Field of application of high strength steel circular tubes for steel and composite columns from an economic point of view

This paper presents the results of a global comparison between high strength steel and normal steel circular tube used to build steel and composite columns submitted to static loading, as regards the economic aspects. The comparison is based on an optimum design taking into account the strength, stability and stiffness conditions of Eurocode 3 and 4. The automatic implementation of the algorithms allows achieving a high amount of case studies, covering the realistic possibilities of building columns. The investigations are realized on simple columns, columns included in braced or un-braced frames and whole frames. The field of application of high strength steel (vs normal steel), regarding the total cost of the member, is provided in a chart clearly indicating where the use of high strength steel becomes economic.     

欧盟规范EN 1994对钢管混凝土构件设计的规定

欧盟标准化协会于2004年颁布了最新的钢-混凝土组合结构设计规范EN 1994,内容包括钢管混凝土柱、型钢混凝土柱以及钢-混凝土组合梁。和以前版本相比,EN 1994关于钢管混凝土构件的设计条文作了许多改动,包含了高强钢管从而应用范围更广,对混凝土收缩和徐变的考虑更加细致。本文介绍这些条文规定并通过实例说明设计中应注意的问题。     

Numerical simulation of concrete encased steel composite columns

This paper investigates the behaviour of pin-ended axially loaded concrete encased steel composite columns. A nonlinear 3-D finite element model was developed to analyse the inelastic behaviour of steel, concrete, longitudinal and transverse reinforcement bars as well as the effect of concrete confinement of the concrete encased steel composite columns. The interface between the steel section and concrete, the longitudinal and transverse reinforcement bars, and the reinforcement bars and concrete were also considered that allowed the bond behaviour to be modeled and the different components to retain their profile during the deformation of the column. Furthermore, the initial overall (out-of-straightness) geometric imperfection was carefully incorporated in the model. The finite element model has been validated against published experimental results. The main objective of the study was to understand the structural response and modes of failure of the columns and to assess the composite column strengths against current design codes. The study covered slender, non-slender, stub and long concrete encased steel composite columns. The concrete strengths varied from normal to high strength (20-110 MPa). The steel section yield stresses also varied from normal to high strength (275-690 MPa). Furthermore, the variables that influence the composite column behaviour and strength comprising different slenderness ratios, concrete strength and steel yield stress were investigated in a parametric study. It is shown that the increase in structural steel strength has a small effect on the composite column strength for the columns having higher relative slenderness ratios due to the flexural buckling failure mode. The composite column strengths obtained from the finite element analysis were compared with the design strengths calculated using the American Institute for Steel Construction AISC and Eurocode 4 for composite columns. Generally, it is shown that the EC 4 accurately predicted the design strength for the concrete encased steel composite columns having a concrete cylinder strength of 30 MPa and structural steel yield stresses of 275 and 460 MPa, which are in the limits of the code, which otherwise, was generally conservative. The AISC predictions were quite conservative for all the concrete encased steel composite columns.     

水泥窑尾预热器钢塔架优化设计研究

水泥窑尾预热器塔架是新型干法水泥生产线中的重要构筑物,塔架的结构设计一般参照高层民用建筑进行,但由于荷载条件不同、结构布置受到工艺要求和设备安装限制,塔架在结构布置及性能等方面有一定特殊性。通过对采用钢框架-支撑体系的某水泥窑窑尾预热器塔架进行优化设计,在多方案比选基础上,结合工艺要求,确定了调整钢柱布置减小钢梁跨度、采用方钢管柱和方钢管混凝土柱代替H型钢柱的优化设计方案,塔架主体钢结构用钢量降低约25%。同时研究了窑尾塔架结构的受力特点。     

型钢混凝土组合柱正截面承载力的分析与评估

本文采用一种可对复杂截面形式的型钢混凝土偏压柱进行截面设计和分析的数值迭代计算机方法,首先分析了一非对称多边形角柱的正截面承载力;在此基础上,通过实例计算对《型钢混凝土组合结构技术规程》中建议的组合柱正截面承载力简化计算方法进行了分析和评估,获得了一些对组合柱设计有用的结论和建议。     

门式刚架的参数优化及设计建议

根据设计经验和规范的建议,本文选取了门式刚架的常用建筑尺寸和梁柱形状,在满足规范对门式刚架强度、刚度和稳定的前提下,以单位面积用钢量最小为优化目标,对影响刚架用钢量的主要离散参数（如结构形式、荷载、柱距、跨度、高度、坡度和梁柱构件等）进行了优化分析和设计.根据分析结果,提出了结构的最优布置及诸参数的建议取值,以供设计参考.     

大跨度钢-混凝土组合梁分析与设计

结合某工程大跨度钢一混凝土组合梁设计,通过对混凝土楼板和钢梁上、下翼缘厚度的优选分析,针对组合梁中混凝土翼板厚度和钢梁截面的选取方法以及梁柱连接和梁梁拼接的节.k设计与构造措施提出了一些设计建议,可供类似工程设计参考.     

Eccentrically loaded concrete encased steel composite columns

This paper presents a nonlinear 3-D finite element model for eccentrically loaded concrete encased steel composite columns. The columns were pin-ended subjected to an eccentric load acting along the major axis, with eccentricity varied from 0.125 to 0.375 of the overall depth (D) of the column sections. The model accounted for the inelastic behaviour of steel, concrete, longitudinal and transverse reinforcement bars as well as the effect of concrete confinement of the concrete encased steel composite columns. The interface between the steel section and concrete, the longitudinal and transverse reinforcement bars, and the reinforcement bars and concrete were also considered allowing the bond behaviour to be modelled and the different components to retain its profile during the deformation of the column. The initial overall geometric imperfection was carefully incorporated in the model. The finite element model has been validated against existing test results. The concrete strengths varied from normal to high strength (30–110 MPa). The steel section yield stresses also varied from normal to high strength (275–690 MPa). Furthermore, the variables that influence the eccentrically loaded composite column behaviour and strength comprising different eccentricities, different column dimensions, different structural steel sizes, different concrete strengths, and different structural steel yield stresses were investigated in a parametric study. Generally, it is shown that the effect on the composite column strength owing to the increase in structural steel yield stress is significant for eccentrically loaded columns with small eccentricity of 0.125D. On the other hand, for columns with higher eccentricity 0.375D, the effect on the composite column strength due to the increase in structural steel yield stress is significant for columns with concrete strengths lower than 70 MPa. The strength of composite columns obtained from the finite element analysis were compared with the design strengths calculated using the Eurocode 4 for composite columns. Generally, it is shown that the EC4 accurately predicted the eccentrically loaded composite columns, while overestimated the moment.     

Strength of slender concrete filled high strength steel box columns

The use of thin walled steel sections coupled with concrete infill has been used on various building projects with great advantage. The currently available international standards for composite structures are limited to the design of concrete filled steel columns with compact sections. However, there is limited research work in the literature available which is concerned with slender concrete filled thin-walled steel columns. This paper presents a comprehensive experimental study of thin walled steel sections utilising high strength steel of a thin walled nature and filled with normal strength concrete. A numerical model is developed herein in order to study the behaviour of slender concrete filled high strength steel columns incorporating material and geometric non-linearities. For this analysis, the equilibrium of the member is investigated in the deformed state, using the idealised stress–strain relationships for both the steel and concrete materials, considering the elastic and plastic ranges. This paper presents both an experimental and theoretical treatment of coupled local and global buckling of concrete filled high strength steel columns sometimes termed interaction buckling. The experimental results of columns with high strength steel casings conducted herein by the authors are used for comparison. The effect of the confined concrete core is also addressed and the method shows good agreement with the experimental results of concrete filled steel columns with compact sections. The behaviour of concrete filled steel slender columns affected by elastic or inelastic local buckling is also investigated and compared with relevant experimental results. The paper then concludes with a design recommendation for the strength evaluation of slender composite columns using high strength steel plates with thin-walled steel sections, paying particular attention to existing codes of practice so as not to deviate from current design methodologies.     

型钢-方钢管自密实高强混凝土轴压短柱受力性能的试验研究

提出了一种重载柱设计的模式,即型钢-方钢管自密实高强混凝土柱。该组合柱是在方钢管中填充自密实高强混凝土和型钢而形成。通过13根型钢-方钢管自密实高强混凝土短柱的轴心受压试验,研究了该组合柱的受力性能。试验结果表明自密实试件与经过振捣的试件的受力性能几乎没有差别;型钢的存在有效地延缓或抑制了高强混凝土中剪切裂缝的产生从而提高了构件的延性;混凝土强度、方钢管的宽厚比和型钢的用量对构件的强度和延性有着显著影响。最后给出了型钢-方钢管自密实高强混凝土轴心受压短柱强度承载力的计算公式,计算结果与试验结果吻合良好。     

Investigation of concrete encased steel composite columns at elevated temperatures

This paper presents a nonlinear 3-D finite element model investigating the behaviour of concrete encased steel composite columns at elevated temperatures. The composite columns were pin-ended axially loaded columns having different cross-sectional dimensions, different structural steel sections, different coarse aggregates and different load ratios during fire. The nonlinear material properties of steel, concrete, longitudinal and transverse reinforcement bars as well as the effect of concrete confinement at ambient and elevated temperatures were considered in the finite element models. The interface between the steel section and concrete, the longitudinal and transverse reinforcement bars, and the reinforcement bars and concrete were also considered allowing the bond behaviour to be modelled and the different components to retain its profile during the deformation of the column. The initial overall (out-of-straightness) geometric imperfection was carefully included in the model. The finite element model has been validated against published tests conducted at elevated temperatures. The time–temperature relationships, deformed shapes at failure, time–axial displacement relationships, failure modes and fire resistances of the columns were evaluated by the finite element model. It has been shown that the finite element model can accurately predict the behaviour of the columns at elevated temperatures. Furthermore, the variables that influence the fire resistance and behaviour of the composite columns comprising different load ratios during fire, different coarse aggregates and different slenderness ratios were investigated in parametric studies. It is shown that the fire resistance of the columns generally increases with the decrease in the column slenderness ratio as well as the increase in the structural steel ratio. It is also shown that the time–axial displacement relationship is considerably affected by the coarse aggregate. The fire resistances of the composite columns obtained from the finite element analyses were compared with the design values obtained from the Eurocode 4 for composite columns at elevated temperatures. It is shown that the EC4 is conservative for all the concrete encased steel composite columns, except for the columns having a load ratio of 0.5 as well as the columns having a slenderness ratio of 0.69 and a load ratio of 0.4.     

钢结构次梁设计模式与经济性比较研究

钢梁设计模式有：弹性设计、考虑屈曲后强度设计和组合梁设计。由这3种设计模式出发,着眼于钢结构次梁设计,在相同的荷载和几何条件假设下,比较分析了满足承载能力和正常使用极限状态要求的次梁用钢量,得出组合梁设计为最优设计模式。在钢结构设计中,次梁设计宜优先采取组合梁设计或考虑屈曲后强度设计,腹板局部稳定的控制可采用临界剪切应力法,腹板高厚比不必局限于规范规定的限值80槡235/fy,在满足结构安全的前提下,应使经济参数最优化。     

武钢技术中心科技大厦结构设计与研究

本文介绍了武钢技术中心科技大厦结构设计中的一系列有特点的问题,包括弹性组合楼板对结构平面布置不规则的高层钢结构受力性能的影响、平面局部凸出楼梯间的处理、新钢材的应用、钢管混凝土柱与混凝土梁节点的选型与比较等,为类似工程设计提供一定的参考和借鉴。     

竖向荷载下半刚性连接组合框架的实用设计方法(Ⅱ)——梁与柱设计及算例

虽然在钢框架结构设计中考虑半刚性连接和楼板的组合效应会产生良好的结构经济性,但是在实际工程中仍很难应用,主要原因是缺乏合适简便的设计方法。本文在国内外研究的基础上,结合我国钢结构设计规范GB50017-2003,给出了竖向荷载下半刚性连接组合框架的实用设计建议方法。设计建议方法包括满足两个极限状态的节点、梁、柱设计,较好地解决了梁挠度和柱有效长度系数计算中节点连接刚度的合理选取、半刚性特征对梁挠度和柱计算长度的影响。该方法不仅反映了节点和框架的实际性能,而且简便实用,符合工程师对普通钢框架的设计习惯。本文为全文的第二部分,介绍梁与柱设计。并通过一个算例,说明竖向荷载下半刚性连接组合框架的实用设计过程及经济性。     

钢管混凝土柱防火保护层厚度实用计算方法研究

在对以往钢管混凝土柱耐火极限影响因素系统研究的基础上 ,提出了按规范ISO -834或GB9978-88规定的标准升温曲线升温作用下钢管混凝土柱防火保护层厚度的实用计算方法 ,计算结果与数值计算和试验结果均吻合较好 ,且略偏于安全。该方法可供有关工程实践和规程制订参考     

某新建钢结构厂房柱下独立基础加固处理

针对某新建钢结构厂房,在上部结构大部分完工时检测发现:钢柱下钢筋混凝土独立基础的混凝土强度达不到C10的强度等级,提出采用钢和混凝土组合结构的方法对其基础进行加固,使基础的承载力满足要求。通过分析边柱和中柱不同的受力特点,分别设计计算了两种加固方案用于边柱和中柱,并对施工方法和顺序进行研究探讨。加固后的混凝土独立基础,不仅满足强度要求,而且经济、适用,施工方法简便,达到了预期的目的。该设计及施工方案可供同类工程加固处理参考。     

组合T形截面钢管混凝土柱偏心受压试验研究

在分析各种异形钢管混凝土柱工程应用的基础上,提出组合T形截面钢管混凝土柱。考虑长细比、偏心距等参数的影响,设计制作18个组合T形钢管混凝土柱试件。通过偏心受压试验,对长细比16.0<λ≤28.8的组合T形钢管混凝土柱压弯性能进行研究,考察试件的破坏形态,实测试件的荷载-应变曲线和荷载-柱中挠度曲线,分析各参数对试件偏心受压力学性能的影响。通过试验数据回归分析,参考国内外相关规范,提出组合T形截面钢管混凝土柱偏心受压承载力计算公式。试验结果表明：偏心受压柱均为弯曲失稳破坏,长细比越大,弯曲破坏特征越明显;偏心距越大,试件极限承载力越低。研究表明,组合T形钢管混凝土柱的两个组成部分能很好地协同工作,力学性能较好;所提出的承载力计算公式可供工程设计参考。图10表3参8     

台湾第一部钢骨钢筋混凝土构造(SRC)设计规范之设计理念与重点内容

本文主要阐述台湾第一部钢骨钢筋混凝土构造(SteelReinforcedConcrete,SRC)设计规范之发展过程与重点内容,包括SRC构造之建筑与力学特色、SRC构造之设计理念、SRC构造之强度计算方法、耐震设计与SRC梁柱接头之设计细则等。台湾“SRC构造设计规范”可以适用于由钢梁或包覆型SRC梁、包覆型SRC柱或钢管混凝土柱(CFT)共同组成之SRC建筑构造。过去多年以来,由于台湾的建筑设计规范并未明订SRC构造设计之规定,使得工程师在进行SRC构造设计时缺乏一套依循的标准。所幸在“内政部”建筑研究所推动之下,台湾SRC构造设计规范草案终于在2003年底经过“内政部”建筑技术审议委员会审查通过。“内政部”于2004年1月16日公布修正建筑法规中之“建筑技术规则”,增列“第七章:钢骨钢筋混凝土构造”,由第496条至520条明订SRC构造设计之相关规定。随后并公布“钢骨钢筋混凝土构造设计规范与解说”自2004年7月1日起正式施行。从此以后,台湾从事SRC构造设计之业者与相关审查机构将可以有明确的设计规范可以依循。由于台湾的钢骨构造(S)与钢筋混凝土构造(RC)设计规范主要是参考美国AISC及ACI规范而订定,为了使S、RC及SRC三种构造的设计规范能够具有一贯性,因此台湾“SRC构造设计规范”的研拟过程亦朝着结合AISC与ACI规范的方向进行。为了彰显SRC构造之设计理念,本文提出一个称为“SRC优生学”的新观念,并比喻说:“一个经过适当设计的SRC构造,就像是S构造与RC构造结婚生下来的‘优生宝宝’。”这正是一个成功的SRC构造设计所欲达成的目标。换言之,一个细心设计的SRC构造,不但可以享受到S构造与RC构造的优点,更可以利用这两种构造“互相截长补短”,达到更安全与更经济的双赢目标。     

内置钢骨组合L形截面钢管混凝土短柱轴压性能试验研究

为提高异形截面钢管混凝土柱的轴压承载力,提出内置钢骨组合异形截面钢管混凝土柱。考虑套箍指标、配骨率等参数的影响,设计制作12个内置钢骨组合L形截面钢管混凝土短柱及3个未配置钢骨的组合L形截面钢管混凝土短柱两类试件;通过轴心受压试验,考察试件的破坏形态,实测试件的荷载-纵向应变曲线和承载力,分析各参数对试件力学性能的影响,并对比两类组合柱轴压性能的差异。在试验研究基础上,参考国内外相关规范,提出内置钢骨组合L形截面钢管混凝土短柱轴心受压承载力计算式。研究表明,内置钢骨组合L形截面钢管混凝土短柱轴压承载力高,增大套箍指标和配骨率可以明显提高试件承载力,所提出的承载力计算式可供工程设计参考。     

Einsatz von hochfesten Stählen und Betonen bei Hohlprofil‐Verbundstützen

Composite columns made of high‐strength steel and high‐strength concrete. The paper deals with the use of composite columns made of high‐strength steel and high‐strength concrete. Based on the design methods in Eurocode 4‐1‐1 and DIN 18800‐5 a simplified design method is presented for composite columns with high strength concrete and high strength steel in combination with massive inner steel core‐profiles. The ultimate strength of these special type of columns is significantly influenced by the residual stresses in the core profiles resulting from the cooling process during fabrication. Based on Finite Element studies new models are presented for the determination of the distribution of residual stress taking into account the steel grade, the dimensions of the core profiles and the cooling conditions during fabrication.