Symmetric and antisymmetric lateral-torsional buckling of prestressed steel I-beams

Until now, there are no analytical solutions published of the lateral-torsional buckling (LTB) of the prestressed steel I-beams. In this paper, the symmetric and antisymmetric elastic LTB buckling performance of prestressed steel I-beams, with rectilinear tendons, under equal end moments has been examined. Firstly, a simplified mechanical model is put forward. Secondly, based upon the Euler-Beam model & the Kirchhoff-Plate model, the strain energy equation as well as the potential energy of the prestressed steel I-beam are derived in detail. Then the total potential equation and the differential equilibrium equations along with the boundary conditions are obtained. As a result, the analytical solutions of the symmetric and antisymmetric elastic LTB of prestressed I-beams are obtained, for the first time, and the correctness of the analytical solution of the critical moment of the symmetric buckling of the prestressed I-beam is verified by those simulated by using ANSYS. Finally, parameter analysis is carried out. It is found that: (1) the critical moment of the prestressed steel I-beam, with rectilinear tendons, under equal end moments can be determined by that of the symmetric buckling; (2) the critical prestressing force can be determined by that of the symmetric buckling or antisymmetric buckling depending on the relationship between the dimensionless eccentricity and its threshold value.