Feasibility of using cold formed steel for medium span roof structures in Sri Lanka

Abstract

Cold formed steel members have been widely used in industrial and commercial buildings over the world with increasing interest and even in the residential development. In the past it was used mostly in non-load bearing structural systems that is partition and architectural feature elements, but it is now used even in the structural systems, and are effective in reducing the self-weight of structure. Cost of Construction around various parts of the world depends on various factors based on the structural category, availability of material, labour cost, material cost, technology available and use, serviceability limit requirements and standard structural design requirements, so on. Therefore light weight structure itself would not be an effective solution for every construction and structural system. Steel construction industry in Sri Lanka; mostly depends on hot rolled steel member / section for their structural solution. The other type of steel, that is cold formed sections / members available for construction, is very uncommon as a structural element, but it is still using as purlin, for steel roof structures. Feasibility of using cold formed steel in structural roof system has not been specifically studied yet, and construction industry is still waiting for such a detail study to overcome the excessive cost of steel construction in Sri Lanka. This research is based on the 4-case studies, that were already completed using hot rolled steel members for its structural roof system, contain 4.0m, 8.0m, 10.0m, & 12.0m span parallel girder trusses and pitched trusses. Bay spacing for selected cases were pre-defined according to the column grid of the particular building and was 3.0m, 4.0m, 3.2m, and 6.0m respectively. Under this study, aforesaid roof structures were totally replaced by cold formed steel system (lipped channel sections), and checked the structural ability to reach the design requirements followed by ultimate limit state and serviceability limit state, under feasible limit of cost.