Literatura académica sobre el tema "Cold formed elements"
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Artículos de revistas sobre el tema "Cold formed elements"
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Bitarafan, Mahdi, Youssef Hussein- Zadeh, Farzad Pichkah y Shahin Lale Arefi. "Finite Elements Modeling and Analysis of Cold-Formed Steel Frame Shear Walls". International Journal of Engineering and Technology 4, n.º 6 (2012): 719–22. http://dx.doi.org/10.7763/ijet.2012.v4.471.
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Lee, Yeong Huei, Cher Siang Tan, Shahrin Mohammad, Mahmood Md Tahir y Poi Ngian Shek. "Review on Cold-Formed Steel Connections". Scientific World Journal 2014 (2014): 1–11. http://dx.doi.org/10.1155/2014/951216.
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The concept of cold-formed light steel framing construction has been widespread after understanding its structural characteristics with massive research works over the years. Connection serves as one of the important elements for light steel framing in order to achieve its structural stability. Compared to hot-rolled steel sections, cold-formed steel connections perform dissimilarity due to the thin-walled behaviour. This paper aims to review current researches on cold-formed steel connections, particularly for screw connections, storage rack connections, welded connections, and bolted connections. The performance of these connections in the design of cold-formed steel structures is discussed.
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Rasmussen, Kim J. R., Tim Burns y Paul Bezkorovainy. "Design of Stiffened Elements in Cold-Formed Stainless Steel Sections". Journal of Structural Engineering 130, n.º 11 (noviembre de 2004): 1764–71. http://dx.doi.org/10.1061/(asce)0733-9445(2004)130:11(1764).
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Norlin, Bert y Torsten Höglund. "Bearing Length on Cold-Formed Sections". Key Engineering Materials 710 (septiembre de 2016): 421–26. http://dx.doi.org/10.4028/www.scientific.net/kem.710.421.
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The effective bearing length of trapezoidal sheeting on cold formed sections at inner supports is 10 mm according to EN 1999-1-4 (aluminium) and EN 1993-1-3 (steel). In the original design provisions the effective bearing length on Z-sections was the actual width of the loaded flange. In order to find out the appropriate effective bearing length, FEM calculations were made on simply supported beams with C-, Z-and Sigma-cross-section. Contact elements between the trough of the trapezoidal sheeting and the loaded flange of the beam made it possible to evaluate the contact area. This area and the stresses in the trapezoidal sheeting show that the effective bearing length is very small for C-sections. For Z-sections and for Sigma sections with large folds in the web the contact area is the flange width, unless the flange width versus profile height is large and the plate thickness is small.
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Cucu, Vlad, Daniel Constantin y Dan-Ilie Buliga. "Structural Efficiency Of Cold-Formed Steel Purlins". International conference KNOWLEDGE-BASED ORGANIZATION 21, n.º 3 (1 de junio de 2015): 809–14. http://dx.doi.org/10.1515/kbo-2015-0137.
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Abstract Cold-formed steel structures represents an alternative to classic buildings made of hot rolled steel profiles which bring a lot of savings based on advanced calculations and also some practical measures in order to provide optimum strength and weight ratio. Due to these advantages, cold-formed steel structures are used in more technical fields including automotive industry, storage industry, military sheltering and of course building industry. The paper is focused on the economic impact of using lightweight members for the main applications of these structures – roof structures and cladding support. The comparison will be made between classic system with hot formed purlins and advanced lightweight purlins made of cold-formed steel elements, in the same practical situation.
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Garifullin, Marsel, Darya Trubina y Nikolai Vatin. "Local Buckling of Cold-Formed Steel Members with Edge Stiffened Holes". Applied Mechanics and Materials 725-726 (enero de 2015): 697–702. http://dx.doi.org/10.4028/www.scientific.net/amm.725-726.697.
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Cold formed steel members with edge stiffened holes are a new generation of cold formed members recently developed by the building industry. Very little research has been performed on such sections to determine their local and distortional buckling capacity. This article provides the numerical results of elastic local buckling analysis of cold-formed lipped channels with edge stiffened holes. For flexural elements values of critical buckling moments are calculated and the influence of hole spacing and diameter on elastic buckling capacity is determined.
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Chung, K. F. "Structural Performance of Cold-Formed Steel Structures with Bolted Connections". Advances in Structural Engineering 8, n.º 3 (julio de 2005): 231–45. http://dx.doi.org/10.1260/1369433054349132.
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This paper presents a number of experimental and theoretical investigations into the structural behaviour of cold-formed steel structures with bolted connections. Firstly, the basic deformation characteristics of bolted fastenings between cold-formed steel strips in lap shear tests is described, and advanced finite element modelling with solid elements as well as contact elements is carried out for comparison. Secondly, the structural behaviour of lapped Z sections with bolted moment connections is reported, and both analytical and numerical predictions on strength and stiffness of lapped Z sections are presented. Finally, the structural performance of double span lapped Z purlins is investigated numerically where the effects of lapped Z sections over internal supports on the internal force distributions along the purlin members are examined. The description is intended to provide both analysis and design methods as well as understandings to structural engineers, enabling them to design and build cold-formed steel structures rationally with improved structural performance.
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kumar, Udaya y Dr Aravind Kumar B. Harwalkar. "Analysis of Retrofitted Cold Formed Steel Multistory Building Frame". International Journal of Innovative Technology and Exploring Engineering 10, n.º 11 (30 de septiembre de 2021): 29–39. http://dx.doi.org/10.35940/ijitee.k9468.09101121.
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The cold formed steel section are increasingly used as a structural elements in low rise buildings in recent times, due to the advantages like economic production, easy transportation, low labor cost and high strength to weight ratio. In the current work a G+3 storied building frame is studied for seismic and wind load using Staad-pro software. Light gauge section is taken for beam and slab elements. The seismic analysis is carried out by Equivalent static method. After analysis the results such as story displacement, story drift, Base shear and time period are compared for different models. The building frame is also analyzed for wind load. In the current work cross bracing using Light gauge element used as a retrofitting technique. The retrofitted building frame is analyzed for wind and seismic loads and results obtained for time period, storey displacement, storey drift and base shear values are compared with the corresponding values of base frame. The results of retrofitted frame showed shortening in time period, storey displacement and story drift values in X&Z directions indicating the increased ductility, Stiffness and strength of structure. Hence the proposed retrofitting technique could be believed to achieve success results in increased strength and ductility values required by wind and seismic loading.
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Moskvichev, Egor. "Distribution of material properties in finite element models of inhomogeneous elements of structures". EPJ Web of Conferences 221 (2019): 01034. http://dx.doi.org/10.1051/epjconf/201922101034.
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This paper discusses an approach to finite element modelling of structure elements considering material inhomogeneity. This approach is based on the functional dependence of mechanical properties on the spatial coordinates of finite elements. It allows modelling gradient transitions between different materials, which avoid stress discontinuities during strength analysis. The finite element models of cold formed angle, welded joint and thermal barrier coating, created by this method, have been presented.
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Kamal, Ahmed Youssef y Nader Nabih Khalil. "Composite concrete beam with multi-web cold-formed steel section". Challenge Journal of Concrete Research Letters 10, n.º 2 (27 de junio de 2019): 20. http://dx.doi.org/10.20528/cjcrl.2019.02.001.
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Lately, structural engineers use cold-formed steel sections (CFS) in buildings due to its light-weight and easy shaping. Encasing the cold-formed steel sections by concrete avoiding the structure elements some of its disadvantages especially buckling. This paper reports an experimental test program for beams with a multi-web cold-formed steel section encased by reinforced concrete. Eleven (full-scale) specimens have tested under mid-span concentrated load, the experimental test program designed to cover many cold-formed steel section variables such as (web number, web height, and the steel section length). Comparison between the experimental results for specimens with encased steel cold-formed section and that for reference beam have presented. The experimental results show that the cold-formed steel webs number has a noticeable influence on the structural behaviour of the beam, such as increasing the beam load capacity. The beam load capacity, failure mode and the beam ductility have analysed, and some preparatory criteria for a sufficient outline have presented.
Tesis sobre el tema "Cold formed elements"
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Ye, Jun. "More efficient cold-formed steel elements and bolted connections". Thesis, University of Sheffield, 2016. http://etheses.whiterose.ac.uk/15276/.
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Modern society is challenged by economic and environmental issues, requiring engineers to develop more efficient structures. Using cold-formed steel (CFS) frame in construction industry can lead to more sustainable design, since it requires less material to carry the same load compared with other materials. However, the application of CFS structural systems is limited to low story buildings due to the inherent weaknesses of premature buckling behaviour of members and the low ductility of connections. Consequently, current design guidelines of CFS systems are very conservative especially in the case of seismic design. Furthermore, there is no generic optimisation framework for the CFS elements, capable of taking into account both manufacturing/construction constraints and post-buckling behaviour. This study aims to better understand, to predict, and to optimise CFS elements based on their strength and post-buckling behaviour. The optimised elements can be then included in full-structure modelling to develop more efficient CFS structural connections with high ductility and energy dissipation capacity, suitable for multi-story buildings in seismic regions. The geometrical dimensions of manufacturable CFS cross-sections were optimised regarding their maximum compressive and bending strength. All the sections were considered to have a fix coil width and thickness while the optimisation was performed based on effective width method suggested in EC3. The optimised solutions were achieved using Particle Swarm Optimisation (PSO) algorithm. The accuracy of the optimisation procedure was assessed using experimentally validated nonlinear Finite Element (FE) analyses accounting for the effect of imperfections To allow for the development of a new ‘folded-flange’ beam cross-section, the effective width method in EC3 was extended to deal with the presence of multiple distortional buckling modes. Improved strength were achieved for CFS elements by using the proposed optimisation framework. A non-linear shape optimisation method was presented for the optimum design of CFS beam sections based on their post-buckling behaviour. A developed PSO algorithm was linked to the ABAQUS finite element programme for inelastic post-buckling analysis and optimisation. The results also demonstrate that the optimised sections develop larger plastic area, which is particularly important in seismic design of moment-resisting frames. An experimental programme was carried out at the University of Sheffield to investigate the design and optimisation, considering interactive buckling in cold-formed steel channels under compression and bending. Both standard and optimised sections were tested. The specimen imperfections were measured using a specially designed set-up with laser displacement. Material tests were also carried out to determine the tensile properties of the flat plate and of the cold-worked corners. A total of 36 columns with three lengths and 6 back-to-back beams were completed. The column specimens were tested under a concentrically applied load and with pin-ended boundary conditions while the beams were tested in a four-point bending configuration. Based on the tests, numerical models were proposed and calibrated and the proposed optimisation framework was verified. A numerical study on the structural behaviour of CFS bolted beam-to-column connections under cyclic loading was presented. An innovative two node element which can take into account the slippage-bearing effects was proposed and implemented using an ABAQUS user defined subroutine. The connection performance in terms of strength, ductility, energy dissipation capacity and damping coefficient were investigated. The effects of bolt configuration, cross-sectional shapes and thicknesses on the connection performance were therefore examined. It is indicated that the proposed numerical model is robust and computationally efficient to simulate the failure modes and moment-rotation response of CFS bolted moment resisting connections.
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Sabbagh, Alireza Bagheri. "Cold-formed steel elements for earthquake resistant moment frame buildings". Thesis, University of Sheffield, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.548557.
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Nuttayasakul, Nuthaporn. "Experimental and Analytical Studies of the Behavior of Cold-Formed Steel Roof Truss Elements". Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/29765.
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Cold-formed steel roof truss systems that use complex stiffener patterns in existing hat shape members for both top and bottom chord elements are a growing trend in the North American steel framing industry. When designing cold-formed steel sections, a structural engineer typically tries to improve the local buckling behavior of the cold-formed steel elements. The complex hat shape has proved to limit the negative influence of local buckling, however, distortional buckling can be the controlling mode of failure in the design of chord members with intermediate unbraced lengths. The chord member may be subjected to both bending and compression because of the continuity of the top and bottom chords. These members are not typically braced between panel points in a truss.
Current 2001 North American Specifications (NAS 2001) do not provide an explicit check for distortional buckling. This dissertation focuses on the behavior of complex hat shape members commonly used for both the top and bottom chord elements of a cold-formed steel truss. The results of flexural tests of complex hat shape members are described. In addition, stub column tests of nested C-sections used as web members and full scale cold-formed steel roof truss tests are reported.
Numerical analyses using finite strip and finite element procedures were developed for the complex hat shape chord member in bending to compare with experimental results. Both elastic buckling and inelastic postbuckling finite element analyses were performed. A parametric study was also conducted to investigate the factors that affect the ultimate strength behavior of a particular complex hat shape.
The experimental results and numerical analyses confirmed that modifications to the 2001 North American Specification are necessary to better predict the flexural strength of complex hat shape members, especially those members subjected to distortional buckling. Either finite strip or finite element analysis can be used to better predict the flexural strength of complex hat shape members. Better understanding of the flexural behavior of these complex hat shapes is necessary to obtain efficient, safe design of a truss system. The results of these analyses will be presented in the dissertation.Ph. D.
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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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Soroori, Rad Behrooz H. "Experiments on Cold-Formed Steel Beams with Holes". Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/42698.
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Experimental testing and elastic buckling studies were performed on 68 C-section cold-formed steel joists with unstiffened rectangular web holes. Four Steel Stud Manufacturers Association (SSMA) cross-section types; 800S200-33, 800S200-43, 1000S162-54, and 1200S162-97, were evaluated to explore the influence of holes on local, distortional, and global bucking failure modes. Hole depth was varied in the tests to identify trends in ultimate strength. Ultimate strength was observed to decrease with increasing hole depth for 800S200-33, 1200S162-97 cross-sections. Due to small number of specimen and unidentified behavior of the beams, a more in depth study of the behavior of 800S200-43 and 1000S162-54 beams are necessary. Local buckling of the unstiffened strip above the hole was observed to accompany distortional buckling at the hole for the locally slender 800S200-33 and 1000S162-54 cross-sections. Thin shell finite element eigen-buckling analysis of each joist specimen, including measured cross-section dimensions and tested boundary and loading conditions, were conducted in parallel with the experiments to identify those elastic buckling mode shapes which influence load-deformation response. The distortional and lateral-torsional buckling moments were observed to decrease with increasing hole depth while a contrasting behavior was captured for local buckling modes. A modification to the AISI Direct Strength Method equations for beams with slotted web-holes was compared against the experimental results with predictions lower than tested strength. Initial cross-section imperfections led to inclined webs which decreased the capacity of the beams. The use of a water-jet cutting process was employed successfully to produce accurate holes sizes and locations in each joist specimen and is recommended for researchers and manufacturers as a method for custom fabrication of cold-formed steel members.Master of Science
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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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Guner, Alper. "Assessment Of Roll-formed Products Including The Cold Forming Effects". Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608396/index.pdf.
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Roll-forming is an efficient sheet forming process that is used in manufacturing long parts with constant cross-section. The theoretical, experimental and numerical analyses of the process are limited since the sheet takes a complex 3D shape during the process.
In this study proper finite element method models to simulate the roll-forming process are examined both numerically and experimentally. In addition, the applicability of 2D plane strain models to the simulation of the process is investigated. To reveal the deformation of the sheet, important geometrical
parameters of the sheet and the rollers are introduced. The effect of these parameters on the strain hardening and deformation of the sheet is analyzed at distinct parts of the sheet that undergoes different types of deformations. Having
revealed the deformation mechanisms, the assumptions behind the theoretical knowledge is criticized.
The mentioned studies are verified with a case study in which a roll-formed product is analyzed under service loads. The manufacturing of the product and service load application are simulated and the results are compared with the experiments. In addition, effects of cold forming on the behaviour of the product under service loads are examined.
It is concluded that under some conditions, 2D plane strain simulations can be used to predict the strain hardening in the material that occurs during roll-forming and this hardening has a considerable effect on the response of the material under
loading.
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Vora, Hitesh. "Shear Wall Tests and Finite Element Analysis of Cold-Formed Steel Structural Members". Thesis, University of North Texas, 2008. https://digital.library.unt.edu/ark:/67531/metadc9726/.
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The research was focused on the three major structural elements of a typical cold-formed steel building - shear wall, floor joist, and column. Part 1 of the thesis explored wider options in the steel sheet sheathing for shear walls. An experimental research was conducted on 0.030 in and 0.033 in. (2:1 and 4:1 aspect ratios) and 0.027 in. (2:1 aspect ratio) steel sheet shear walls and the results provided nominal shear strengths for the American Iron and Steel Institute Lateral Design Standard. Part 2 of this thesis optimized the web hole profile for a new generation C-joist, and the web crippling strength was analyzed by finite element analysis. The results indicated an average 43% increase of web crippling strength for the new C-joist compared to the normal C-joist without web hole. To improve the structural efficiency of a cold-formed steel column, a new generation sigma (NGS) shaped column section was developed in Part 3 of this thesis. The geometry of NGS was optimized by the elastic and inelastic analysis using finite strip and finite element analysis. The results showed an average increment in axial compression strength for a single NGS section over a C-section was 117% for a 2 ft. long section and 135% for an 8 ft. long section; and for a double NGS section over a C-section was 75% for a 2 ft. long section and 103% for an 8 ft. long section.
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Vora, Hitesh Yu Cheng. "Shear wall tests and finite element analysis of cold-formed steel structural members". [Denton, Tex.] : University of North Texas, 2008. http://digital.library.unt.edu/permalink/meta-dc-9726.
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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.
Libros sobre el tema "Cold formed elements"
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Petersson, Magnus. Denmark and Norway. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198790501.003.0021.
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Denmark and Norway joined NATO in 1949. Since then, their goal has been to be a loyal alliance member. After the cold war, the two countries e transformed their defence forces into small, capabilities-based semi-professional and highly mobile units suitable for coalition warfare far away from their territories. They have participated in all major US- and NATO-led operations since 1991. The defence transformation since the end of the cold war has been more far-reaching in Denmark than in Norway. Norway kept the focus on its territory during the whole period, and saved important elements of its territorial defence, while Denmark shut down whole services, such as submarines and stationary ground-to-air defence, which in some ways became a problem after the Ukraine crisis started in 2014, when the defence of the territory again came more into focus.
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Wood, Ian. The Roman Origins of the Northumbrian Kingdom. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198777601.003.0005.
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The origins of Northumbria have received very much less attention than those of southern English kingdoms, for which Bede, the Historia Brittonum and the Anglo-Saxon Chronicle preserve origin legends. By contrast there is no origin legend recounting the arrival of Angles or Saxons from the continent in the area north of the Humber. Moreover, the archaeological record suggests a far smaller influx of migrants to the North than to the South. The excavations at Birdoswald, however, suggest continuity through the fifth and sixth centuries, while the written and epigraphic evidence suggests that there was a significantly Germanic element to the Wall-zone population even before the sixth century. As limitanei, rather than comitatenses, these would not have been taken out of Britannia by Constantine III in 406. The Bernicii are likely, therefore, to have been largely formed out of a regrouping of forces already on the Wall before 410. Similarly, there are some indications that the core of the Deiri included groups already based in the York/Malton region in the late Roman Empire. The transformation of the remnants of the Roman army, which would have been partially Germanic, may well explain how an Anglian kingdom of Northumbrian could emerge, with very little in the way of immigration.
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Bruce, Steve. Does Danger Make People Religious? Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198786580.003.0010.
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This chapter takes an interesting proposition—that danger makes people particularly receptive to religion—and uses the examples of the supposed piety of miners and fishermen to explore three very different sorts of social explanation. It could indeed be the case that unpredictably dangerous work disposes people to consider their mortality or to find supernatural ways of dampening anxiety. Or it could be that the unusual social structure of fishing villages and mining communities (generally isolated and introverted) insulates religious traditions from secularizing forces. Or it could be that the piety of these communities is a social myth based on the romantic assumption that those who work close to the elements should be more open to the supernatural than is the cosseted urban office worker. As well as addressing the substantive proposition, it considers practical problems of measuring piety.
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O'Connor, Terry. Animals in urban life in Medieval to Early Modern England. Editado por Umberto Albarella, Mauro Rizzetto, Hannah Russ, Kim Vickers y Sarah Viner-Daniels. Oxford University Press, 2017. http://dx.doi.org/10.1093/oxfordhb/9780199686476.013.13.
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Animals formed an essential part of urban life in England from Medieval times onwards, economically, socially, and ecologically. As livestock, they provided meat and other carcass resources, traction power, wool, and dairy produce. The close integration of livestock with everyday urban life is reflected in the ubiquity of butchered cattle, and sheep and pig bones, and the sight, sound, and smell of livestock would have been everyday experiences. Horses are probably under-represented in the animal bone record, given their likely importance as pack and riding animals. Poultry and, later, rabbits were important as livestock that poorer households could raise and trade. Other animals provided companionship, although the differentiation of companion animals is not unproblematic. The commensal scavengers such as crows and rodents were a central element of the urban scene, becoming stigmatized as ‘vermin’ at least by the sixteenth century.
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Newcomb, Lori Humphrey. Cross-Sections (2). Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780199580033.003.0004.
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This chapter looks at Elizabethan prose fiction. Once combed mainly for formal features that might presage the novel, Elizabethan prose fiction is today appreciated for its own distinctive energy and heterogeneity. However, prose fiction in the sixteenth century still was largely an experimental genre. For writers willing to move beyond set forms, prose narrative offered new freedoms to enhance the status of English letters while drawing freely on Continental sources, to develop prose style while incorporating verse elements, to claim usefulness while indulging writerly and readerly pleasure, and to vaunt exclusivity while driving the expansion of the leisure-reading audience. Above all, fiction was the genre in which writers could best experiment with ways to reconcile literary ambition and unapologetic commercialism.
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Leffler, Melvyn P. Safeguarding Democratic Capitalism. Princeton University Press, 2019. http://dx.doi.org/10.23943/princeton/9780691196510.001.0001.
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This book gathers together decades of writing by the author, to address important questions about U.S. national security policy from the end of World War I to the global war on terror. Why did the United States withdraw strategically from Europe after World War I and not after World War II? How did World War II reshape Americans' understanding of their vital interests? What caused the United States to achieve victory in the long Cold War? To what extent did 9/11 transform U.S. national security policy? Is budgetary austerity a fundamental threat to U.S. national interests? The wide-ranging chapters explain how foreign policy evolved into national security policy. The book stresses the competing priorities that forced policymakers to make agonizing trade-offs and illuminates the travails of the policymaking process itself. While assessing the course of U.S. national security policy, the author also interrogates the evolution of his own scholarship. Over time, slowly and almost unconsciously, the author's work has married elements of revisionism with realism to form a unique synthesis that uses threat perception as a lens to understand how and why policymakers reconcile the pressures emanating from external dangers and internal priorities.
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Brooks, Jeffrey y Sergei I. Zhuk. The Distinctiveness of Soviet Culture. Editado por Simon Dixon. Oxford University Press, 2014. http://dx.doi.org/10.1093/oxfordhb/9780199236701.013.025.
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The quintessentially Soviet element of cultural development in the USSR between 1932 and 1991 was Socialist Realism. The period prior to the 1930s was its preface and that from the mid-1950s a long post-script. By the mid-1980s, Soviet publics had moved irreversibly beyond Socialist Realism in all the arts, and no viable new contender could assume the particularist mantle. The best official offerings to compete with new Western movements after 1945 were too little and too late. In the absence of a viable particularist contender and with institutions of isolationism eroding, Soviet culture inexorably drew closer to its counterparts abroad. By 1991 it had been gone so long that its formal passing was hardly noticed.
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Trudell, Scott A. Occasion. Editado por Henry S. Turner. Oxford University Press, 2017. http://dx.doi.org/10.1093/oxfordhb/9780199641352.013.12.
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This chapter examines the volatility of occasional entertainments in space and time as a reflection of how adaptable the conventions of early modern theatre could be. It considers how occasional entertainments, fully interactive with the richly physical and symbolic ecologies around them, reveal the role of a fixed stage in the design and procurement of early modern theatricality. It shows that poetic verse was a relatively insignificant element in the entertainments, pageants, and Lord Mayors shows of the period and explains how print became a way to transform the contingencies of occasion into an enduring ‘poesy’: in print, the noise, rain, mud, crowds, bored monarchs, tired children, and sheer formal incoherence of the event all resolved into a grand and silent art.
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Peake, Hayden B. Counterintelligence. Oxford University Press, 2017. http://dx.doi.org/10.1093/acrefore/9780190846626.013.134.
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“Counterintelligence” (CI) is a term with multiple meanings—its definitions vary, even when applied to a single nation. Yet it can be understood by identifying the common CI functions in a source. These include: handling double agents, defectors, deception operations, and covert communications; handling and detecting moles or penetrations; and dealing with security threats in general. Antecedent elements of what is today called counterintelligence may be found in various histories of intelligence and warfare. The existence of security services can be traced back to ancient Egypt, Assyria, Persia, Greece, Rome, China, and Muscovy, among others. With the rise of the nation-state, rulers began creating secret political police organizations to safeguard their existence. In the case of the United States, it was not until the Civil War that there was anything like a domestic counterintelligence agency, and even then it was not a statutory organization. After World War I, however, former intelligence officers, agents, defectors, and journalists began publishing accounts of counterintelligence and domestic security operations. These topics were often discussed side-by-side. The number of scholarship on CI grew as World War II and the Cold War followed. In particular, the so-called “Cambridge Five” case—which involved five Cambridge graduates who were recruited as Soviet spies in the 1930s—had generated considerable literature and was furthermore considered an important case study in Western and Soviet intelligence services.
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Trevor C, Hartley. Part II Jurisdiction, 13 Choice-of-Court Agreements. Oxford University Press, 2017. http://dx.doi.org/10.1093/law/9780198729006.003.0013.
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This chapter considers choice-of-court agreements under Brussels 2012, Lugano 2007, and Hague. The issue is considered based on the assumption that the courts of only one country are involved. Several provisions in all three instruments are relevant. In the case of Brussels 2012, the most important for present purposes is Article 25; in the case of Lugano 2007, it is Article 23; in the case of Hague, the whole Convention could be regarded as relevant, since all of it is concerned with choice-of-court agreements. The discussions cover the nature of choice-of-court agreements, relevant provisions, location of the designated court, the need for an international element, asymmetric choice-of-court agreements, indirect designation, formal validity and consent, substantive validity, severability, disputes covered, parties covered, the obligation to hear the case, and the obligation to decline jurisdiction.
Capítulos de libros sobre el tema "Cold formed elements"
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Thulin, Frederick A. y John D. Brock. "Structural Evaluation of Cold-Formed Sheet Steel Concrete Reinforcement Using Finite Elements and Tests". En Computational Mechanics ’86, 965–71. Tokyo: Springer Japan, 1986. http://dx.doi.org/10.1007/978-4-431-68042-0_139.
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Ajeesh, S. S. y S. Arul Jayachandran. "TWLIGHT-IITM—A Computational Utility for Elastic Buckling Stress Predictions of Cold-Formed Steel Elements". En Lecture Notes in Civil Engineering, 389–401. Singapore: Springer Singapore, 2018. http://dx.doi.org/10.1007/978-981-13-0362-3_31.
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Blum, H. y K. Rasmussen. "Finite element modeling and parametric study of cold-formed steel portal frames". En Insights and Innovations in Structural Engineering, Mechanics and Computation, 1062–67. Taylor & Francis Group, 6000 Broken Sound Parkway NW, Suite 300, Boca Raton, FL 33487-2742: CRC Press, 2016. http://dx.doi.org/10.1201/9781315641645-175.
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Huynh, Minh Toan, Cao Hung Pham y Gregory J. Hancock. "On the Finite Element Modeling of the Screwed Connections of Cold-Formed Steel". En Lecture Notes in Civil Engineering, 224–32. Singapore: Springer Singapore, 2017. http://dx.doi.org/10.1007/978-981-10-6713-6_21.
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Pham, Ngoc Hieu. "Effects of Hole Locations on the Elastic Global Buckling Loads of Cold-Formed Steel Channel Members with Perforations Under Compression or Bending". En Lecture Notes in Civil Engineering, 57–69. Singapore: Springer Singapore, 2022. http://dx.doi.org/10.1007/978-981-19-1260-3_6.
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AbstractCold-formed steel members with perforations have been commonly applied to meet the demands for technical installations. The design of the perforated members was regulated in Specification AISI S100-16 using the Direct Strength Method (DSM). This method is based on elastic buckling analyses to predict the capacities of cold-formed steel members. The determination of elastic buckling loads is compulsory for the application of the DSM method in the design and has been presented in the Specification. The specification regulations are only applied for symmetrical and evenly spaced holes. The paper, therefore, investigates the effects of unsymmetrical, unevenly spaced and eccentric holes on the elastic global buckling loads of perforated channel members using finite element analyses. The effect of symmetrical and evenly web holes on the elastic global buckling loads of cold-formed steel channel members in comparison with those of gross section members is also investigated.
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De’nan, Fatimah, Kok Keong Choong, Jessica Si Jia Loo y Nor Salwani Hashim. "Finite Element Analysis of the Screw Arrangement Effects on the Connection Behaviour for Cold Formed Steel Truss Systems". En Proceedings of AICCE'19, 229–47. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-32816-0_14.
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Ramos, Kenneth S., Stefano Guerra y Randa El-Zein. "Precision Medicine Approaches for Stratification and Development of Novel Therapies of Latin(x) Patients at Risk of Lung Malignancy". En Advancing the Science of Cancer in Latinos, 89–98. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-14436-3_8.
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AbstractPrecision medicine has emerged as an optimal health-care delivery platform, which emphasizes integration of individual patient characteristics into patient care. For lung cancer, precision approaches have focused mostly on targeted therapies directed at tyrosine kinases and immunotherapy. It is proposed that refinements should focus on improved risk stratification of patients at heightened risk of lung malignancy, namely patients with chronic obstructive pulmonary disease (COPD). African ancestry is associated with worsened clinical outcomes in COPD and lung cancer, which is relevant for Latinx populations given that varying degrees of African ancestry exist among several Latinx subgroups. The work reviewed here focuses on ORF1p, a protein encoded by Long Interspersed Element-1 (LINE-1) and associated with genetic instability. Because high expression of ORF1p is associated with poor prognosis in patients with non-small-cell lung cancer (NSCLC), it is hypothesized that circulating ORF1p can be monitored as a proxy of genetic instability in patients with COPD and lung cancer. Circulating ORF1p levels correlate with FEV1 deficits and airflow limitation (the hallmark of COPD) in former smokers, and tissue expression of ORF1p is increased in TP53 mutant NSCLC compared to wildtype. Understanding the role of ORF1p in COPD and lung cancer and its utility as a biomarker of genetic instability may lead to advances in lung cancer care and development of novel targeted therapies.
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Bergan, Sjur y Liviu Matei. "The Future of the Bologna Process and the European Higher Education Area: New Perspectives on a Recurring Topic". En European Higher Education Area: Challenges for a New Decade, 361–73. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-56316-5_23.
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Abstract The future of the Bologna Process and the European Higher Education Area (EHEA) have been debated for more than 20 years (Bergan and Deca 2018). From the very start, even as the implementation of this continental-wide project in higher education got underway and in parallel to historical analyses (“looking back” too) that begun slowly to emerge, the future of the EHEA has been a constant preoccupation. It is perhaps in the nature of things that while the future can be close or distant, it never quite arrives, like a textitfata morgana, so that any discussion of “the future” can in principle be endless. Or, it could be that in this case discussions about the future indicate continuing uncertainty about the substance, shape and timeline of a European area for higher education. As we are completing the second decade of the Bologna Process and, if we take a formal approach, the first decade of the EHEA, this debate nevertheless takes on added urgency and includes some new elements. We are encouraged by the fact that few if any voices have been heard advocating an end to the EHEA. We therefore disregard this option here.
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"Strength of Thin Elements and Design Criteria". En Cold-Formed Steel Design, 47–95. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2010. http://dx.doi.org/10.1002/9780470949825.ch3.
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"Miscellaneous Cold-Formed Steel Elements and Systems". En Bracing Cold-Formed Steel Structures, 54–66. Reston, VA: American Society of Civil Engineers, 2005. http://dx.doi.org/10.1061/9780784408179.ch04.
Texto completoActas de conferencias sobre el tema "Cold formed elements"
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Garcia, João Pedro Magalhães, Eduardo de Miranda Batista y Juarez Moara Santos Franco. "STABILITY AND RESISTANCE OF STRUCTURAL COLD-FORMED STEEL ELEMENTS WITH STIFFENED SECTIONS". En XXXVIII Iberian-Latin American Congress on Computational Methods in Engineering. Florianopolis, Brazil: ABMEC Brazilian Association of Computational Methods in Engineering, 2017. http://dx.doi.org/10.20906/cps/cilamce2017-0463.
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Ungureanu, Viorel, Ivan Lukačević, Ioan Both y Mircea Burca. "Numerical investigation of built-up cold-formed steel beams connected by spot welding". En IABSE Congress, New York, New York 2019: The Evolving Metropolis. Zurich, Switzerland: International Association for Bridge and Structural Engineering (IABSE), 2019. http://dx.doi.org/10.2749/newyork.2019.1065.
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<p>Built-up cold-formed steel elements are efficient structural elements, very attractive due to material savings, but also for ease of construction. The connection between the built-up beam components can be easily obtained by screws, but the developments in the welding process also led to other solutions like spot welding. The WELLFORMED research project, conducted within the CEMSIG Research Center of the Politehnica University of Timisoara, proposes to study a new technological solution for built-up beams made of corrugated steel sheets for the web and thin-walled cold-formed steel profiles for the flanges, connected by spot welding. Within the research project, the experimental work included tensile-shear tests on the lap joint welded specimens, where different combinations of steel sheets with various thicknesses were tested and, tests on two full-scale beams in bending. The paper briefly summarizes the results of the experimental program and extends the research by numerical analyses to demonstrate the potential of this solution for standardization and industrial manufacturing. Based on the validation of the numerical model, the paper presents the influence of several parameters i.e.: (1) the initial imperfections, (2) the number and distance between spot welding on flanges, (3) the thickness of the flanges, (4) the thickness of the corrugated web and (5) the thickness of the shear panel. From the parametric study, it results that the bearing capacity of the corrugated web beams made of cold-formed steel components is highly affected by the stability of the components and less affected by the configuration and the number of spot welding.</p>
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Stangherlin Gomes, Victor y LUIZ CARLOS MARCOS VIEIRA JUNIOR. "Finite Element Modeling of Cold-Formed Steel Members". En XXIV Congresso de Iniciação Científica da UNICAMP - 2016. Campinas - SP, Brazil: Galoa, 2016. http://dx.doi.org/10.19146/pibic-2016-51495.
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Liu, Yacheng, Weidong Fan, Xiang Zhang y Naixing Wu. "Analysis on High Temperature Corrosion Behaviors of Boiler Steels Under High-Chlorine Coal Ash". En ASME 2017 Power Conference Joint With ICOPE-17 collocated with the ASME 2017 11th International Conference on Energy Sustainability, the ASME 2017 15th International Conference on Fuel Cell Science, Engineering and Technology, and the ASME 2017 Nuclear Forum. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/power-icope2017-3215.
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Chlorine is a harmful constituent in coal, contributing to severe high temperature corrosion on the super-heater and re-heater tubes in utility boiler firing high-chlorine coal (more than 0.3 wt.%). Characteristics of the corrosion contain not only the formed products on the metal surface, but also intergranular attack inner the alloy, resulting in great potential safety hazard and economic loss. The prevailing Cl-related mechanisms of high temperature corrosion involve active oxidation and fluxing, which mean both corrosive elements in the flue gas and deposits on the boiler metal surface can accelerate the corrosion. Cl2 as a catalyst in active oxidation can be released by sulfuration of alkali metal chlorides or reactivity by alkali metal chlorides with chromium/chromium oxide and iron/iron oxide or oxidation of HCl. However, the formation of low-melting eutectics (such as NaCl-Na2CrO4) in mechanism of fluxing can be an induction of severe corrosion because the rate of molten corrosion is much higher than chemical corrosion. Lab-scale experiments simulating the flue gas species, temperature gradient from hot flue gas (950 °C) to cold metal (610 °C), and deposit (four various Cl-containing coal ash) on the specimens were conducted in a tube furnace to investigate the corrosion of three common boiler steels (12Cr1MoVG, T91, TP347H). Furthermore, with the aid of the scanning electronic microscope associated with energy dispersive spectrometer (SEM-EDX) and X-ray diffraction instrument (XRD), the appearance and microstructure, the element contents, and composition of corrosion products on the specimens after corrosion have been analyzed. For high-chlorine coal, there existed white crystal on the surface of specimens (T91, TP347H) after corrosion test, and the XRD result showed NaCl, which can be explained by evaporation-condensation mechanism. However, no white crystal was detected for 12Cr1MoVG and it can be inferred that thick corrosion product layer with high thermal resistance was formed and 12Cr1MoVG suffered severe degradation. Through comparisons of alloy elements corroded in various oxidizers (Cl2, O2, and S), it can be seen that as the metal temperature increases, the negative value of Gibbs free energy for alloy elements corroded in Cl2 becomes higher, but the value is less corroded in O2 or S. Thus, alloy elements tend to be easier combined with Cl2, and Cl-induced corrosion is aggravated with the temperature increases. Similar results can be obtained by increased equilibrium vapor pressures of metal chlorides, evaporating easily and diffusing towards further to be oxidation. In comparison with high-chlorine coal, the corrosivity of low-chlorine coals on specimens were weak, especially for TP347H characterized with higher contents of Cr and Ni. Furthermore, the higher the ratio of Cl/2S or Cl/Na in the coal ash is, the more severe corrosion the specimens suffer.
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Rehman, Mufaiz y Rashmi Sakalle. "Finite elemental analysis of industrial structure using cold formed steel". En PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON SUSTAINABLE MATERIALS AND STRUCTURES FOR CIVIL INFRASTRUCTURES (SMSCI2019). AIP Publishing, 2019. http://dx.doi.org/10.1063/1.5127138.
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Yao, Jian, Jia Xu y Li Xing. "Finite element analysis of bonding connections between cold-formed steel Z sections". En 2011 Second International Conference on Mechanic Automation and Control Engineering (MACE). IEEE, 2011. http://dx.doi.org/10.1109/mace.2011.5988356.
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Kraus, Martin, Philipp Frey, Tobias Kleffel, Dietmar Drummer y Marion Merklein. "Mechanical joining without auxiliary element by cold formed pins for multi-material-systems". En PROCEEDINGS OF THE 22ND INTERNATIONAL ESAFORM CONFERENCE ON MATERIAL FORMING: ESAFORM 2019. AIP Publishing, 2019. http://dx.doi.org/10.1063/1.5112570.
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Poursadrollah, Arash. "Finite element reliability analysis of flexural buckling of cold-formed hollow section members". En INTERNATIONAL CONFERENCE OF NUMERICAL ANALYSIS AND APPLIED MATHEMATICS ICNAAM 2020. AIP Publishing, 2022. http://dx.doi.org/10.1063/5.0081516.
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Cirstian, Felicia, Jason Patrick Sauter, Constantin Vintila, Gheorghe Albulescu, Cosmin Constantin Badescu y Maximilian Ene. "Remediating a Landslide Affected Well for Subsequent Abandonment - Challenges Overcome and Solutions Applied". En Abu Dhabi International Petroleum Exhibition & Conference. SPE, 2021. http://dx.doi.org/10.2118/207491-ms.
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Abstract Control/Tracking Number 21 ADIP-P-4946-SPE Abstract Description This paper will present a case study to describe the well integrity complications of an onshore gas well in Romania affected by a landslide event, the challenges overcome during the land consolidation/excavation around the well, and the remediation solution of the well's casings. After being severely affected by a landslide, the subject well stopped production having a surface deviation from the original position of 5m and a landslide plane at cca 25m. The primary scope of the project was to restore the integrity of the well in order to safely abandon the well so that people and environment were not exposed to risk or danger. The project was elaborated through a collaborative effort of multidisciplinary teams including company personnel, such as well integrity engineers, completion engineers, geologists, abandonment team members, civil engineers, HSSE and construction, as well as several service providers. As part of the Phase to consolidate the well's surrounding area, additional risk mitigations were identified through HAZID workshops and implemented, such as creating gas drainage shafts, utilizing ATEX equipment and cold cutting tools for casings, tools, and organizing Rescue People Services. These elements and more aspects were elements of safety included in the project to better assure the success. The project has several milestones, the first being the consolidation of the well surroundings using 33 cement pillar rings with a total diameter of 8m and depth of 32m. A gas relief column was necessary to ensure the gas infiltration was exhausted from the soil. Once the ring was formed around the well, the excavation commenced inside the ring, avoiding impact with the conductor pipe of the well. This activity posed notable HSSE challenges, requiring solutions derived from HAZID workshops based on evaluations of the various discipline teams and certified parties. Following the excavation, the planned casing remediation included cold cutting the casing using diamond encrusted equipment, due to the gas presence at the well area. Casing restoration was planned for use of bolts to reconnect the casings, thus preventing welding.
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Firdaus, Muhammad, Anis Saggaff y Mahmood Md Tahir. "Finite element analysis of composite beam-to-column connection with cold-formed steel section". En PROCEEDINGS OF THE 3RD INTERNATIONAL CONFERENCE ON CONSTRUCTION AND BUILDING ENGINEERING (ICONBUILD) 2017: Smart Construction Towards Global Challenges. Author(s), 2017. http://dx.doi.org/10.1063/1.5011504.
Texto completoInformes sobre el tema "Cold formed elements"
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Shmulevich, Itzhak, Shrini Upadhyaya, Dror Rubinstein, Zvika Asaf y Jeffrey P. Mitchell. Developing Simulation Tool for the Prediction of Cohesive Behavior Agricultural Materials Using Discrete Element Modeling. United States Department of Agriculture, octubre de 2011. http://dx.doi.org/10.32747/2011.7697108.bard.
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The underlying similarity between soils, grains, fertilizers, concentrated animal feed, pellets, and mixtures is that they are all granular materials used in agriculture. Modeling such materials is a complex process due to the spatial variability of such media, the origin of the material (natural or biological), the nonlinearity of these materials, the contact phenomenon and flow that occur at the interface zone and between these granular materials, as well as the dynamic effect of the interaction process. The lack of a tool for studying such materials has limited the understanding of the phenomena relevant to them, which in turn has led to energy loss and poor quality products. The objective of this study was to develop a reliable prediction simulation tool for cohesive agricultural particle materials using Discrete Element Modeling (DEM). The specific objectives of this study were (1) to develop and verify a 3D cohesionless agricultural soil-tillage tool interaction model that enables the prediction of displacement and flow in the soil media, as well as forces acting on various tillage tools, using the discrete element method; (2) to develop a micro model for the DEM formulation by creating a cohesive contact model based on liquid bridge forces for various agriculture materials; (3) to extend the model to include both plastic and cohesive behavior of various materials, such as grain and soil structures (e.g., compaction level), textures (e.g., clay, loam, several grains), and moisture contents; (4) to develop a method to obtain the parameters for the cohesion contact model to represent specific materials. A DEM model was developed that can represent both plastic and cohesive behavior of soil. Soil cohesive behavior was achieved by considering tensile force between elements. The developed DEM model well represented the effect of wedge shape on soil behavior and reaction force. Laboratory test results showed that wedge penetration resistance in highly compacted soil was two times greater than that in low compacted soil, whereas DEM simulation with parameters obtained from the test of low compacted soil could not simply be extended to that of high compacted soil. The modified model took into account soil failure strength that could be changed with soil compaction. A three dimensional representation composed of normal displacement, shear failure strength and tensile failure strength was proposed to design mechanical properties between elements. The model based on the liquid bridge theory. An inter particle tension force measurement tool was developed and calibrated A comprehensive study of the parameters of the contact model for the DEM taking into account the cohesive/water-bridge was performed on various agricultural grains using this measurement tool. The modified DEM model was compared and validated against the test results. With the newly developed model and procedure for determination of DEM parameters, we could reproduce the high compacted soil behavior and reaction forces both qualitatively and quantitatively for the soil conditions and wedge shapes used in this study. Moreover, the effect of wedge shape on soil behavior and reaction force was well represented with the same parameters. During the research we made use of the commercial PFC3D to analyze soil tillage implements. An investigation was made of three different head drillers. A comparison of three commonly used soil tillage systems was completed, such as moldboard plow, disc plow and chisel plow. It can be concluded that the soil condition after plowing by the specific implement can be predicted by the DEM model. The chisel plow is the most economic tool for increasing soil porosity. The moldboard is the best tool for soil manipulation. It can be concluded that the discrete element simulation can be used as a reliable engineering tool for soil-implement interaction quantitatively and qualitatively.
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de Caritat, Patrice, Brent McInnes y Stephen Rowins. Towards a heavy mineral map of the Australian continent: a feasibility study. Geoscience Australia, 2020. http://dx.doi.org/10.11636/record.2020.031.
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Heavy minerals (HMs) are minerals with a specific gravity greater than 2.9 g/cm3. They are commonly highly resistant to physical and chemical weathering, and therefore persist in sediments as lasting indicators of the (former) presence of the rocks they formed in. The presence/absence of certain HMs, their associations with other HMs, their concentration levels, and the geochemical patterns they form in maps or 3D models can be indicative of geological processes that contributed to their formation. Furthermore trace element and isotopic analyses of HMs have been used to vector to mineralisation or constrain timing of geological processes. The positive role of HMs in mineral exploration is well established in other countries, but comparatively little understood in Australia. Here we present the results of a pilot project that was designed to establish, test and assess a workflow to produce a HM map (or atlas of maps) and dataset for Australia. This would represent a critical step in the ability to detect anomalous HM patterns as it would establish the background HM characteristics (i.e., unrelated to mineralisation). Further the extremely rich dataset produced would be a valuable input into any future machine learning/big data-based prospectivity analysis. The pilot project consisted in selecting ten sites from the National Geochemical Survey of Australia (NGSA) and separating and analysing the HM contents from the 75-430 µm grain-size fraction of the top (0-10 cm depth) sediment samples. A workflow was established and tested based on the density separation of the HM-rich phase by combining a shake table and the use of dense liquids. The automated mineralogy quantification was performed on a TESCAN® Integrated Mineral Analyser (TIMA) that identified and mapped thousands of grains in a matter of minutes for each sample. The results indicated that: (1) the NGSA samples are appropriate for HM analysis; (2) over 40 HMs were effectively identified and quantified using TIMA automated quantitative mineralogy; (3) the resultant HMs’ mineralogy is consistent with the samples’ bulk geochemistry and regional geological setting; and (4) the HM makeup of the NGSA samples varied across the country, as shown by the mineral mounts and preliminary maps. Based on these observations, HM mapping of the continent using NGSA samples will likely result in coherent and interpretable geological patterns relating to bedrock lithology, metamorphic grade, degree of alteration and mineralisation. It could assist in geological investigations especially where outcrop is minimal, challenging to correctly attribute due to extensive weathering, or simply difficult to access. It is believed that a continental-scale HM atlas for Australia could assist in derisking mineral exploration and lead to investment, e.g., via tenement uptake, exploration, discovery and ultimately exploitation. As some HMs are hosts for technology critical elements such as rare earth elements, their systematic and internally consistent quantification and mapping could lead to resource discovery essential for a more sustainable, lower-carbon economy.
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Wang, Wei, Michael Brown, Matteo Ciantia y Yaseen Sharif. DEM simulation of cyclic tests on an offshore screw pile for floating wind. University of Dundee, diciembre de 2021. http://dx.doi.org/10.20933/100001231.
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Screw piles need to be upscaled for offshore use e.g. being an alternative foundation and anchor form for offshore floating wind turbines, although the high demand of vertical installation forces could prevent its application if conventional pitch-matched installation is used. Recent studies, using numerical and centrifuge physical tests, indicated that the vertical installation force can be reduced by adopting over-flighting which also improved axial uplift capacity of the screw pile. The current study extends the scope to axial cyclic performance with respect to the installation approach. Using quasi-static discrete element method (DEM) simulation it was found that the over-flighted screw pile showed a lower displacement accumulation rate, compared to a pitch-matched installed pile, in terms of load-controlled cyclic tests. Sensitivity analysis of the setup of the cyclic loading servo shows the maximum velocity during the tests should be limited to avoid significant exaggeration of the pile displacement accumulation but this may lead to very high run durations.
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Roesler, Jeffery, Roberto Montemayor, John DeSantis y Prakhar Gupta. Evaluation of Premature Cracking in Urban Concrete Pavement. Illinois Center for Transportation, enero de 2021. http://dx.doi.org/10.36501/0197-9191/21-001.
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This study investigated the causes for premature, transverse cracking on urban jointed plain concrete pavements in Illinois. A field survey of 67 sections throughout Illinois coupled with ultrasonic evaluation was completed to synthesize the extent of premature cracking on urban JPCP. The visual survey showed some transverse and longitudinal cracks were a result of improper slab geometry (excessive slab length and width). Ultrasonic tests over the contraction joints determined some notched joints had not activated and adjacent transverse cracks were likely formed as a result. Three-dimensional finite-element analyses confirmed that cracking would not develop as a result of normal environmental factors and slab-base frictional restraint. The concrete mixture also did not appear to be a contributing factor to the premature cracks. Finally, the lack of lubrication on dowel bars was determined to potentially be a primary mechanism that could restrain the transverse contraction joints, produce excessive tensile stresses in the slab, and cause premature transverse cracks to develop.
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Matte, S., M. Constantin y R. Stevenson. Mineralogical and geochemical characterisation of the Kipawa syenite complex, Quebec: implications for rare-earth element deposits. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/329212.
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The Kipawa rare-earth element (REE) deposit is located in the Parautochton zone of the Grenville Province 55 km south of the boundary with the Superior Province. The deposit is part of the Kipawa syenite complex of peralkaline syenites, gneisses, and amphibolites that are intercalated with calc-silicate rocks and marbles overlain by a peralkaline gneissic granite. The REE deposit is principally composed of eudialyte, mosandrite and britholite, and less abundant minerals such as xenotime, monazite or euxenite. The Kipawa Complex outcrops as a series of thin, folded sheet imbricates located between regional metasediments, suggesting a regional tectonic control. Several hypotheses for the origin of the complex have been suggested: crustal contamination of mantle-derived magmas, crustal melting, fluid alteration, metamorphism, and hydrothermal activity. Our objective is to characterize the mineralogical, geochemical, and isotopic composition of the Kipawa complex in order to improve our understanding of the formation and the post-formation processes, and the age of the complex. The complex has been deformed and metamorphosed with evidence of melting-recrystallization textures among REE and Zr rich magmatic and post magmatic minerals. Major and trace element geochemistry obtained by ICP-MS suggest that syenites, granites and monzonite of the complex have within-plate A2 type anorogenic signatures, and our analyses indicate a strong crustal signature based on TIMS whole rock Nd isotopes. We have analyzed zircon grains by SEM, EPMA, ICP-MS and MC-ICP-MS coupled with laser ablation (Lu-Hf). Initial isotopic results also support a strong crustal signature. Taken together, these results suggest that alkaline magmas of the Kipawa complex/deposit could have formed by partial melting of the mantle followed by strong crustal contamination or by melting of metasomatized continental crust. These processes and origins strongly differ compare to most alkaline complexes in the world. Additional TIMS and LA-MC-ICP-MS analyses are planned to investigate whether all lithologies share the same strong crustal signature.
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Carlson, John. Nuclear verification in a Middle East WMD-Free Zone: Lessons from Past Verification Cases and Other Precedents. The United Nations Institute for Disarmament Research, enero de 2021. http://dx.doi.org/10.37559/wmdfz/21/nv/01.
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Verification will be of critical importance to achieving and maintaining a Middle East zone free of weapons of mass destruction (ME WMD). Effective verification arrangements would serve a vital national security objective for each state in the region by reducing tensions, removing the motivation to proliferate, and mitigating the risk of a virtual nuclear arms race (or war). In view of the high levels of tension and mistrust within the zone, ensuring effective verification will be especially demanding. The paper examines specific elements of the future nuclear verification of the zone, including: Which states should be included? What prohibitions and obligations should apply in the zone and how would they be verified? How could elimination of nuclear weapons in the zone be achieved? On what basis would the zone treaty enter into force? The paper also examines a number of existing treaties and arrangements as well as the lessons learned from past verification cases which regional states can draw on in developing verification for a Middle East nuclear-weapon-free zone.
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Al-Qadi, Imad, Egemen Okte, Aravind Ramakrishnan, Qingwen Zhou y Watheq Sayeh. Truck Platooning on Flexible Pavements in Illinois. Illinois Center for Transportation, mayo de 2021. http://dx.doi.org/10.36501/0197-9191/21-010.
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Truck platoons have many benefits over traditional truck mobility. Truck platoons have the potential to improve safety and reduce fuel consumption between 5% and 15%, based on platoon configuration. In Illinois, trucks carry more than 50% of freight tonnage and constitute 25% of the traffic on interstates. Therefore, expected fuel savings would be significant for trucks. Deployment of truck platoons within interstate highways may have a direct effect on flexible pavement performance, as the time between consecutive axle loads (i.e., resting time) is expected to decrease significantly. Moreover, platoons could potentially accelerate pavement damage accumulation due to trucks’ channelized position, decreasing pavement service life and increasing maintenance and rehabilitation costs. The main objective of this project was to quantify the effects of truck platoons on pavements and to provide guidelines to control corresponding potential pavement damage. Finite-element models were utilized to quantify the impact of rest period on pavement damage. Recovered and accumulated strains were predicted by fitting exponential functions to the calculated strain profiles. The results suggested that strain accumulation was negligible at a truck spacing greater that 10 ft. A new methodology to control pavement damage due to truck platoons was introduced. The method optimizes trucks’ lateral positions on the pavements, and an increase in pavement service life could be achieved if all platoons follow this optimization method. Life cycle assessment and life cycle cost analysis were conducted for fully autonomous, human-driven, and mixed-traffic regimes. For example, for an analysis period of 45 years, channelized truck platoons could save life cycle costs and environmental impacts by 28% and 21% compared with human-driven trucks, respectively. Furthermore, optimum truck platoon configuration could reduce life cycle costs and environmental impacts by 48% and 36%, respectively, compared with human-driven trucks. In contrast, channelized traffic could increase pavement roughness, increasing fuel consumption by 15%, even though platooning vehicles still benefit from reduction in air drag forces. Given that truck platoons are expected to be connected only in the first phase, no actions are required by the agency. However, in the second phase when truck platoons are also expected to be autonomous, a protocol for driving trends should be established per the recommendation of this study.
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Pullammanappallil, Pratap, Haim Kalman y Jennifer Curtis. Investigation of particulate flow behavior in a continuous, high solids, leach-bed biogasification system. United States Department of Agriculture, enero de 2015. http://dx.doi.org/10.32747/2015.7600038.bard.
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Recent concerns regarding global warming and energy security have accelerated research and developmental efforts to produce biofuels from agricultural and forestry residues, and energy crops. Anaerobic digestion is a promising process for producing biogas-biofuel from biomass feedstocks. However, there is a need for new reactor designs and operating considerations to process fibrous biomass feedstocks. In this research project, the multiphase flow behavior of biomass particles was investigated. The objective was accomplished through both simulation and experimentation. The simulations included both particle-level and bulk flow simulations. Successful computational fluid dynamics (CFD) simulation of multiphase flow in the digester is dependent on the accuracy of constitutive models which describe (1) the particle phase stress due to particle interactions, (2) the particle phase dissipation due to inelastic interactions between particles and (3) the drag force between the fibres and the digester fluid. Discrete Element Method (DEM) simulations of Homogeneous Cooling Systems (HCS) were used to develop a particle phase dissipation rate model for non-spherical particle systems that was incorporated in a two-fluid CFDmultiphase flow model framework. Two types of frictionless, elongated particle models were compared in the HCS simulations: glued-sphere and true cylinder. A new model for drag for elongated fibres was developed which depends on Reynolds number, solids fraction, and fibre aspect ratio. Schulze shear test results could be used to calibrate particle-particle friction for DEM simulations. Several experimental measurements were taken for biomass particles like olive pulp, orange peels, wheat straw, semolina, and wheat grains. Using a compression tester, the breakage force, breakage energy, yield force, elastic stiffness and Young’s modulus were measured. Measurements were made in a shear tester to determine unconfined yield stress, major principal stress, effective angle of internal friction and internal friction angle. A liquid fludized bed system was used to determine critical velocity of fluidization for these materials. Transport measurements for pneumatic conveying were also assessed. Anaerobic digestion experiments were conducted using orange peel waste, olive pulp and wheat straw. Orange peel waste and olive pulp could be anaerobically digested to produce high methane yields. Wheat straw was not digestible. In a packed bed reactor, anaerobic digestion was not initiated above bulk densities of 100 kg/m³ for peel waste and 75 kg/m³ for olive pulp. Interestingly, after the digestion has been initiated and balanced methanogenesis established, the decomposing biomass could be packed to higher densities and successfully digested. These observations provided useful insights for high throughput reactor designs. Another outcome from this project was the development of low cost devices to measure methane content of biogas for off-line (US$37), field (US$50), and online (US$107) applications.
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Neyedley, K., J. J. Hanley, P. Mercier-Langevin y M. Fayek. Ore mineralogy, pyrite chemistry, and S isotope systematics of magmatic-hydrothermal Au mineralization associated with the Mooshla Intrusive Complex (MIC), Doyon-Bousquet-LaRonde mining camp, Abitibi greenstone belt, Québec. Natural Resources Canada/CMSS/Information Management, 2021. http://dx.doi.org/10.4095/328985.
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The Mooshla Intrusive Complex (MIC) is an Archean polyphase magmatic body located in the Doyon-Bousquet-LaRonde (DBL) mining camp of the Abitibi greenstone belt, Québec. The MIC is spatially associated with numerous gold (Au)-rich VMS, epizonal 'intrusion-related' Au-Cu vein systems, and shear zone-hosted (orogenic?) Au deposits. To elucidate genetic links between deposits and the MIC, mineralized samples from two of the epizonal 'intrusion-related' Au-Cu vein systems (Doyon and Grand Duc Au-Cu) have been characterized using a variety of analytical techniques. Preliminary results indicate gold (as electrum) from both deposits occurs relatively late in the systems as it is primarily observed along fractures in pyrite and gangue minerals. At Grand Duc gold appears to have formed syn- to post-crystallization relative to base metal sulphides (e.g. chalcopyrite, sphalerite, pyrrhotite), whereas base metal sulphides at Doyon are relatively rare. The accessory ore mineral assemblage at Doyon is relatively simple compared to Grand Duc, consisting of petzite (Ag3AuTe2), calaverite (AuTe2), and hessite (Ag2Te), while accessory ore minerals at Grand Duc are comprised of tellurobismuthite (Bi2Te3), volynskite (AgBiTe2), native Te, tsumoite (BiTe) or tetradymite (Bi2Te2S), altaite (PbTe), petzite, calaverite, and hessite. Pyrite trace element distribution maps from representative pyrite grains from Doyon and Grand Duc were collected and confirm petrographic observations that Au occurs relatively late. Pyrite from Doyon appears to have been initially trace-element poor, then became enriched in As, followed by the ore metal stage consisting of Au-Ag-Te-Bi-Pb-Cu enrichment and lastly a Co-Ni-Se(?) stage enrichment. Grand Duc pyrite is more complex with initial enrichments in Co-Se-As (Stage 1) followed by an increase in As-Co(?) concentrations (Stage 2). The ore metal stage (Stage 3) is indicated by another increase in As coupled with Au-Ag-Bi-Te-Sb-Pb-Ni-Cu-Zn-Sn-Cd-In enrichment. The final stage of pyrite growth (Stage 4) is represented by the same element assemblage as Stage 3 but at lower concentrations. Preliminary sulphur isotope data from Grand Duc indicates pyrite, pyrrhotite, and chalcopyrite all have similar delta-34S values (~1.5 � 1 permille) with no core-to-rim variations. Pyrite from Doyon has slightly higher delta-34S values (~2.5 � 1 permille) compared to Grand Duc but similarly does not show much core-to-rim variation. At Grand Duc, the occurrence of Au concentrating along the rim of pyrite grains and associated with an enrichment in As and other metals (Sb-Ag-Bi-Te) shares similarities with porphyry and epithermal deposits, and the overall metal association of Au with Te and Bi is a hallmark of other intrusion-related gold systems. The occurrence of the ore metal-rich rims on pyrite from Grand Duc could be related to fluid boiling which results in the destabilization of gold-bearing aqueous complexes. Pyrite from Doyon does not show this inferred boiling texture but shares characteristics of dissolution-reprecipitation processes, where metals in the pyrite lattice are dissolved and then reconcentrated into discrete mineral phases that commonly precipitate in voids and fractures created during pyrite dissolution.
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Chen, Yona, Jeffrey Buyer y Yitzhak Hadar. Microbial Activity in the Rhizosphere in Relation to the Iron Nutrition of Plants. United States Department of Agriculture, octubre de 1993. http://dx.doi.org/10.32747/1993.7613020.bard.
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Iron is the fourth most abundant element in the soil, but since it forms insoluble hydroxides at neutral and basic pH, it often falls short of meeting the basic requirements of plants and microorganisms. Most aerobic and facultative aerobic microorganisms possess a high-affinity Fe transport system in which siderophores are excreted and the consequent Fe complex is taken up via a cognate specific receptor and a transport pathway. The role of the siderophore in Fe uptake by plants and microorganisms was the focus of this study. In this research Rhizopus arrhizus was found to produce a novel siderophore named Rhizoferrin when grown under Fe deficiency. This compound was purified and its chemical structure was elucidated. Fe-Rhizoferrin was found to alleviate Fe deficiency when applied to several plants grown in nutrient solutions. It was concluded that Fe-Rhizoferrin is the most efficient Fe source for plants when compared with other among microbial siderophores known to date and its activity equals that of the most efficient synthetic commercial iron fertilizer-Fe EDDHA. Siderophores produced by several rhizosphere organisms including Rhizopus Pseudomonas were purified. Monoclonal antibodies were produced and used to develop a method for detection of the siderophores produced by plant-growth-promoting microorganisms in barley rhizosphere. The presence of an Fe-ferrichrome uptake in fluorescent Pseudomonas spp. was demonstrated, and its structural requirements were mapped in P. putida with the help of biomimetic ferrichrome analogs. Using competition experiments, it was shown that FOB, Cop B and FC share at least one common determinant in their uptake pathway. Since FC analogs did not affect FOB or Cop-mediated 55Fe uptake, it could be concluded that these siderophores make use of a different receptor(s) than FC. Therefore, recognition of Cop, FOB and FC proceeds through different receptors having different structural requirements. On the other hand, the phytosiderophores mugineic acid (MA and DMA), were utilized indirectly via ligand exchange by P. putida. Receptors from different biological systems seem to differ in their structural requirements for siderophore recognition and uptake. The design of genus- or species-specific drugs, probes or chemicals, along with an understanding of plant-microbe and microbe-microbe relationships as well as developing methods to detect siderophores using monoclonal antibodies are useful for manipulating the composition of the rhizosphere microbial population for better plant growth, Fe-nutrition and protection from diseases.