Dissertations / Theses on the topic 'Cold-formed steel structures'
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Feng, Ran. "Design of cold-formed stainless steel tubular joints." Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B41290628.
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Zhou, Feng. "Web crippling of cold-formed stainless steel tubular sections." Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B37228316.
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Feng, Ran, and 馮然. "Design of cold-formed stainless steel tubular joints." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B41290628.
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Uygar, Celaletdin. "Seismic Design Of Cold Formed Steel Structures In Residential Applications." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607294/index.pdf.
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ABSTRACT
SEISMIC DESIGN OF COLD FORMED STEEL STRUCTURES IN
RESIDENTIAL APPLICATIONS
Uygar, Celaletdin
M.Sc., Department of Civil Engineering
Supervisor: Prof. Dr. Çetin Yilmaz May 2005, 82 pages In this study, lateral load bearing capacities of cold formed steel framed wall panels are investigated. For this purpose lateral load bearing alternatives are analyzed numerically by computer models and results are compared with already done experimental studies and approved codes. In residential cold formed steel construction, walls are generally covered with cladding material like oriented strand board (OSB) or plywood on the exterior wall surface and these sheathed light gauge steel walls behave as shear walls with significant capacity. Oriented strand board is used in analytical models since OSB claddings are most commonly used in residential applications. The strength of shear walls depends on different parameters like screw spacing, strength of sheathing, size of fasteners used and aspect ratio. SAP2000 software is used for structural analysis of walls and joint force outputs are collected by Microsoft Excel. The yield strength of shear walls at which first screw connection reaches its shear capacity is calculated and load carrying capacity per meter length is found. The nonlinear analysis is also done by modeling the screw connections between OSB and frame as non-linear link and the nominal shear capacities of walls are calculated for different screw spacing combinations. The results are consistent with the values in shear wall design Guide and International Building Code 2003. The other lateral load bearing method is flat strap X-bracing on wall surfaces. Various parameters like wall frame section thickness, flat strap area, aspect ratio and bracing number are investigated and results are evaluated. The shear walls in which X-bracing and OSB sheathing used together are also analyzed and the results are compared with separate analyses.
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Davies, Russell John. "The behaviour of press-joining in cold-formed steel structures." Thesis, University of Edinburgh, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.534541.
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Zhou, Feng, and 周鋒. "Web crippling of cold-formed stainless steel tubular sections." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B37228316.
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Zhao, Wen-Bin. "Behaviour and design of cold-formed steel hollow flange sections under axial compression." Thesis, Queensland University of Technology, 2006. https://eprints.qut.edu.au/16909/1/Wen-Bin_Zhao_Thesis.pdf.
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The use of cold-formed steel structures is increasing rapidly around the world due to the many advances in construction and manufacturing technologies and relevant standards. However, the structural behaviour of these thin-walled steel structures is characterised by a range of buckling modes such as local buckling, distortional buckling or flexural torsional buckling. These buckling problems generally lead to severe reduction and complicated calculations of their member strengths. Therefore it is important to eliminate or delay these buckling problems and simplify the strength calculations of cold-formed steel members.
The Hollow Flange Beam with two triangular hollow flanges, developed by Palmer Tube Mills Pty Ltd in the mid-1990s, has an innovative section that can delay the above buckling problems efficiently. This structural member is considered to combine the advantages of hot-rolled I-sections and conventional cold-formed sections such as C- and Z-sections (Dempsey, 1990). However, this structural product was discontinued in 1997 due to the complicated manufacturing process and the expensive electric resistance welding method associated with severe residual stresses (Doan and Mahendran, 1996). In this thesis, new fastening methods using spot-weld, screw fastener and self-pierced rivet were considered for the triangular Hollow Flange Beams (HFBs) and the new rectangular hollow flange beams (RHFBs). The structural behaviour of these types of members in axial compression was focused in this research project. The objective of this research was to develop suitable design models for the members with triangular and rectangular hollow flanges using new fastening methods so that their behaviour and ultimate strength can be predicted accurately under axial compression.
In the first stage of this research a large number of finite element analyses (FEA) was conducted to study the behaviour of the electric resistance welded, triangular HFBs (ERW-HFBs) under axial compression. Experimental results from previous researchers were used to verify the finite element model and its results. Appropriate design rules based on the current design codes were recommended. Further, a series of finite element models was developed to simulate the corresponding HFBs fastened using lap-welds (called LW-HFBs) and screw fasteners or spot-welds or self-piercing rivets (called S-HFBs). Since the test specimens of LW-HFBs and S-HFBs were unavailable, the finite element results were verified by comparison with the experimental results of ERW-HFB with reasonable agreement.
In the second stage of this research, a total of 51 members with rectangular hollow flanges including the RHFBs made from a single plate and 3PRHFBs made from three plates fastened with spot-welds and screws was tested under axial compression. The finite element models based on the tests were then developed that included the new fasteners, contact simulations, geometric imperfections and residual stresses. The improved finite element models were able to simulate local buckling, yielding, global buckling and local/global buckling interaction failure associated with gap opening as agreed well with the corresponding full-scale experimental results. Extensive parametric studies for the RHFBs made from a single plate and the 3PRHFBs made from three plates were undertaken using finite element analyses. The analytical results were compared with the predictions using the current design rules based on AS 4100, AS/NZS 4600 and the new direct strength method. Appropriate design formulae based on the direct strength method for RHFBs and 3PRHFBs were developed. This thesis has thus enabled the accurate prediction of the behaviour and strength of the new compression members with hollow flanges and paved the way for economical and efficient use of these members in the industry.
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Zhao, Wen-Bin. "Behaviour and design of cold-formed steel hollow flange sections under axial compression." Queensland University of Technology, 2006. http://eprints.qut.edu.au/16909/.
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The use of cold-formed steel structures is increasing rapidly around the world due to the many advances in construction and manufacturing technologies and relevant standards. However, the structural behaviour of these thin-walled steel structures is characterised by a range of buckling modes such as local buckling, distortional buckling or flexural torsional buckling. These buckling problems generally lead to severe reduction and complicated calculations of their member strengths. Therefore it is important to eliminate or delay these buckling problems and simplify the strength calculations of cold-formed steel members.
The Hollow Flange Beam with two triangular hollow flanges, developed by Palmer Tube Mills Pty Ltd in the mid-1990s, has an innovative section that can delay the above buckling problems efficiently. This structural member is considered to combine the advantages of hot-rolled I-sections and conventional cold-formed sections such as C- and Z-sections (Dempsey, 1990). However, this structural product was discontinued in 1997 due to the complicated manufacturing process and the expensive electric resistance welding method associated with severe residual stresses (Doan and Mahendran, 1996). In this thesis, new fastening methods using spot-weld, screw fastener and self-pierced rivet were considered for the triangular Hollow Flange Beams (HFBs) and the new rectangular hollow flange beams (RHFBs). The structural behaviour of these types of members in axial compression was focused in this research project. The objective of this research was to develop suitable design models for the members with triangular and rectangular hollow flanges using new fastening methods so that their behaviour and ultimate strength can be predicted accurately under axial compression.
In the first stage of this research a large number of finite element analyses (FEA) was conducted to study the behaviour of the electric resistance welded, triangular HFBs (ERW-HFBs) under axial compression. Experimental results from previous researchers were used to verify the finite element model and its results. Appropriate design rules based on the current design codes were recommended. Further, a series of finite element models was developed to simulate the corresponding HFBs fastened using lap-welds (called LW-HFBs) and screw fasteners or spot-welds or self-piercing rivets (called S-HFBs). Since the test specimens of LW-HFBs and S-HFBs were unavailable, the finite element results were verified by comparison with the experimental results of ERW-HFB with reasonable agreement.
In the second stage of this research, a total of 51 members with rectangular hollow flanges including the RHFBs made from a single plate and 3PRHFBs made from three plates fastened with spot-welds and screws was tested under axial compression. The finite element models based on the tests were then developed that included the new fasteners, contact simulations, geometric imperfections and residual stresses. The improved finite element models were able to simulate local buckling, yielding, global buckling and local/global buckling interaction failure associated with gap opening as agreed well with the corresponding full-scale experimental results. Extensive parametric studies for the RHFBs made from a single plate and the 3PRHFBs made from three plates were undertaken using finite element analyses. The analytical results were compared with the predictions using the current design rules based on AS 4100, AS/NZS 4600 and the new direct strength method. Appropriate design formulae based on the direct strength method for RHFBs and 3PRHFBs were developed. This thesis has thus enabled the accurate prediction of the behaviour and strength of the new compression members with hollow flanges and paved the way for economical and efficient use of these members in the industry.
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Cheng, Shanshan. "Fire performance of cold-formed steel sections." Thesis, University of Plymouth, 2015. http://hdl.handle.net/10026.1/3316.
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Thin-walled cold-formed steel (CFS) has exhibited inherent structural and architectural advantages over other constructional materials, for example, high strength-to-weight ratio, ease of fabrication, economy in transportation and the flexibility of sectional profiles, which make CFS ideal for modern residential and industrial buildings. They have been increasingly used as purlins as the intermediate members in a roof system, or load-bearing components in low- and mid-rise buildings. However, using CFS members in building structures has been facing challenges due to the lack of knowledge to the fire performance of CFS at elevated temperatures and the lack of fire design guidelines. Among all available design specifications of CFS, EN1993-1-2 is the only one which provided design guidelines for CFS at elevated temperatures, which, however, is based on the same theory and material properties of hot-rolled steel. Since the material properties of CFS are found to be considerably different from those of hot-rolled steel, the applicability of hot-rolled steel design guidelines into CFS needs to be verified. Besides, the effect of non-uniform temperature distribution on the failure of CFS members is not properly addressed in literature and has not been specified in the existing design guidelines. Therefore, a better understanding of fire performance of CFS members is of great significance to further explore the potential application of CFS. Since CFS members are always with thin thickness (normally from 0.9 to 8 mm), open cross-section, and great flexural rigidity about one axis at the expense of low flexural rigidity about a perpendicular axis, the members are usually susceptible to various buckling modes which often govern the ultimate failure of CFS members. When CFS members are exposed to a fire, not only the reduced mechanical properties will influence the buckling capacity of CFS members, but also the thermal strains which can lead additional stresses in loaded members. The buckling behaviour of the member can be analysed based on uniformly reduced material properties when the member is unprotected or uniformly protected surrounded by a fire that the temperature distribution within the member is uniform. However if the temperature distribution in a member is not uniform, which usually happens in walls and/or roof panels when CFS members are protected by plaster boards and exposed to fire on one side, the analysis of the member becomes very complicated since the mechanical properties such as Young’s modulus and yield strength and thermal strains vary within the member. This project has the aim of providing better understanding of the buckling performance of CFS channel members under non-uniform temperatures. The primary objective is to investigate the fire performance of plasterboard protected CFS members exposed to fire on one side, in the aspects of pre-buckling stress distribution, elastic buckling behaviour and nonlinear failure models. Heat transfer analyses of one-side protected CFS members have been conducted firstly to investigate the temperature distributions within the cross-section, which have been applied to the analytical study for the prediction of flexural buckling loads of CFS columns at elevated temperatures. A simplified numerical method based on the second order elastic – plastic analysis has also been proposed for the calculation of the flexural buckling load of CFS columns under non-uniform temperature distributions. The effects of temperature distributions and stress-strain relationships on the flexure buckling of CFS columns are discussed. Afterwards a modified finite strip method combined with the classical Fourier series solutions have been presented to investigate the elastic buckling behaviour of CFS members at elevated temperatures, in which the effects of temperatures on both strain and mechanical properties have been considered. The variations of the elastic buckling loads/moments, buckling modes and slenderness of CFS columns/beams with increasing temperatures have been examined. The finite element method is also used to carry out the failure analysis of one-side protected beams at elevated temperatures. The effects of geometric imperfection, stress-strain relationships and temperature distributions on the ultimate moment capacities of CFS beams under uniform and non-uniform temperature distributions are examined. At the end the direct strength method based design methods have been discussed and corresponding recommendations for the designing of CFS beams at elevated temperatures are presented. This thesis has contributed to improve the knowledge of the buckling and failure behaviour of CFS members at elevated temperatures, and the essential data provided in the numerical studies has laid the foundation for further design-oriented studies.
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Shamim, Iman. "Seismic design of lateral resisting cold-formed steel framed (CFS) structures." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=117113.
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Seismic design provisions for wood sheathed / cold-formed steel (CFS) framed shear walls and CFS strap braced walls are available in the AISI S213-07 Standard. However, the National Building Code of Canada (NBCC), as well as the CSA S136 and the AISI S213 Standards, at present, do not address the seismic design of steel sheathed / CFS framed shear walls for use in Canada. The existing design guidelines for CFS framed shear walls are based on data obtained from static tests carried out under both monotonic and reversed cyclic loading protocols. The objective of this research was to develop seismic design provisions for the CFS framed shear walls forming part of the seismic force resisting system of a building, with the intent to recommend that they be included in the NBCC and AISI S213. The approach involved shake table testing of single- and double-storey CFS framed steel and wood sheathed shear walls, numerical modeling of the tested shear walls, and, lastly, non-linear time history dynamic analyses of building archetypes following the Federal Emergency Management Agency (FEMA) P695 methodology. Overall, seven wood sheathed and ten steel sheathed CFS framed shear walls were tested on the Ecole Polytechnique de Montréal structural laboratory shake table. The wall specimens were full-scale single- and double-storey walls and, most, were constructed with the blocking in the CFS frame. A wood sheathed shear wall was tested with a gypsum panel on one side of the specimen in order to investigate the effects of non-structural components. The dynamic test program included impact tests, harmonic forced vibration tests, and ground motion tests representative of the seismic hazard in Quebec and Vancouver, Canada. The seismic performance of the dynamically tested shear walls, i.e. force vs. displacement hysteretic behaviour and failure modes, was primarily similar to the static tests. Inclusion of the blocking increased the shear strength of the tested shear walls by almost 50%. OpenSees software was used for the numerical modelling of the dynamically tested walls. The inelastic behaviour of the shear walls was replicated by using the Pinching04 material; additional zerolength spring elements were included in the model to represent frame stiffness, anchor rod stiffness and the CFS framing. The wall models were calibrated based on the results of the dynamic tests, as well as data obtained from the calibration of previously performed static tests. Moreover, to provide experimental data to complete the model calibration procedure a series of static tests was conducted on blocked CFS bare frames and stud-to-track connections. The archetype buildings (twelve in total) were two, four and five storey office and residential buildings located in Halifax, Montreal and Vancouver, Canada. The buildings designed with Rd = 2.0 and Ro = 1.3 satisfied the FEMA P695 collapse capacity requirements. Inclusion of gypsum panel in two of the archetype buildings increased the collapse margin ratio by 20% on average.Dispositions de conception sismique pour les murs de contreventement encadrés de l'acier formé à froid (CFS) ou gainés en bois sont disponibles dans les normes AISI S213-07. Toutefois, le Code national du bâtiment du Canada (NBCC), la CSA S136 et les normes AISI S213, à l'heure actuelle, ne répondent pas à la conception sismique pour les murs de contreventement encadrés en CFS pour utilisation au Canada. La directive existante sur la conception des murs de contreventement encadrés en CFS est basé sur les données obtenues à partir des essais statiques menés sous les protocoles de chargement cyclique monotones et aussi inversées.Cette recherche visait à élaborer des dispositions de conception sismique pour les murs de contreventement encadres en CFS comme une partie du système de résistance contre des forces sismiques de bâtiment. Ces conceptions peuvent être inclus dans le NBCC et AISI S213. Cette approche a consisté les essais avec la table de vibration sur les murs de contreventement, sur une ou deux étages, encadrés en CFS ou gainés en bois, la modélisation numérique des murs de contreventement, et enfin, analyses non linéaires dynamiques de construction de archétypes suivant la méthodologie de la Federal Emergency Management Agency (FEMA) P695. Au total, sept murs de contreventement gainés en bois et dix encadrés en CFS ont été mesurées en utilisant la table de vibration au laboratoire de structure de l'Ecole Polytechnique de Montréal. Les échantillons de mur étaient de pleine échelle en simple ou double étages et, la plupart, ont été faites avec un blocage dans le cadre CFS. Un mur de contreventement gainé en bois a été testé avec un panneau de gypse dans un côté de l'échantillon afin d'étudier des effets des éléments non structurels. L'essai dynamique a compris des testes de choc, de vibration harmonique forcée, et de mouvement du sol, représentant le danger sismique au Québec et à Vancouver, au Canada. La performance sismique des murs de contreventement, c'est à dire la force contre le comportement hystérétique de déplacement des modes de défaillance, était essentiellement similaire aux essais statiques. Inclusion du blocage augmente la résistance des murs de contreventement de près de 50%. Le logiciel OpenSees a été utilisé pour la modélisation numérique des murs qui était dynamiquement testés. Le comportement inélastique des murs de contreventement a été reproduit en utilisant le matériel Pinching04; des éléments de ressort supplémentaire de longueurs zéro ont été inclus dans le modèle pour représenter la rigidité du cadre, de la tige d'ancrage et le cadrage CFS. Les modèles des murs ont été calibrés sur la base des résultats des essais dynamiques, ainsi que les données obtenues par la calibration des testes statistiques qui obtenues auparavant. En outre, pour fournir des données expérimentales pour compléter la procédure de calibration du modèle, une série de tests statiques a été fait sur des cadres en CFS bloqués et les connexions stud-to-track. Les bâtiments (douze au total) étaient en deux, quatre, et cinq étages de type commercial et résidentiel à Halifax, Montréal et Vancouver, au Canada. Les bâtiments conçus avec Rd = 2.0 et Ro = 1.3 satisfait aux exigences de capacité d'effondrement FEMA P695. L'inclusion de panneau de gypse dans deux des bâtiments archétype augmente le ratio de CMR de 20% en moyenne.
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Sapiee, Siti Fairuz Binti. "Behaviour and strength of screw connections in cold-formed steel structures." Thesis, Curtin University, 2013. http://hdl.handle.net/20.500.11937/1367.
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Self-drilling screws are the primary means of fastening cold-formed steel members in cold-formed thin-gauge steel construction. This study was carried out to investigate the behaviour and strength of single-shear connections formed with self-drilling screws. The influences of the number of screws, screw spacing and screw patterns on the strength of self-drilling screw connections were determined. It was found that the numbers of screws and screw spacing affect the performance of the screw connection significantly as compared to screw patterns.
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Lui, Wing Man. "Design of cold-formed high strength stainless steel tubular columns and beam-columns /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202004%20LUI.
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Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2004.Includes bibliographical references (leaves 149-154). Also available in electronic version. Access restricted to campus users.
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Blum, Hannah Beth. "Long-Span Cold-Formed Steel Double Channel Portal Frames." Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/16290.
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A comprehensive study on long-span cold-formed steel portal frames composed of back-to-back channel sections is presented. The aim of the study is to determine appropriate design guidelines in order for engineers to safely and efficiently build larger frames. The system analyzed herein is a haunched portal frame with a knee brace connected between the column and rafter. The objectives of the research were achieved through an extensive experimental study as well as numerical investigations. A comprehensive experimental program was completed to determine the strength and behavior of the frames. A total of nine full scale portal frame systems were tested, eight of which had unbraced columns. Variations to the frame layout, including modifications to the knee connection and the addition of sleeve stiffeners, were tested for both vertical and combined wind and vertical loading conditions. Column base rotational stiffness was quantified in the full scale experiments and in separate component tests. An advanced shell finite element model was created and calibrated with measured material and sections properties and column base stiffness, and was validated with the experimental results. A parametric study was completed to determine the effects of various configurations of the knee brace connection, as well as column base stiffness, on frame ultimate load. A larger span model was created to determine the suitability of the frame design for larger spans. A design procedure was developed to determine frame design loads. An energy method approach was employed to calculate the elastic buckling capacity of the column, which considers the elastic torsional restraint provided by the knee connection. A calibrated beam element model was used to determine the internal actions of the frame. A reliability check was completed and it was determined that the developed design method is suitable to design cold-formed steel portal frames.
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Young, B. (Ben). "The behaviour and design of cold-formed channel columns." Thesis, Faculty of Engineering, 1997. http://hdl.handle.net/2123/13673.
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Rinchen. "Long-span cold-formed steel single C-section portal frames." Thesis, The University of Sydney, 2018. http://hdl.handle.net/2123/18882.
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This thesis presents a comprehensive study of long-span cold-formed steel single C-section portal frames. The study includes the formulation of a nonlinear beam finite element for thin-walled sections, a series of full-scale frame tests and component tests, finite element modelling and advanced analysis followed by the formulation of design guidelines. The study was aimed at exploring the structural behaviour through experiment and numerical analysis towards developing provisions for the design of cold-formed steel portal frames using Advanced Analysis. A nonlinear thin-walled beam element for general open cross-sections was formulated, incorporating warping effect and non-coincident location of the shear centre and the centroid. It was successfully implemented in the geometric nonlinear analysis framework of the OpenSees finite element software. Towards investigating the behaviour and determining the ultimate strength, six full-scale tests on cold-formed steel single C-section portal frames were conducted. Separate tests were performed on frame connections, point-fastener connections and coupons to obtain the material parameters required for numerical modelling. Advanced shell finite element models of the full-scale frames and frame connections were created and validated against experimental results. The bolts and screws used for the connections between components were represented by point-based deformable fasteners. The force-deformation characteristics of the deformable fasteners were incorporated and successfully implemented in the Advanced Analysis. The strength of cold-formed steel single C-section portal frames determined by the Direct Strength Method and the Direct Design Method were compared. To account for inherent uncertainties in the strength of CFS portal frames, system resistance factors were derived. It was concluded that the Direct Design Method using Advanced Analysis is the likely future method for the design of cold-formed steel portal frames.
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Rasmussen, Kim J. R. "Stability of thin-walled structural members and systems." Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/18194.
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This DEng thesis consists of 83 articles containing research material on the stability of thin-walled structural members and systems with emphasis on metal structures. Metal structures are used widely in the construction industry. They include structural members and frames made from rolled and fabricated steel, cold-formed steel, stainless steel and aluminium. Common to these products is the desire to minimise the cross-sectional area to reduce weight and cost. Structural cross-sections are therefore thin-walled and prone to buckling, and an overriding consideration in the design of metal structures is to account for buckling in determining the strength of sections, members and frames. Specifically, the thesis is concerned with determining the reduction in buckling capacity and strength of structural members and frames caused by cross-sectional buckling and material softening. The thesis presents research under the headings Stainless Steel Structures - Hollow Sections, covering tubular columns, beams and welded connections; Stainless Steel Structures - Open Sections, addressing the effect of distortional buckling and interaction buckling on the design of stainless steel columns and beams; Analysis of Locally Buckled Members and Frames, describing a theory to determine the buckling loads of locally and/or distortionally buckled members and frames; Behaviour and Design of Members and Sections Composed Solely or Predominantly from Unstiffened Elements, outlining analytical, numerical and experimental research to advance the understanding of the behaviour and design of singly symmetric cross-sections made up entirely or predominantly from plate elements, including angle sections, T-sections and plain channel sections; Cold-formed Steel Structural Systems, describing numerical and experimental investigations of steel storage racks including selective and drive-in racking systems; and System-based Design of Steel Structures, developing a general framework for designing steel structural framing systems by advanced analysis, termed the Direct Design Method. The thesis also highlights the implementation of the research outcomes in national and international specifications for the design of steel, cold-formed steel and stainless steel structures.
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Henriques, De Sena Cardoso Francisco Manuel. "System reliability-based criteria for designing cold-formed steel structures by advanced analysis." Thesis, The University of Sydney, 2015. http://hdl.handle.net/2123/14498.
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This doctoral thesis develops a system-reliability based approach for designing cold-formed steel structures by advanced analysis. Specifically, this doctoral thesis carries out the underpinning structural analyses and reliability studies that enable the implementation of the next generation of system-based design-by-analysis steel specifications, i.e., specifications that establish a design approach where analysis and capacity checks are carried out in a single step. The study begins by developing and validating finite element (FE) models and advanced analyses that are capable of accurately predicting the behaviour and system strength of cold-formed steel structures. The modelling scheme includes a rational methodology for incorporating frame, member and sectional geometric imperfections, the ability to assign semi-rigid behaviour to the joints, the flexibility to represent the geometry of complex cross-sections and takes into account the detrimental effect of local and distortional buckling while determining the ultimate capacity of the structure. It follows the survey and statistical characterisation of the variability of the geometric and material parameters affecting the strength of cold-formed structures. Based on the collected data and the developed FE models, Monte-Carlo type of simulations are performed to determine system strength distributions and statistics of several representative frame configurations and failure modes. Reliability studies using the first-order reliability method (FORM) are then carried out to derive system resistance factors s corresponding to certain system reliability indices and representative frames are categorised on their structural reliability features. The study concludes by establishing guidelines for the design of cold-formed steel structures based on the nominal system strength as obtained by advanced analysis and category of structural reliability.
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Wilkinson, Simon James. "An investigation into the behaviour of steel proprietary support structures." Thesis, Nottingham Trent University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369256.
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Gunawan, Leonardus. "Numerical models to simulate the thermal performance of LSF wall panels." Thesis, Queensland University of Technology, 2011. https://eprints.qut.edu.au/49856/1/Leonardus_Gunawan_Thesis.pdf.
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Fire safety of buildings has been recognised as very important by the building industry and the community at large. Gypsum plasterboards are widely used to protect light gauge steel frame (LSF) walls all over the world. Gypsum contains free and chemically bound water in its crystal structure. Plasterboard also contains gypsum (CaSO4.2H2O) and calcium carbonate (CaCO3). The dehydration of gypsum and the decomposition of calcium carbonate absorb heat, and thus are able to protect LSF walls from fires. Kolarkar and Mahendran (2008) developed an innovative composite wall panel system, where the insulation was sandwiched between two plasterboards to improve the thermal and structural performance of LSF wall panels under fire conditions. In order to understand the performance of gypsum plasterboards and LSF wall panels under standard fire conditions, many experiments were conducted in the Fire Research Laboratory of Queensland University of Technology (Kolarkar, 2010). Fire tests were conducted on single, double and triple layers of Type X gypsum plasterboards and load bearing LSF wall panels under standard fire conditions. However, suitable numerical models have not been developed to investigate the thermal performance of LSF walls using the innovative composite panels under standard fire conditions. Continued reliance on expensive and time consuming fire tests is not acceptable. Therefore this research developed suitable numerical models to investigate the thermal performance of both plasterboard assemblies and load bearing LSF wall panels. SAFIR, a finite element program, was used to investigate the thermal performance of gypsum plasterboard assemblies and LSF wall panels under standard fire conditions. Appropriate values of important thermal properties were proposed for plasterboards and insulations based on laboratory tests, literature review and comparisons of finite element analysis results of small scale plasterboard assemblies from this research and corresponding experimental results from Kolarkar (2010). The important thermal properties (thermal conductivity, specific heat capacity and density) of gypsum plasterboard and insulation materials were proposed as functions of temperature and used in the numerical models of load bearing LSF wall panels. Using these thermal properties, the developed finite element models were able to accurately predict the time temperature profiles of plasterboard assemblies while they predicted them reasonably well for load bearing LSF wall systems despite the many complexities that are present in these LSF wall systems under fires. This thesis presents the details of the finite element models of plasterboard assemblies and load bearing LSF wall panels including those with the composite panels developed by Kolarkar and Mahendran (2008). It examines and compares the thermal performance of composite panels developed based on different insulating materials of varying densities and thicknesses based on 11 small scale tests, and makes suitable recommendations for improved fire performance of stud wall panels protected by these composite panels. It also presents the thermal performance data of LSF wall systems and demonstrates the superior performance of LSF wall systems using the composite panels. Using the developed finite element of models of LSF walls, this thesis has proposed new LSF wall systems with increased fire rating. The developed finite element models are particularly useful in comparing the thermal performance of different wall panel systems without time consuming and expensive fire tests.
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Morello, Denise. "Seismic performance of multi-storey structures designed with cold-formed steel wood sheathed shear walls." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40764.
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Despite the widespread use of cold-formed steel (CFS) in Canada, the 2005 National Building Code of Canada (NBCC) do not address the seismic design. Previous research conducted at McGill University resulted in the development of a design procedure and seismic force modification factors related to ductility and overstrength, Rd and Ro, for the CFS frame wood sheathed shear wall system. Based on this prior research, the American Iron and Steel Institute (AISI) included the design procedure and the force modification factors for the wood sheathed shear walls into the North American Lateral Standard for Cold-Formed Steel Framing (AISI S213). In order for this information to be included in the NBCC it was necessary to validate the design procedure, the R values and the 20 m height limit detailed in the AISI S213 by conducting dynamic analyses as well as dynamic tests. Fourteen structures (4, 6 & 7 storeys) were designed and modeled using two different software packages: Ruaumoko and SAPWood. Two different seismic force resisting systems were validated: CFS frame wood sheathed shear walls (Rd = 1.5, Ro = 1.7) and a combination system whereby wood sheathed shear walls and gypsum walls work together (Rd = 1.5, Ro = 1.7). Two seismically active regions in Canada were selected for the design of the structures: Montreal, QC and Vancouver, BC. The performance of the modeled structures was then evaluated based on the ATC-63 methodology developed for the Federal Emergency Management Agency (FEMA) in the United States. Given the performance of the models, the shear wall design approach documented in AISI S213 was proven to be satisfactory according to the ATC-63 methodology. The walls provided the necessary shear resistance when subjected to the suite of earthquake records scaled beyond the design level excitation and the structures maintained interstorey drifts far below the recommended 2% limit under design level earthquakes. The seven storey structures proved that buildiLa construction de structures en acier formé à froid est beaucoup utiliser au Canada dans le secteur résidentiel et commercial. De plus, les murs de refends créés à l’aide des panneaux de bois faisant déjà parti du bâtiment sont un système efficace pour résister les forces latérales provenant d’un séisme. Malgré l’aspect pratique présenté par ces murs de refends, le Code National du Bâtiment du Canada (CNB) et la norme CSA S136 de l’Association Canadienne de Normalisation ne fournissent aucune directive pour leur conception. Pourtant, une limite de 20 mètres pour la hauteur et des facteurs de modification de force (Rd, Ro) compatible avec le CNB ont été incluses par l’American Iron and Steel Institute dans la norme américaine, AISI S213. Cette norme adresse la conception des systèmes de reprise des forces latérales en acier formé à froid. L’importance de valider les directives incluses dans le AISI S213 avec des analyses dynamiques et des essais dynamiques était la motivation derrière cette recherche.Quatorze structures (4, 6 & 7 étages) ont été conçues et ensuite modélisées à l’aide de deux logiciels : Ruaumoko et SAPWood. Deux systèmes de murs de refends ont été traités : un système constitué de murs de refends en acier formé à froid avec des panneaux de bois (Rd = 2.5 and Ro =1.7) et un autre système comprenant de ces mêmes murs de refends mais travaillant avec les murs de gypse (Rd = 1.5 and Ro =1.7). De plus, deux régions de forte séismicité, Montréal, QC et Vancouver, BC, ont été incluses dans la recherche. La performance de ces structures a été évaluée selon l’ATC-63, développé pour le Federal Emergency Management Agency (FEMA) au États-Unis.Le niveau de performance des modèles, déterminé selon le ATC-63, a confirmé la réussite de ces deux systèmes. Les murs ont démontré une résistance au cisaillement suffisante alors qu’ils étaient soumis à 45 séismes calibrés au-delà
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Li, Xilin. "Modal decomposition of instabilities and its applications in analysis and design of cold-formed steel structures." Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/18962/.
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The construction industry has witnessed a widespread of cold-formed steel structures (CFS) in the recent years. However, despite its advantages due to the thin-walled nature of such kind of structures they are highly susceptible to instabilities including coupled instabilities. Currently the modal decomposition method used to analyse these coupled instabilities still has space of improvement. For example, the method generates overly rigid distortional and global modes, and an increased computational effort is needed when dealing with complex cross-sections. Regarding the design of CFS, the existing design code is cumbersome to implement since different empiral formulas are proposed for different types of buckling. In addition, an overly conservative prediction of the ultimate load is obtained for sections where there is significant disparity between the slenderness values of different parts. The aim of the project is to improve the modal decomposition methods and to exploit its application aspects in the analysis and design of CFS undergoing coupled instabilities. First, two new modal decomposition methods are developed, namely the polarisation method and the nodal force method. Both of the methods are based on the finite strip method (FSM), and are aimed at overcoming the disadvantages of the existing method. Second, the nodal force method is applied to analyse the deformed shape of CFS columns in the post-buckling stage, in which the contributions of buckling modes are traced until the column fails. This lays a foundation for the development of design approaches dealing with coupled instabilities. In addition, the modal decomposition method is applied to the statistical analysis of geometric imperfections of CFS specimens, which leads to a scientific charactorisation of geometric imperfections. Finally, a design approach is developed based on the concept of the direct strength method (DSM). In the proposed design approach, the initial post-buckling stiffness is considered as an input parameter in addition to the critical load. These input parameters are then used to establish a multi-linear model approximating the elastic post-buckling behaviour, which is linked to the ultimate load using empirical formulas. In the proposed design approach, two improvements are made. First, a unified design formula is used for different types of buckling, which are distinguished by the difference in post-buckling stiffness. Second, the overly conservative prediction of the ultimate load, when one part of the section is significantly slender, is avoided. This is due to the fact that in these cases, the reduction of the stiffness when buckling occurs is comparably minor.
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Koen, Damien Joseph. "Structural Capacity of Light Gauge Steel Storage Rack Uprights." Thesis, The University of Sydney, 2008. http://hdl.handle.net/2123/3880.
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This report investigates the down-aisle buckling load capacity of steel storage rack uprights. The effects of discrete torsional restraints provided by the frame bracing in the cross-aisle direction is considered in this report. Since current theoretical methods used to predict the buckling capacity of rack uprights appear to be over-conservative and complex, this research may provide engineers an alternative method of design using detailed finite element analysis. In this study, the results from experimental testing of upright frames with K-bracing are compared to finite element predictions of displacements and maximum axial loads. The finite element analysis is then used to determine the buckling loads on braced and un-braced uprights of various lengths. The upright capacities can then be compared with standard design methods which generally do not accurately take into account the torsional resistance that the cross-aisle frame bracing provides to the upright. The information contained in this report would be beneficial to engineers or manufacturers who are involved in the design of rack uprights or other discretely braced complex light gauge steel members subject to axial loads.
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Koen, Damien Joseph. "Structural Capacity of Light Gauge Steel Storage Rack Uprights." University of Sydney, 2008. http://hdl.handle.net/2123/3880.
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Master of Engineering (Research)This report investigates the down-aisle buckling load capacity of steel storage rack uprights. The effects of discrete torsional restraints provided by the frame bracing in the cross-aisle direction is considered in this report. Since current theoretical methods used to predict the buckling capacity of rack uprights appear to be over-conservative and complex, this research may provide engineers an alternative method of design using detailed finite element analysis. In this study, the results from experimental testing of upright frames with K-bracing are compared to finite element predictions of displacements and maximum axial loads. The finite element analysis is then used to determine the buckling loads on braced and un-braced uprights of various lengths. The upright capacities can then be compared with standard design methods which generally do not accurately take into account the torsional resistance that the cross-aisle frame bracing provides to the upright. The information contained in this report would be beneficial to engineers or manufacturers who are involved in the design of rack uprights or other discretely braced complex light gauge steel members subject to axial loads.
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Talebian, Nima. "Upright Frame Shear Stiffness and Upright Biaxial Bending in the Design of Cold-Formed Steel Storage Rack-Supported Buildings." Thesis, Griffith University, 2018. http://hdl.handle.net/10072/381685.
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Steel storage racks are commonly used worldwide to store goods on pallets and represent freestanding structures to design. Recently, a new type of storage systems has gained popularity in which the rack system supports both the building enclosure and the stored goods. These new rack structures are referred to as “rack-supported buildings” or “clad racks”. Due to combined actions of wind loading and stored pallets, uprights undergo a combination of biaxial bending and compression. Existing design rules may not be adequate for this type of combined loading. Furthermore in clad racks, as the outer rack frames must withstand cross-aisle horizontal actions due to wind loading, accurately determining the transverse shear stiffness of the upright frames is essential. Indeed, this stiffness is needed in calculating the elastic buckling load, performing earthquake design and serviceability checks. This thesis is motivated by the two aforementioned aspects relative to clad racks and investigates first the factor affecting the transverse shear stiffness of steel storage rack upright frames and second the biaxial bending behaviour of the uprights.
International racking design specifications recommend different approaches to evaluate the shear stiffness. The Rack Manufacturers Institute (RMI) specification conservatively uses an analytical solution based on Timoshenko and Gere's theory while the European (EN15512) and Australian (AS4084) specifications recommend experimental testing to be conducted. Discrepancy between Finite Element Analyses (FEA) and experimental test results is likely attributed to the local deformations occurring at the bolted joints. In the first part of this thesis, an advanced FEA model to accurately capture the transverse shear stiffness of upright frames is developed and verified against published experimental test results. Based on the FE model, the factors contributing to the transverse shear deformation of the frames with Cee-bracing members are quantified and discussed for lip-to-lip and back-to-back bracing patterns.
In cold-formed steel structures international specifications, a linear interaction equation is typically used to account for members subject to biaxial bending and may be inaccurate. In the second part of this thesis, the biaxial bending capacity of the uprights is experimentally investigated and the actual interactive relationship between bending of the uprights about the major and minor axes, for local and distortional buckling is determined. Two types of regularly perforated and non-perforated storage rack uprights are investigated. An advanced finite element model to determine the biaxial bending capacity of cold-formed steel storage rack upright sections is validated against the experimental tests and parametric studies are performed to analyse the biaxial response of slender, semi-compact and compact unperforated storage rack upright cross-sections in local and distortional buckling failure modes only. The results from the parametric studies are used to verify the accuracy of different forms of published direct strength method (DSM) equations.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Eng & Built Env
Science, Environment, Engineering and Technology
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Freitas, Márcio Felix de. "Ligações metálicas constituídas por parafusos auto-atarraxantes." Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-22032016-101755/.
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O emprego de parafusos auto-atarraxantes em ligações metálicas, nos últimos anos, têm aumentado de forma significativa, principalmente como dispositivo de ligação entre componentes leves da construção metálica, como por exemplo, nas ligações entre telhas metálicas e terças. Tais ligações apresentam modos de falha diferentes dos observados para as ligações parafusadas convencionais, em função do tipo de parafuso e das reduzidas espessuras dos elementos conectados, definidos como \"pull-out\" e \"pull-over\". No Brasil, a carência de estudos específicos nesse tema foi uma das razões da omissão da recente norma brasileira de dimensionamento de estruturas de aço constituídas por perfis formados a frio - NBR 14762:2001, quanto a procedimentos específicos para o projeto de ligações com parafusos auto-atarraxantes. Nesse trabalho foi desenvolvido um estudo abrangente sobre as ligações metálicas com parafusos auto-atarraxantes, com ênfase na ligação telha-terça, onde são apresentados os procedimentos e as recomendações das principais normas estrangeiras, bem como os ensaios padronizados para caracterização dos parafusos e avaliação do comportamento estrutural e resistência de ligações. São apresentados também os resultados de uma investigação experimental, com base no ensaio padrão do AISI (1996) (American Iron and Steel Institute), em 27 corpos-de-prova com variação no diâmetro do parafuso e espessura dos componentes da ligação (terça e telha), com o objetivo principal de avaliar as expressões das AISI (2001b e 1996) para dimensionamento. Como conclusão, são relatadas as dificuldades associadas ao ensaio padrão, que apesar de sua concepção simples, conduz à elevada variabilidade nos resultados, indicando a necessidade da adoção de ensaios mais representativos e confiáveis.The use of screws in steel connections has increased significantly in recent years, mainly as connecting devices between light-gage components in steel construction, as, for example, in joints between metal roofing and purlins. These connections exhibit different failure modes from those displayed by conventional bolted connections, due to the type of fastener and the reduced thicknesses of the connected elements, defined as pull-out and pull-over. In Brazil, the lack of specific studies of this theme was one of the reasons for the omission of specific procedures for the design of screw connections from the new edition of the brazilian code for cold-formed steel members - NBR 14762:2001. The work reported here involved a comprehensive study of steel connections using screws, with emphasis on the sheating-purlin connection. A presentation is made of the procedures and recommendations of the main foreign codes, as well as of standardized tests for characterizing screws and evaluating the structural behavior and strength of connections. Also presented are the results of an experimental investigation based on the standard test of the AISI (1996) (American Iron and Steel Institute) applied to 27 test specimens with varying screw diameters and connector component thicknesses (purlin and sheeting), whose main purpose was to evaluate the AISI\'s design equations (2001b e 1996). To conclude, a report is made of the difficulties associated with the standard test, which, despite its simple conception, leads to considerably variable results, indicating the need for the adoption of more representative and reliable tests.
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Mendes, Cristiane Lopes. "Estudo teórico de perfis formados a frio em situação de incêndio." Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-05042016-134851/.
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Com a publicação das normas NBR 14323:1999 Dimensionamento de estruturas de aço de edifícios em situação de incêndio e NBR 14432:2000 Exigências de resistência ao fogo de elementos construtivos de edificações, despertou-se, ainda mais, a preocupação com o dimensionamento das estruturas em caso de incêndio. Quando o aço é exposto a altas temperaturas apresenta reduções na resistência ao escoamento e no módulo de elasticidade. Em função dessas reduções, a NBR 14432:2000 apresenta tempos requeridos de resistência ao fogo, com os quais, pode-se optar pelo dimensionamento da estrutura, apresentado na NBR 14323:1999, ou pelo revestimento térmico. No entanto, essa última norma não permite a utilização do método simplificado de dimensionamento para perfis formados a frio. Quanto aos revestimentos térmicos, o mais utilizado no Brasil é a argamassa projetada, não adequada aos perfis formados a frio. O presente trabalho faz um breve histórico sobre estruturas de aço em situação de incêndio, sobre perfis formados a frio em temperatura ambiente e em situação de incêndio, além de apresentar tipos de revestimentos térmicos e suas aplicações. Finalmente sugere uma possível maneira de dimensionamento por meio da NBR 14762:2001 Dimensionamento de estruturas de aço constituídas por perfis formados a frio com adaptações para situação de incêndio e de proteção desses perfis em situação de incêndio.The interest in design of steel structures in fire situation carried out in consequence of publication of Brazilians codes ABNT/NBR 14323:1999 named \"Steel structures fire design - Procedure\" and ABNT/NBR 14432:2000 \"Fire-resistance requirements for building construction elements - Procedure\". When the steel is exposed to elevated temperatures (for example, fire situation) reductions in the strength and deformation properties must be considered. In this sense, the code ABNT/NBR 14432:2000 prescribes values of parameter TRRF (Fire strength required time), with are used for design of steel structures using a simplified method prescribed in ABNT/NBR 14323:1999, or specifying fireproofing. However, this last code doesn\'t prescribe a simplified method for cold-formed steel in fire condition, and the fireproofing materials largely used in Brazil are the sprays, which are not appropriate to cold-formed profiles. In this sense, the main goal of the present work is show a brief context about steel structures in fire conditions, in special cold-formed profiles in room temperature and fire situation, and many types of fire protection materials used in steel structures and its applications. Finally, is suggested a design method to cold-formed profiles in fire, adopting the code ABNT/NBR 14762:2001 \"Design of cold-formed steel structures\", in which appropriate adaptations are considered, as well as a protection procedure to this profiles in fire conditions.
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Júnior, Enio Carlos Mesacasa. "Comportamento estrutural e dimensionamento de cantoneiras de aço formadas a frio submetidas à compressão." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-17052012-093741/.
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Envolto ao já conhecido comportamento de cantoneiras esbeltas de abas iguais, questões aparentemente contraditórias tem sido reportadas em estudos experimentais de diversos autores, entre elas a ocorrência de modos de instabilidade em desacordo com aqueles obtidos via análise de estabilidade elástica, e forças axiais resistentes muito diferentes dos resultados teóricos (em geral, conservadoramente). Nestas condições, este trabalho procura analisar a fundo o comportamento das cantoneiras esbeltas de abas iguais, de modo a contribuir com o entendimento dos fenômenos que dificultam a interpretação dos resultados experimentais, dentre os quais, o afastamento longitudinal entre a rótula e a extremidade das barras (no caso de barras com extremidades rotuladas), e o sentido da imperfeição global de flexão em torno do eixo de menor inércia, o qual mostrou-se um fator chave na determinação do comportamento das cantoneiras, especialmente para comprimentos próximos da transição entre os dois modos globais de instabilidade elástica. Para esta faixa de comprimentos, diferentes níveis de interação entre os dois modos globais podem ser obtidos. Ademais, estudos experimentais realizados por diversos autores, aqui complementados por uma série de ensaios realizados em cantoneiras com extremidades engastadas, formam um vasto banco de resultados, que é utilizado para (além de comparações nos estudos teóricos) avaliar diversos procedimentos de previsão teórica sugeridos por diferentes autores, ou advindos de interpretações a partir do procedimento normativo, à luz do comportamento teórico estudado na primeira etapa do trabalho. Assim, destes procedimentos, apenas um baseado no Método da Resistência Direta, e dois baseados no Método das Larguras Efetivas demonstraram bons resultados, sendo que todos eles, desconsiderando o modo de flexo-torção como um modo global de instabilidade. Ao fim, comenta-se da necessidade de se expandir alguns estudos específicos, pois ao adotar-se um procedimento baseado somente no modo global de flexão, apesar de se mostrar estatisticamente mais eficiente, verifica-se a possível ocorrência de resultados demasiadamente contra a segurança.On the well known behavior of equal-leg angle columns, some questions apparently paradoxical have been reported in experimental results from several authors, including the occurrence of different instability modes from the expected by the elastic stability analysis, and maximum axial compressive load expressly different (generally conservative) from theoretical previsions. Therefore, the aim of this work is to improve the knowledge about the equal-leg angle columns behavior, contributing to the understanding of the features that complicate the interpretation of experimental results, among which, the longitudinal distance between the end sections and the center of hinges (pin-ended columns), and also the direction of the minor-axis flexural initial imperfection, which proved to play a key role in the post-critical column behavior, specially for column lengths near of the transition between global buckling modes (major-axis flexural-torsional and minor-axis flexural modes). On this range of lengths, different modal interaction amplitudes can be obtained, only with the direction of the minor-axis flexural initial imperfection (i.e., the amplitude of this imperfection plays a negligible influence on the column behavior). Furthermore, putting together a fairly large column ultimate strength data bank comprising experimental test results performed by several authors, collected from the available literature, and new experimental results on fixed-ended angle columns performed in this work, important comparisons with theoretical studies can be showed as well as evaluation of several ultimate strength theoretical prevision procedures, either those suggested by another authors as those arising from interpretations of normative procedures in the light of theoretical behavior verified in the first stage of labor. In conclusion, only one procedure based on Direct Strength Method and two procedures based on Effective Width Method exhibited accurate results, all of which neglecting the flexural-torsional mode as a global mode. Thus, it is important to mention that some additional studies are needed, because if adopted a procedure based only in the minor-axis flexural mode, despite being statistically advantageous, it is verified the possibility to occurs quite unconservative results.
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Javaroni, Carlos Eduardo. "Perfis de aço conformados a frio submetidos à flexão: análise teórico-experimental." Universidade de São Paulo, 1999. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-11122017-112750/.
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Atualmente, os perfis de chapa dobrada têm encontrado intensa aplicação como elementos estruturais nas construções em aço e como consequência, estão sujeitos aos mais diversos tipos de carregamentos. Este trabalho apresenta os aspectos gerais do dimensionamento de perfis de chapa dobrada submetidos à flexão enquanto utilizados como vigas propriamente dito e, também, enquanto utilizados como terças. Analisam-se seções tipo U, tipo U enrijecido e tipo Z enrijecido. Os ensaios em perfis fletidos foram realizados sobre 3 diferentes condições de carregamento, com dois vãos distintos, em um total de sessenta e quatro perfis ensaiados. Para os perfis conectados às telhas de aço, os ensaios foram realizados em uma \"caixa de sucção\" desenvolvida especificamente para este projeto. Os perfis foram conectados às telhas pela mesa por meio de parafusos auto-brocantes, sendo realizados quinze ensaios. Os resultados dos ensaios são comparados com os resultados teóricos, resultados normatizados e resultados de alguns procedimentos aproximados.Nowadays, the cold-formed steel members have intense application as structural elements in constructions and, in consequence, they are subjected to several types of loads. This work presents the general aspects of the study of cold-formed steel members subjected to flexion used as beams and, also, as purlins. Sections of type U, type C and type Z are analysed. The tests in beams were carried out under three different conditions of loads, with two distinct spans, in total of sixty four tests. For the purlins connected to roof system, the tests were in a \"suction box\", developed especially for this project. The purlins were connected to the roof system by the flange by using self-drilling screws, being carried out fifteen tests. The results of those tests are compared with the theoretical results, design specification provisions and results of some approximated procedures.
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Maia, Wanderson Fernando. "Análise teórica e experimental de barras em dupla cantoneira de aço formada a frio submetidas à compressão." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-10102012-083428/.
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Barras compostas em dupla cantoneira são constituídas por duas seções idênticas dispostas paralelamente, afastadas entre si e ligadas uma a outra apenas em alguns pontos ao longo do comprimento, por meio de chapas separadoras. O sistema aqui apresentado é bastante utilizado, principalmente em estruturas treliçadas leves, no entanto, não existem estudos específicos sobre seu comportamento, como conseqüência as normas de cálculo não fornecem subsídios para o projeto desse componente estrutural. É relevante estudar o comportamento de barras em dupla cantoneira, já que neste caso, além dos modos de instabilidade associados à cantoneira isolada, poderão ocorrer modos de instabilidade associados à barra composta em função da presença das chapas separadoras, que tendem a modificar o comportamento do sistema. Apresenta-se no trabalho análises numérica e experimental sobre o comportamento de barras submetidas à compressão centrada e excêntrica. Nas análises variou-se o número de chapas separadoras buscando estudar a eficiência das mesmas na força normal resistente das barras. Os resultados mostraram que a introdução de chapas separadoras melhorou significativamente o comportamento das barras, principalmente para compressão excêntrica. Foram observados modos de instabilidade por flexo-torção, por flexão e combinação dos dois modos. Para comparação dos resultados, inicialmente foram adotadas duas hipóteses de cálculo com base no procedimento da ABNT NBR 14762:2010, considerando compressão centrada. No primeiro procedimento considerou-se cada cantoneira como uma barra isolada independente da presença das chapas separadoras, admitiu-se instabilidades local, por flexo-torção e por flexão; no segundo considerou-se barra composta admitindo-se apenas instabilidades local e por flexão em relação ao eixo principal de menor inércia do conjunto. Em geral, os resultados das análises numérica e experimental apresentaram valores intermediários aos obtidos pelas duas hipóteses adotadas inicialmente. Com os resultados obtidos nas análises numérica e experimental são recomendados procedimentos para o dimensionamento desse componente estrutural.Double-angle members with batten plates consist of two identical angles set up in parallel, spaced apart, and connected to each other by batten plates at specified points along the length. The system presented herein is widely used, especially in light truss structures; however, there are no standard design procedures specific for the design of this structural component. Studying the behavior of double angle members is interesting, because in this case, besides the critical modes of the single angle, they also show critical modes, due to the presence of the batten plates that sometimes interfere with the behavior of the system. This work presents a numerical and experimental study of members under concentric and eccentric axial compression. The number of batten plates is changed to study the influence on the nominal axial strength. The use of batten plates significantly increases the strength of the system, especially for members under eccentric compression. The buckling modes observed were flexural-torsional, flexural and combination of the modes. Initially, two design hypotheses are compared to the results obtained: (i) non-composite action (no interaction between angles), with only local, flexural, and flexural-torsional buckling considered; (ii) composite action (full interaction between angles), and only considering local and minor-axis flexural buckling of the pair of angles. The two design hypotheses ignore load eccentricity. The hypotheses are based upon recommendations in ABNT NBR 14762:2010. In general, numerical and experimental results for angles connected by bolted batten plates fall in between the design curves defined by methods (i) and (ii). With the results obtained in numerical and experimental analysis, procedures are recommended for the design of this structural component.
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Neto, Alomir Hélio Fávero. "Terças em perfis de aço formados a frio com continuidade nos apoios: ênfase ao estudo das ligações de alma parafusadas com transpasse ou luva." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-07012014-142940/.
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Terças de aço formadas a frio são muito utilizadas em sistemas de cobertura e fechamento. Para conferir continuidade entre tramos adjacentes e possibilitar um melhor aproveitamento de material, são empregadas ligações parafusadas por transpasse e com luva. O comportamento estrutural dessas ligações é muito dependente da sua configuração geométrica e do nível de carregamento. Com base em uma série de nove experimentos e análises teóricas, o comportamento estrutural dessas ligações foi investigado no tocante aos esforços resistentes e à rigidez. Observou-se que o modo de falha tem sempre uma componente distorcional significativa e uma resistência menor que a prevista pela metodologia atual de projeto. No caso do momento fletor resistente, a distribuição de tensões de flexão oblíqua é a que melhor se aproxima do comportamento real das terças, sendo possível a partir de uma análise de estabilidade elástica considerando tal comportamento, e, baseado no método da resistência direta e na curva de dimensionamento do modo distorcional, obter uma previsão segura do momento fletor resistente. Além disso, a rigidez da ligação, com relação aos deslocamentos verticais é bastante dependente do tipo de ligação, sendo que as terças com ligações por luva são mais deformáveis que terças sem ligações. Por outro lado, terças com ligações por transpasse são menos deformáveis que terças fisicamente contínuas. As parcelas de rigidez da ligação são apresentadas, e a componente de deformação do furo é a mais significativa. Uma expressão para deduzir a rigidez rotacional da ligação é apresentada, juntamente com um modelo de barras para modelagem da ligação. Os resultados teóricos se ajustam muito bem aos experimentais. Conclui-se em linhas gerais, que as ligações por transpasse podem ser consideradas plenamente satisfatórias do ponto de vista de comportamento estrutural, sendo que terças com essas ligações são mais resistentes e rígidas que terças com continuidade física. O mesmo não ocorre nas terças com ligações por luva, porém, dada a limitação no número de ensaios, tais ligações carecem mais estudos.Cold-formed steel purlins are widely used in roofs and wall systems. The continuity of long runs of cold-formed steel purlins is guaranteed by sleeve and overlap bolted connections, which allows a better load distribution and material savings. The structural behavior of these connections is highly dependent on their geometric configuration and load level. The strength and stiffness of these connections were determined through a series of nine experiments, numerical and analytical analysis. Results have shown that distortional buckling has a major contribution on the stability analysis of the cold-formed steel purlin. To safely determine the flexural strength of the purlin, one must consider unrestrained bending stress distribution and distortional buckling. The connection type influences the rigidity of the purlin thus the vertical displacement. Purlins with overlapped connections are stiffer than physically continuous ones, although purlins with sleeved connections are not. The bearing deformation at the connection region is responsible for a reduction in the system stiffness. To account for the change in stiffness and determine the vertical displacement, an expression for the bearing stiffness and a beam model are proposed. The results of this model show good agreement with experimental data. The general conclusion of this research is: overlapped bolted connections enhance the structural response of the purlins when compared to physically continuous ones. The same does not hold true for purlins with sleeved connections.
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Junior, Luiz Carlos Marcos Vieira. "Análise numérica do comportamento estrutural e da resistência de terças de aço restringidas pelas telhas." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-01102007-091559/.
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Terças e longarinas metálicas são geralmente projetadas no Brasil desconsiderando a interação com as telhas, ou seja, como barras isoladas, apesar da norma brasileira NBR 14762:2001 apresentar um procedimento de cálculo que leva em consideração tal interação (método do fator R). O comportamento estrutural do sistema terça-telha é complexo e a análise completa deve considerar a não-linearidade geométrica e física, bem como a influência do contato e da conexão terça-telha. Foram analisados modelos numéricos propostos na literatura e desenvolvido um modelo via método dos elementos finitos (MEF) que incorpora as não-linearidades e o contato terça-telha. O modelo foi calibrado com resultados experimentais e posteriormente foi realizada uma análise paramétrica, a qual permitiu gerar expressões que relacionam a força (vento de sucção) com os deslocamentos. Foi também analisada a viabilidade da aplicação do método da resistência direta (MRD) ao dimensionamento de terças restringidas pela telha, empregando o método das faixas finitas (MFF) para a análise de estabilidade elástica, em que a restrição promovida pela telha foi modelada por meio de vínculos elásticos na mesa conectada com a telha. Foram considerados dois casos de distribuição de tensões normais: (i) tensões oriundas somente da flexão e (ii) tensões oriundas da flexão e torção. Em ambos os casos o momento resistente apresentou diferenças relativamente elevadas em relação ao obtido pelo método do fator R, refletindo a necessidade de uma abordagem específica do método para o sistema terça-telha.The structural behavior of purlin-sheeting system is complex and the complete analysis should consider the physical and geometrical nonlinearity, as well as the influence of the purlin-sheeting contact and connection. The brazilian code NBR 14762:2001 provides a design procedure to consider the interaction between a purlin or girt connected to the sheeting (factor R method). In Brazil purlins and girts are typically designed as isolated beams, without consideration for this purlin-sheeting combination. Numerical models proposed in the literature were analyzed and a finite element model (FEM) was developed considering nonlinearities and the contact between purlin and sheeting. The model was validated through experimental results and then implemented in a parametrical analysis. Expressions were generated using the parametrical results to relate the loading (wind uplift) to the displacements. The direct strength method (DSM) was analyzed to the designed of purlins restrained by sheeting. The finite strip method (FSM) was used for elastic buckling determination. The restraint applied to the sheeting was modeled using an elastic foundation on the flange connected to the sheeting. Two stress distributions were considered: (i) bending stresses and (ii) bending and warping stresses. In both cases the nominal flexural strength presented considerable differences compared to the factor R design method, reflecting the necessity of a specific study to evaluate the viability of the DSM approach for purlin design.
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Chodraui, Gustavo Monteiro de Barros. "Flambagem por distorção da seção transversal em perfis de aço formados a frio submetidos à compressão centrada e à flexão"." Universidade de São Paulo, 2003. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-18072003-124917/.
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Os perfis de aço formados a frio apresentam, em geral, elevada relação largura/espessura, tornando-os suscetíveis à flambagem local, caracterizada por uma flambagem de chapa, mas que também pode ocasionar um outro modo de flambagem, denominado flambagem por distorção, desconsiderado no dimensionamento de perfis laminados, mas que pode resultar crítico principalmente nos perfis com enrijecedores de borda e constituídos por aço de elevada resistência mecânica. Tal fenômeno é caracterizado pela perda de estabilidade do conjunto formado pelo elemento comprimido e seu enrijecedor de borda, alterando a forma inicial da seção transversal. Portanto, as normas mais atuais têm apresentado procedimentos para avaliar a resistência de barras com base na flambagem por distorção, como o procedimento simplificado da norma australiana AS/NZS 4600:1996, proposto por HANCOCK e que foi também adotado pela recente norma brasileira NBR 14762:2001, o método direto de resistência, recentemente proposto para incorporação à especificação do AISI (American Iron and Steel Institute) e a GBT (Generalized Beam Theory).Nesse trabalho é feita uma abordagem dos procedimentos propostos para a avaliação da flambagem por distorção em barras submetidas à compressão centrada e à flexão, comparando-se os resultados obtidos pelo procedimento da norma brasileira, pela análise elástica via método das faixas finitas - MFF e pela análise via método dos elementos finitos - MEF, admitindo barras sem e com imperfeições iniciais. É feita também uma abordagem com relação aos outros procedimentos internacionais para a avaliação do fenômeno.Cold-formed steel members present, in many cases, an elevated width/thickness ratio (thin-walled members), which probably lead up to the local buckling, which is characterized by a plate buckling, and also may lead up to another buckling mode, called distortional buckling, not considered on the design of hot-rolled members, but which may result critical in cold-formed members, specially in the ones with edge stiffeners and made with high strength steel. Such phenomena is characterized by the instability of the group formed by the compression flange and its stiffener, changing the initial shape of the cross section. Nowadays, codes present procedures to evaluate members resistance also due to distortional buckling, as the simplified method in the Australian code, AS/NZS 4600:1996, proposed by HANCOCK, which was adopted by the new Brazilian code, NBR 14762:2001, the Direct Strenght Method, recently proposed as an AISI (American Iron and Steel Institute) Draft, and the GBT (Generalilzed Beam Theory).This work talks about procedures proposed to evaluate distortional buckling in members under compression and bending, comparing results obtained by the method showed in the brazilian code, by numerical Finite Strip Method elastic analisys - FSM, and by Finite Element Method analisys FEM, on members with and without initial imperfections. It is also done an explanation related to other international procedures to evaluate the phenomena.
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Almeida, Saulo José de Castro. "Análise numérica de perfis de aço formados a frio comprimidos considerando imperfeições geométricas iniciais." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-03122007-093434/.
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O presente trabalho apresenta proposta de análise numérica de perfis de aço formados a frio submetidos à compressão centrada. Trata-se de investigação, realizada por meio de elementos finitos, com vistas à análise da influência de imperfeições geométricas iniciais presentes em perfis U simples e U enrijecido, sob os aspectos de sua forma, magnitude e sentido. A imperfeição geométrica é adotada na forma de modos de falha local, global e distorcional, observando a suscetibilidade a tais modos para a seção de interesse. Cada tipo de imperfeição é avaliado de forma isolada e, em seguida, de forma associada (conjunta). São apresentados aspectos referentes à estratégia de modelagem adotada na construção dos modelos numéricos, bem como aspectos de interesse com relação às análises não-lineares aqui consideradas. Para fins de obtenção da força de colapso, fica examinada a possibilidade de empregar modos de falha isolados para representar as imperfeições geométricas, porém, com a amplitude previamente ajustada. Para os casos de imperfeições associadas, para representar a imperfeição geométrica, se destaca o papel do sentido da imperfeição do tipo global com relação a sua associação às imperfeições dos tipos local e distorcional para perfis U enrijecidos, bem como à imperfeição do tipo local para perfis U simples.The work presents a numerical analysis on cold-formed steel members compressed between pinned ends. One is about an inquiry carried through in finite elements in which it was studied the influence of initial geometric imperfections, existing in plain channels and lipped channels, under the aspects of its form, magnitude and signal. The geometric imperfection is adopted on the forms of the local, global and distortional buckling modes, observing the susceptibility to such modes for each type of section. Each imperfection is evaluated on the isolated way and after that of associated way. Referring aspects to the strategy of modeling adopted in the construction of the numerical models are presented, as well as aspects of interest with regard to the developed nonlinear analyses. For ends of attainment of the ultimate load, it is examined the possibility to use isolated buckling modes to represent the geometric imperfections, as long as the amplitude it is adjusted. The cases that had applied coupled imperfection to represent the geometric imperfection detach the paper of the signal of the imperfection of the global type with regard to its association to the imperfections of the types local and distortional for lipped channels and, to the one of the local type for plain channels.
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Bolandim, Emerson Alexandro. "Análise de confiabilidade em ligações parafusadas em chapas finas e perfis de aço formados a frio." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-27062011-140302/.
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Este trabalho apresenta uma investigação de modelos analíticos de previsão da força de tração resistente para ligações parafusadas em chapas finas e perfis de aço formados a frio, de acordo com quatro especificações de projeto (ABNT NBR 14762:2010, ANSI AISI S100:2007-S, AS/NZS 4600:2005 e EUROCODE 3 Parte1.3:2010). O estudo envolveu 404 resultados experimentais de ligações parafusadas, sendo: 232 ligações em chapas finas, 104 ligações em cantoneiras e 68 ligações em perfis U, em que diversas configurações geométricas foram analisadas. No total 1616 análises de força resistente foram realizadas de modo que estatísticas da variável aleatória erro de modelo pudessem ser construídas. Dessa forma, a análise de erro de modelo consistiu da plotagem das probabilidades do erro de modelo, para que em seguida testes de aderência pudessem ser então aplicados de modo satisfatório, validando funções teóricas de distribuição de probabilidades para a representação da informação estatística dessa variável aleatória. Uma análise de regressão foi utilizada nas ligações parafusadas para descrever a variação do erro de modelo com a espessura da chapa e para descrever a incerteza de modelo. As análises realizadas mostraram que os modelos brasileiros e americanos conseguem prever, em média, a ruptura da seção líquida de maneira mais eficiente do que as outras especificações, pois utilizam coeficientes de redução da área líquida, e também apontam que todos os modelos apresentam uma grande variabilidade dos resultados em torno da média, o que faz com que a confiabilidade dos modelos seja prejudicada. A análise de confiabilidade, utilizada para avaliar o nível de segurança das especificações de projeto, incluiu o erro de modelo e outros parâmetros aleatórios como a resistência à ruptura do aço, ação permanente (D) e variável (L), totalizando 7092 análises em ligações parafusadas, revelando que a contribuição da variável aleatória erro de modelo na segurança dessas ligações é considerável, especialmente para razões de carregamento (Ln/Dn) entre 0,50 e 2,50. Cabe ainda observar que as especificações de projeto foram avaliadas de acordo com critérios de confiabilidade uniforme e suficiente, demonstrando que a uniformidade é alcançada de maneira mais fácil para as quatro especificações, para razões de carregamento (Ln/Dn) maiores que 2,0, e que a suficiência de segurança, na maioria das análises realizadas, não foi alcançada, principalmente para o modo de ruína de esmagamento da parede do furo, em que os índices de confiabilidade para as ligações situaram-se em torno de 2,0 a 2,5, abaixo do valor alvo de 3,5 estabelecido pelo AISI e 3,8 estabelecido pelo EUROCODE. Além disso, ao se tratar da ruptura da seção líquida, os modelos brasileiro, americano e australiano também não atingiram níveis desejáveis de segurança, contudo, fornecem probabilidades de falha bem abaixo das obtidas para o modo de ruína de esmagamento. Por fim, análises de sensibilidade revelaram que os parâmetros x/L e d/g, presentes nos modelos analíticos de previsão da ruptura da seção líquida, para a especificação brasileira e americana, não interferem na segurança estrutural das ligações.This work presents an investigation of analytical models for predicting the tensile strength to bolted connections in thin sheets and cold-formed steel members, according to four design specifications (ABNT NBR 14762:2010, ANSI AISI S100:2007-S, AS/NZS 4600:2005 and Eurocode 3 Parte1.3:2010). The study involved 404 experimental results of bolted connections, as follows: 232 connections in thin sheets, 104 connections in angles and 68 connections in channels, in which various geometric configurations were analyzed. A total of 1616 strength analysis were performed so that statistics of the random variable model error could be constructed. Thus, the model error analysis consists of plotting the probability of error model, then for the adherence tests could then be applied satisfactorily validating theoretical functions of probability distribution for the statistical representation of random variable. A regression was used in bolted connections to describe the variation of the model error with the thickness of the sheet and to describe the model uncertainty. The analysis showed that the models can predict Brazilians and Americans, on average, net section fracture more efficiently than the other specifications, for use of coefficient of reduction of net area, and also note that all models showed a great variability of results around the mean, which makes the reliability of the models is affected. The reliability analysis used to assess the safety level of design specifications, included the model error and other random parameters such as tensile strength of steel, dead (D) and live (L) loads, totaling 7092 analysis on bolted connections, revealing that the contribution the random variable model error in the security of these connections is considerable, especially for load ratios (Ln/Dn) between 0.50 and 2.50. It should also be noted that the design specifications were evaluated according to sufficient and uniform reliability criteria showing that uniformity is achieved more easily for the four specifications, for load ratios (Ln/Dn) higher than 2.0, and that the sufficiency of security, most of the analysis, is not achieved, especially for the failure modes of bearing of the hole, in which the reliability index for the connections are located around 2.0 to 2.5, below the target value of 3.5 indicated by AISI and 3.8 indicated by EUROCODE. Furthermore, when dealing with the net section fracture, the models Brazilian, American and Australian also did not reach desirable levels of security, however, provided failure probabilities well below those obtained for the failure modes of bearing. Finally, sensitivity analysis revealed that the parameters x/L and d/g, present in the analytical models for predicting the net section fracture, the specification for Brazilian and U.S., do not affect the structural safety of the connections.
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Baságlia, Cilmar Donizeti. "Sobre o comportamento estrutural de terças de aço considerando a interação com as telhas." Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-06042016-104944/.
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Nos últimos anos tem sido observada uma significativa redução do uso das telhas pesadas nas edificações industriais, como as telhas de fibrocimento, por exemplo, e a preferência por telhas mais leves e que permitem maior racionalização da construção, como as telhas metálicas (aço zincado e alumínio). Assim, a fixação por meio de ganchos foi naturalmente sendo substituída por parafusos auto-atarraxantes, permitindo uma elevada eficiência estrutural da interação terça-telha, portanto, as terças que eram tratadas como elementos estruturais independentes passaram a ser projetadas com base no comportamento conjunto com as telhas. Diante disso, este trabalho apresenta um estudo sobre o comportamento estrutural de terças de aço considerando a interação terça-telha, com ênfase na distorção lateral. Para tanto, são analisados os modelos teóricos encontrados na literatura e os procedimentos normativos, bem como são desenvolvidas análises numéricas de sistemas representativos de coberturas, via método dos elementos finitos (MEF), que incluem os efeitos da não-linearidade física e geométrica. Através destes modelos numéricos, validados por resultados experimentais de ensaios realizados na EESC-USP, é realizada uma avaliação da influência da rigidez à flexão da terça, da conexão telha-terça, do tipo de seção da terça e da presença e posicionamento de tirantes de travamento lateral das terças. Neste contexto, concluiu-se que as telhas, desde que fixadas adequadamente as terças, contribuem para a estabilidade lateral, impondo mecanismos de falha que diferem substancialmente dos mecanismos clássicos da teoria da estabilidade elástica.Recent years have seen a significant reduction in the use of heavy sheeting such as fiber cement roof sheets in industrial buildings, and an increasing preference for lighter sheeting that allows for greater rationalization of the construction, such as metallic sheeting (zinc-coated and aluminum). Thus, fixing by means of hooks was naturally replaced by screws, allowing for high structural efficiency of the purlin-sheeting combination, and purlins, which heretofore had been treated as independent structural elements, began to be designed based on their combined behavior with sheeting. This paper discusses the findings of a comprehensive on the structural behaviour of steel purlins under wind uplift considering the purlin-sheeting combination, with emphasis on lateral distortional. To this end, an analysis is made of the theoretical models available in the literature and in standard procedures, and systems representative of roofs are analyzed numerically via the finite elements method (FEM), including the effects of physical and geometrical nonlinearity. Based on these numerical models, which are validated by the experimental results of tests conducted at School of Engineering of São Carlos - University of São Paulo, an evaluation is made of the influence of the purlin\'s flexural stiffness, the sheeting-purlin connection, the type of purlin section (channel and Z-sections), and the number of rows of bridging (bracing). In this context, it was concluded that sheeting, provided it is properly fixed to the purlins, contributes toward lateral stability, imposing failure modes that differ considerably from the classic mechanisms of the theory of elastic stability.
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Gilio, Fernando Henrique Santana. "Terças de aço formadas a frio com continuidade nos apoios por meio de luvas." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-06042016-111403/.
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Há basicamente dois sistemas empregados para promover a continuidade das terças de múltiplos vãos: transpasse e luva. Do ponto de vista do transporte e da montagem, o sistema de luvas é vantajoso em relação ao sistema de transpasse, uma vez que conduz a barras de menor comprimento. Entretanto, o emprego de luvas tem sido pouco explorado, devido principalmente ao pouco conhecimento sobre o comportamento estrutural do sistema e, consequentemente, pela ausência de recomendações de projeto disponibilizadas pelas normas e manuais técnicos. Neste trabalho foram analisadas a rigidez e a resistência de terças de seção transversal Z contínuas por meio de luvas. Para tanto, uma série de quinze protótipos de terças de aço formadas a frio foi submetida a ensaios de flexão, variando-se a altura do perfil, espessura e comprimento da luva e o vão. Foi conduzida uma análise da viabilidade do método da resistência direta (MRD) ao dimensionamento de terças contínuas por meio de luvas. Em relação à rigidez, curvas momento-rotação calibradas experimentalmente foram implementadas em modelos numéricos por meio de molas rotacionais, buscando simular o comportamento não linear da ligação. Posteriormente, uma análise paramétrica foi realizada, resultando na expressão momento-rotação proposta com base nas variáveis investigadas. Essa expressão representa a rigidez da ligação, que aliada a um modelo simples barra-mola, permite a avaliação mais precisa dos esforços solicitantes e deslocamentos de terças com luvas.There are basically two systems employed to promote the continuity of multi-span purlins: overlap and sleeve. From the point of view of transport and assemblage, the sleeve system is advantageous in relation to the overlap system since it leads to shorter length bars. However, the use of sleeves has not been hardly explored mainly due to lack of knowledge about the system structural behavior and, therefore, the absence of design recommendations provided by standards and technical manuals. This study analyzed the stiffness and strength of continuous Z-section purlins with sleeved bolted connection. In order to develop the study a series of fifteen prototype were tested in bending; their cross-section height, thickness, sleeve length and span were varied. A viability analysis of the Direct Strength Method (DSM) for design of continuous sleeve purlins was conducted. In relation to stiffness, moment-rotation curves were calibrated experimentally and implemented in numerical models through rotational springs to simulate the nonlinear behavior of the connection. Afterwards, a moment-rotation expression based on the studied variables and a parametric analysis was proposed. This expression represents the connection stiffness and, when implemented in a simple spring-beam model, allows a more accurate prediction of the internal efforts and displacements in the purlin-sleeve system.
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Silva, Julio Cesar Martins da. "Análise teórica-experimental de perfis de aço formados a frio devido à instabilidade por distorção na flexão." Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-03062016-135325/.
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Apresenta-se neste trabalho um estudo teórico-experimental sobre a instabilidade de perfis formados a frio submetidos à flexão. A instabilidade distorcional se faz comum na presença de tensões de compressão atuando sobre perfis enrijecidos e fabricados com aços de elevada resistência mecânica. A parte teórica abrange os métodos de cálculo analíticos e numéricos para a análise de instabilidade distorcional de perfis de seção aberta formados a frio. Na parte experimental inclui-se o estudo de perfis formados a frio com seções do tipo U enrijecidos submetidos aos ensaios à flexão. Nestes ensaios variou-se a altura de alma e espessura de chapa procurando-se abranger maior número de condições geométricas para análise da estabilidade distorcional. Inclui-se também a análise de instabilidade numérica dos perfis do programa experimental através do método de resistência direta via método das faixas finitas. Com base nos resultados experimentais, numéricos e na análise teórica do problema, verificou-se o procedimento adotado pela NBR14762/2001 e efetuou-se comparação entre curvas de resistência propostas para o dimensionamento de perfis formados a frio à flexão. Foi verificado que o fenômeno de instabilidade distorcional pode ser o estado limite último crítico para o dimensionamento dos perfis formados a frio.This work present a study theoretical-experimental about the distortional buckling of cold-formed steel members under bending. The distortional buckling is common for members with edge-stiffened sections and manufactured with steel of high strength. The theorical part present the analitic and numerical methods for stability analysis by distortional buckling. The experimental part included the study of cold-formed with sections channel altering flange width and thickness by proof in flexural members. Included too the numerical analysis by Direct Strength Method in Finite Strip Method on members with the same configurations of experimental investigation. Based on the experimental measurements, numerical analysis and in the theorical analysis of work, verified the procedures adopted in brazilian code NBR14762/2001 and compared with others distortional curve proposed for to design of cold-formed members under bending. Verified that the distortional buckling may control the design being the critical mode for the ultimate limit state.
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Branquinho, Maria Ávila. "Sobre o comportamento estrutural e o dimensionamento de cantoneiras de aço formadas a frio submetidas à compressão e conectadas por uma aba." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-30032017-103451/.
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A cantoneira de abas iguais é encontrada laminada ou formada a frio. Quando laminada, normalmente possui abas compactas, isto é, se submetida à compressão, não apresenta instabilidade local e, para a faixa usual de comprimentos, não apresenta também o modo global de flexo-torção como dominante. Quando formada a frio, estes modos predominam, uma vez que a relação largura-espessura torna-se elevada. A elevada esbeltez das abas, juntamente com as peculiaridades do seu comportamento mecânico, pode conduzir a significativas divergências entre a força axial resistente (experimental) quando comparada aos valores oriundos dos procedimentos de cálculo apresentados pelas normas. As divergências são ainda maiores quando se considera a cantoneira em sua situação mais usual: sob compressão excêntrica devido à ligação parafusada ou soldada em uma das abas. No presente trabalho foi analisado o comportamento mecânico das cantoneiras formadas a frio e conectadas pela aba por dois parafusos e desenvolvida uma formulação baseada no método do comprimento de flambagem equivalente, bem como identificados seus modos de instabilidade e a respectiva participação modal para diversas faixas de esbeltez. Para validar esta formulação, foi realizada uma análise de confiabilidade que resultou em índices de confiabilidade (β) de acordo com as exigências normativas.The equal-leg angle is found hot-rolled or cold-formed. When hot-rolled, it usually has compact legs, that is, if subjected to compression it does not present local buckling and it does not present a global flexo-torsion buckling mode as dominant for the usual range of lengths. When cold-formed, these modes predominate, since the width-to-thickness ratio becomes high. The high slenderness of the legs, together with the peculiarities of its mechanical behavior, can lead to significant divergences between the axial strength (experimental) and the values from standard\'s procedures. The divergences are even greater when considering the angle in its most usual loading situation: under eccentric compression due to bolted or welded connection in one leg. In the present work the mechanical behavior of the cold-formed angles connected by the leg by two bolts was analyzed in order to propose a formulation based on the equivalent buckling length method, as well as, to define its buckling modes and the respective modal participation for different slenderness ranges. To validate this formulation, a reliability analysis was performed that resulted in reliability indexes (β) according to the design standards requirements.
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Anapayan, Tharmarajah. "Flexural behaviour and design of hollow flange steel beams." Thesis, Queensland University of Technology, 2010. https://eprints.qut.edu.au/36210/1/Tharmarajah_Anapayan_Thesis.pdf.
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The LiteSteel Beam (LSB) is a new hollow flange channel section developed by OneSteel Australian Tube Mills using a patented Dual Electric Resistance Welding technique. The LSB has a unique geometry consisting of torsionally rigid rectangular hollow flanges and a relatively slender web. It is commonly used as rafters, floor joists and bearers and roof beams in residential, industrial and commercial buildings. It is on average 40% lighter than traditional hot-rolled steel beams of equivalent performance. The LSB flexural members are subjected to a relatively new Lateral Distortional Buckling mode, which reduces the member moment capacity. Unlike the commonly observed lateral torsional buckling of steel beams, lateral distortional buckling of LSBs is characterised by simultaneous lateral deflection, twist and web distortion. Current member moment capacity design rules for lateral distortional buckling in AS/NZS 4600 (SA, 2005) do not include the effect of section geometry of hollow flange beams although its effect is considered to be important. Therefore detailed experimental and finite element analyses (FEA) were carried out to investigate the lateral distortional buckling behaviour of LSBs including the effect of section geometry. The results showed that the current design rules in AS/NZS 4600 (SA, 2005) are over-conservative in the inelastic lateral buckling region. New improved design rules were therefore developed for LSBs based on both FEA and experimental results. A geometrical parameter (K) defined as the ratio of the flange torsional rigidity to the major axis flexural rigidity of the web (GJf/EIxweb) was identified as the critical parameter affecting the lateral distortional buckling of hollow flange beams. The effect of section geometry was then included in the new design rules using the new parameter (K). The new design rule developed by including this parameter was found to be accurate in calculating the member moment capacities of not only LSBs, but also other types of hollow flange steel beams such as Hollow Flange Beams (HFBs), Monosymmetric Hollow Flange Beams (MHFBs) and Rectangular Hollow Flange Beams (RHFBs). The inelastic reserve bending capacity of LSBs has not been investigated yet although the section moment capacity tests of LSBs in the past revealed that inelastic reserve bending capacity is present in LSBs. However, the Australian and American cold-formed steel design codes limit them to the first yield moment. Therefore both experimental and FEA were carried out to investigate the section moment capacity behaviour of LSBs. A comparison of the section moment capacity results from FEA, experiments and current cold-formed steel design codes showed that compact and non-compact LSB sections classified based on AS 4100 (SA, 1998) have some inelastic reserve capacity while slender LSBs do not have any inelastic reserve capacity beyond their first yield moment. It was found that Shifferaw and Schafer’s (2008) proposed equations and Eurocode 3 Part 1.3 (ECS, 2006) design equations can be used to include the inelastic bending capacities of compact and non-compact LSBs in design. As a simple design approach, the section moment capacity of compact LSB sections can be taken as 1.10 times their first yield moment while it is the first yield moment for non-compact sections. For slender LSB sections, current cold-formed steel codes can be used to predict their section moment capacities. It was believed that the use of transverse web stiffeners could improve the lateral distortional buckling moment capacities of LSBs. However, currently there are no design equations to predict the elastic lateral distortional buckling and member moment capacities of LSBs with web stiffeners under uniform moment conditions. Therefore, a detailed study was conducted using FEA to simulate both experimental and ideal conditions of LSB flexural members. It was shown that the use of 3 to 5 mm steel plate stiffeners welded or screwed to the inner faces of the top and bottom flanges of LSBs at third span points and supports provided an optimum web stiffener arrangement. Suitable design rules were developed to calculate the improved elastic buckling and ultimate moment capacities of LSBs with these optimum web stiffeners. A design rule using the geometrical parameter K was also developed to improve the accuracy of ultimate moment capacity predictions. This thesis presents the details and results of the experimental and numerical studies of the section and member moment capacities of LSBs conducted in this research. It includes the recommendations made regarding the accuracy of current design rules as well as the new design rules for lateral distortional buckling. The new design rules include the effects of section geometry of hollow flange steel beams. This thesis also developed a method of using web stiffeners to reduce the lateral distortional buckling effects, and associated design rules to calculate the improved moment capacities.
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Abdel-Rahman, Nabil Mahmoud. "Cold-formed steel compression members with perforations." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ30065.pdf.
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N'emedi, Zsolt V. "Development of performance sections for cold-formed steel residential construction." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-08222009-040502/.
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Kyvelou, Pinelopi. "Structural behaviour of composite cold-formed steel systems." Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/50694.
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The topic of this thesis is the investigation of the structural behaviour of cold-formed steel flooring and purlin systems, taking into consideration the beneficial effect of interaction between structural components. Experiments have been conducted on flooring systems comprising cold-formed steel joists and wood-based particle boards, considering the typical screw fixings employed in current practice as well as alternative means of shear connection. The experimental findings showed that mobilisation of composite action within this type of system, through enhancement, beyond that currently used, of the employed shear connection, is feasible, bringing corresponding increases in capacity and stiffness. In order for the influence of the key parameters to be further examined, a finite element model simulating the examined systems has been developed, validated and employed for parametric studies. Analyses confirmed the experimental findings, showing that significant benefits in terms of capacity and stiffness can be achieved, especially for systems comprising thinner steel sections. Based on the obtained experimental and numerical results, a full design method, following the fundamental concepts of current design codes for composite structures, has been devised, providing accurate predictions of moment capacity and flexural stiffness. Finally, a numerical investigation has been performed on continuous two-span roof systems comprising cold-formed steel purlins, accounting for their interaction with the corrugated sheeting. The study showed that moment redistribution is possible within these systems, but usually accompanied by a reduction of the moment capacity of the central support. A previously devised method for the design of continuous purlin systems, making direct use of cross-section capacities at key locations, together with a factor to allow for the fall-off in moment at the central support, has been assessed and advanced.
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Huynh, Minh Toan. "Structural Behaviour of Cold-Formed Steel Screwed Connections." Thesis, The University of Sydney, 2020. https://hdl.handle.net/2123/22098.
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This thesis presents a study on the behaviour of connections using screws in cold-formed steel structures. The first part of the thesis studies the behaviour of the screw connectors using simple connection tests and Finite Element (FE) modelling. Specimens were assembled by using 2 or 3 screws connecting two cold-reduced sheet steels with various grades and thicknesses. Two types of limit states were investigated: (i) screw shear failure and (ii) bearing and tilting failure. A set of revised design equations for strength of screwed connections in bearing and tilting is proposed. A reliability analysis is performed using the proposed equations, which allow for an improvement in the capacity reduction factor in current design standards. Furthermore, an FE model, which contains fracture characteristics of both the screws and the sheet steels, is developed to give better understanding of the screw behaviour with respect to different limit states. In the second stage of the research, a dual-actuator test apparatus was set up in order to test shear connections from cold-formed steel channels to hollow sections. Each connection contained an angle cleat and two screws. Different amount of shear force and connection rotation to transfer into the connection in each test. Two limit states involving failure of the screws and failure of the sheets were investigated. Finally, an analytical model for the connection is developed using the relation between bearing force and deformation of individual screws from the first stage of the thesis. An FE model is also developed, which demonstrates how to apply actual geometry of the screws into a simulation at a structure scale. It is concluded that a simple connection carrying shear with bearing and tilting failure mode has better strength conserving capability when dealing with high rotation compared with a connection with shear fracture of the screws.
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Zhang, Jiahui, and 张佳慧. "Cold-formed steel built-up compression members with longitudinal stiffeners." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/206457.
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In this study, the structural behaviour of cold-formed steel built-up compression members with longitudinal stiffeners was investigated by experiments and numerical simulation. The influence of different screw spacings on the ultimate strengths of built-up compression members was also investigated. In current design specifications, generally there are no direct and explicit design rules for cold-formed steel built-up sections. Therefore, design rules for built-up open sections and closed sections have been proposed.
The test program was conducted for cold-formed steel built-up sections, which were compressed axially between fixed ends with various column lengths ranged from 300 to 3200 mm. Two identical open sections were connected by self-tapping screws to form a built-up section. The material properties and initial geometric imperfections of the test specimens were measured. The experimental investigation consisted of built-up open sections with edge and web stiffeners, and built-up closed sections with inward or outward web stiffeners. In total, 47 specimens were tested with a screw spacing of 100 mm, and another 25 specimens were tested with screw spacings of 300 and 600 mm.
A further investigation on the structural behaviour of cold-formed steel built-up compression members was performed using finite element analysis (FEA). Firstly, accurate and reliable finite element models (FEMs) were developed and verified against the test results. Secondly, extensive parametric studies of cross-section geometry and the screw spacing were carried out by the verified FEMs. The parametric study contained 442 specimens for built-up open sections, built-up closed sections, and built-up sections with different screw spacings. Therefore, the complex structural behaviour of built-up compression members with edge and web stiffeners, together with different spacings of self-tapping screws were studied thoroughly, as reported in this thesis.
The current direct strength method (DSM) is a favored design method for cold-formed steel columns and beams due to its ease of calculation. However, DSM does not cover the design of cold-formed steel built-up sections. The appropriateness of DSM for cold-formed steel built-up compression members was accessed by both experimental and numerical investigation. It was found that the current DSM is not quite suitable for the design of built-up compression members. Therefore, the current DSM was modified for built-up open and closed sections. The results show that the modified design rules are generally conservative and reliable for the design of built-up compression members. In addition, design recommendations are proposed for built-up sections with different screw spacings. The reliability of the current and modified design rules was evaluated using reliability analysis.published_or_final_version
Civil Engineering
Doctoral
Doctor of Philosophy
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Silva, Juliana Maria Mazzeti. "Terças de aço em perfis formados a frio com alma enrijecida: ênfase na força cortante e na interação momento fletor-força cortante." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-05062018-095440/.
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A utilização de aços de alta resistência em terças formadas a frio faz com que as espessuras sejam cada vez mais reduzidas e, como consequência, os fenômenos de instabilidade mais pronunciados. Para melhorar a eficiência estrutural, enrijecedores longitudinais podem ser inseridos na alma, aumentando a resistência em relação ao modo de instabilidade local. Ainda que a utilização de seções com alma enrijecida seja uma prática comum, os procedimentos adequados para seu dimensionamento são pouco abordados na literatura. O objetivo deste trabalho foi estudar o comportamento estrutural de terças formadas a frio de seção transversal ZAE, com enrijecedores de borda a 90º e dois enrijecedores longitudinais na alma. Para tanto, foram realizadas análises teórica e experimental de um conjunto formado por terças com alma enrijecida ZAE e suas equivalentes de alma plana, as seções Z com enrijecedores de borda a 90°. Apesar de ter sido dada ênfase às solicitações por força cortante e por combinação de momento fletor e força cortante, foram realizados ensaios complementares para avaliar a predominância de momento fletor. As alterações nos esforços críticos elásticos devido à presença dos enrijecedores foram analisadas teoricamente, e os dados experimentais e numéricos foram utilizados para prever a interação. Os resultados teóricos indicaram que os enrijecedores longitudinais têm pequena influência nos modos de instabilidade distorcional e global, porém grande influência no modo local, promovendo um aumento significativo das tensões críticas em relação às seções correspondentes de alma plana. Já os resultados experimentais mostraram que a capacidade resistente das seções Z foi superior a das seções ZAE, devido principalmente à mobilização do campo de tração e à maior restrição rotacional da mesa conferida pela ligação. Os protótipos sem restrição à distorção apresentaram falha prematura, ocasionada pela rotação da mesa na região dos apoios. Considerando os protótipos com restrição à distorção, os resultados atenderam às curvas de interação circular e trilinear. Concluiu-se que o projeto de terças com alma enrijecida pode ser realizado utilizando a expressão de interação trilinear e o momento fletor resistente do modo distorcional.The use of high strength steel in cold-formed purlins leads to a reduction in thickness and, as a consequence, the instability becomes more significant. In order to improve the structural efficiency of the sections, longitudinal stiffeners can be inserted into the web, increasing the strength in relation to local buckling. Although the use of sections with stiffened web is a common practice, the appropriate procedures for design are rarely discussed in scientific literature. The purpose of this work was to study the structural behavior of cold-formed steel purlins ZAE-sections, with 90º lips and two longitudinal stiffeners in the web. Therefore, theoretical and experimental analyses were performed, involving a set of purlins with stiffened web ZAE-sections and their equivalent plain web, the Z-sections with 90º lips. Although emphasis was given in shear and combined bending and shear, additional experimental tests were performed to evaluate the predominance of bending. Changes in critical elastic buckling stresses due to longitudinal stiffeners were evaluated and experimental and numerical data were used to predict the interation. Theoretical results indicated that longitudinal stiffeners of the ZAE-sections have little influence on distortional and global buckling. However, it has a great influence on local buckling, promoting a significant increase of the critical stresses in relation to the Z-sections. Experimental results showed that the ultimate strength of the Z-sections was higher than ZAE-sections, mainly due to the development of tension field action and the rotational restraint of the web conferred by the connection. The prototypes without distortion restraint presented premature failure, caused by rotation of the web in the region of the supports. Considering the distortion-constrained prototypes, the results satisfied the \"circular\" and \"trilinear\" interaction curves. It was concluded that design of purlins with stiffened web can be performed using the \"trilinear\" interaction expression and the distortional buckling moment capacity.
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Padilla-Llano, David Alberto. "A Framework for Cyclic Simulation of Thin-Walled Cold-Formed Steel Members in Structural Systems." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/52904.
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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.
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Leal, Davi Fagundes. "Sobre perfis de aço formados a frio compostos por dupla cantoneira com seção \"T\" submetidos à compressão." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-15072013-104844/.
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Atualmente, dentre os perfis de aço formados a frio (PFF) mais utilizados em sistemas estruturais correntes, merecem destaque aqueles compostos por duas cantoneiras ligadas entre si por meio de presilhas, apresentando seção na forma de \"T\". Embora tenha utilização bastante difundida, pouco se sabe sobre o comportamento estrutural deste tipo de perfil, principalmente em relação aos modos de instabilidade a ele associados. No presente trabalho, são desenvolvidos, com base em ferramentas disponibilizadas no código computacional ANSYS, modelos numéricos em elementos finitos com a finalidade de se investigar o comportamento estrutural dos referidos perfis submetidos à compressão e, com isso, contribuir para futuras revisões nas especificações da ABNT NBR 14762:2010 referentes aos PFF compostos. Por meio de análises não-lineares, foi investigada a influência de diversos fatores na resposta estrutural dos perfis, como: a forma de introdução do carregamento (compressão centrada ou excêntrica), as condições de vinculação, a esbeltez global, as imperfeições geométricas iniciais, a espessura das cantoneiras e o número de presilhas. Os resultados numéricos indicam que os valores de força normal de compressão resistente, obtidos conforme a ABNT NBR 14762:2010, podem resultar bastantes conservadores, principalmente nos casos de menor esbeltez global. Adicionalmente, a quantidade e a distribuição das presilhas se mostram bastante influentes, tanto na capacidade resistente como nos modos de instabilidade predominantes dos perfis. Por fim, o trabalho prevê uma investigação introdutória sobre os perfis dupla cantoneira sob temperaturas elevadas, a fim de se verificar, em caráter exploratório, o seu desempenho em situação de incêndio. As análises termoestruturais realizadas apresentaram como resultado tempos de resistência ao fogo bem abaixo do valor mínimo especificado pela ABNT NBR 14432:2001, apontando à necessidade do uso de revestimento térmico nesses perfis e de estudos mais aprofundados sobre o assunto.Nowadays, among cold-formed steel members (PFF) commonly used in current structural systems, deserve to be highlighted those composed by two angles connected through intermediate fastener (stitch-fillers) forming a \"T\" section. Although its widespread use, little is known about its structural behavior, especially in what concerns instability modes. In this study, based on tools available on the ANSYS code, numerical finite element models were developed in order to investigate the structural behavior of these profiles under compression to contribute to future revisions of the ABNT NBR 14762:2010 specifications regarding PFF compounds. By using non-linear analysis, we investigated the influence of various factors in the structural response, namely, the loading introduction (compression-centric or eccentric), the boundary conditions, the global slenderness, the geometric imperfections, the angle thickness and the number stitch-fillers. The numerical results indicated that the compression resistance, obtained according to ABNT NBR 14762:2010, it is quite conservative, especially in cases of small global slenderness. Additionally, the stitch-fillers distribution proved its great influence both in the bearing capacity as in the determination of the instability modes. Finally, the study makes an introductory research on double angle profiles under high temperatures, in order to verify its performance under fire. The thermal analysis showed fire resistance results inferior to the minimum specified by ABNT NBR 14432:2001, indicating the need of using fire protection and further studies this subject.
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Zhang, Hanwen. "Connections in cold-formed steel modular building structure systems." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8181/.
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Modular construction has been used for many years. Cold-formed steel with its advantages is commonly utilized in the modules. However, the challenge comes to the connections. Connections generally take substantial part of the expenditures. An easy erection and effective connection method could considerably achieve great cost saving and structural improvement. Current norms and specifications cannot cover the requirements in the design. This research investigated the connections in the cold-formed steel modular panel structure through experimental, analytical and numerical methods. FEMs were developed to predict the behaviours of the purlin-to-sheeting, stud-to-track and joist-to-post connections. A modified calculation method for the rotational stiffness of purlin-to-sheeting connection was proposed. This research also carried out parametric studies to figure out the influence of variables on connection performance. In the investigation, a series of tests about screw and bolt joints under pure and mixed loading scenarios were conducted. The results of the established FE models presented a great accordance with the test outcomes. The connection configurations applied in cold-formed steel panel system with high strength material were introduced in this research. It was proved that the proposed connecting methods can provide great improvement to the structural behaviour under normal and abnormal loading conditions.
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Afshan, Sheida. "Structural behaviour of cold-formed stainless steel tubular members." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/23660.
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This thesis examines the behaviour of cold-formed stainless steel tubular structural members, with an emphasis on ferritic stainless steels. Owing to the high comparative expense of stainless steel relative to traditional carbon steel, this study aims to identify and develop means of utilising the material more efficiently. A comprehensive material test programme was carried out as part of an extensive study into the prediction of strength enhancements in cold-formed structural sections that arise during production. Material tests on a total of 51 flat coupons and 28 corner coupons, extracted from a total of 18 cross-sections formed from a wide range of materials, were performed. A new, simple and universal predictive model for harnessing the cold-formed induced strength enhancements was developed which offers, on average, 19% and 36% strength enhancements for the cross-section flat faces and corner regions, respectively, relative to the strength of the unformed material. Ferritic stainless steels, having no or very low nickel content, offer a more viable alternative for structural applications to the more commonly used austenitic stainless steels, reducing both the level and variability of the initial material cost. There is currently limited information available on the structural performance of this type of stainless steel. Therefore, to overcome this limitation, a series of material, cross-section and member tests have been performed on two ferritic grades - EN 1.4003 and EN 1.4509. The experimental results were used to assess the applicability of the current codified design provisions to ferritic stainless steel structural components. Moreover, the elevated temperature performance of ferritic stainless steels, covering the material response and the flexural buckling behaviour, was investigated through analysis of experimental and numerical results, leading to proposals for suitable design recommendations. Finally, simplifications and refinements to the recently developed continuous strength method (CSM) were made. Comparison of the predicted capacities with over 140 collected test results on stainless steel stub columns and cross-sections in bending shows that the CSM offers improved accuracy and reduced scatter relative to the current design methods. The reliability of the approach has been demonstrated by statistical analyses, enabling its use in structural design standards.
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Ganesan, Karthik. "Resistance Factor for Cold-Formed Steel Compression Members." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/33694.
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This research investigates if the LRFD strength reduction factor for cold-formed steel compression members can be increased above its current value of Ï c = 0.85, which was established by the LRFD Cold-Formed Steel Design Manual (1991) on the basis of 264 column tests. The resistance factor in the Canadian code for cold-formed steel compression members is also evaluated. A total of 675 concentrically loaded plain and lipped C-section columns, plain and lipped Z-section columns, hat and angle columns, including members with holes, are considered in the study. The predicted strengths are calculated with the AISI-S100-07 Main Specification and the AISI Direct Strength Method. The test-to-predicted strength statistics are employed with the first order second moment reliability approach in AISI-S100-07 Chapter F as well as a higher order method to calculate the resistance factor per cross-section type, ultimate limit state, and considering partially and fully effective columns. The observed trends support a higher resistance factor for columns buckling in a distortional buckling limit state and an expansion of the current DSM prequalified limits. The results also show that DSM predicts the column capacity more accurately than the Main Specification. The test-to-predicted ratios for plain and lipped angle columns exhibit a high coefficient of variation and become more and more conservative as global slenderness increases. It is concluded that fundamental research on the mechanics of angle compression members is needed to improve existing design methods.Master of Science