Cold Formed Steel

The seismic behavior of sheathed cold-formed steel (SCFS) structures is characterized by the lateral response of shear walls. Basically, if cold-formed steel (CFS) structures are designed according to the “sheathing-design” methodology, then the seismic behavior of shear walls is strongly influenced by the sheathing-to-frame connections response, characterized by a remarkable nonlinear response and a strong pinching of hysteresis loops. In this paper the results of an extensive parametric non linear dynamic analysis, carried out on one story buildings by means of incremental dynamic analysis (IDA), using an ad hoc model of the hysteresis response of SCFS shear walls, are presented. An extended number of wall configurations has been considered investigating several parameters such as sheathing panel typology, wall geometry, external screw spacing, seismic weight and soil type. Based on IDA results, three behavior factors have been defined, which take into account overstrength, ductility and both overstrength and ductility, respectively. Finally, a design nomograph for the seismic design of single-storey SCFS frame structures developed on the basis of non-linear dynamic analysis results is presented. This last aims to complete a proposal of a design methodology, already presented by the author in the last years.► The seismic behavior of sheathed CFS shear walls is under investigation. ► Parametric non linear dynamic analysis results of SCFS structures are presented. ► Three behavior factors for sheathed CFS structures have been defined. ► A nomograph for the seismic design of SCFS frame structures is presented. ► The procedure applicability is demonstrated through the design of a typical house.

Steel storage racks are three-dimensional framed structures fabricated from cold formed steel sections, wherein hook-in end connectors are used to make beam–column connections which are basically boltless and semi-rigid in nature. Different types of beam end connectors with different geometry of the connected members are available, making it impossible to develop a generalized analytical model. Only very few theoretical models are available to evaluate the performance of the joints for some typical connectors. More often experimental evaluation and numerical studies are needed to predict the behaviour of every different type of connectors. In the present study eighteen experiments were conducted on a commercially available pallet rack connection by varying the most influencing parameters such as thickness of the column, depth of the connector and the depth of the beam. The main objective of this work is to quantify the beam to column joint, flexibility of commonly used pallet rack frame and to develop a general Frye–Morris type/three parameter power model type moment versus relative rotation relationship. A companion finite element shell model that simulates the experimental behaviour closely is developed using ABAQUS finite element software, which is also used for further parametric studies. Using the three major variables as size parameters, a Frye–Morris type of equation has been proposed. Some calibration studies have also been carried out. Using the ultimate moment capacity, initial connection stiffness and the shape parameter obtained, a three parameter power model has also been proposed to represent the moment–rotation behaviour of the boltless connections.

A finite element analysis model for the post-local buckling behaviour of cold-formed steel (CFS) members subjected to axial compression has been developed. The finite element model consists of a Total Lagrangian nonlinear 9-node “assumed strain” shell finite element, and experimental-based material properties models to represent the body of the CFS sections. Experimentally derived residual stress variations, and initial geometric imperfections have also been incorporated. A special loading technique and a displacement solution algorithm were employed to obtain a uniform displacement condition at the loading edges. Details of a test program involving 20 non-perforated, and perforated cold-formed stub-column steel sections have been presented in the second part of the paper. The comparison between the test results, and the finite element results was performed for axial and lateral displacement behaviour, buckling loads, ultimate loads, and axial stress distribution. The comparison forms the basis for the evaluation of the efficiency, and the accuracy of the finite element model, and it indicated that the finite element analysis model constructed herein gives accurate and consistent results for the behaviour of the cold-formed steel members subjected to axial compression.

The “green” benefits of CFS construction can be re-garded in terms of:
shorter build times;
reduced material waste;
reduced environmental impact;
less noise, airborne contamination and CO2 emissions
reduced overall transport requirements;
less disruption to local services, infrastructure and road closures;
flexibility in long-term use;
greater build accuracy;
ease of extension and adaptation;
safer working conditions in factories for construction workers;
recycling and re-use of the elements.
All these advantages show a construction technology that have left the experimental phase by years and present itself fit by now to be widely used especially in housing sector. Obstacles to an increased utilization of CFS systems are often associated with the ability of the design and construction community to respond to the opportunity and new ways of working rather than to any fundamental shortcomings in light steel framed solutions.

This paper describes a series of bending and compression tests to investigate the Class 1 or compact web slenderness limit for cold-formed rectangular hollow sections (RHS) for use in plastic design.Details of the test rig are supplied and the results given. The results show that the rate at which the rotation capacity decreases with increasing axial compression is dependent on the aspect ratio of the section, but further finite element simulation is required to investigate the effect of geometric imperfections

In architettura non è frequente descrivere un nuovo sistema tecnologico, un nuovo modo di sviluppare e considerare le correlazioni e gli aspetti tecnici tra le parti che costituiscono il sistema ambientale e, così, l’edificio. Non è frequente perché nella pratica edilizia difficilmente entrano innovazioni radicali, in virtù delle quali si possa descrivere una nuova articolazione di elementi tecnici, pratiche costruttive, strategie progettuali e obiettivi. L’innovazione della componente materiale dell’architettura è più spesso figlia delle trasformazioni che delle rivoluzioni.
Il sistema tecnologico che prevede l’impiego dei profili in acciaio sagomato a freddo (Cold Formed Steel, CFS) porta al progetto, la produzione e la messa in opera di telai leggeri (Lightweight Steel Frame, LSF) e l’evoluzione tecnica della produzione industrializzata consente di progettare edifici con lo stesso livello di dettaglio che si ha nel disegno industriale di oggetti prodotti on demand. Progettare edifici con strutture a telaio realizzate con acciaio spesso un millimetro (o poco più) non è usuale nel contesto italiano. Altrettanto nuovo è descrivere come sia possibile impiegare tale tecnologia, quali sono le pratiche consolidate e quali i confini d’innovazione sui quali fondare il proprio progetto. Per affrontare queste sfide è importante tener saldi quegli esempi, pochi, che hanno per primi in Italia mostrato le potenzialità del materiale e del processo progettuale che porta alla costruzione di un edificio in lightweight steel frame.
Ampliando il contesto di riferimenti, uscendo dall’ambito italiano, è possibile leggere le recenti evoluzioni di un quadro normativo europeo: strumenti per la progettazione e ambito di ricerca ingegneristica. Si trovano edifici che impiegano l’acciaio sagomato a freddo in abbinamento con legno, calcestruzzo armato e acciaio: le aste di CFS vengono sfruttate per la loro leggerezza, la pre- cisa esecuzione e la semplice lavorabilità sia in stabilimento che in cantiere.
I rimandi alle prime normative per il dimensionamento strutturale portano al confronto con le ricerche della Cornell University e i rendiconti degli istituti e dei consorzi di costruttori americani.
Il confronto con il nuovo contesto economico dell’edilizia e alcune sue industrie forti, mostra come la costruzione in LSF possa ampliare il mercato e offrire una radicale innovazione nel modo di progettare.
Lo studio del contesto storico smorza l’euforia di chi pensa di trovarsi al confronto con una profonda novità, una radicale trasformazione dei modi di costruire. Lo studio del contesto storico carica di consapevolezza e fonda le intenzioni di chi ha dinnanzi a sé la possibilità di impiegare una soluzione che non è solamente strutturale ma è tecnologica, di sistema.
Un sistema che non è complesso nella lavorazione in cantiere ma che è raffinato nella preparazione in officina e innovativo per gli spunti che derivano dall’impiego di software avanzati, che consentono non solo la progettazione di un edificio nel luogo e per le esigenze espresse ma anche lo sviluppo dell’architettura più complessa, che è fatta delle relazioni con la nuova dimensione dell’ecocompatibilità, con la quale ogni realizzazione e produzione è chiamata a confronto.
Il sistema LSF è frutto delle innovazioni incrementali: le prime lavorazioni del metallo a spessori sottili impiegate in architettura hanno sviluppato dettagli, hanno prodotto macchinari e hanno subito e sfruttato le contaminazioni con altri settori. Le rivoluzioni industriali hanno portato i progettisti e i pensatori a paragonare gli edifici ad automobili, ad aerei e a navi: si parla di industria- lizzazione edilizia e di progetti che gli architetti stessi riconoscevano come di rottura rispetto ad una prassi produttiva che, di fatto, non esisteva se non nell’artigianalità del cantiere.
Il sistema LSF deve molto anche ai grandi sconvolgimenti della storia. La conquista del west ha costellato l’America di edifici in telaio di legno (balloon frame), tanto simile al telaio d’acciaio realizzato con profili leggeri. La ricostruzione postbellica giapponese ha consentito di sviluppare una prefabbricazione dell’edilizia che sta ancora innovando e ricercando i limiti delle costruzioni in acciaio sagomato a freddo.
Il sistema LSF si offre alle innovazioni radicali del nostro tempo. Progettare con l’acciaio sagomato a freddo sposta il tempo dello sviluppo dell’architettura dal cantiere al progetto.
La costruzione di un’architettura complessa non allunga i tempi di produzione delle aste o la messa in opera ma porta il progettista a sviluppare articolati sistemi di relazione e dialogo con le figure specialistiche necessarie a rendere altamente prestazionali gli edifici. Anche il confronto con gli utenti e i committenti può essere ampliato e i nuovi scenari di innovazione e sviluppo prefigurati dalle ricerche mostrano come questo dialogo possa essere duraturo quanto e più del tempo di vita utile del costruito e possa coinvolgere molte più persone di quante vivranno o vedranno il nuovo edificio.

A diaphragm is an assembly of planar structural elements interconnected to each other to provide in-plane bracing system and transmit in-plane forces. The diaphragm geometry, supporting frame, type of the panel profiles, the way the panels are attached to each other and to the diaphragm frame govern the overall behavior of diaphragm systems. Full scale testing is the best way to understand the overall behavior and determine the strength and stiffness of diaphragm systems. This paper is a result of experimental and analytical studies on aluminum roof panel assemblies. The main purpose is to check the applicability of Metal Construction Association's (MCA) " Primer on Diaphragm Design " for the strength and stiffness equations when applied over a range of panel depths, thicknesses and profiles. Five full scale cantilever tests were conducted at Virginia Tech, Blacksburg, Virginia. The tests were conducted in accordance with the AISI " Cantilever Test Method for Cold-Formed Steel Diaphragms ". While the diaphragm shear stiffness development is similar for both MCA and Steel Deck Institute's (SDI) " Diaphragm Design Manual " , the only difference is the panel edge term (K). The results of this study show remarkably narrow scatter in tested-to-calculated strength ratios. The tested-to-calculated stiffness ratios compare very well, supporting the proposed use of panel edge term (K ¼2/3) for aluminum diaphragms. The results indicate that the panel thickness limit can be raised safely to 1.27 mm (0.050 in.) for MCA procedures. The test data further indicate that the MCA strength and stiffness formulations work well for panels with depths through 101.6 mm (4 in.).

As technology advances, the search for a durable and stronger construction material continues. The necessity for an eco-friendly, economical, and faster methods of construction is crucial. Many smart materials and construction methods have been put to test in the past few years, while others are still under development. In this article, the study of LGS (Light Gauge is steel) is carried out to determine the problems, effectiveness, advantages and disadvantages of using this construction method.

Seismic design provisions of Cold-Formed Steel–Special Bolted Moment Frames in the proposed AISI Seismic Standard were developed on the basis that ductility capacity is provided through bolt slippage and bearing in bolted beam-to-column moment connections, and that beams and columns are to remain elastic at the design story drift to resist the maximum force that can be developed in the connections. Based on the instantaneous centre of rotation analysis procedure, both the slip and bearing components of the connection resistance, expressed in the form of column shear and story drift, are presented and design values tabulated.

The effective sectional area concept was adopted to conduct the analysis of cold-formed Tension members. ANSYS software was utilized to simulate the behavior of cold formed steel angle under tension load. The paper describes the results from a finite element investigation into the load capacity tension members of single angle sections and double angles sections of 1.5 mm and 1.6 mm under plain (without Lipped) and with Lipped conditions subjected to tension. Results were recorded as the load carrying capacity increases for connected to the opposite side of the gusset than the connected to same side. It observed load vs deflection, Analyses are compared with experimental results.

In recent years important research activity has been undertaken in order to evaluate the earthquake performance of light-gauge steel-framed house structures. Almost all studies approach the problem of seismic response of these structures by characterising, experimentally and numerically, the performance of wall panels. Usually, the overall behavior of wall panels is mainly addressed. However, according to experimental evidences, the performance of the wall panels, as a whole, is governed by the performance of the connectors e.g.: sheeting-to-sheeting connectors, and sheeting-to-framing connectors. On the other hand the global behavior of the 3D structure of the house is significantly influenced by non-structural elements, traditionally not considered in the design procedures. The present paper summarizes the research activity carried out in the last few years at the Politehnica University of Timisoara, under the coordination of the author, with the aim to evaluate the performance and to characterise for design purpose the specific features of these structures. Monotonic and cyclic tests on full-scale shear panels, tests on connection details, and in situ ambiental vibration tests on a house under construction are reviewed and concluded in the following paper.

The use of cold-formed open thin-walled steel sections in the various types of engineering construction has increased with the economic necessity of providing high strength with low weight and cost. Thus open thin-walled sections are replacing massive reinforced concrete beams in many types of construction. The developed algorithm for this study obtains the optimum cross-sectional dimensions of cold-formed open thin-walled steel beams under general loading. The width, depth, and wall thickness of the thin-walled section is treated as design variables and the displacement as well as stress limitation is taken into account in the algorithm presented. Since the existence of torsional moments in thin-walled sections, warping must be considered. Vlasov theory is used to calculate the normal and shear stresses that occur due to warping. The optimum design problem obtained turn out to be mixed integer and discrete programming problem. Harmony search algorithm is used to obtain its solution. This technique is a recent numerical optimization technique which mimics the musical performance process. The recent studies with the harmony search method have shown its effectiveness and robustness in finding the optimum solution of combinatorial optimization problems. A design example is included to demonstrate the efficiency of the optimum design algorithm developed.

This paper presents the analysis of cold formed steel frames with light weight concrete as infill material. Light weight material is usually being chosen for earthquake resistant design in order to reduce inertia force of the building, gives lateral confinement, strength and Stiffness to the hollow structural components. Connection design has become more critical in cold formed structures. Moment resisting frame with semi-rigid beam to column connections are analysed in the present study. The safe connection details of the frame having seated angles with stiffener plates are analysed by FEM software ANSYS. Stiffeners are provided at different locations to seated angles to facilitate increase in stiffness of connection. The analysis showed better results for connection with middle stiffener plate as centroid of both seat angle and stiffener plate coincides. The results drawn from the analysis would provide valuable suggestions to the design engineers.

The effective sectional area concept was adopted to conduct the analysis of cold-formed Tension members. ANSYS software was utilized to simulate the behavior of cold formed steel angle under tension load. The paper describes the results from a finite element investigation into the load capacity tension members of single angle sections of 2mm and double angles sections of 2mm under plain (without Lipped) and with Lipped conditions subjected to tension. Comparisons were made between the test results and the predictions based on both the Experimental investigation and the ANSYS analysis. Results also comparisons were made by the International codes BIS, AISI, AS/NZS and BS.

Thin walled cold-formed steel sections are widely used in the construction industry as primary structural and nonstructural components because of their light weight and high strength properties. SupaCee sections are new sections with
strengthened cross section than the traditional lipped channel section. This study investigated the distortional buckling
behaviour of cold formed SupaCee beams provided with various shapes of web perforations and also with crimped flanges. Web
openings are provided in the beam sections to allow access for building services like electric wires and pipelines. Past researches
have shown that the introduction of holes causes reduction of both buckling capacity and strength of the member. In this study,
the effect of web hole shapes in the distortional buckling of cold-formed SupaCee beams were analysed and the best perforated
SupaCee model was compared with the model without web openings. Crimps were introduced into the flanges of best perforated
model obtained for the strengthening purpose. The finite element modelling and analysis is done by using ANSYS workbench
16.1 software. From this investigation it is obtained that SupaCee beam with hexagonal web perforations shows the best result
and introduction of crimped flanges increased the buckling resistance of the section. The comparison study with the nonperforated model shows that the introduction of holes into the SupaCee beam section reduced the load carrying capacity of the
member.

Penelitian ini dilakukan karena dilatarbelakangi oleh fakta bahwa struktur rangka atap cold-formed steel (CFS) selain memiliki kelemahan akibat pengaruh inersia penampang juga memiliki sensitivitas pada sambungan yang memicu kegagalan struktur. Perlemahan pada struktur rangka atap CFS menyebabkan kekakuan yang relatif lebih rendah, sehingga kegagalan tekuk lentur dan torsi dapat terjadi. Selain itu, perlemahan pada sambungan CFS juga mengurangi kapasitas struktur untuk menahan beban yang bekerja. Hal tersebut menyebabkan deformasi yang berlebihan serta struktur tidak sesuai digunakan sebagai elemen utama penahan beban karena transfer gaya terjadi secara tidak merata. Oleh karena itu, berbagai penelitian dilakukan sebagai upaya peningkatan perilaku struktur CFS khususnya pada daerah sambungan rangka atap sehingga struktur dapat digunakan dengan aman dan kelebihan yang dimiliki jenis struktur ini dapat dimanfaatkan. Penelitian ini bertujuan untuk menganalisis perilaku sambungan CFS yaitu untuk mengetahui kapasitas sambungan dalam memikul beban maksimum melalui permodelan secara numerik. Material yang digunakan pada penelitian ini adalah profil CFS berdasarkan design code, sedangkan 2 jenis adhesive yaitu Sikadur 31 CF Normal dan JB weld diberikan pada sambungan rangka CFS. Studi numerik dilakukan dengan dua buah benda uji yaitu sambungan truss dengan sudut 45˚ dan 90˚ menggunakan dimensi penampang 76 × 44 × 11 × 1 mm. Kemudian, variasi baut yang digunakan adalah 2 baut dan 3 baut, sedangkan untuk variasi adhesive berdasarkan fraksi volume dari luasan area sambungan adalah 100%, 75% dan 50%. Pemilihan variasi jumlah baut dan adhesive yang berbeda dilakukan untuk mengetahui konfigurasi yang optimum dalam mereduksi beban yang terjadi. Studi juga melihat perilaku beban-deformasi dan juga mode kerusakan pada sambungan sesuai dengan variasi model. Hasil penelitian diharapkan dapat meningkatkan perilaku struktur dalam memikul beban khususnya dalam peningkatan kapasitas sambungan sehingga struktur CFS memiliki kekakuan awal yang baik serta memiliki daktilitas yang cukup signifikan.

Light gauge steel lipped channel sectiοns are being used pοpularly in shοps, factοries, autοmοbile engineering and industries οn accοunt οf their high strength tο width ratiο, simplicity in cοnstructiοn, flexibility in fabricatiοn and high structural efficiency. A lοt οf research wοrk has been carried οut tο study the structural behaviοr οf axially lοaded light gauge steel lipped cοlumn sectiοns cοnsidering different parameters. Hοwever, structural behaviοr οf light gauge steel lipped channel sectiοns under eccentric lοading has nοt received much attentiοn. The present paper fοcuses οn the review οf behaviοur οf the light gauge cοlumn sectiοn under lοading.

An inelastic semi-analytical finite strip method is used to analyse the local buckling behaviour of cold formed steel plates of composite steel-concrete structural elements at elevated temperatures. The decrease in yield stress and elastic modulus of the cold ...

Cold-formed steel sections are used joists, Barriers and floor decking in construction industry for past several decades. The development of the cold formed steel tubular sections is being used in beams, columns and truss members of residential buildings and industrial buildings. Generally a tubular section fails due to torsional buckling, local buckling and distortional buckling. In order to overcome this failure in-filled material is used to avoid those buckling. This will have limiting width- to- thickness ratio or diameter –to-thickness ratio. In the present study in-filled material is used as light weight concrete. A non-linear Finite Element modeling is done to analyze cold-formed steel in-filled frame section for residential building under static loading using ANSYS12.WORKBENCH. Beam column joints are connected by welding through gusset plate. Deflection characteristics, stresses and strains to the frame are analysed.