Flexural behaviour of CFS stacked built‐up beams: experiments, finite element modelling and direct strength method

This paper presents the initial results and findings from the experimental and numerical study of recently developed CFS stacked built‐up beams. The specimens are constructed by joining either three or four 75×150 lipped channel sections using screws. A cap of LC 89×41.3 with a nominal thickness of 1.2 mm screwed to the open flange to provide a closed section with a greater flexural capacity. A six‐point loading system was considered to study the flexural behavior of these built‐up beams. The load‐displacement curves, strength and failure modes are reported. A nonlinear elastic‐plastic finite element (FE) model is developed. The bending strengths are also calculated using the direct strength method (DSM) in the North American Specification (AISI) and Australian/New Zealand Standard (AS/NZs) for cold‐formed steel structures. Both results obtained from the FE and the direct strength methods are compared against the experimental.