度影响较大,受混凝土强度影响较小,夹层混凝土对组合抗扭强度提高的作用...     

设平板加劲肋矩形钢管混凝土柱静载下ABAQUS本构模型的研究

对设平板加劲肋钢管混凝土柱静载下ABAQUS本构模型进行研究.首先对收集的设平板加劲肋钢管混凝土短柱轴压试验进行介绍;从混凝土本构模型、钢材本构模型、钢-混凝土界面黏结模型以及初始缺陷、残余应力的引入等方面入手进行分析;对比分析了 Schneider模型、Saenz模型、韩林海模型及陶忠模型四种核心混凝土受压本构关系,在此基础上提出了考虑设肋钢管约束效应的核心混凝土单轴受压应力-应变本构关系;对钢材本构、钢-混凝土界面本构等模型进行了对比分析.通过采用本构模型进行了有限元仿真模拟,与收集到的58根设肋钢管混凝土轴压试件试验结果进行对比.对比结果表明,采用的ABAQUS本构模型形式简单,能够准确地模拟设平板加劲肋普通截面钢管混凝土柱轴压力学性能,可为类似结构的分析提供参考.     

钢管混凝土柱轴压力-弯矩-扭矩空间复合受力拟静力试验研究

采用自行设计的压力-弯矩-扭矩复合受力加载装置,基于力-位移混合控制加载方法,完成了8个钢管混凝土柱试件在压-弯-扭等复合荷载作用下的拟静力试验,变化了截面形式、加载方式和弯扭比等参数。试验结果表明：圆钢管混凝土柱和矩形钢管混凝土柱在压-弯-扭等复合受力往复荷载作用下的滞回曲线较为饱满,没有“捏拢”现象产生,具有较好的耗能能力;弯扭比较大的矩形钢管混凝土试件在扭转角较大时由于钢管底部局部屈曲较为明显,存在承载力退化现象;钢管混凝土截面轴向应变基本满足平截面假定;弯矩的存在将削弱钢管混凝土柱的受扭能力;在压-弯-扭等复合受力往复荷载作用下,钢管剪应变与扭转角之间存在较好的线性关系。对试验实测结果和已有文献分析表明：在弯扭比较大时由主压应力导致钢管表面发生局部鼓曲而破坏,弯扭比较小时,主拉应变将导致钢管混凝土柱表面在低周往复荷载作用下开裂。研究成果可为进一步开发考虑扭转作用的钢管混凝土纤维梁单元提供基础性依据。     

中空钢管混凝土轴压短柱有限元分析与验证

为了研究中空钢管混凝土(HCFST)短柱的轴压性能,本文采用有限元软件ABAQUS对5根已有中空钢管混凝土短柱轴压试验进行数值模拟分析。通过选择合理的材料本构模型,建立该类短柱的有限元模型,获得轴压短柱的荷载-位移全过程曲线,与已有的试验结果进行对比,二者吻合良好。验证了本文有限元建模方法的合理性和可实施性,为中空钢管混凝土短柱在实际工程中的推广应用提供技术支撑。     

钢管高强混凝土组合柱轴心抗压数值分析

为研究钢管高强混凝土组合柱的轴心抗压性能,利用高强混凝土和钢管混凝土本构关系,对组合柱轴心抗压受力全过程进行了数值计算,计算轴力-纵向应变曲线与试验结果吻合良好;并与钢筋混凝土柱进行了对比,定量分析了套箍指标、混凝土强度和配箍特征值对轴压承载力和纵向应变延性的影响.     

型钢混凝土柱复合受扭性能的非线性有限元分析

基于4个比例为1:2的H型钢混凝土柱在单调荷载下的复合受扭试验,运用ABAQUS建立相应的有限元分析模型。通过对比开裂扭矩、极限扭矩和扭矩-扭率曲线,验证了有限元分析在型钢混凝土复合受扭性能研究方面的有效性,分析了轴压比、扭弯比和混凝土强度对型钢混凝土柱复合受扭性能的影响。研究结果表明,提高轴压比可提高型钢混凝土柱的极限扭矩,但对其后期延性不利;扭弯比的减小使弯曲损伤加大,对于构件极限抗扭不利;提高混凝土强度可提高构件的极限扭矩,但后期延性变差。     

Behavior of square hollow steel tubes and steel tubes filled with concrete

This paper investigates the occurrence of local buckling in bare steel and concrete-filled tubes to study how different depth-to-thickness ratios affect the response of the steel component. The experimental set-up and results of 24 tests are presented in this paper. Specimens with values of depth-to-thickness ratios in the range of 50–125 have been considered. The presence of the concrete has been observed to affect the exhibited buckling mode and to significantly increase the buckling bearing capacity of the concrete-filled steel tubes. A numerical model has been developed using the commercial software ABAQUS and has been validated against the experimental results of this study. From a design viewpoint, it has been observed that local buckling needs to be included in the calculation of the contribution of the steel component to the bearing capacity of a concrete-filled tube when its depth-to-thickness ratio is over 50. For a slender plate, i.e., with a depth-to-thickness ratio over 120, its post-buckling behavior could be included in the calculation of the steel contribution as it evidently increases its bearing capacity. Finally, an equation for the calculation of the bearing capacity of composite sections with both stocky and slender steel elements has been proposed and validated against extensive experimental results available in the literature.     

初应力对方钢管混凝土轴压性能的影响研究

考虑钢管初应力的影响，采用通用有限元分析软件对方钢管混凝土轴心受压构件进行了受力全过程的分析，并以此为基础，分析了不同钢管初应力系数对钢管混凝土构件轴压工作性能的影响，为其进一步的研究提供了基础。     

Three-dimensional behavior of geosynthetic tubes

Geosynthetic tubes filled with pressurized slurry are used for various purposes (e.g., as dikes or breakwaters). The three-dimensional behavior of such structures is investigated. The tubes are assumed to be comprised of two rectangular sheets connected at their edges, and to rest on a tensionless elastic foundation. As the slurry is pumped in, the top surface rises and the outer portion of the bottom surface lifts off the foundation. For tubes with aspect ratios of 2:1 and 5:1, the deflected shapes, mid-surface stresses, and contact regions with the foundation are determined with the use of the finite element method and thin shell elements. Wrinkling occurs close to the long edges of the tubes.     

Experiments on tubes conveying fluid

Tests are conducted for tubes conveying fluid for six types of support condition. The objectives are to understand the dynamic characteristics of such systems for different support conditions and to examine the transition from one instability mechanism to another.     

Moment-curvature-axial-compression-pressure relationship of structural tubes

For tubular members in deepwater offshore platforms which are sealed from the water, the high external hydrostatic pressure introduces an additional compressive hoop stress to the tube. In this paper, the effect of this external hydrostatic pressure on axial load and moment carrying capacity of imperfect inelastic tubular beam-columns is investigated parametrically from the standpoint of beam-column theory. Against the background of this information, modified AISC beam-column interaction equations and sectional-capacity interaction equations are proposed for practical use.     

Elastic buckling of elliptical tubes

Hot-rolled and cold-formed structural steel tubular members of elliptical cross-section have recently been introduced into the construction sector. However, there is currently limited knowledge of their structural behaviour and stability, and comprehensive design guidance is not yet available. This paper examines the elastic buckling response of elliptical hollow sections in compression, which has been shown to be intermediate between that of circular hollow sections and flat plates. The transition between these two boundaries is dependant upon both the aspect ratio and relative thickness of the section. Based on the results of numerical and analytical studies, formulae to accurately predict the elastic buckling stress of elliptical tubes have been proposed, and shortcomings of existing expressions have been highlighted. Length effects have also been investigated. The findings have been employed to derive slenderness parameters in a system of cross-section classification for elliptical hollow sections, and form the basis for the development of effective section properties for slender elliptical tubes.     

Multiobjective optimization for tapered circular tubes

As more and more new functional requirements are placed, some novel development of sectional configurations of the structural members has been increasingly introduced. This paper presents the optimal design for tapered tubes of three different configurations, namely hollow single, foam-filled single and collinear double tubes. To represent complex crashworthiness objective functions, a surrogate model method, more specifically, response surface method (RSM), was adopted in this study. The design of experiments (DoEs) of the factorial design and Latin Hypercube Sampling techniques is employed to construct the response surface models of specific energy absorption (SEA) and the maximum impact load (MaxL), respectively. In this paper, the linearly weighted average, geometrical average and particle swarm optimization methods are utilized in the multiobjective optimization for these three different tapered tube cases, respectively. A comparison is made among the different tapered profiles with the different optimization algorithms, and the crashworthiness merits of foam-filled tapered tubes are identified.     

Foundation connections for circular concrete-filled tubes

Concrete filled steel tubes (CFTs) promote economical and rapid construction. They offer increased strength and stiffness relative to structural steel and reinforced concrete. The steel tube serves as formwork and reinforcement to the concrete fill, thereby reducing the labor requirements. CFT components encourage the optimal behavior of each material (concrete and steel) while providing a symbiotic relationship between the two to mitigate undesirable failure modes. The fill increases the compressive strength and stiffness, delays and restrains local buckling of the tube, and enhances ductility and resistance if composite action is achieved.Both rectangular and circular CFT have been employed, but circular CFT provide better performance, because they provide increased confinement of the concrete and composite action. A missing component for circular CFT construction is reliable and ductile connections. The research described herein that investigated and develops design procedures for simple and economical connections of circular CFT piers or columns to reinforced concrete foundations, pile caps and wide cap beams (bridge construction) is presented and evaluated. The connection requires no dowels or internal reinforcement connecting the tube to the footing or cap beam. Experiments and analytical studies evaluate the inelastic seismic performance and establish design criteria for the connection. The seismic performance of a CFT column and connection assembly is compared to a conventional reinforced concrete column. The research shows that the proposed connection develops the full capacity of the composite column. The assembly provides excellent ductility and inelastic deformation capacity under seismic loading while mitigating damage even at larger drift demands.     

Elastic local post-buckling of elliptical tubes

The elastic local post-buckling behaviour of elliptical tubes under compression is analysed in this paper. A brief outline of the local, distortional and global buckling behaviour of EHS tubes is firstly provided, where it is shown that local buckling modes govern the stability of short to intermediate length tubes while distortional modes control the stability of intermediate length to moderately long tubes and global buckling dominates the behaviour of longer tubes. Following this, an in-depth numerical study employing shell finite element modelling, of the elastic local post-buckling behaviour of compressed elliptical hollow section (EHS) tubes is presented. It is concluded that EHS tubes with a low to moderate aspect ratio can support loads up to their limit loads but are imperfection sensitive (shell-type behaviour), while EHS tubes with a moderate to high aspect ratio can carry loads higher than their limit loads (plate-type behaviour) and are imperfection insensitive. The slope of the ascending post-buckling path increases with the EHS aspect ratio and can reach values up to 40% of the slope of the linear primary path. The bound imperfection amplitude concept, separating the imperfection amplitude ranges where the EHS tube is sensitive and insensitive, is proposed. It is also found that, for increasing EHS aspect ratio, the compressive stresses grow and accumulate near the zones of minimum radius of curvature while the zones of maximum radius of curvature possess an approximately uniform and relatively low compressive stress level. Therefore, it is expected that an approach based on the effective width concept widely used for the evaluation of the strength of flat plates may be adapted to the design of EHS tubes with moderate to high aspect ratios.     

Deflections of highly inflated fabric tubes

Inflatable beams made of modern textile materials with important mechanical characteristics can be inflated at high pressure. The aim of the paper is to present experimental, analytical and numerical results on the deflections of highly inflated fabric tubes submitted to bending loads. Experiments are displayed and we show that tube behaviour looks like that of inflatable panels (Thin-Walled Struct. 40 (2002) 523–536). Equilibrium equations are once again written in the deformed state to take into account the geometrical stiffness and the following forces. The influence of the shear stress cannot be neglected and Timoshenko’s beam theory is used. A new inflatable tube theory is established and simple analytical formulas are given for a cantilever-inflated tube. Comparisons between analytical and experimental results are shown. A new inflatable finite tube element is constructed by use of algebraic operations, because the compliance matrix of the cantilever beam is not symmetric. Comparisons between experimental, analytical and numerical results prove the accuracy of this beam theory and on this new finite element for solving problems on the deflections of highly inflated tubes.