Strength behaviour of cold-formed steel channels under predominantly shear with high aspect ratios

• Experiments on cold-formed steel channels predominantly shear with aspect ratios exceeding the limit of 2.0 is performed. • A dual test rig is used to determine the effects of predominantly shear actions across a test span. • A Finite Element Modelling (FEM) is developed using the commercial finite element program ABAQUS to verify against the test results. • Combined bending and shear become notably significant when the span aspect ratio in predominantly shear exceeds the limit of 2.5. • A new design approach for sections subject to predominantly shear using the average bending moment concept is developed. In the current Australian and New Zealand Standard (AS/NZS 4600) and American Specification (AISI S100) for the design of cold-formed steel structures, the Direct Strength Method (DSM) for the shear design of stiffened members is specifically limited to a stiffened shear span aspect ratio of 2.0, where the designed span in high shear shall not exceed twice the web depth. An experimental program was undertaken to test varying span aspect ratios exceeding the current limit of 2.0 in predominantly shear, aiming to find out the actual limitations in shear and to confirm the significant effects of bending at such ranges of high shear spans. For situations with higher span aspect ratios, the rules based traditionally on either combined bending and shear or unstiffened shear spans could be alternatively applied. However, this approach may not accurately predict the ultimate shear strengths and is inconsistent with the ultimate failure behaviour of member segments subjected to predominantly shear with high aspect ratios. In this study, a finite element modelling program was conducted to demonstrate effective shear spans, motivating a new design approach for predominantly shear using the average bending moment concept.