冷弯厚壁型钢考虑冷弯效应的屈服强度计算方法研究

为研究冷弯效应对壁厚6.0 mm以上的冷弯厚壁型钢屈服强度的影响,对4种不同截面、不同厚度的冷弯厚壁型钢进行了截面不同部位的材性试验研究,同时对现有国内冷弯厚壁型钢的材性试验和短柱试验数据进行了汇总。在简要回顾国内外冷弯厚壁型钢考虑冷弯效应的屈服强度计算公式及其理论依据的基础上,将各国规范计算值与试验值进行了对比。结果表明：冷弯效应对冷弯厚壁型钢的屈服强度影响较大,其影响程度与板件的宽厚比关系明显;我国规范、北美、澳洲/新西兰规范公式,以及朱爱珠基于我国规范提出的修正公式计算结果偏于保守,而欧洲规范的计算结果略偏大;我国GB 50018-2002《冷弯薄壁型钢结构技术规范》中计算方法理论依据充分,且在计算结果偏于安全的同时变异系数较小,更适合于工程应用。     

冷弯型钢的产品系列及在建筑工程上的应用

如何在建筑工程中尽量推广采用冷弯型钢这种新型高效经济钢材，是冷弯生产厂和建筑设计部门应予高度重视的课题．本文就冷弯型钢的产品系列及在建筑工程上的应用问题作一探讨。     

冷弯厚壁矩形型钢管冷弯效应

针对断面规格为□200×300×9.2的冷弯厚壁矩形型钢管,进行了平板、弯角、相应母材和短柱试件的力学性能试验。结合冷弯生产工艺,分析了平板、弯角试件力学性能随冷弯道次的变化规律,并与相关厚壁型钢冷作硬化效应作了比较。运用国内外冷弯型钢设计规范和相关文献中的修正公式,对该厚壁冷弯方形型钢全截面强度进行了设计和对比分析。结果表明：国内薄壁和国外厚壁公式都不可直接用于本冷弯厚壁矩形型钢强度设计,国外公式更偏于危险;魏氏体组织是造成带焊缝板件强度高而塑性差的主要原因;焊接热使板件受到低温“退火”而强度降低,从而导致两竖直侧平板件强度甚至低于母材。图8表8参10 关键词：冷弯厚壁矩形型钢管; 静载试验; 力学性能; 冷作硬化效应; 结构强度设计     

Residual stresses in cold-rolled profiles

Structural steel members obtained by cold-forming have become more and more popular in steel construction. They allow for lightening the weight and thus provide appreciable savings over conventional hot-rolled sections.Cold-forming leads to changes in the main structural characteristics of the virgin material. Among them the increase of the yield strength due to strain-hardening and of the ultimate strength due to strain-ageing and the birth of residual stresses which play an important role in the behaviour of the profiles under compression loads.The aim of the paper is to propose a theoretical method for predicting residual stresses due to cold-rolling. The numerical results obtained lead to a better knowledge of the characteristics of the cold-rolling (elastic spring-back, effect of the ratio of the thickness versus the radius of the corner, distribution and size of the residual stresses with respect to the dimensions of the profiles).     

Shear buckling characteristics of cold-formed steel channel beams

Cold-formed steel members are increasingly used as primary structural elements in the building industries around the world due to the availability of thin and high strength steels and advanced cold-forming technologies. Cold-formed lipped channel beams (LCB) are commonly used as flexural members such as floor joists and bearers. However, their shear capacities are determined based on conservative design rules. For the shear design of LCB web panels, their elastic shear buckling strength must be determined accurately including the potential post-buckling strength. Currently the elastic shear buckling coefficients of LCB web panels are determined by assuming conservatively that the web panels are simply supported at the junction between their flange and web elements. Hence finite element analyses were conducted to investigate the elastic shear buckling behavior of LCBs. An improved equation for the higher elastic shear buckling coefficient of LCBs was proposed based on finite element analysis results and included in the ultimate shear capacity equations of the North American cold-formed steel codes. Finite element analyses show that relatively short span LCBs without flange restraints are subjected to a new combined shear and flange distortion action due to the unbalanced shear flow. They also show that significant post-buckling strength is available for LCBs subjected to shear. New equations were also proposed in which post-buckling strength of LCBs was included.     

Experimental studies of the shear behaviour and strength of lipped channel beams with web openings

Cold-formed steel members are increasingly used as primary structural elements in the building industries around the world due to the availability of thin and high strength steels and advanced cold-forming technologies. Cold-formed lipped channel beams (LCB) are commonly used as flexural members such as floor joists and bearers. However, their shear capacities are determined based on conservative design rules. Current practice in flooring systems is to include openings in the web element of floor joists or bearers so that building services can be located within them. Shear behaviour of LCBs with web openings is more complicated while their shear strengths are considerably reduced by the presence of web openings. However, limited research has been undertaken on the shear behaviour and strength of LCBs with web openings. Hence a detailed experimental study involving 40 shear tests was undertaken to investigate the shear behaviour and strength of LCBs with web openings. Simply supported test specimens of LCBs with aspect ratios of 1.0 and 1.5 were loaded at mid-span until failure. This paper presents the details of this experimental study and the results of their shear capacities and behavioural characteristics. Experimental results showed that the current design rules in cold-formed steel structures design codes are very conservative for the shear design of LCBs with web openings. Improved design equations have been proposed for the shear strength of LCBs with web openings based on the experimental results from this study.     

Experimental study of web crippling behaviour of hollow flange channel beams under two flange load cases

This paper presents the details of an experimental study of a cold-formed steel hollow flange channel beam known as LiteSteel beam (LSB) subject to web crippling under End Two Flange (ETF) and Interior Two Flange (ITF) load cases. The LSB sections with two rectangular hollow flanges are made using a simultaneous cold-forming and electric resistance welding process. Due to the geometry of the LSB, and its unique residual stress characteristics and initial geometric imperfections, much of the existing research for common cold-formed steel sections is not directly applicable to LSB. Experimental and numerical studies have been carried out to evaluate the behaviour and design of LSBs subject to pure bending, predominant shear and combined actions. To date, however, no investigation has been conducted on the web crippling behaviour and strength of LSB sections. Hence an experimental study was conducted to investigate the web crippling behaviour and capacities of LSBs. Twenty-eight web crippling tests were conducted under ETF and ITF load cases, and the ultimate web crippling capacities were compared with the predictions from the design equations in AS/NZS 4600 and AISI S100. This comparison showed that AS/NZS 4600 and AISI S100 web crippling design equations are unconservative for LSB sections under ETF and ITF load cases. Hence new equations were proposed to determine the web crippling capacities of LSBs based on experimental results. Suitable design rules were also developed under the direct strength method (DSM) format.     

Elastic shear buckling characteristics of LiteSteel beams

LiteSteel beam (LSB) is a new cold-formed steel hollow flange channel beam. The unique LSB section is produced by a patented manufacturing process involving simultaneous cold-forming and dual electric resistance welding. To date, limited research has been undertaken on the shear buckling behaviour of LSBs with torsionally rigid, rectangular hollow flanges. For the shear design of LSB web panels, their elastic shear buckling strength must be determined accurately including the potential post-buckling strength. Currently the elastic shear buckling coefficients of web panels are determined by assuming conservatively that the web panels are simply supported at the junction between the flange and web elements. Therefore finite element analyses were carried out to investigate the elastic shear buckling behaviour of LSB sections including the effect of true support conditions at the junction between their flange and web elements. An improved equation for the higher elastic shear buckling coefficient of LSBs was developed and included in the shear capacity equations of Australian cold-formed steel codes. Predicted ultimate shear capacity results were compared with available experimental results, both of which showed considerable improvement to the shear capacities of LSBs. A study on the shear flow distribution of LSBs was also undertaken prior to the elastic buckling analysis study. This paper presents the details of this investigation and the results including the shear flow distribution of LSBs.     

不锈钢轴心受压柱弯曲屈曲承载力分析

为给我国《不锈钢结构技术规范》中轴心受压柱弯曲屈曲稳定部分的编制提供依据,对国外已有的同类构件的设计方法和试验研究数据进行搜集和对比。结果表明：目前的欧洲不锈钢结构设计规范和美国冷成型不锈钢结构设计规范中计算该类构件的公式均存在一定不足。依据搜集到的199个方管、矩形管、圆管、椭圆管、焊接H形钢和冷弯C型钢截面柱的试验数据,根据冷弯效应及残余应力对轴心受压构件稳定性能的影响,将构件依据截面形式分为A、B、C三类,其中方管、矩形管和冷弯C型钢为A类,圆管和椭圆管为B类,焊接H形钢为C类,三类轴心受压稳定曲线均采用Perry公式形式表达。与试验数据对比表明：采用三类曲线能较好地估算构件的稳定承载力且离散性较小。对提出的计算式进行可靠度分析,结果表明其可靠度指标β满足我国GB 50068-2001《建筑结构可靠度设计统一标准》的要求。     

卷边槽钢柱和卷边角钢柱的试验研究

冷弯薄壁型钢可以看成是由几块相互联系的平板组成,薄板在初始屈服后,还有相当大的潜在能力,本文通过39根卷边槽钢柱和卷边角钢柱进行了试验研究,并与理论值进行了比较,结果显示理论值与试验实测值吻合较好。     

A finite strip method for the elastic—plastic large dlisplacement analysis of thin-walled and cold-formed steel sections

A large deflection elastic—plastic analysis has been developed using the finite strip method of structural analysis to determine the non-linear local buckling behaviour of thin-walled and cold-formed sections in compression. The analysis accounts for plate geometric imperfections, the variation of yield stress around a section, the stress—strain characteristics of the material forming the section and complex patterns of residual stress produced by the cold-forming process.

The analysis is verified against reliable solutions for the non-linear buckling behaviour of plates and plate assemblies in axial compression and the non-linear overall buckling behaviour of a strut. The analysis is further compared with the results of plates with a rounded stress—strain curve typical of cold-formed steel and aluminium.     

Q690高强钢端板连接梁柱节点抗震性能试验研究

对3个齐平式端板螺栓连接节点试件进行低周反复荷载试验,其中1个为普通钢端板节点试件,另2个为Q690高强钢端板节点试件。通过改变端板和柱的尺寸与材料,得到普通钢与高强钢端板节点、刚性柱和非刚性柱节点的性能差别,并与欧洲规范EC3的计算结果进行对比。结果表明：Q690高强钢端板节点的受弯承载能力比Q345钢端板节点高30%,但因其端板弹性变形能力较强,易于导致螺栓破坏,因此,需提高螺栓的承载力以提高其延性;刚性柱节点的受弯承载能力与非刚性柱节点基本相同,但其转动能力、延性、耗能能力等抗震性能明显优于非刚性柱节点;EC3组件法普通钢节点承载能力的预测公式可直接用于高强钢端板节点,但转动刚度及破坏模式的预测方法并不适用于高强钢端板节点。     

Prediction of the squash loads of concrete-filled tubular section columns with local buckling

This paper describes a series of compression tests of circular hollow steel (CHS) sections and circular concrete-filled tubular (CFT) sections. The diameter to thickness ratios of the test specimens ranged 45–140. This range was set to investigate the effect of local buckling in the circular steel skin on the ultimate strength of CFT columns. The confining effect against filled-in concrete was also studied. A squash load formula for CFT stub columns is proposed to account for the post-local-buckling strength of steel skin. The ultimate strength of steel skin was predicted by a kind of Direct Strength Method (DSM). The proposed DSM does not require the computation of the effective area of the steel skin, but uses the gross area of the steel skin and the design strength formula based on various test results. The compressive strength formula of the filled-in concrete accounting for the strength ratio of steel skin to filled-in concrete is also proposed to consider the increase in compressive strength of the filled-in concrete, due to the confining effect of the steel skin. The design strengths of CFT columns were compared with the test results for verification.     

Design of high strength steel columns at elevated temperatures

The main objective of this paper is to study the behaviour and design of high strength steel columns at elevated temperatures using finite element analysis. In this study, equations predicting the yield strength and elastic modulus of high strength steel and mild steel at elevated temperatures are proposed. In addition, stress-strain curve model for high strength steel and mild steel materials at elevated temperatures is also proposed. The numerical analysis was performed on high strength steel columns over a range of column lengths for various temperatures. The nonlinear finite element model was verified against experimental results of columns at normal room and elevated temperatures. The effects of initial local and overall geometrical imperfections have been taken into consideration in the analysis. The material properties and stress-strain curves at elevated temperatures used in the finite element model were obtained from the proposed equations based on the material tests. Two series of box and I-section columns were studied using the finite element analysis to investigate the strength and behaviour of high strength steel columns at elevated temperatures. Both fixed-ended stub columns and pin-ended slender columns were considered. The column strengths predicted from the finite element analysis were compared with the design strengths predicted using the American, European and Australian specifications for hot-rolled steel columns at elevated temperatures by substituting the reduced material properties. In addition, the direct strength method, which was developed for the design of cold-formed steel columns at normal room temperature, was also used in this study to predict the high strength steel column strengths at elevated temperatures. The suitability of these design rules for high strength steel columns at elevated temperatures is assessed. Generally, it is shown that the American and European specifications as well as the direct strength method conservatively predicted the column strengths of high strength steel at elevated temperatures. The European Code predictions are slightly more conservative than the American Specification and the direct strength method predictions.     

G550级高强薄板钢材的材性及应用

近年来,壁厚不大于1 mm、屈服强度达550 MPa的高强冷弯薄壁型钢已在国外实际工程中开始应用.为了促进高强冷弯薄壁型钢结构在中国的推广应用,验证高强钢材对中国冷弯薄壁型钢结构技术规范相关设计规定的适应性,本项目开展了G550级冷弯薄壁型钢的材性和轴压构件受力性能的系列试验研究,以期提出适用G550级钢材构件的设计计算建议.首先对t为0.48,0.60,0.75,1.00 mm 4种厚度G550级冷轧镀层薄板进行了材性试验研究,考察和分析了其材性特征,讨论了在中国推广和应用高强冷弯薄壁型钢时可能存在的主要问题及相应对策.材性试验结果可用于构件的试验研究和分析.     

Q690钢材高温后的力学性能试验研究

通过升温、冷却和拉伸试验,对历经300~900℃高温后的Q690钢材在自然冷却和浸水冷却条件下的力学性能展开试验研究。结果表明：经高温冷却的Q690钢材在不同温度和不同冷却方式下有不同的外观特征;受热温度超过500℃时,高温冷却对Q690钢材的弹性模量影响很小,对其强度和伸长率影响较大;当受热温度不超过700℃时,Q690钢材高温后的强度和伸长率在两种冷却方式下具有基本相同的变化规律;在700~800℃之间,不同冷却方式对Q690钢材高温后强度和伸长率产生影响,且随温度升高差别愈加明显,自然冷却条件下强度降低且伸长率增大,浸水冷却条件下强度增大且伸长率减小。将Q690钢材高温后力学性能与Q235钢材和Q460钢材比较,认为不同强度等级钢材高温后的力学性能差别显著,在自然冷却条件下较高强度钢材（Q690）的强度衰减和延性增长大于较低强度钢材（Q235和Q460）的。根据试验结果,建立了不同冷却条件下的高温后各力学参数与受热温度之间的数学模型,该模型可用于火灾后Q690钢结构的承载能力的评估。     

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.     

高强钢轴心受压构件的稳定性研究

高强钢轴心压杆的稳定性是目前高强铜应用和研究的重点。在分析了目前高强钢轴心受压构件稳定性研究现状和高强钢稳定性设计方法存在的不足的基础上,结合大型有限元分析软件ANSYS的稳定分析功能及模型试验方法,对高强钢轴压心受构件的整体稳定性进行了研究,提出了以材料屈服强度和构件长细比为参数计算高强铜轴心受压构件稳定系数的计算公...     

欧特克发布基于BIM的概念设计软件--Autodesk Infrastructure Modeler 2012

欧特克有限公司宣布,欧特克建筑信息模型（BIM）基础设施产品组合新增面向概念设计的Autodesk Infrastructure Modeler 2012软件。基于BIM的基础设施产品组合主要用于规划、设计、建设和管理更具可持续性的基础设施。新产品将与2012版欧特克基础设施设计套件配套,可帮助业内专业人士提高效率,并...