Nonlinear Study on the Mechanical Performance of Built-Up Cold-Formed Steel Concrete-Filled Columns under Compression

Given their numerous functional and architectural benefits,such as improved bearing capacity and increased resistance to elastic instability modes,cold-formed steel(CFS)built-up sections have become increasingly developed and used in recent years,particularly in the construction industry.This paper presents an analytical and numerical study of assembled CFS two single channel-shaped columns with different slenderness and configurations(backto-back,face-to-face,and box).These columns were joined by double-row rivets for the back-to-back and box configurations,whereas they were welded together for the face-to-face design.The built-up columns were filled with ordinary concrete of good strength.Finite element models were applied,using ABAQUS software,to assess mechanical performance and study the influence of assembly techniques on the behavior of cold-formed columns under axial compression.Analytical approaches based on Eurocode 3 and Eurocode 4 recommendations for un-filled and concrete-filled columns respectively were followed for the numerical analysis,and concrete confinement effects were also considered per American Concrete Institute(ACI)standards for face-to-face and box configurations.The obtained results indicated a good correlation between the numerical results and the proposed analytical methodology which did not exceed 8%.The failure modes showed that the columns failed due to instabilities such as local and global buckling.

Numerical Analysis of Cold-Formed Thin-Walled Steel Short Columns with Pitting Corrosion during Bridge Construction

Pitting corrosion is harmful during bridge construction,which will lead to uneven roughness of steel surfaces and reduce the thickness of steel.Hence,the effect of pitting corrosion on the mechanical properties of cold-formed thin-walled steel stub columns is studied,and the empirical formulas are established through regression fitting to predict the ultimate load of web and flange under pitting corrosion.In detail,the failure modes and load-displacement curves of specimens with different locations,area ratios,and depths are obtained through a large number of non-linear finite element analysis.As for the specimens with pitting corrosion on the web,all the specimens are subject to local buckling failure,and the failure mode will not change with pitting corrosion,but the failure location will change with pitting corrosion location;the size,location,and area ratio of pitting corrosion have little influence on the ultimate load of cold-formed thin-walled steel short columns,but the loss rate of pitting corrosion section area has a greater impact on the ultimate bearing capacity.As for the specimen with flange pitting corrosion,the location and area ratio of pitting corrosion have less influence on the ultimate load of cold-formed thin-walled steel short columns,and the section area loss rate has greater influence on the ultimate bearing capacity;the impact of web pitting corrosion on the ultimate load is greater than that of flange pitting corrosion under the same condition of pitting corrosion section area.The prediction formulas of limit load which are suitable for pitting corrosion of web and flange are established,which can provide a reference for performance evaluation of corroded cold-formed thin-walled steel.

Some Advances in the Application of Weathering and Cold-Formed Steel in Transmission Tower

Application of weathering and cold-formed steel in transmission lines can reduce steel consumption and environmental pollution. Some advances in the studies on the weathering and cold-formed steel in transmission tower are introduced. Firstly, corrosion-resistant tests of weathering steel samples under different simulating technical atmospheres were carried out separately for 240 hours. It shows that the corrosion degree of joint samples is higher than that of single chip samples, and the corrosion-resistant performance of weathering steel is superior to common carbon steel. The corrosion-resistance of weathering steel meets with the requirement of transmission tower. Secondly, experiments and finite element analysis for cold-formed angles and a 220kV prototype tower were completed, and the stability coeffi-cient fitting curves as well as the modification formulas of slenderness ratio for cold-formed members were determined. According to the structural characteristics of transmission towers, four sections of cold-formed angles with different sections and slenderness ratios were selected in this study. The finite element model well predicted the buckling behav-iour of the cold-formed members. Ultimate loads calculating by the fitting curve were well agreed to the experimental values, especially for the members with small slenderness ratios. Weight of the cold-formed steel tower can be reduced by more than 5 percent after considering the strength enhancement. Cost of the weathering and cold-formed steel transmission tower is nearly equivalent to that of hot-rolled steel tower with hot galvanizing.

Corner strength enhancement of high strength cold-formed steel at normal room and elevated temperatures

In this study, the suitability of current design methods for the 0.2% proof yield strength of the comer regions for high strength cold-formed steel at normal room temperature was investigated. The current standard predictions are generally accurate for outer comer specimen but conservative for inner comer specimen. Based on the experimental results, an analytical model to predict the comer strength of high strength cold-formed steel at normal room temperature was also proposed. The comparison indicated that the proposed model predicted well the comer strength of high strength cold-formed steel not only at normal room temperature but also at elevated temperatures. It is shown that the predictions obtained from the proposed model agree well with the test results. Generally the comer strength enhancement of high strength cold-formed steel decreases when the temperature increases.

Mechanical Properties of Two Kinds of New Cold-Formed Flange-Closed Welding Section Members

The hollow flange beam(HFB) is a unique cold-formed steel section developed in Australia for use as a flexural member.It′s a particular cross section with two torsion rigid closed triangular flanges and a comparatively flexible web,and it is a type of high efficient cross section.This paper presents two kinds of new cold-formed flange-closed welding sections named HF1 and HF2 according to different section component and parameters of HFB.Nonlinear finite element method has been adopted to investigate the mechanical properties such as buckling mode,deformation process,rigidity,ductility and correlation curve of two kinds of new section members which being subjected to axial compression,flexure,combined compression and bending.Systematical comparisons of the consumed steel quantities of per unit load carrying capacity between new section members and the same section dimensions of cold-formed C-section members have been carried out.Some conclusions can be drawn from above work that the new sections have some superior properties including higher load carrying capacity and section modulus,sufficient section stiffness,and difficult occurrence for the sub element local buckling.The new sections are suitable for bearing flexure,compression,combined compression and bending.The new sections′ consumed steel quantities of per unit load carrying capacity are almost half as those of the same dimension C-section members′.The experimental investigation is carried out further on the new cold-formed flange-closed welding section members and can be used in the practical engineering.

嵌套加强的LQ550高强冷弯薄壁C型钢连续檩条受力性能研究

为提高LQ550级高强冷弯薄壁C型钢连续檩条的承载能力,采用在支座处嵌套的方法来加强连续檩条。对未加强和采用两种嵌套方式加强的檩条共7组试件进行三点受弯试验,得到了试件的承载性能和破坏形态,试验结果表明加强后的试件出现跨中局部屈曲和嵌套端部局部屈曲两种破坏形态。采用ABAQUS软件建立了非线性有限元模型对嵌套加强的檩条进行数值模拟,有限元分析得到的承载力和破坏形态与试验结果吻合良好,验证了有限元模型的准确性。基于验证的有限元模型,分析了两种嵌套方式和不同嵌套长度对檩条承载力的提升,且表明嵌套檩条的长度宜取为连续檩条跨度的1/5~1/4。

装配式双拼钢围檩的拼接节点承载性能研究

结合某下穿通道基坑开挖的装配式钢结构支护体系,对双拼钢围檩拼接节点及相关组合桩和支撑进行现场测试,获取围檩承担的荷载数据,进而建立有限元分析模型。对比有限元计算值与实测值,分析拼接节点的承载性能。结果表明,依据等值梁法所得的组合桩内力可以用于围檩的荷载计算;拼接节点的有限元计算结果与现场监测数据较吻合,可为装配式双拼钢围檩的应用提供参考。

光伏支架高强冷弯C型钢檩条的受弯性能研究

为研究光伏支架中高强冷弯C型钢檩条的受弯性能,对5种布置方式下的LQ550高强冷弯C型钢檩条(下文简称为“C型钢檩条”)开展了跨间6个加载点集中加载试验。建立C型钢檩条有限元模型,并通过试验得到的C型钢檩条受弯性能验证模型的准确性,并依此模型探究檩条相对长细比对其受弯稳定承载力的影响规律。参照GB 50018—2002《冷弯薄壁型钢结构技术规范》的规定,分析了撑杆约束对檩条受弯稳定承载力的有利作用。结合实际项目,对采用C型钢撑杆的光伏支架开展现场加载试验。研究结果表明:1)檩条的抗弯刚度和受弯稳定承载力通过在跨间设置撑杆约束后明显提高,且设置C型钢撑杆约束的提高效果强于圆管撑杆。2)C型钢撑杆可视为理想侧向支承,檩条平面外计算长度系数可以根据C型钢撑杆的设置情况取值。3)现场加载试验证明C型钢撑杆对檩条扭转具有良好的约束效果,充分验证了采用C型钢撑杆体系的新型光伏支架结构的适用性。

一种光伏跟踪支架檩条强度分析方法

针对某光伏电站跟踪支架檩条损坏案例,提出一种强度分析方法。首先,根据光伏跟踪支架的结构特点,分析风荷载的结构传力机理。其次,根据风洞试验数据,计算不均匀风荷载的大小,并采用有限元分析方法,对跟踪支架的檩条进行强度分析,其损坏位置与实际情况相符。最后,提出改进结构,以减小檩条所受应力。文章提出的分析方法,能更为真实地反映实际情况,预告失效风险,为光伏跟踪支架檩条的强度分析提供更为准确的评估方法。

早强水泥基砂浆增强H型钢节点承压能力试验研究

装配式钢结构支护体系在基坑支护中被逐步推广。针对H型钢围檩的局部承压能力低的难题,使用早强水泥基砂浆填充承压节点区。试验研究表明,填充早强水泥基砂浆可以有效约束H型钢翼缘和腹板的屈曲及变形,增强H型钢承压节点的局部承载能力。

物流仓库结构优化设计探讨

详细介绍了某物流仓库主体刚架和支撑系统、围护结构檩条系统的截面选型、钢结构防火涂料以及配套装配式挡墙等结构优化设计措施,通过精心设计和优化,上部结构用钢量节省14.3%,基础、挡墙混凝土用量节省30%。

基于BIM技术的装配式钢围檩施工工艺

基坑支护工程中传统钢围檩多使用长尺寸出厂成品H型钢,需频繁切割、焊接,材料一次性损耗较大。装配式钢围檩增加了H型钢的周转使用次数,同时拥有运输便捷、安拆方便、低碳环保等优点。从装配式钢围檩施工工艺入手,对以“BIM技术指导、现场拼装”为核心理论的装配式钢围檩施工工艺进行了研究分析,研究结果可为同类型装配式钢围檩的应用提供借鉴。

大型透水式防撞墩施工技术

为满足海洋环境保护的相关要求大连湾海底隧道防撞墩工程作为沉管主体的保护结构,采用透水式结构。施工过程中为解决该结构没顶沉箱水上作业难度高、潮差段底模支立难度大等难题,采用一种大型钢结构提前安放至沉箱顶部,作为沉箱接高段,辅助沉箱安装。同时该钢结构作为海上施工平台,用以辅助灌注桩及箱内施工,实现“一物多用”。上部结构采用一种可调托架作为底模支撑,解决了潮差段焊接牛腿困难的难题,缩短了工期且保证安全质量要求。

火灾下加设光伏板的下撑式檩条结构受力性能研究

轻钢厂房在加设光伏板后,增加的屋面恒荷载将导致简支檩条变形增大,往往会超出规范允许的限值,可采用下撑式檩条对结构进行加固,提高檩条的刚度和承载力。鉴于轻钢厂房的屋面檩条一般不进行被动防火保护,故有必要对火灾下加设光伏板的下撑式檩条结构的受力性能进行研究。研究结果表明:常温下,简支檩条的变形才是影响檩条安全的关键因素,通过采用下撑式檩条结构可有效提高檩条的刚度和承载力;火灾下,采用下撑式檩条仍然可以有效提高檩条的刚度,但对于檩条承载力的提高较为有限。因此,对于采用下撑式檩条加固的屋面,应该对下撑式檩条进行被动防火保护,比如刷防火涂料,确保下撑式檩条可以有效发挥作用。

大型圆竹拱-钢拱组合结构建筑施工技术

合理利用竹材作为建筑材料,在创造经济效益的同时,对推动绿色低碳建造方式具有重要意义。但因圆竹特性与节点构造的复杂特性,限制了其在大型公共建筑中的发展。将竹拱与钢拱进行组合,利用钢拱为竹拱提供中间支撑,从而满足圆竹在大空间建筑上的使用需求。结合实际工程,详细介绍了大型圆竹拱–钢拱组合穹顶式建筑施工技术,以期为同类工程提供参考。

一种考虑檩条锚固柔性的光伏跟踪支架扭转固有频率分析方法

文章针对光伏跟踪支架扭转固有频率计算结果准确度不高的问题,提出了一种考虑了檩条锚固柔性给跟踪支架整体扭转频率带来影响的分析方法,并通过试验对仿真结果进行了验证。其次,对某电站跟踪支架进行了结构改造,提升了其扭转固有频率,并通过现场测试再次验证了分析方法的准确性。

多阵列屋面分布式光伏电站中光伏支架结构的分析研究

针对建设在钢筋混凝土屋面上方的多阵列屋面分布式光伏电站,以其光伏支架结构设计中的若干影响因素为研究对象,从光伏支架的结构组成及设计流程出发,结合其受力特点和方式,研究阵列排布方式、相邻立柱间距、檩条间距、斜撑支撑点位置、光伏支架倾角、相邻光伏支架间距这6种因素对光伏支架承载力的影响。研究结果表明:在采用同样材料、规格光伏支架的前提下,这6种影响因素对光伏支架的承载力均存在具有一定规律的影响。1)同样列数的情况下,优先选用“竖向组件2行”的阵列排布方式,对应的光伏支架承载力性能较优且排布更为合理;2)相邻立柱间距设置在光伏组件长边水平投影长度的60%~70%范围内时,对应的光伏支架承载力性能较优;3)檩条间距设置为光伏组件长边水平投影长度的70%左右时,可以保证光伏组件自身的刚度和较大的承载力,且方便施工时的安装操作;4)当斜撑支撑点位置与斜梁高侧端点的距离为整个斜梁长度的35%~60%时,对应的光伏支架承载力性能较优;5)当采用配重式支架基础时,光伏支架倾角通常采用5°~20°的小角度,以减少产生的光伏附加荷载,从而确保光伏支架主体结构的安全性;6)当相邻光伏支架间距采用光伏组件短边长度的150%~200%(即每榀光伏支架承担约1.5~2.0块光伏组件)时,对应的光伏支架承载力性能较优,且经济性较好。所得结论和规律可为后续多阵列屋面分布式光伏电站的光伏支架结构设计提供参考。

建筑工程地基基础及围檩中的施工技术应用研究

建筑基础基坑施工中如何拥有一个安全稳定的围檩,避免施工过程中的基坑失稳,是一个较难的问题。基础基坑施工时,经常受周边环境地下障碍物、暗浜淤泥等影响,施工难度较大。基础基坑施工过程中方法是否正确选用,对工程质量会产生一定的影响。浦东17-4地块E-8单元项目地基施工过程中,加固地基时选用了深层搅拌法,起到了良好效果。相比其他方法具有更高的稳定性和牢固度,为后续围檩、桩基及基坑施工起到了积极作用。

基坑钢围檩极限承载能力研究

在基坑中,钢支撑的极限承载能力与围檩的受力密切相关。通过精细化数值计算方法研究钢支撑系统特殊节点构造中围檩的极限承载能力。结果表明,伺服支撑直接作用下围檩极限承载力随偏心距增大而降低;伺服系统的端头圆板构造,较钢支撑直接作用下钢围檩的承载力小很多,设置钢垫板以及加密加劲肋可提高端头圆板模型承载能力。总结的经验可供类似工程参考。

简支C形钢檩条内嵌式连续化加固技术研究

简支变连续加固方式是解决现有檩条加固方式用钢量大、施工效率低等问题的有效方法。采用有限元软件ABAQUS对不同跨度L的简支C形钢檩条内嵌式连续化加固,搭接长度系数α取值0.02~0.20,根据连续性指标β得出简支C形钢檩条合理的嵌套搭接长度,并对比分析简支C形钢檩条支座处采用螺栓连接和结构胶粘结两种连接方式的连接性能。结果表明:简支C形钢檩条内嵌式连续化加固的搭接长度宜≥10%L且当α取0.10时,内嵌式C形钢檩条的β能够达到90%且能够满足檩条加固要求;综合考虑简支C形钢檩条支座处两种连接方式的施工操作性和加固成本,简支C形钢檩条内嵌式连续化加固可优先选择螺栓连接。