Experimental and numerical study of connection effects in long-span cold-formed steel double channel portal frames

Cold-formed steel haunched portal frames are popular structures in industrial and residential sectors. They are commonly used in rural areas for sheds, garages, and shelters, and are now being constructed with spans of up to 30 m in Australia. As these large structures are relatively new to the market, there is limited data on their behavior and design recommendations, including connection stiffness and design. Numerical and experimental parametric studies were conducted on a haunched portal frame composed of back-to-back lipped channel sections bolted through the webs for the main frame members, and back-to-back L-brackets bolted though the webs at the connections. An advanced shell finite element model was created and validated with experimental results to confirm the suitability of the modeling technique. The validated finite element model was then used for parametric studies to determine the effects of various components of the frame, including column base connection stiffness and modifications to the knee brace-to-column connection design, on the frame capacity and behavior. An experimental program was conducted to quantify column base connection stiffness where the connection was comprised of L-brackets bolted through the column flanges at the base. Stiffness was quantified for bending about the column major and minor axes for various thickness L-brackets and for a U-bracket Apex in-plane connection stiffness was quantified experimentally for several rafter channel thicknesses and depths. Discussions of the results of the parametric studies are presented in addition to the resulting design recommendations for constructing effective long-span cold-formed steel portal frames. (C) 2018 Elsevier Ltd. All rights reserved.