Load-bearing composite structures commonly consist of slender beam elements with thin-walled cross-sections, resulting in a structural response that is inherently complex. Such structures are more susceptible to stability loss and exhibit an increased risk of buckling and excessive deformation under external loads [1,2]. Accurately identifying the stability limits of deformation modes is a critical aspect of the design process. The objective of this study is to conduct a large-displacement nonlinear analysis of thin-walled beam-type structures while accounting for shear deformation effects. The cross-section is discretized into multiple rectangular segments, each composed of orthotropic layers arranged in an angle-ply laminate. The analysis is performed entirely using a numerical model developed by the authors, and the results are validated through comparison with available studies in the literature. To incorporate shear deformation effects, Timoshenko’s theory for non-uniform bending and a modified Vlasov’s theory for non-uniform (warping) torsion are employed. Furthermore, an enhanced shear-deformable beam formulation is presented that captures bending–bending and bending–warping torsion coupling due to shear deformation [3,4]. These coupling effects arise in asymmetric cross-sections where the principal bending and shear axes are misaligned [5]. The geometric stiffness of the element is derived using the updated Lagrangian (UL) incremental formulation [3], together with a nonlinear cross-sectional displacement field that includes second-order displacement terms associated with large rotations. ACKNOWLEDGEMENT: This work was supported by the Croatian Science Foundation under the project number [HRZZ-IP-2024-05-6868]. This work was Funded by the European Union – NextGenerationEU under project numbers (uniri-mz-25-3; uniri-iz-25-95 and uniri-iz-25-233).