Cold Formed Steel Structures

The goal of the present research is the distortional-global (D-G) buckling interaction of cold-formed steel (CFS) lipped channel (LC) columns, in its buckling, structural behavior and strength nature. Some studies on this topic have been conducted in the literature, however, the D-G interaction is not well known and needs more attention.
For an elastic buckling analysis, a software entitled FStr Computer Application Program is developed. The application is based on the Finite Strip Method, mainly focused in a simple and accessible interface. The FStr program generates the modal shapes and insert as initial geometric imperfections in the finite element software ANSYS, in order to perform a geometric and material nonlinear analysis. Both, the FStr program and the finite element model are validated with available numerical examples and laboratory tests from the literature. Moreover, for the structural behavior and column strength, it is carried out stability paths from previous nonlinear analysis, for different combination of initial geometric imperfection of global and distortional modes. The buckling mode combination as initial geometric imperfection helps to understand the D-G buckling interaction, which is difficult to predict with a simple elastic buckling analysis. The results of the initial imperfection combination have shown that, for high yielding steel, the global initial geometric imperfection provides the most detrimental ultimate load. Additionally, a parametric study varying the column’s length have shown that the nominal axial strength for global buckling equation, already in the standards, is enough to cover the DG coupled phenomenon.

As our country (India) is the fastest growing country across the globe and need of shelter with higher land cost in major cities like Mumbai, Delhi, Ahmedabad, Vadodara where further horizontal expansion is not much possible due to space shortage, we are left with the solution of vertical expansion. In India reinforced concrete structures are mostly used since this is the most convenient & economic system for low-rise buildings. However, after a certain height of structure for medium to high-rise buildings this type of structure is no longer economic because of increased dead load, less stiffness, span restriction, low natural frequency and hazardous formwork. So, the Structural engineers are facing the challenge of striving for the most efficient and economical design solution while ensuring that the final design of a building must be serviceable for its intended function, habitable for its occupants and safe over its design lifetime. Steel and concrete composite structures are becoming a more and more common solution for buildings, since its structural efficiency and fast erection methods make its use economically competitive. Use of composite material is of particular interest, due to its significant potential in improving the overall performance through rather modest changes in manufacturing and constructional technologies. The results of this work show that the Steel Structures are the best solution for high rise structure as compared to R.C.C structure as shown in literature is for commercial buildings having large span. Comparative study includes deflection, axial force and shear force, bending moment in column and beam, cost. In this project study of various multi-storeyed residential buildings like G+7, G+14, G+21 are analysed by using STAAD-Pro software.

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.).

The objective of this paper is to present an efficient spring-element and frame-element based finite element model of an OSB sheathed cold-formed steel framed shear wall that includes nonlinear hysteretic behavior from damage at the stud-to-sheathing connectors and the potential for buckling of the chord studs. The model is developed in OpenSees and has the potential to be an important building block tool towards modeling full structures framed from cold-formed steel. The authors have recently shown that OpenSees models that include nonlinear stud-to-sheathing fasteners, calibrated only to fastener-level tests, are capable of predicting full shear wall hysteretic performance as long as chord stud buckling or other limit states do not occur. Further, in other work, the authors have experimentally characterized the hysteretic performance of chord studs and developed phenomenological models appropriate for the frame-element in OpenSees. In this work, the two models are brought together to provide a highly adept shear wall model capable of capturing both fastener-based and member-based limit states in the shear wall. The model provides a means to explore the role of gravity load in the shear wall performance, and to study sensitivity of shear walls to these two competing limit states. Thus, the model provides practical design advantages and also provides a means to explore reliability of the shear wall as a system. The long-term goals of the work are to create advanced analysis tools for cold-formed steel seismic design and system reliability knowledge that supports the use of those tools in models and designs of complete buildings.

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.

The wide availability of high strength cold-formed steel profile enable engineers to use it for structural purpose. Due to its low strength to weight ratio, the building with cold-formed steel profiles is suitable for region with high seismic activity. Application of such thin and small section profile requires truss assembly for column and beams, requiring more efforts in modeling and resulting in large degree of freedom model. An interactive parametric-based layout oriented approach has been developed to model a cold-formed steel building easily. Using this approach, it is easier to include bracings and window/doors openings.

Sustainable development in construction industry is emerging as a major issue among cities and communities in the current century. As global climate change becomes an increasingly serious concern for the future and construction industry dependence on fossil fuels for energy creates greater adverse influence on human health and natural environment, an interest in high-efficient, low environmental impact buildings has begun to transform the notion of building design, construction, and operation. As it stands, the most of the standard buildings in the world consume an extraordinary amount of resources while taking an enormous toll on the environment. The utilization of cold-formed thin-walled open steel sections in structural sites supplies green structural opportunities demanding less material and cost while providing high strength. The developed algorithm for this study obtains the optimum geometric dimensions of cold-formed thin-walled open steel sections under various external loading. Moreover, this design algorithm takes into account of the effect of geometric nonlinearity as well as effect of warping. Also the displacement and stress constraints are included in the formulation of the design problem. The optimum design problem obtained turn out to be mixed integer and discrete programming problem. Artificial Bee Colony (ABC) algorithm is used to obtain its solution. This technique is a recent numerical optimization technique which mimics the intelligent behavior of honey bee swarm. The recent studies with the ABC 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.

The objective of this paper is to explore the potential impact of the use of advanced high strength steel (AHSS) to form traditional cold-formed steel structural members. In this study, shell finite element models are constructed, and geometric and material nonlinear collapse analysis performed, on simulated lipped channel cross-section cold-formed steel members roll-formed from AHSS. AHSS sheet is currently being used in automotive applications with thickness ranging from 0.35 to 0.8 mm (0.0138 to 0.0315 in.) and yield strengths from 350 to 1250 MPa (51 to 181 ksi). However, AHSS has not yet been employed in cold-formed steel construction. To assess the impact of the adoption of AHSS on cold-formed steel member strength a group of forty standard structural lipped channel cross-sections are chosen from the Steel Framing Industry Association product list and simulated with AHSS material properties. The stress-strain models used in this study are based on AHSS in production, including dual-phase and martensitic steels. The simulations consider compression with work on bending about the major axis in progress. Three different bracing conditions are employed so that the impact of local, distortional, and global buckling, including interactions can be explored. Due to the higher yield stresses of AHSS the potential for interaction and mode switching is anticipated to be greater in these members compared with conventional mild steels. The simulations provide a direct means to assess the increase in strength created by the application of AHSS, while also allowing for future exploration of the increase in buckling mode interaction, imperfection sensitivity, and strain demands inherent in the larger capacities. The work is intended to be an initial step in a longer-term effort to foster innovation in the application of new steels in cold-formed steel construction.

This paper proposes a semi analytical complex finite strip method using bubble functions to study the local, distortional and global buckling of stiffened as well as unstiffened cold formed steel I-sections under compression and bending loading conditions. The method is programmed and used to investigate the elastic buckling of mono and doubly symmetric I-sections containing longitudinal flange stiffeners. The effect of longitudinal flange stiffeners on the stability of cold-formed I-section members is surveyed. Furthermore, a comparison between stiffened and unstiffened cold-formed I-sections is made for different buckling modes. The accuracy of bubble finite strip method in predicting the buckling stresses of monosymmetric cold-formed I-section beams in comparison with Generalized Beam Theory (GBT method) will be established. Case studies are performed for different geometric properties of the sections and the stiffeners on the buckling strength of cold-formed steel I-sections.

A novel form of thin-walled composite beams has been developed by bonding cold-formed steel (CFS) and engineered cementitious composites (ECC). Apart from the superior material strength and ductility of CFS and ECC, the proposed CFS/ECC composite system also benefits from the lightweight concept of thin-walled sections and improved buckling performance due to the ECC restraints on CFS. An experimental study, utilising cold-formed steel sections with a yield strength of 450 MPa and engineered cementitious composites with an ultimate tensile strength of 7 MPa, was conducted to investigate the improvement of the innovated structural system over the traditional CFS structures. Two series of composite CFS/ECC beams, namely, short- and long-span Series, were prepared and tested to monitor the shear and flexural behaviours of the novel composite system. Three locations of thin-layered ECC; outside, inside, and in–out of the CFS section were proposed to determine the perfect composite action between ECC and CFS. The load capacity of the composite beams (ECC—in composite beams) increased to eight times those of the bare CFS members in the short-span Series and up to four times in the long-span Series. The failure modes of the novel composite beams were more ductile compared to the bare CFS. Numerical modelling was conducted and validated using the results obtained from the experimental study. This FE model was employed in a small-scale parametric study to investigate the influence of beam spans on the structural behaviour of the composite CFS/ECC beams.

The paper aims to investigate the possibilities offered by the design and production paradigms of Industry 4.0 in the Architecture, Engineering & Construction industry, through the coordination between systems for the integrated management of the design process (Building Information Modeling) and rapid prototyping tools (Computer Aided Manufacturing). Is hereby proposed an interpretation of the meaning that an industrial transformation of the AEC industry takes over for the Architectural design, simulating a methodology in a BIM environment for the design of residential buildings in Cold-Formed Steel with drywall envelopes, exploiting the potential of digital manufacturing and computational design advanced tools.

The wide availability of high strength cold-formed steel profile enable engineers to use it for structural purpose. Due to its low strength to weight ratio, the building with cold-formed steel profiles is suitable for region with high seismic activity. Application of such thin and small section profile requires truss assembly for column and beams, requiring more efforts in modeling and resulting in large degree of freedom model. An interactive parametric-based layout oriented approach has been developed to model a cold-formed steel building easily. Using this approach, it is easier to include bracings and window/doors openings.

This paper describes the most important aspects of the second part of a cold formed steel member connections research that is currently being done at the Universidad Nacional de Colombia. In this second stage the behaviour of two different connections are studied,, that is, extended continuity plates connection and side plates connection. This study looks at the results of a finite element analysis of the models, experimental testing on models (cyclic and monotonic tests), analysis and comparison between theoretical and experimental results, hysteretic curves of the connections, approximate calculation of energy dissipation coefficient for structures that use the types of connections studied, and finally, the application of whole results to cold formed steel frames design when these connections are used.