INNOVATIVE DESIGN AND ERECTION SOLUTION FOR PORTAL FRAME INDUSTRIAL STEEL BUILDING ROOFS

摘要

Traditional design and erection of long span steel portal frames for industrial buildings consists of individual column and rafter assemblies,with bolted connections at knee (Column-Beam) and apex joints (ridge). This method ensures expediency for an offsite member fabrication and application of the galvanized coating to individual members,before transportation to the work site followed by assembling and erection at the site. This traditional approach however also inherits safety risks associated with working at heights during member erection,alignment and jointing of individual member connections and during placement and fixing of cladding elements. In view of expediting the onsite construction and to mitigate the risk of working at height during erection,designers worked in tandem with contractors and fabricators to rearrange roof elements so as to allow the whole roof to be pre-fabricated on the ground and be lifted for installation matching with the column alignment. In particular,the portal connection at the column-beam knee joint was relocated and redesigned to suit installation ease. The impact of the proposed solution to the design is investigated herein. A rigorous risk analysis was employed to better understand the modes of failure and frame behavior,which in turn assisted in better identifying the design risks. Furthermore,the benefits achieved in the erection process through increased safety and efficiency are also highlighted.