<p>This study uses numerical analysis in Abaqus software to evaluate the design and performance of channel and I-section purlins under biaxial bending and torsional moments. Current design equations in standard codes from India, Britain, the United States, Europe, Canada, and Japan are analyzed to address their treatment of torsional effects. The investigation highlights that most codes neglect the torsional impacts caused by eccentric load application, except for Canadian and Japanese standards. A novel equation is proposed and validated to include torsional effects, offering a more accurate and economical approach for designing open-thin sections. Numerical simulations were conducted on various purlin sections, incorporating real-world loads and material properties. The results reveal discrepancies in stress predictions and section sufficiency when comparing classical methods, code equations, and Abaqus outputs. Indian and British code-based designs often failed to account for torsion, rendering sections unsafe in certain scenarios. In contrast, Japanese and American standards yielded smaller, yet safe sections. The proposed methodology consistently aligned with Abaqus simulations, demonstrating its reliability. The research underscores the critical role of torsional effects in structural purlin design, providing insights for future code revisions. It recommends extending this approach to closed sections and exploring broader applications of the proposed equations in structural engineering.</p>