Bending torsion of steel thin-walled beams, considering support warping stiffness

Steel thin-walled profiles are the backbone of modern lightweight construction, offering exceptional efficiency in terms of material use and assembly speed. However, their inherent susceptibility to buckling under complex loading conditions, especially bending torsion, has limited their broader application in advanced structural systems. This paper introduces a groundbreaking method for analyzing the bending-torsion behavior of steel thin-walled C-profile beams, specifically focusing on the critical but often overlooked factor of support warping stiffness. Unlike conventional studies that primarily examine local or global buckling resistance, this research pioneers a comprehensive approach that integrates the warping stiffness of supports into the structural analysis. Through the introduction of novel coefficients—warping (0.377–0.484) and bending (0.616–0.672)—this study established a new paradigm in the design and stability analysis of thin-walled beams. Our findings reveal that incorporating support warping stiffness can dramatically increase normal stresses by 2–4 times within the span, a revelation that significantly alters existing design assumptions. The study also demonstrated how sectorial stiffness, a key parameter, directly enhances the warping stiffness of the supports, while the bending stiffness of the beam has negligible impact on the compliance factor. This novel insight provided a substantial leap forward in accurately predicting the complex interaction between bending and torsion in lightweight steel structures. By addressing a critical gap in the literature, this research not only advances the theoretical understanding of thin-walled profiles but also offers practical implications for optimizing the structural design of modern construction systems, enhancing both performance and safety. •A method was developed for determining the bimoment in beams with support warping stiffness.•A method is proposed for determining the actual reference values of the bending moment and bimoment from numerically obtained values of the reference normal stresses.•Range of values of the coefficients are revealed, considering warping and bending finite stiffness of thin-walled profiles, for the case when stud profiles are supported inside track profiles of various thicknesses and high of 150 mm.•With an increase in the sectorial stiffness of the profile, the support warping stiffness increases, while with increase in bending stiffness of the beam, the complian