Finite element modeling protocols and parametric analyses for short cold-formed steel zee-section beam-columns

摘要

A modeling protocol for shell finite element modeling of cold-formed steel Zee-sections is proposed via a parametric study on specimens previously tested in an experimental study on cold-formed steel Zee-section beam-columns under bi-axial moments and axial force. The experimental dataset consists of twenty-two short Zee-section beam-columns with nominal 178 mm [7 in.] deep webs, 57 mm [2.25 in.] wide flanges 19.5 mm [0.766 in.] long lips at 48 deg. and a short member length of 305 mm [12 in.]. The numerical models include geometric and material nonlinear shell finite element collapse analyses in ABAQUS. The parameters include residual stresses and strains from roll-forming, geometrical dimensions, and geometric imperfection pattern and magnitude. The numerical results verify the experimentally observed high sensitivity of the Zee-sections to lip (local and/or distortional) buckling. The strength surface of the Zee-section beam-columns, generated numerically, exhibits regions where significantly more strength in cold-formed steel beam-columns is expected when compared to a linear interaction surface as adopted in the current design methods. The potential for further improvement of the current approach for predicting the strength of cold-formed steel beam-columns is discussed.