Maximum steady stress of various cross-section beams under combined loadings during creep

In the simplified method based on stress classification for estimating the stress at the steady stage during creep, an empirical correction factor is needed to account for the relaxation of primary bending stress during creep. An analysis of a rectangular beam subjected to tensile loading and bending moment during creep is carried out to demonstrate the applicability of the Kt, which is the correction factor proposed by the ASME code, in this work. In view of the effects of material creep property and the primary membrane stress on the relaxation of the primary bending stress, a method for accessing the parameter Kt is proposed and validated. The results reveal that the parameter Kt will increase with the tensile loading due to the relaxation of the primary bending stress accelerated by the primary membrane stress. Good agreement between the results of inelastic analysis and the modified method is observed for the beams with different material properties, combined loadings, and cross-section shapes.