初始荷载下中空钢管混凝土柱轴向强度

与传统的钢管混凝土柱相比,中空钢管混凝土(CFDST)柱具有很多优点,诸如自重轻和良好的循环性能。CFDST柱可能被用于桥梁,高层建筑,高架桥和输电塔结构中。内外钢管将承担来自上部结构和浇筑的湿混凝土的初始荷载。由这些初始荷载造成的钢管初应力和变形会影响CFDST构件的性能。因此,对外钢管单独承担初始荷载和内外钢管同时承担初始荷载时,CFDST柱的轴力性能进行讨论。建立通用的有限元模型预测钢管负荷时CFDST柱的性能。通过承担初始荷载和不承担初始荷载的CFDST柱的试验结果对该有限元模型进行验证。讨论初始荷载水平、长细比、空心率和材料强度对轴向强度的影响。最后,给出初始荷载下的CFDST柱的极限强度计算公式。     

偏心受压下锥形中空夹层钢管混凝土柱的性能

锥形中空夹层管混凝土(CFDST)柱常被用于输电塔并有可能成为另一种类型的复合框架结构。然而,尚未对偏心受压下锥形中空夹层钢管混凝土柱的性能进行研究,对不同偏心荷载作用下的锥形中空夹层混凝土柱进行研究。数值研究也使用了有限元模型对锥形构件的性能进行了预测。比较锥形构件和直角构件的强度和应力分布。通过数值计算研究锥形柱的稳定性。最后,使用"等效柱"的概念预测偏心受压下锥形中空夹层钢管混凝土柱的荷载力。     

空间网架结构钢管混凝土柱节点力学性能足尺试验及分析

采用足尺试验与数值仿真相结合的方法研究空间网架结构中的钢管混凝土柱节点的受力及抗震性能。试验荷载逐级加载到设计荷载的1.6倍并观测柱节点的变形与应力。试验结果表明试验荷载下柱节点钢结构部分基本处于弹性状态,混凝土极小部分区域超出压应力极限,钢管与混凝土粘接良好。非线性有限元分析结果揭示了柱节点在低周往复荷载作用下的滞回耗能能力和破坏特征,指出了柱节点承载的薄弱位置,给出了柱节点的极限承载力。结果表明,足尺试验与数值计算相结合的方法可以全面揭示柱节点的受力特性及抗震性能。     

温度和荷载共同作用下钢管混凝土短柱的性能分析

采用有限元模型研究温度与荷载共同作用下的钢管混凝土短柱的荷载-变形关系。该模型用来模拟一系列各种温度和力学加载条件下的钢管混凝土短柱试验,包括高温测试、常温下构件残余强度测试,以及无初始荷载的ISO-834标准温度下的构件测试。预测结果以及试验结果的对比表明:模型可以准确预测构件的荷载-变形关系。然后采用该有限元模型分析在具有初始荷载、加热和制冷条件下完全加载过程中的钢管混凝土短柱的性能,以观察构件横截面的应力分布和各个加载阶段的应力发展情况。所有构件在制冷过程之后都加载至极限强度,利用一系列参数对其残余应力进行了分析。结果发现:在温度和荷载共同作用下的构件极限强度,要比只有温度作用而无初始荷载的构件极限强度略低,但是在极限强度时,前者的最大应变显著增加。     

方钢管配筋混凝土柱耐火极限影响因素分析及实用计算方法研究

利用方钢管配筋混凝土柱耐火极限的理论计算方法,对标准升温曲线升温及火灾有效荷载作用下,截面尺寸、构件长细比、截面含钢率、材料强度、荷载偏心率以及钢筋配筋率和钢筋强度对方钢管配筋混凝土柱耐火极限的影响进行分析。并在此基础上,提出按规范ISO-834和《建筑构件耐火试验方法》(GB 9978-88)规定的标准升温曲线升温作用下,钢管配筋混凝土柱耐火极限的实用计算方法,计算结果与数值计算和试验结果均吻合较好。     

锥形中空钢管混凝土(CFDST)短柱的性能

目前,虽然锥形中空钢管混凝土(CFDST)柱被用于中国的输电塔中,但是关于这类输电塔中构件性能的信息仍很缺乏。因此,本文对锥形CFDST短柱的轴压性能进行研究。研究的参数包括锥角和截面尺寸。通过建立有限元模型分析锥形构件的性能。结果表明,钢管和夹层混凝土不受锥角影响,能够很好地协同工作。锥形CFDST短柱的失效模式与直线型的类似,失效出现在最小截面附近。通过应力分析讨论锥形构件的约束效应。最后,给出用于计算锥形CFDST短柱极限强度的建议公式。     

预压低碳钢和不锈钢空心钢管与钢管混凝土柱的冲击性能

研究受静力横向荷载和预压轴向冲击荷载下低碳钢和不锈钢空心钢管与钢管混凝土柱的性能。在柱中部或1/4处施加横向荷载。近来,在University of Western Sydney和University of Wollongong进行了3组试验,获得了受横向静力荷载和预压或无预压冲击荷载下的低碳钢和不锈钢空心钢管与钢管混凝土柱的性能。介绍关于对柱施加轴向和横向荷载的第三组试验的试验结果。研究静力和冲击荷载下低碳钢和不锈钢空心钢管与钢管混凝土柱的有限元建模方法。使用有限元分析软件ABAQUS建立一个包括非线性材料性能、钢的加强角性能和预压荷载三维的非线性有限元模型,从而模拟静力和冲击试验。研究主要目的是比较低碳钢和不锈钢空心钢管与钢管混凝土柱性能的试验结果和数值结果。此外,比较冲击荷载下内填钢管和空心钢管的性能。荷载-挠度响应和极限强度的试验结果与有限元结果较为一致。同时,比较静力和冲击荷载下空心与不锈钢钢管混凝土柱和空心与低碳钢钢管混凝土柱的结果。一般来讲,与低碳钢试验构件相比,不锈钢试验构件的强度更高,耗能能力更好。     

长期荷载作用下内配工字型钢方钢管混凝土偏压柱力学性能分析

利用ABAQUS软件建立了考虑长期荷载作用下的内配工字型钢方钢管混凝土偏压柱的数值分析模型。通过与已有试验数据对比,验证了数值模型的合理性。在此基础上,对该类新型组合柱的荷载-挠度曲线、材料应力发展和分布、材料接触应力等进行全过程分析,同时与不考虑长期荷载作用的结果进行对比,并对长期荷载作用下组合柱承载力的影响因素进行参数分析。结果表明:长期荷载作用下组合柱产生了内力重分布,加速了混凝土受拉区和钢材的塑性发展,降低了钢管和型钢对混凝土的约束作用;考虑长期荷载作用的组合柱极限承载力较一次加载的情况有所减小,对应的跨中挠度增大;在计算参数范围内,长期荷载使内配型钢方钢管混凝土偏压柱承载力降低幅度在15%以内。     

火灾后中空夹层高强钢管混凝土柱轴压机理分析

为了研究火灾后中空夹层高强钢管混凝土柱(高强CFDST)受压力学性能,选用合理的夹芯混凝土本构关系,利用ABAQUS有限元分析软件建立了计算模型,通过试验对有限元模型进行了验证,验证结果吻合较好。剖析了不同受火时间、空心率、外钢管屈服强度和混凝土抗压强度对火灾后高强CFDST受压力学性能的影响,对其典型曲线进行机理分析,揭示内外钢管与混凝土之间的相互作用力。结果表明:随着受火时间的增加,高强CFDST极限承载力减小;随着外钢管屈服强度由Q345变为Q460,核心混凝土和外钢管承载力占总承载力的比例发生了变化,核心混凝土由60%变为30%,外钢管由25%变为50%;高强外钢管屈服强度的变化对火灾后高强CFDST的极限承载力影响较大。     

外套方钢管自密实混凝土加固RC方柱 轴压性能受力分析

在5根外套方钢管自密实混凝土加固RC方形截面短柱和2根未加固RC方形截面短柱轴压试验的基础上,采用大型有限元软件ABAQUS建立有限元计算模型,将计算得到的极限荷载和荷载-纵向位移曲线与试验结果进行对比,二者吻合良好。在此基础上,进行组合结构加固柱的轴压工作机理分析和参数分析,结果表明:钢管在组合结构加固柱达到极限荷载前就已屈服;原柱、钢管和新增混凝土持荷分配的变化规律与所处的加载阶段有关。提高新增混凝土强度,极限荷载下新增混凝土的持荷比例增大,原柱和钢管的持荷比例减小;增大钢管壁厚或提高钢管屈服强度,极限荷载下钢管的持荷比例增大,原柱和新增混凝土的持荷比例减小。     

Concrete-filled double skin steel tubular (CFDST) columns subjected to long-term sustained loading

This paper carried out a series of tests on concrete-filled double skin steel tubes (CFDST) columns under long-term sustained loading condition. The test process included two stages, i.e. long-term service test and ultimate strength test. Numerical models on analysis of the CFDST column under long-term sustained loading were presented. A comparison of results calculated using these models showed generally good agreement with the test results. Additionally, a detailed analysis was performed to analyse the long-term behaviour of CFDST columns. Finally, simplified formula for calculating the ultimate strength of CFDST columns subjected to long-term sustained loading was proposed.     

中空夹层钢管混凝土柱在长期荷载作用下的力学性能研究

基于美国混凝土协会ACI 209(1992)提供的混凝土徐变和收缩模型,对长期荷载作用下中空夹层钢管混凝土柱的变形和承载力进行计算。分析加荷龄期、持荷时间、长期荷载比、名义含钢率、钢材屈服强度、内钢管厚度、混凝土强度、空心率、长细比和荷载偏心率等参数对中空夹层钢管混凝土柱变形特性和承载力的影响。最后,在系统分析各影响因素的基础上,提出长期荷载作用对中空夹层钢管混凝土柱承载力影响系数的计算方法。     

Analysis of thin-walled steel RHS columns filled with concrete under long-term sustained loads

The present study is an attempt to predict the time-dependent behavior of concrete-filled thin walled steel RHS (rectangular hollow section) columns by means of a model that is proposed by the ACI Specifications (ACI Committee 209,1992) [1]. A theoretical model of analysis to account for shrinkage and creep effects on concrete-filled steel RHS columns under sustained loading is presented, and is a development of the analysis used for short-term loading (Han et al, 2001a) [2]. A comparison of results calculated using this model shows good agreement with test results. The main objectives of this paper were threefold: firstly, to report a series of tests on the behavior of concrete-filled steel RHS columns under long-term sustained loading, in addition to providing further tests on the static ultimate strength of the composite columns. Secondly, to analyze influence of several parameters, such as changing steel ratio, long-term sustained load level, slenderness ratio, strength of the materials and depth-to-width ratio on the capacities of the concrete-filled steel RHS columns. And finally, to develop formulas for the calculations of the ultimate strength of the concrete-filled steel RHS columns with long-term sustained loading effects are considered, such formulas should be suitable for incorporation into building codes.     

局部加载下中空夹层钢管混凝土的试验研究

对局部受压下的中空夹层钢管混凝土进行试验研究。分别对含内外两层钢管的14个圆形构件和15个方形试件进行试验,试验参数包含:空心率、顶端板厚度、局压面积比。结果表明:局部受压下中空夹层钢管混凝土呈现延性。各试验参数对局部受压中空夹层钢管混凝土短柱的性能和破坏模型有很大影响。最后,提出分析局部受压下中空夹层钢管混凝土承载力的简化计算模型。     

长期荷载作用下带脱空缺陷钢管混凝土柱的受力性能研究

为研究长期荷载作用对带脱空缺陷钢管混凝土柱受力性能的影响,以脱空类型、脱空率和长期荷载比为主要参数,对长期荷载作用下带脱空缺陷钢管混凝土短柱的变形特性和承载力进行了试验研究。试验结果表明：在长期荷载作用下,与普通无脱空缺陷钢管混凝土柱类似,脱空缺陷钢管混凝土柱徐变系数终值的上限值为0.9;长期荷载比大的脱空缺陷钢管混凝土柱较长期荷载比小的脱空缺陷钢管混凝土柱的承载力略大。采用有限元分析软件ABAQUS,对考虑长期荷载作用影响时脱空构件的受力性能进行分析,有限元计算结果和试验结果吻合良好。利用验证过的有限元模型,系统地分析了长细比、含钢率、钢管屈服强度、混凝土强度、长期荷载比、脱空率和荷载偏心率等参数对长期荷载作用下带脱空缺陷钢管混凝土柱的承载力影响规律。结果表明,混凝土脱空缺陷对考虑长期荷载作用的承载力影响系数的不利影响小于1.5%;现有的考虑长期荷载影响的普通钢管混凝土柱的设计方法可用于预测带脱空缺陷钢管混凝土柱的承载力。     

Analysis of axially loaded concrete filled circular hollow double steel tubular columns exposed to fire

A series of new unified design formulas for calculating the temperature field and fire resistance under axial compressive loading of a circular solid or hollow concrete filled double steel tubular (CFDST) short and slender columns exposed to fire are presented in this paper. The results of the experiments are firstly derived from exploring the fundamental behavior of the CFSDT slender columns under the ISO 834 standard fire and temperature distributions. Failure modes and axial deformation versus time curves are also obtained and discussed. It was realized that a solid or slender CFDST column has different temperature fields, stronger limiting temperature and better fire resistance, as compared to columns filled with plain concrete. Also, the load ratio and steel ratio have no evident difference between the results of the solid and hollow CFDST columns. A three-dimensional finite element analysis (FEA) model is developed to calculate the temperature field of CFDST columns. After calibration of the FE model, the influences of important parameters on the temperature field of the composite columns are investigated and a unified formula for calculating average temperatures of the columns’ cross-section is obtained. Combining the average temperature with the “Unified theory” under axial compression, a simplified design method is put forward, which provides a unified formulation for both the plain CFST and CFDST columns relating to the axial bearing capacity at room and elevated temperature. The proposed formulas are calibrated through comparisons with fire tests on the columns, and it was found that the method produces safe results on average.     

夹层钢管混凝土梁-柱在循环荷载作用下的性能分析

夹层钢管混凝土(CFDST)在桥梁和建筑的建设中具有很大的潜能。轴力和循环加载的弯曲荷载作用下,弯矩曲率曲线(M-(?)),柱侧向荷载-侧移曲线(P-Δ)模型的研究信息非常有限。建立了一个力学模型,用于分析轴向恒荷载和循环加载的弯曲荷载作用下的CFDST梁-柱。预测的组合梁柱的循环反应性能与试验结果一致。基于这个理论模型,对组合梁柱有关弯矩曲率曲线(M-(?)),侧向荷载-侧移曲线(P-Δ)的性能进行了参数分析。最后,提出了计算弯矩曲率曲线(M-(?)),侧向荷载-侧移曲线(P-Δ)的简化模型。     

Fire performance of self-consolidating concrete filled double skin steel tubular columns: Experiments

An investigation into the fire performance of self-consolidating concrete (SCC) filled double skin tubular columns (CFDST) during the standard fire test is reported. Six full size SCC filled CFDST columns were designed for the fire tests. Detail failure modes of overall specimens and each component in the columns as well as temperatures, deformation and fire endurance were presented. Fire performance of the CFDST columns were studied through analysis of the limiting temperature of the outer tube, composite action between steel and concrete and effect of a number of parameters on the fire endurance. It showed that the limiting temperature in the CFDST columns is significantly higher than that in concrete filled steel tubular (CFST) columns or critical temperature in steel structural components. Strong evidence was found to prove the existence of composite action between steel and concrete in the CFDST columns during fire exposure. Effect of a number of parameters on the fire endurance of the composite columns was identified. Investigation into the fire performance of the columns also reveals possible solutions to improve the fire resistance of CFDST members.