Effective material model for cold-formed rectangular hollow sections in beam element-based advanced analysis

This study develops and validates an effective material model for cold-formed rectangular hollow sections. Advanced design methods utilize non-linear finite element analysis in design. An accurate calculation model, which is usually beam element-based, is crucial such that the design outcome is safe but economical. Unfortunately, cold-formed sections have non-linear residual stress distribution over the material thickness, that cannot be explicitly modelled in general-purpose beam elements. Additionally, corner regions of cold-formed sections have higher material strength compared to flat regions. This beneficial feature is usually disregarded by assuming the flat region properties for the entire cross-section. This study develops an effective material model that replicates a stress-strain curve that would be obtained if the tensile test was made for the entire cross-section instead of a separate tensile coupon. Consequently, the effects of residual stresses and corner strength enhancements are included in the effective material model such that their consideration in beam element-based advanced design method is effortless. The effective material model is validated for the steel grade S700 against numerical shell element buckling tests and excellent modelling accuracy is achieved.