Lateral Torsional Buckling Strength of High-Strength Steel Beam Under Various Moment Gradients

To date, many research studies related to the Lateral Torsional Buckling (LTB) behavior of Normal Strength Steel (NSS) beams have been conducted, and therefore, the guidance for calculating the LTB strength of NSS beams is quite comprehensive in the existing design codes. As the application of High-Strength Steel (HSS) having yield strength more than 690 MPa or 100 ksi has become increasingly popular for its excellent ratio of strength to weight, many design standards allow the use of HSS with grades up to 690 MPa. However, AISC 360–22 does not endorse the use of HSS due to the lack of adequate experimental or numerical investigations that necessitate the assessment of the LTB performance of HSS beams. Thus, this research numerically examines the LTB capacity of HSS I-shape beams under various moment gradients. A detailed three-dimensional finite element (FE) model of HSS I-beams was developed in ABAQUS, considering both material as well as geometric nonlinearities. As HSS exhibits different material and residual stress characteristics than NSS, experimentally measured material properties and residual stress patterns specific to HSS were integrated into the model. Initially, the established FE model underwent validation through the utilization of preexisting test data, after which it was utilized for carrying out a comprehensive and in-depth parametric investigation. In the parametric study, a wide range of parameters, including the grades of steel, length of the beam, and linear and nonlinear moment gradients, were taken into account to ascertain the LTB strength of HSS beams. Finally, the extracted numerical findings were contrasted with the values acquired from the LTB strength equations of AISC 360–22.