Parametric Study of Cold-Formed Steel Sections and Design Methodology

Abstract

With more and more advancement in the field of science and technology, man is rigorously looking for advance and innovative construction materials. Cold Formed Steel (CFS) is the one of the new material in the construction industry. Several Codes and Guidelines has been introduced for cold formed section such as IS 801-1975, AISI S100-2007, Eurocode 3 (EN 1993), AS/NZS 4600 and others. CFS sections have advantages like light weight, remoulability, post reserve strength etc. as compared to hot rolled sections. CFS sections are extremely thin walled. This configuration gives them advantageous post reserve strength when used as structural element as compared to hot rolled sections. Simultaneously, this also give rise to problems related to plate buckling and cross-sectional distortion. However, research is needed to develop firm basis for such sections in comparison to typically used hot rolled sections. Hence study is conducted with hot rolled sections (such as I shaped, channel, angle, tee, zee.) and CFS sections (such as angle, channel, channel with lips, open hat, closed hat, sigma) to compare their behaviour and effect in complete framed structures. Various Parameters like Time Period, Displacement, Storey Drifts, other Seismic Performance Parameters and Quantity of Steel, calculated using the commercial software SAP 2000 are computed. Critical location and magnitude of maximum stress concentration is also studied with the help of FEA software ABAQUS which is an important study for CFS sections. Newly introduced method known as Direct Strength Method(DSM) has been used and compared with the existing guidelines for flexure and axial member. Buckling Analysis and behaviour is an important criterion in DSM. Here, buckling analysis is carried in CUFSM software. Parametric study such as effect of longitudinal stiffener in CFS cross-section, behaviour of different configuration of CFS like folded-flange and sigma is carried out. Design charts has also been developed for flexure member of CFS as per DSM. These can be extended for other types of members and cross-sections and with other provisions which when published in the respective codes. This study showed that Direct Strength Method can be used as an alternative to Effective Width Method given in IS 801-1975. Also, the upgrade in capacity of the cross-section through longitudinal stiffener is also proved through buckling analysis. The parametric study showed that the angle of 110˚ and 120˚ are the optimized one for folded flange sections when used as flexure and axial member respectively. Also, the angle of 45˚ proves to be beneficial in case of sigma section.