某超高层钢管混凝土柱——伸臂桁架节点分析

某61层框架—核心筒结构超高层建筑,主体结构形式为钢管混凝土框架—伸臂桁架—钢筋混凝土核心筒。研究了伸臂桁架、带状桁架与钢管混凝土框架柱连接节点的最不利工况,对其进行设计,并采用ANSYS分析了其受力特点,结果表明加强环对节点的约束效应明显,焊缝是控制节点强度的主要因素。     

上海中心大厦伸臂桁架与巨柱和核心筒连接的静力性能试验研究

超高层框架-核心筒结构体系中,伸臂桁架连接着外围巨柱框架与内部核心筒,需传递巨大内力,其连接构造、传力机制等非常复杂。以上海中心大厦工程为背景,选取钢骨混凝土巨柱-伸臂桁架-环带桁架连接区域和伸臂桁架-核心筒连接区域进行了单调静力加载试验,并进行了有限元分析和简化模型计算分析。结果表明：伸臂桁架能够有效连接相邻构件并可靠传力,其破坏模式表现为伸臂桁架斜腹杆的受压屈曲以及上、下弦杆的弯曲变形,具有较好的延性;伸臂桁架与巨柱和核心筒连接的节点板虽然部分区域进入塑性,但塑性变形不明显,表明连接区域的承载力远高于杆件的承载力;有限元分析及简化模型分析结果与试验结果吻合良好;简化模型反映了伸臂桁架的非线性受力机理,可对其失效荷载进行准确预测,并可根据结构性能设计要求进行伸臂桁架分析和构件截面选择。     

武汉中心伸臂桁架设计与研究

武汉中心塔楼采用巨柱框架-核心筒-伸臂桁架体系。在设计过程中对伸臂桁架道数、位置、立面形式、截面的确定进行了分析研究;结合建筑、机电的要求进行了伸臂杆件入墙延伸段的设计,并针对不同墙厚条件设计了嵌入式和外包式两种伸臂桁架入墙节点形式;对伸臂桁架杆件与钢管混凝土柱连接的构造方式进行了比选,并结合施工过程分析探讨了伸臂杆件延迟封闭的必要性。最终选用了设置3道伸臂桁架的结构方案并确定了各道桁架的具体做法。     

某超高层结构关键节点有限元分析

为抵抗水平地震作用和风荷载,某450m超高层采用"巨型框架-核心筒-伸臂桁架"的结构体系。该体系有两种关键节点,巨柱与伸臂桁架节点、核心筒与伸臂桁架节点。文中采用ABAQUS通用有限元分析软件,建立了两类节点的精细化有限元模型,分析了控制工况下节点各构件的应力状态。结果表明两种关键节点均满足中震不屈服的抗震性能目标,且满足强节点弱构件的抗震设计要求。     

某超限高层办公楼结构设计

某超限高层办公楼采用钢管混凝土叠合柱框架-钢筋混凝土核心筒-伸臂桁架结构体系。地处较高烈度区的Ⅳ类场地,存在高度超限、构件间断、承载力突变、局部穿层柱等不规则项,属于超限高层建筑。结构设计过程中进行了小震弹性分析和大震动力弹塑性分析,针对结构的薄弱部位采取了一系列有效的加强措施。采用基于性能的设计方法进行结构抗震设计,可以实现预期的D级抗震性能目标。同时还对框架柱的选型进行了比对分析,对外围框架柱与核心筒的竖向变形进行了施工模拟分析,对加强层伸臂桁架节点进行了有限元分析,分析结果表明:结构安全可靠,满足预设的性能目标。     

某超高层结构连接节点的非线性有限元分析

某超高层采用框架-核心筒结构体系,在内筒与核心筒之间采用伸臂桁架连接。介绍了这种结构形式的特点,利用有限元软件LS-DYNA分析了在控制工况作用下伸臂桁架与混凝土核心筒连接节点的工作性能,考察了伸臂桁架对混凝土墙体的影响及节点的破坏形态。结果显示,在荷载标准组合作用下,混凝土剪力墙及节点满足设计要求;在最不利工况作用下,混凝土剪力墙满足承载力极限状态要求;采用铸钢节点后满足强节点的设计要求。     

超高层建筑结构加强层耗能减震技术及连接节点设计研究

在框架-核心筒结构体系中,加强层可显著提高结构抗侧刚度、减小结构侧移,但会带来结构刚度、内力突变等不利影响。以某超高层建筑为工程背景,研究了黏滞阻尼器在伸臂桁架体系中的应用及在多遇地震和罕遇地震作用下的减震效果,研究了设置黏滞阻尼器的环带桁架在超高层建筑中的较优位置和减震效率。结果表明：黏滞阻尼器在伸臂桁架结构中的设置可以减小核心筒剪力墙的塑性损伤,减小结构的动力响应;设置黏滞阻尼器的环带桁架宜布置在层间相对速度大的位置,随超高层结构高度增加,阻尼器的减震效率降低。通过对伸臂桁架与外框柱、核心筒连接节点的设计及构造的分析,提出了连接节点的设计建议。     

加强层伸臂桁架-复式钢管高强混凝土柱节点有限元分析

基于巨型框架-核心筒结构体系中加强层伸臂桁架与巨型框架柱连接节点受力的特殊性,提出一种伸臂桁架-复式钢管高强混凝土柱的连接节点形式,运用ABAQUS软件并结合深圳某超高层结构设计,对该节点展开详细的数值模拟分析。研究揭示了该节点的受力机理,并证明其在传力上的可靠性,可为该类节点在超高层结构中的应用提供参考。     

重庆国金中心塔楼伸臂桁架施工技术

重庆国金中心项目T1塔楼为带有加强层的框架-核心筒结构,核心筒剪力墙采用顶模体系施工。为减小结构侧移、提高外框架抗倾覆能力,在加强层设置了伸臂桁架-腰桁架结构。由于伸臂桁架层结构复杂、构件体型庞大、节点复杂、核心筒内外存在沉降差且穿插有顶模体系、土建施工,因此对吊装、节点处理、矫正、焊接、终固均提出较高要求,施工难度大、危险性较高、施工质量难以控制。主要介绍了复杂条件下超高层建筑伸臂桁架结构的施工方法。     

600米级超高层钢结构节点可实施性设计重点探讨

超高层建筑高度超过600m后,其主体结构一般采用巨型框架-核心筒-伸臂桁架结构体系,核心筒下部为内嵌单层钢板的组合剪力墙,巨型框架由巨型柱和环带桁架组成,有时也设巨型支撑,这些结构构件尺寸巨大,节点尤其是钢结构节点非常复杂,施工难度很大。通过对在建的3座600m级超高层建筑施工案例的分析,探讨了600m以上超高层钢结构节点的施工可行性研究要点,提出这类结构需进行可实施性设计的必要性和建议,同时指出了可实施性设计的工作重点。     

Ultimate bearing capacity factor and whole process analysis for large size concrete filled steel tube columns

Based on the general theory of concrete filled steel tube (CFT), nonlinear analysis of large size CFT is performed using ANSYS, a commercially available finite element (FE) programme. A nonlinear 3-D finite element analysis (FEA) model is developed to predict the behaviour of axially loaded CFT columns. Comparisons between the predicted results and the curves of axially loaded CFT column published in the open literature show that the trend of the curves fit well. This also shows that the constitutive relation model and the basic assumptions can accurately predict the behaviour of the large size CFT. The FEA model is then used to investigate the influence of steel tube wall thickness, the width to thickness of built-in stiffener for ultimate bearing capacity of large size square CFT and so on. In addition, the whole construction process of large size rectangular CFT with holes in the middle vertical plate is analysed. The study presents the main influential factors for CFT ultimate bearing capacity and the concrete crack distribution.     

Material effect for predicting the fire resistance of concrete-filled square steel tube column under constant axial load

This paper presents a critical review of the performance of the currently available material models with regard to the mechanical behaviour of a concrete-filled steel tube (CFT) column at elevated temperatures. For this purpose, numerical heat transfer analysis and nonlinear thermal stress analysis were carried out by taking into account the existing material properties, such as the thermal and mechanical properties of concrete and steel. In addition, ten CFT column specimens with rectangular cross-sections of 300-350 mm in size were heated for two hours in accordance with KSF 2257 (equivalent to ASTM E119 and JIS A 1304). On comparing the numerical analysis and experimental results, it can be observed that we can validate and employ the existing material models such as EUROCODE, AIJ CODE, Lie’s material model, and Yin’s material model.     

约束钢管混凝土柱的开发研究(英文)

本文提出了一种更适合抗震设计的新型钢管混凝土体系———约束钢管混凝土柱体系。它建立在清楚的力学概念基础上,其设计着眼于在可能出现塑性铰的部位附加横向约束以控制钢管的局部屈曲和更有效地约束混凝土。这一新型钢管混凝土柱体系兼具了钢管混凝土及套管混凝土柱两者的优点,克服了传统钢管混凝土柱的抗震缺陷,为抗震地区的高层结构和桥梁设计提供了理想的选择。在本研究的第一阶段,作者们对FRP约束的圆钢管柱和钢板约束的方钢管柱进行了模拟地震力的加载试验。其结果验证了约束钢管混凝土柱的良好抗震性能。     

Cyclic behaviours of concrete-filled steel tubular columns with pre-load after exposure to fire

This paper reports experimental results of cyclic behaviours of eight concrete-filled steel tubular (CFT) columns after exposure to fire under sustained axial load. The specimens were heated by a stackable electrical furnace and blowing liquefied petroleum gas fire into the furnace simultaneously in order to simulate the real fire attack. The furnace heating can be controlled easily and safely in such a hybrid heating method using gas and electricity that the average temperature in the furnace followed as closely as possible the ISO-834 standard fire curve. After the CFT columns had been axially loaded and heated for a specified duration of time, the specimens were cooled down to room temperature according to the ISO-834 fire standard while the axial load was kept constant. Finally, the columns were subjected to lateral cyclic loading under constant axial load. The sustained pre-load led to significant residual deformations of CFT columns during the cooling phase. Two columns were found to have suffered local buckling of steel tube and three columns have suffered steel weld rupture during the fire exposure. Therefore, it is recommended that more than two vent holes or vent holes with larger diameter should be used in a CFT column and engineers should pay much attention to reasonable selection and construction of steel sections. Compared with the fire-damaged columns without pre-load and that at room temperature, the post-fire ductility and energy absorption capacity of CFT with pre-load had no obvious deterioration and the axial load level had no obvious influence on the residual strength of fire-damaged CFT. The experimental results can provide a basis for fire-damage assessment of CFT columns.     

Static analysis of cable-stayed bridge with CFT arch ribs

A new type of cable supported bridge, cable-stayed CFT arch bridge, was proposed and its static strength was studied in this paper. Arch ribs consist of concrete filled steel tubes (CFT). CFTs have high resistance against bending moments and compressive axial forces and are ideal as arch ribs. A cable-stayed CFT arch bridge with a main-span of 300 m was designed and the safety of its structural members was checked by the limit state design method. Large deformation analysis was used to obtain sectional forces. The CFT arch ribs and the steel box girders and towers of the designed bridge satisfied the required safety criteria for ultimate design loads. The applied loads were further increased until the bridge collapsed when the arch ribs buckled. The amount of steel required for the cable-stayed CFT arch bridge was significantly lower than that for the cable-stayed bridge. It has been found that the proposed cable-stayed CFT arch bridge is feasible and potentially economical.     

钢管混凝土柱-钢筋混凝土梁节点及受力特点

节点是框架结构中的关键部位。它的力学性能直接影响结构的内力分配,进而影响结构的整体性能。钢管混凝土组合结构由于其承载力高、延性好和施工便捷,被广泛应用于高层和超高层建筑中。但该结构形式与钢筋混凝土结构相比,节点构造较为复杂,制约了钢管混凝土组合结构的发展。目前,在实际工程中采用的钢管混凝土柱-钢筋混凝土梁的节点形式很多,如现浇钢筋混凝土梁外环板式节点、穿心弯剪牛腿式节点、穿心抗剪牛腿式节点和双梁夹柱穿心抗剪牛腿式节点等。每种节点形式都有其优缺点和适用范围。本文对上述几种常用钢管混凝土柱-钢筋混凝土梁节点形式进行了介绍,并对其优缺点及设计要点进行了分析。在此基础上,作者又提出了一种构造简单、传力明确,便于工厂化施工的新型节点。     

Mechanical behavior of stirrup-confined circular concrete-filled steel tubular stub columns under axial loading

通过井字形拉筋、米字形拉筋和圆环箍筋等3组拉筋约束形式带拉筋圆钢管混凝土短柱轴压性能对比试验,研究不同拉筋约束形式、拉筋体积配箍率对圆钢管混凝土轴压短柱的承载力和延性等的影响;采用合理的混凝土三轴受力本构模型和钢材本构模型,应用ABAQUS非线性有限元分析软件对带拉筋圆钢管混凝土轴压短柱进行三维有限元分析,有限元计算结果与试验结果吻合较好;在此基础上,分析了带拉筋圆钢管混凝土轴压短柱中钢管、拉筋或箍筋、核心混凝土之间的组合作用。结果表明：井字形拉筋圆钢管混凝土轴压短柱的承载力最高,延性最好,钢管、拉筋和核心混凝土之间的组合作用最强;提高体积配箍率可以有效提高圆钢管混凝土短柱的轴压承载力和延性。     

Flexural behavior of concrete filled non-uni-thickness walled rectangular steel tube

This paper presents an experimental study on the mechanical behavior of non-uni-thickness walled rectangular concrete-filled steel tube (CFT) beams subjected to pure bending. Three specimens were fabricated and tested to investigate the relation of bending moment vs. deflection of the composite beam. First, the ultimate flexural strength of non-uni-thickness walled rectangular CFT is compared to the predicted strength of corresponding uni-thickness walled CFT beams based on current design codes. Then a nonlinear finite element model is developed and verified with experimental results. The FEM model is used to investigate the effect of the steel wall thickness ratio on the bending strength of the composite beam. Both experimental and analytical results suggest that a non-uni-thickness walled rectangular CFT beam exhibits adequate ductility, and the flexural strength of a non-uni-thickness walled CFT beam is superior to that of a uni-thickness walled CFT beam.     

Finite element analysis of CFT columns subjected to an axial compressive force and bending moment in combination

Proper material constitutive models for concrete-filled tube (CFT) columns subjected to an axial compressive force and bending moment in combination are proposed and verified in this paper by using the nonlinear finite element program ABAQUS compared against experimental data. In the numerical analysis, the cross sections of the CFT columns are categorized into three groups, i.e., ones with circular sections, ones with square sections, and ones with square sections stiffened with reinforcing ties.It is shown that the steel tubes can provide a good confining effect on the concrete core when the axial compressive force is large. The confining effect of a square CFT stiffened by reinforcing ties is stronger than that of the same square CFT without stiffening ties but weaker than that of a circular CFT. Nevertheless, when the spacing of reinforcing ties is small, a CFT with a square section might possibly achieve the same confining effect as one with a circular section.     

Investigation of Proposed Concrete Filled Steel Tube Connections under Reversed Cyclic Loading

Concrete-filled steel tube (CFT) columns are used in the primary lateral resistance systems. The objective of this research is to analyse the behavior of the steel beam to CFT column connections. A three-dimensional numerical model for simulating the behavior of CFT connections was developed with the aid of the general purpose nonlinear finite element analysis package ABAQUS. In this paper, 90 CFT connection specimens include simple and moment connections that were tested under reversed cyclic loading. Shear capacity of joint, moment-drift response, energy absorption, and displacement ductility were studied in those models. The results have indicated that, the hysteresis curve of CFT columns was plump; no pinch phenomenon can be found; the damage and degradation degree of the strength and stiffness of specimens is lower; and high energy dissipation capacity can be achieved. Improvement in the behavior of CFT connection depends on the beam characteristics and column features.