Cold-formed steel framing of residential and light commercial buildings continues to grow in popularity due to its structural and material advantages. The North American steel industry is actively performing research studies and developing design standards to assist in the cost-effectiveness of cold-formed steel in these markets. Cold-formed steel L-headers are structural components used over wall openings to transfer the loads to adjacent king studs. Recently, there has been an increased interest in L-headers among homebuilders primarily due to their ease of installation and low material cost. Design of the L-headers in North America is currently governed by the North American Standard for Cold Formed Steel Framing – Header Design, in combination with the North American Specification for Design of Cold Formed Steel Structural Members. However, the design provisions in the AISI - Header Design Standard are particularly limiting. For instance, the method for evaluation of span deflections for both single and double L-headers, and uplift flexural strength for single L-headers is currently not available primarily due to lack of research on the issues. Presented in this thesis are the findings from an extensive laboratory testing program of full-scale single and double cold-formed steel L-headers. The objective of the research was to investigate the structural behavior of L-headers under both gravity and uplift loads. From the analysis, improved ultimate flexural strength design expressions and new vertical deflection expressions for single and double L-header assemblies were developed. The concept of semi-rigid members was introduced to evaluate the flexural behavior and deflection performance of L-header assemblies.

Made available in DSpace on 2014-06-11T19:25:21Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-05-02Bitstream added on 2014-06-13T20:32:47Z : No. of bitstreams: 1 vergilio_sal_me_ilha.pdf: 3337665 bytes, checksum: 50e13409fecfd3249ea5cb1d7e6b9c79 (MD5) / Este trabalho trata da análise dos tipos de ligações usualmente empregadas em trelliças de cobertura constituídas por perfís de aço formados a frio. O escopo da análise engloba seu comportamento estrutural e modelos de cálculo. Além disso, apresenta e comenta os procedimentos indicados na norma brasileira NBR 14762:2010 Dimensionamento de estruturas de aço constituídas por perfís formado a frio (ABNT - ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS),pela NBR 8800:2008 Projeto de estruturas de aço e estruturas mistas de aço e concreto de edifícios - quando referidos pela primeira - e também por reconhecidas normas estrangeiras. Os meios de ligação estudados são parafusos e soldas; os elementos da ligação são as barras, cobrejuntas, chapas de gusset entre outros. As barras pertencentes às treliças são de perfís U ou L e suas combinações. Cada tipo de ligação de barra estudada apresenta as respectivas planilhas eletrônicas... / This work deals with the analysis of connections types commonly used in roof trusses consisting of steel cold-formed profiles. The scope of review includes its structural behavior and calculation models. it also presents and discusses the procedures specified by recognized foreign standards, the Brazilian Standard for cold-formed steel, and welded connections are studied; the connection elements are the bars, joint sheeting and gusset plates, among others... (Complete abstract click electronic access below)

Master of Science / Department of Civil Engineering / Hani Melhem / The combination of cold formed steel (CFS) with structural wood panels exhibits a degree of partial composite action behavior. In the current design and construction codes, CFS and wood sheathing systems are considered separate, in a non-composite manner, due to the absence of sufficient supporting experimental and research data. The problem with previous research is the lack of information to fully define the composite action between CFS and wood sheathing. The scope of this study is to check fundamental information provided in previous research. The approach adopted to solve the problem follows previous experimental procedures conducted at Kansas State University. The objective of the research is to determine the slip modulus with various fastener spacing. Additional results obtained in this study are compared to previous research results.

Orientador: Renato Bertolino Junior / Banca: José Antônio Matthiesen / Banca: João Alberto Venegas Requena / Resumo: Este trabalho trata da análise dos tipos de ligações usualmente empregadas em trelliças de cobertura constituídas por perfís de aço formados a frio. O escopo da análise engloba seu comportamento estrutural e modelos de cálculo. Além disso, apresenta e comenta os procedimentos indicados na norma brasileira NBR 14762:2010 "Dimensionamento de estruturas de aço constituídas por perfís formado a frio" (ABNT - ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS),pela NBR 8800:2008 "Projeto de estruturas de aço e estruturas mistas de aço e concreto de edifícios" - quando referidos pela primeira - e também por reconhecidas normas estrangeiras. Os meios de ligação estudados são parafusos e soldas; os elementos da ligação são as barras, cobrejuntas, chapas de gusset entre outros. As barras pertencentes às treliças são de perfís "U" ou "L" e suas combinações. Cada tipo de ligação de barra estudada apresenta as respectivas planilhas eletrônicas... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This work deals with the analysis of connections types commonly used in roof trusses consisting of steel cold-formed profiles. The scope of review includes its structural behavior and calculation models. it also presents and discusses the procedures specified by recognized foreign standards, the Brazilian Standard for cold-formed steel, and welded connections are studied; the connection elements are the bars, joint sheeting and gusset plates, among others... (Complete abstract click electronic access below) / Mestre

The objective of this research is developing a new method of design for cold-formed steel framed shear wall sheathed by ¾" thick USG structural panel concrete subfloor using a predictive analytical model and comparing the results obtained from the model with those achieved from real testing to verify the analytical model and predicted lateral load-carrying capacity resulted from that. Moreover, investigating the impact of various screw spacings on shear wall design parameter such as ultimate strength, yield strength, elastic stiffness, ductility ratio and amount of energy dissipation is another purpose of this research.

Web crippling is a form of localized buckling that occurs at points of transverse concentrated loading or supports of thin-walled structural members. The theoretical computation of web crippling strength is quite complex as it involves a large number of factors such as initial imperfections, local yielding at load application and instability of web. The existing design provision in North American specification for cold-formed steel C-sections (AISI S100, 2007) to calculate the web-crippling strength is based on the experimental investigation. The objective of this research is to extend the direct strength method to the web crippling strength of cold-formed steel C-sections. ABAQUS is used as a main tool to apply finite element analysis and is used to do the elastic buckling analysis. The work was carried out on C-sections under interior two flange (ITF) loading, end two flange (ETF) loading cases. Total of 128 (58 ITF, 70 ETF) sections were analyzed. Sections with various heights (3.5 in.to 6 in.) and various lengths (21 in. to 36 in.) were considered. Data is collected from the tests conducted in laboratory and the data from the previous researches is used, to extend the direct strength method to cold formed steel sections. Proposing a new design for both the loading cases and calculation of the resistance factors under (AISI S100, 2007) standards is done.

The cold-formed steel framed shear walls with steel sheets and wood-based sheathing are both code approved lateral force resisting system in light-framed construction. In the United States, the current design approach for cold-formed steel shear walls is capacity-based and developed from full-scale tests. The available design provisions provide nominal shear strength for only limited wall configurations. This research focused on the development of analytical models of cold-formed steel framed shear walls with steel sheet and wood-based sheathing to predict the nominal shear strength of the walls at their ultimate capacity level. Effective strip model was developed to predict the nominal shear strength of cold-formed steel framed steel sheet shear walls. The proposed design approach is based on a tension field action of the sheathing, shear capacity of sheathing-to-framing fastener connections, fastener spacing, wall aspect ratio, and material properties. A total of 142 full scale test data was used to verify the proposed design method and the supporting design equations. The proposed design approach shows consistent agreement with the test results and the AISI published nominal strength values. Simplified nominal strength model was developed to predict the nominal shear strength of cold-formed steel framed wood-based panel shear walls. The nominal shear strength is determined based on the shear capacity of individual sheathing-to-framing connections, wall height, and locations of sheathing-to-framing fasteners. The proposed design approach shows a good agreement with 179 full scale shear wall test data. This analytical method requires some efforts in testing of sheathing-to-framing connections to determine their ultimate shear capacity. However, if appropriate sheathing-to-framing connection capacities are provided, the proposed design method provides designers with an analytical tool to determine the nominal strength of the shear walls without conducting full-scale tests.

A prototype rigid wall relocatable shelter was designed and constructed using cold-formed steel (CFS) construction techniques including shear walls with corrugated sheathings. The design of the shelter was to be mechanically sound with adequate thermal performance and resistance to corrosion. Modeling of structural shear walls was performed using ABAQUS and verified with experimental results. At the project's conclusion, a completed full-scale prototype shelter was constructed.

The use of cold-formed steel (CFS) structures has become increasingly popular in different fields of building technology. For example, small housing systems using cold-formed steel for wall structures, framing systems and roof structures, including trusses and shielding materials, have been developed during recent years. The reasons behind the growing popularity of these products include their ease of fabrication, high strength/weight ratio and suitability for a wide range of applications. These advantages can result in more cost-effective designs, as compared with hot-rolled steel, especially in short-span applications. It has been common practice in cold-formed steel construction to cut openings in the web of beams for the passage of service ducts and piping. The provision of such openings reduces the story heights and consequently can result in saving of considerable amount of construction materials. On the other hand, the presence of a large web opening causes localized redistribution of stress around the opening region. The large opening causes loss of strength and changes the buckling characteristics of an entire member. It also affects the flexural stiffness, resulting in poor performance of member under serviceability. It is common practice to reinforce the opening of hot-rolled steel members, but proper reinforcement schemes for CFS perforated members has not been established yet. Various reinforcement schemes for cold-formed steel sections were investigated during this study. Two types of reinforcement schemes (for flexural zones and shear zones) were developed. Fifty-four flexural tests and 33 shear tests were conducted. Two types of sections (lipped channel joists with h/t ratio 180 and 118) were tested in flexure and one type of section (lipped channel joists with h/t ratio 180) was tested in shear. The study also included a finite element based numerical investigation, consisting of parametric studies on the size (web depth and thickness) of joists, size and shape of web openings, reinforcement and associated fastening schemes. It was observed that a 75 percent of opening in the web of CFS channel joist causes up to 25 percent reduction in flexural strength and up to 60 percent reduction in shear strength. Such reduced flexural and shear strengths were re-captured by providing proper reinforcement schemes. The flexural reinforcement schemes recommended by the current AISI Standard were found to be ineffective for the sections having low w /t ratios. Bridging channel reinforcement scheme was also considered in this study. Bridging channel reinforcement scheme was capable of restoring the flexural strength of cold formed steel joist having w /t ratios 118 and 180. Similarly, the reinforcement schemes recommended in AISI Standard were not adequate to restore the shear strength of joist sections. A newly developed Virendeel type reinforcement system was capable of restoring the original shear strength of a cold-formed steel joist section. / Thesis / Doctor of Philosophy (PhD)

Koldioxidutsläppen i världen orsakar stora miljöförstöringar och byggbranschen står för en stor del av utsläppen. Samtidigt som utsläppen behöver minska finns ett behov av att bygga fler idrottshallar i Sverige. Utöver det behöver även kostnaderna hållas så låga som möjligt. Därför syftar denna studie till att klargöra hur stor skillnaden i pris och koldioxidutsläpp är beroende på val av pelare i ett verkligt fall. De pelare som undersökts och jämförts är varmformade konstruktionsrör (VKR), kallformade konstruktionsrör (KKR) och energisnåla kallformade konstruktionsrör (Zero KKR). För att genomföra studien dimensionerades pelare till en idrottshall enligt europeiska standarder, så kallade Eurokoder. Dimensioneringen utgick från stålleverantören Tibnors sortiment. Information om pris och koldioxidutsläpp för de dimensioner som togs fram samlades in från Tibnor och dess återförsäljare. En sammanställning av informationen gjordes i tabeller och diagram för jämförelse. Resultatet visar att det totala priset för pelare till idrottshallen är 20,7% lägre vid val av KKR istället för VKR. Jämförelsen visar även att det går att göra en utsläppsbesparing på 8,7% genom att, genomgående, välja KKR istället för VKR till pelare för den idrottshall som undersökts. Med Zero KKR skulle det vara möjligt att minska koldioxidutsläppen pelarna till idrottshallen orsakar med ytterligare 66,8% och slutsatsen kan dras att användning av Zero KKR alltid skulle bidra till en markant minskning av koldioxidutsläppet. / Carbon dioxide emissions worldwide cause significant environmental damage and the construction industry is responsible for many of these emissions. At the same time that emissions need to be reduced, there is a need to build more sports halls in Sweden. In addition, costs also need to be kept down. Therefore, this study aims to clarify how big the difference in price and carbon dioxide emissions is depending on the choice of columns in a real case. The colums that has been investigated and compared is Hot-Formed Hollow Sections, Cold-Formed Hollow Sections and the energy efficient Zero Cold-Formed Hollow Sections. To do the investigation, columns for a sports hall were dimensioned according to European standards, so-called Eurocodes. Dimensioning was based on the steel supplier Tibnor's range. Data regarding price and carbon dioxide emissions for the dimensions produced were collected from Tibnor and its dealers. A compilation was made in tables and charts for comparison. The result shows that the total price for the columns to the sportshall is 20,7% lower for Cold-Formed Hollow Sections than Hot-Formed Hollow Sections. The comparison also shows that it is possible to save 8.7% on emissons by consistently choosing Cold-Formed Hollow Section instead of Hot-Formed Hollow Sections as pillars for the investigated sports hall. With Zero Cold-Formed Hollow Sections, it would be possible to reduce the carbon dioxide emissions for the columns of the sports hall by a further 66.8% and the conclusion can be drawn that using Zero Cold-Formed Hollow Sections would always contribute to a significant reduction in carbon dioxide emissions.