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.

A Cohesive and Coherent Analysis of The Purloined Letter

The thesis aims to do a research on the cohesion and coherence in The Purloined Letter written by Edgar Allan Poe based on the theories of Halliday and Hasan as well as the Chinese scholars Zhang Delu and Liu Rushan. By the means of them, Poe's ingenious composition and vivid characters emerge in the mind of the readers.

风吸力下冷弯薄壁檩条稳定承载力分析和设计建议

对在风吸力作用下各种常用规格、跨度的冷弯薄壁檩条进行了大量的稳定承载力分析.分析分两部分:一是对简支C型和Z型冷弯薄壁檩条在风吸力作用下的稳定承载力分析,以确定简支檩条在风吸力作用下的稳定承载力;二是嵌套搭接的Z型冷弯薄壁连续檩条在风吸力作用下的稳定承载力分析,以确定搭接长度、跨数等因素对连续檩条在风吸力作用下稳定承载力的影响.有限元分析结果与《门式刚架轻型房屋钢结构技术规程》(CECS 102:2002)中风吸力作用下檩条的稳定承载力公式计算结果对比表明,规程中公式计算结果相对保守.据此,本文提出了简支檩条在风吸力作用下稳定承载力的实用计算公式,以及嵌套搭接的Z型连续檩条在风吸力作用下的设计方法.

拉康式审视下的红字——从《被窃的信》到《红字》

霍桑是美国19世纪颇有争议的重要作家之一。当代霍桑研究开始指向象征主义研究,并开始大量引用现代及后现代结构主义理论。本文将以拉康对爱伦.坡的短篇小说《被窃的信》的解构为借鉴,以索绪尔、拉康和德里达的符号学理论为指导,对霍桑的成名作《红字》中的表征——红字,进行解构,并探索此独特表征所产生的审美效应,即能指"A"的位移所赋予文本的现代感、象征感和节奏感。

Ultimate strength of single shear bolted connections with cold-formed ferritic stainless steel

This paper is focused on the structural behavior of the single shear bolted connections with thin-walled ferritic stainless steel.The purpose of this study is to investigate the ultimate behaviors,such as ultimate strength and fracture mode of the single shear bolted connections of thin-walled ferritic stainless steel(low cost steel) rather than austenitic stainless steel(high cost steel).Bolt arrangement and end distance parallel to the direction of applied load are considered as main variables of the test specimens for bolted connections.Specimens have a constant dimension of edge distance perpendicular to the loading direction,bolt diameter,pitch,and gauge.A monotonic tensile test for specimens has been carried out and some bolted connections with long end distance showed curling(out of plane deformation) occurrence which led to strength reduction.The ultimate behaviors such as fracture mode,ultimate strength are compared with those predicted by current design codes.Further,conditions of curling occurrence and the strength reduction due to curling are investigated and modified strength equations are suggested considering the curling effect.

Bond Performance of Adhesively Bonding Interface of Steel-Bamboo Composite Structure

The steel-bamboo composite structure is a newly developed structure,combining phyllostachys pubescens(also called Moso bamboo)plywood and cold-formed thin-walled steel with structural adhesive.The reliability of steelbamboo interface is the premise of composite effect.13 specimens were prepared to investigate the failure modes and mechanism of the steel-bamboo interface on the basis of push-out test,and the strain difference analysis method was proposed to study the distribution of shear stress.The results show that the main failure modes of steel-bamboo interface are adhesion failure and splitting of bamboo plywood.The shear stress is not evenly distributed along the longitudinal direction of the interface,showing a shape of“larger at two ends and smaller in the middle”.The lower end of the interface is the initial location of the interface failure and the shear stress concentration degree is positively correlated with the thickness of the externally bonded bamboo plate.The shear resistance of steel-bamboo interface can be enhanced by improving the adhesion between steel and structural adhesive and ameliorating the quality of bamboo products.

Structural behavior of intermediate length cold-formed steel rack columns with C-stitches

This article presents an experimental and numerical investigation on the strength and performance of intermediate length rack column sections with C-stitches under axial compression. The test program consisted of 10 axial concentric compression tests on columns with and without C-stitches under pin end conditions for two different geometric lengths. Finite element (FE) models were developed using commercial FE package ABAQUS considering material and geometric nonlinearities as well as initial geometric imperfections. The elastic buckling properties of the section were calculated using readily available linear elastic buckling analysis tools based on Generalized Beam Theory (GBT) and Finite Strip Method (FSM). Obtained FE results were compared with those obtained experimentally, and once verified the developed FE modeling technique was used to carry out a parametric study to examine changes in structural response due to variations in length, depth and spacing of C-stitches. Observed influences of C-stitches on the behavior and resistance of the considered columns were carefully analyzed, and key design aspects are presented herein.

Full-Range Compressive Stress-Strain Curves for Cold-Formed 304 Stainless Steel Circular Hollow Sections After Exposure to Vacuum Brazing

With the rapid development of microscale cellular structures, the small-diameter cold-formed welded stainless steel tubes have recently been used for creating the metallic lat- tice topologies with high mechanical properties. In this paper, to obtain the accurate material properties of the circular hollow section （CHS） under pure compression, a series of concentric compression tests are conducted on the millimeter-scale cold-formed 304 stainless steel circu- lar tubular stub columns after exposure to a vacuum brazing process. The tests cover a total of 18 small-diameter stub tubes with measured thickness-to-diameter ratios （t/D） from 0.023 to 0.201. A generalized three-stage nominal stress-strain model is developed for describing the compressive behavior of the post-brazing CHSs over the full strain range. This mechanical model is especially applicable to computer code implementation. Hence, an interactive computer pro- gram is developed to simultaneously optimize three strain hardening exponents （n1, n2, n3） in the expression of the model to produce the stress-strain curve capable of accurately replicating the test data. To further reduce the number of the model and material parameters on which this model depends, this paper also develops five expressions for determining the 2.5% proof stress （ap2）, n2, the ultimate compressive strength （σp3）, n3, and the ultimate plastic strain （p3%） for given experimental values of three basic material parameters （E0, σ0.01, σ0.2）. These expressions are validated to he effective for the CHSs with t/D 〉_ 0.027. The analytically predicted full-range stress-strain curves have generally shown close agreement with the ones obtained experimentally.

拉康的“三界说”与文学批评

拉康在《被窃的信》研讨班中应用“三界说”做了最具代表性的批评实践。他将充满误认的想象界、符号主导下的象征界与不可知的实在界分别与盲目自信的王后/大臣、识破符号象征价值的大臣/迪潘和无序无知的国王/警察相对应,在文本内搭建起文学场域内的三界,从而揭示出真正的主体正是那封信。

主体难以逃脱的命运——拉康对《窃信案》的文本分析

拉康将爱伦.坡的小说《窃信案》剖析为情节、情节的叙述、叙述的条件三个层面,着力于文本形式结构所呈现的主体的命运以及能指对主体的建构功能。拉康的文本分析提示了一种新的文学批评范式的可能。

解读爱伦·坡《失窃的信》——从西方叙事学和心理同构的角度

本文从西方叙事学的角度,结合心理同构的理论,对爱伦·坡的短篇小说《失窃的信》进行解读,分析小说的内部整体结构,以及叙事模式和心理同构的关系,从而帮助读者挖掘小说的主题,理解推理过程,达到美学的欣赏效果。

由《谈一封被窃的信》到《蝴蝶君》:对黄哲伦作品的拉康式解读

本文通过对《谈〈被窃的信〉》与《蝴蝶君》这两个文本的分析比较,用拉康在《谈〈被窃的信〉》中所运用的精神分析理论对后者进行解构,以避开对《蝴蝶君》的传统后殖民主义与东方主义解读,试图从个人心理的角度阐释戏剧中错综复杂的人物关系以及基于无意识控制下"菲勒斯"如何作用于伽里玛二十年对"蝴蝶"的畸形恋情。

Hot-dip galvanizing of cold-formed steel hollow sections: a state-of-the-art review

A good understanding of the effects of galvanizing on the short-and long-term behaviours of steel components is essential for structural design.This review paper is motivated by a series of recent reports on cracking in galvanized cold-formed tubular steel structures and the limitations of current steel product standards and steel design specifications in this field.The steel-related and galvanizing-related factors,different pre-galvanizing countermeasures for brittle cracking and the available technical documents are summarized.An extensive bibliography is provided as a basis for future research and development in this field.

Dynamic material performance of cold-formed steel hollow sections： a state-of-the-art review

This paper presents a literature review focused on the material performance of cold-formed, carbon steel, hollow structural sections under impulsive （highly dynamic） loading. Impulsive loading, represented by impact and blast, is characterized by a very rapid, time-dependent loading regime in the affected members and materials. Thus, the effect of high-strain-rate loading is initially reviewed. Next the material toughness, an important energy-absorption property and one measure of a material＇s ability to arrest fracture, is considered by means of studying the Charpy V-notch behavior. The response of hollow sections under axial and lateral impact loading is then reviewed. Studies of blast on hollow sections, most of which fall under the categories of contact/near-field loading or far-field loading are presented. Under large-scale field blast experiments, cold-formed hollow sections have shown excellent behavior. Software for modeling blast loading and structural response, the latter including single degree of freedom analysis and explicit finite element analysis, is described and discussed.

Bending tests and finite element analysis of lipped channels with complex edge stiffeners and web stiffeners

In order to study the bearing capacity and stability behavior of cold-formed steel flexural members with complicated sections,a total of 12 specimens divided into 6 groups were tested,including 3 groups of pure bending tests and non-pure bending tests each.There were three types of sections considered in this investigation,including channels with complex edge stiffeners(called B1-section),Σsection with complex edge stiffeners(called B2-section),and channels with complex edge stiffeners and V-type web stiffeners(called B3-section).Local buckling,distortional buckling and interaction buckling between them were observed in tests.The experimental results indicate that the bending strengths of B2-section specimens were the largest of these three types of specimens under the same conditions.It is found that the bending strength of B2-section specimens was increased by 6.47%for pure bending state and 8.12%for non-pure bending state,compared with that of B1-section specimens.Bending strength of B3-section specimens was almost the same with that of B1-section specimens under pure bending,but a little smaller than that of B1-section under non-pure bending state.It is also shown that B2-section specimens have better plastic deformation behavior than the other two sections.In addition,a non-linear finite element model was presented and verified against tests.The finite element analysis results agree well with experimental bending strength and failure modes.

Development of Light Weight Structures to Provide Blast-Resistant Designs

In the past, blast-resistant designs for structures were often constructed with massive type structural systems, which relied more on brute strength than on finesse to achieve the required blast resistance. However, structures composed of COLD-FORMED steel components, such as sheet metal and metal studs, have shown great promise in providing blast resistance with the added benefits of low cost and ease of construction. Some examples of using such structures to provide containment for package handling facilities (PHF) are described in the paper for situations where blast containment is needed, such as a potential package bomb being discovered during the package vetting process. Results from tests and analytic data are used to illustrate aspects of design peculiar to such types of applications. Designs for specific capacities of PHF are described.