Structural behaviour of built-up I-shaped CFS columns.

Area of Science:

• Structural Engineering
• Materials Science
• Mechanical Engineering

Background:

• Cold-formed steel (CFS) members offer fabrication, cost, and transport advantages.
• Thin-walled CFS sections face buckling challenges (local, distortional, global), reducing axial strength.
• Welding is common but costly and time-consuming; screw connections are explored as an alternative.

Purpose of the Study:

• To investigate the efficacy of screw connections in built-up CFS columns as an alternative to welding.
• To analyze the influence of screw spacing on the axial strength and buckling behavior of CFS columns.
• To validate finite element analysis (FEA) models against experimental data and design standards.

Main Methods:

• Nonlinear finite element analysis (FEA) was performed on built-up CFS columns made of double C channels.
• FEA models were verified against experimental test results from existing literature.
• Seventeen different cross-sectional profiles and twelve screw spacings were analyzed through 175 FEA simulations.

Main Results:

• FEA results showed good agreement with experimental tests and design standards (AISI & AS/NZS), with minor overestimation (3.6%) and conservatism (3.0%), respectively.
• Screw spacing at half the local buckling half-wavelength improved elastic buckling loads (local, distortional, global) by up to 22% and nominal axial strength by 11%.
• Double-lane fasteners showed greater improvements (up to 46%), but single-lane fasteners at the optimal spacing are recommended for economic efficiency.

Conclusions:

• Screw connections are a viable and effective method for fabricating built-up CFS columns.
• Optimized screw spacing is crucial for maximizing the axial strength and buckling resistance of CFS columns.
• The study provides valuable data for designing economical and high-performance CFS structural members.