Integrated and coordinated numerical simulations on fabrication processes of high strength S690 cold-formed circular hollow sections

In order to simulate transverse bending and longitudinal welding in fabricating high strength S690 cold-formed circular hollow sections, and more importantly, effects due to these fabrication processes on structural behaviour of these sections under axial compression, an integrated and coordinated numerical modelling approach using coupled analyses is proposed. Details of these mechanical, thermal, thermomechanical and structural analyses of these sections under various boundary and loading conditions imposed during fabrication are presented. Two-dimensional models with large deformation plane strain elements are employed to perform transverse bending while two compatible three-dimensional models with heat transfer elements and stress elements are employed to simulate sequentially coupled heat transfer and thermomechanical analyses to simulate longitudinal welding. These fabrication-induced residual stresses and strains are then incorporated as initial material imperfections into the third compatible three-dimensional model with stress elements for structural analyses under axial compression. These models have been carefully calibrated against data obtained from various stages of fabrication and also from compression tests. The proposed modelling approach is one of the few attempts available in the literature that develops a series of integrated and coordinated models to examine the structural behaviour of high strength S690 cold-formed circular hollow sections under axial compression with a direct simulation on various fabrication processes without the use of simplified residual stress patterns.