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The existing design provision in North American Specification for Cold- Formed Steel Structural Member (AISI S100) for the bearing strength of bolted connections were developed from tests on bolted connected sheets which were restrained by bolt nut and head with or without washers. However, in the cold-formed assemblies, particularly in trusses, the single bolt goes through both sides of the connected sections, making the connected sheets on each side unrestrained. the warping of the unrestrained sheet may reduce the bearing strength of the bolted connection. This research investigates the behavior and strength of bearing failure in bolted connections in cold-formed steel trusses. Tensile tests were conducted on trusses connections with various material thicknesses. It was found that the AISI S100 works well for thick connections but provides unconservative predictions for thin materials. Based on the experimental results, a modified bearing strength method is proposed for calculating the bearing strength of bolted truss connections. the proposed method can be used for any cold-formed steel connections with unrestrained sheet.

Incombustibility is one important advantage of the sheet steel sheathed shear wall over wood panel sheathed shear wall. Compared to shear wall sheathed with plywood and OSB panel, shear wall sheathed with flat sheet steel behaved lower shear strength. Although shear wall sheathed with corrugated sheet steel exhibited high nominal strength and high stiffness, the shear wall usually behaved lower ductility resulting from brittle failure at the connection between the sheathing to frames. This research is aimed at developing modifications on the corrugated sheathing to improve the ductility of the shear wall as well as derive practical response modification factor by establishing correct relationship between ductility factor ? and response modification factor R. Totally 21 monotonic and cyclic full-scale shear wall tests were conducted during the winter break in 2012 by the author in NUCONSTEEL Materials Testing Laboratory in the University of North Texas. The research investigated nineteen 8 ft. × 4 ft. shear walls with 68 mil frames and 27 mil corrugation sheet steel in 11 configurations and two more shear walls sheathed with 6/17-in.OSB and 15/32-in. plywood respectively for comparison. The shear walls, which were in some special cutting arrangement patterns, performed better under lateral load conditions according to the behavior of ductility and shear strength and could be used as lateral system in construction.

Pale, soft, and exudative (PSE) poultry originates during rigor mortis when the muscle pH drops rapidly in high temperature carcasses. This condition results from antemortem stress and/or genetic material in the live animal. PSE poultry is pale in color, has low water-holding capacity, and forms products that are unappealing, dry, and unacceptable to consumers. Since value added products processed with PSE turkey meat display poor protein bind, color, and water retention, enhanced usability could add value to this low value raw material through locating a niche for PSE meat currently utilized in further processed products. Experiment 1 consisted of four broiler breast treatments: 100% PSE, 100% PSE + 1.5% chicken collagen, 100% normal, and 100% normal + 1.5% chicken collagen to test the effects of raw material and chicken collagen. Incorporation of collagen improved (p<0.05) protein bind and CIE L* values in both PSE and normal broiler breast treatments, while decreasing (p<0.05) the cooking and chilling loss of PSE broiler breast treatments. Experiment 2 consisted of four turkey breast treatments: 100% PSE, 100% PSE + 1.5% turkey collagen, 100% normal, and 100% normal + 1.5% turkey collagen to test the effects of raw material and turkey collagen. Addition of turkey collagen improved (p<0.05) the protein bind and CIE L* values in both PSE and normal broiler breast treatments, while decreasing (p<0.05) the cooking and chilling loss of PSE turkey breast treatments. Experiment 3 consisted of five turkey breast treatments: 100% PSE, 100% PSE + 1.5% collagen, 100% PSE + 0.30% kappa/iota carrageenan, 100% PSE + 1.5% soy protein concentrate, and 100% normal to test the effects of raw material, turkey collagen, soy protein concentrate, and carrageenan. Addition of soy protein and turkey collagen both decreased (p<0.05) cooking and chilling loss and increased (p<0.005) the protein bind of 100% PSE. Purge loss was decreased (p<0.05) in PSE raw material when turkey collagen, soy protein concentrate, and kappa/iota carrageenan were utilized. Treatments with collagen displayed similar (p>0.05) CIE L* and CIE a* values to that of normal treatments. No differences (p>0.05) in consumer acceptability existed among the treatments. / Master of Science

Metal building roof systems with C- or Z-section purlins require restraint to resist lateral forces developed within the roof system under gravity loads. The currently available procedures for predicting these forces have been shown to be inaccurate for sloped roofs and difficult to apply to roof configurations with multiple points of anchorage. A new method has been developed that builds on the previous research and accurately addresses roof slope as well as the use of multiple anchorage devices of finite stiffness. The development of this method relied on a stiffness model, similar to that used by previous researchers, which was updated and calibrated to the results of recently completed tests. The calculation procedure explicitly addresses the location and stiffness of anchorage devices as well as the inherent stiffness of the purlin system to accurately distribute the anchorage forces. / Master of Science

The objective of this research is to create a computationally efficient seismic analysis framework for cold-formed steel (CFS) framed-buildings supported by hysteretic nonlinear models for CFS members and screw-fastened connections. Design of CFS structures subjected to lateral seismic forces traditionally relies on the strength of subassemblies subjected to lateral loading of systems, such as strapped/sheathed shear walls and diaphragms, to provide adequate protection against collapse. Enabling performance-based seismic design of CFS buildings requires computationally efficient and accurate modeling tools that predict the nonlinear cyclic behavior of CFS buildings, the individual CFS components and connections. Such models should capture the energy dissipation and damage due to buckling and cross-sectional deformations in thin-walled CFS components subjected to cyclic loads such as those induced by earthquakes. Likewise, models for screw-fastened CFS connections should capture the energy dissipation and damage due to tilting, bearing, or screw shear when subjected to cyclic loading. In this dissertation, an analysis framework for CFS structures that captures the nonlinear cyclic behavior of critical components including axial members, flexural members, and screw fastened connections is presented. A modeling approach to simulate thin-walled behavior in CFS members is introduced where parameters were developed using results from an experimental program that investigated the cyclic behavior and energy dissipation in CFS axial members and flexural members. Energy dissipation and cyclic behavior of CFS members were characterized for members experiencing global, distortional and local buckling. Cyclic behavior and energy dissipation in thin steel plates and members was further investigated through finite element analysis in ABAQUS to provide a strategy for modeling steel columns cyclic behavior including local buckling. Model parameters were developed as generalized functions of the hysteretic energy dissipated and slenderness. The capabilities of the analysis framework are demonstrated through simulations of CFS wood sheathed shear wall cyclic responses validated with experimental results from full scale shear wall tests. / Ph. D.

Master of Science / Department of Architectural Engineering and Construction Science / Sutton F. Stephens / Cold-formed steel studs, though they are a relatively new building material, have become a mainstay in modern construction. They are favored over traditional lumber studs for their high strength to weight ratio and resistance to insects and rot. Due to their relative newness as a material, new advances in their design and implementation are being developed quite rapidly. One such advancement is flange embossing, a technique used to increase the strength of the connection of screws into the studs. Currently, embossed flanges are not specifically addressed in the North American Specification for the Design of Cold-Formed Steel Structural Members (AISI S100), thereby preventing current design equations from being used to calculate an embossed stud's member properties. An experimental investigation was undertaken to determine what effect, if any, flange embossing has on the nominal flexural strength of cold-formed steel studs as determined using the provisions of AISI S100-07. Studs with embossed flanges were tested in bending and their actual flexural strength was computed. This data was then compared with the nominal flexural strength determined using the AISI Specification, without embossing, to determine if these equations would still be appropriate for the design of embossed studs.

In order to predict the strength of shear wall with cold-formed steel framing members, analytical models were reviewed. Multiple analytical models were studied, as well as twenty-one connection tests were performed. The connection tests consist of 50-ksi cold-formed steel framing track, different fastening configurations, and different sheathing thicknesses (1/8" and 1/2"). No.12 screw resulted in the highest peak load of all fastening configurations, while the rivet connection had the lowest peak load. In addition, failure modes were observed after conducting the connection tests including shear in fastening, screw pullout, and bearing in the sheathing. However, only the rivet and No.10 screw fastening configurations were used in the prediction analysis of the shear wall by the elastic model. Six shear wall tests were conducted on both panels (1/2"and 1/8" thickness). After doing the comparison between the experimental and the elastic model, the percentage difference for the 1/8" and the 1/2" polymer composite panels (3''along the edge and 6''along the chord stud), was very small. It was 6.2% for the 1/8" and 2.96% for the 1/2" panels. This means the analytical model can predict the shear wall peak load. However, the percentage difference was slightly higher being 7.4% for the 1/2" polymer composite panels with 6" along the perimeter with the 12" at the chord stud. After comparing the experimental values to the predicted value of shear walls, it was concluded that this model is the most appropriate analytical method for predicting the shear wall capacity framed with cold-formed steel sheathed with polymer composite panels. Many of these configurations were used in a prototype shelter that was constructed and built at the structural testing laboratory at the University of North Texas.

[pt] Este trabalho apresenta um estudo de um sistema de laje mista com o uso de perfis metálicos de chapa dobrada com corrugações na alma e chapa de vedação lateral com mossas seqüencialmente dispostos lado a lado e preenchidos com concreto armado. A principal motivação para este estudo foi o desenvolvimento de um eficiente sistema de laje de rápida construção. O sistema de laje desenvolvido maximiza o espaço livre útil da construção, eliminando a necessidade de formas e escoras tendo assim como conseqüência direta a minimização das perdas construtivas. Este trabalho é iniciado com uma avaliação da forma ideal dos perfis de chapa dobrada de acordo com as suas características estáticas e dinâmicas. Variáveis como peso, altura, espessura, tensão de escoamento, vão máximo, e carga suportada foram estudadas. Além disso foi feito um estudo para confecção das ferramentas de fabricação das corrugações e mossas na alma do perfil e na chapa de vedação lateral de forma eficiente e econômica. Após definição e otimização da seção do perfil metálico, foi efetuado um estudo experimental composto de uma série de três testes em escala real. O objetivo principal dos testes experimentais foi de comprovação dos resultados teóricos de resistência ultima da laje mista com perfis corrugados na alma e efetuar uma comparação com o sistema de laje previamente proposto por Takey. Os testes demostraram a real aderência entre concreto e perfil metálico e sua influência nos estados limites últimos de flexão, cisalhamento e deslizamento. Ensaios tipo push-out também foram executados para estabelecer a carga ultima de deslizamento na interface aço/concreto. A fase final compreendeu a comparação dos resultados experimentais com as normas de projeto de laje mista e com o trabalho desenvolvido por Takey para validação e comparação de resultados do sistema de laje mista. / [en] This work presents an investigation of a composite slab system made of cold formed section profiles with web corrugations and corrugated steel deck plates spanning between suck profiles, both acting compositely with concrete slab cast in place. The main motivation for this work was the development of an efficient slab system associated with easy and fast erection procedures. The proposed slab system also maximises the construction usable space, eliminating the use of temporary propping and, consequently reducing the final construction cost. This work initiates with an evaluation of the ideal cold- formed steel profile geometry according to its static and dynamical characteristics. Variables like weight, height, thickness, yield stress, and collapse load were considered. Additionally, a study of the more suitable fabrication tools to be used in the process of incorporating the corrugations to the profile webs and deck supporting plates was executed. With the optimum steel profile in hand, an experimental investigation of three full scale composite slabs, spanning three meters, was conducted. The main objective of these tests was to access the ultimate limit states associated with the proposed composite slab system and compared it to a previously proposed solution, developed by Takey. The tests made possible the evaluation of the concrete versus steel slippage resistance when compare to the other ultimate limit states associated with flexion and shear. The adopted solution, despite the natural chemical bond present in the steel/concrete interface, enhances its performance due to the action of the web profile corrugations. Push-out tests were also executed to enable the determination of the ultimate slippage load in the steel/concrete interface due to the presence of the proposed corrugations. The final stage of this investigation concerned the comparison of the experimental data to the current composite design standards, and to the previous system, developed by Takey, in order to validate its use.

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.