Behavior of steel I-beams reinforced while under load

Abstract

Steel I-beams often require reinforcing while they are under load. A common method for strengthening steel beams is by welding steel cover plates to the bottom flanges of the existing members. Very limited research has been conducted on the behavior of I-beams reinforced under load. This paper presents a finite element (FE) based study on steel I-beams welded with steel cover plates while under load. A series of simply supported steel I-beams reinforced with cover plates welded at the bottom flanges are analysed. FE analysis shows that with increased preload, the capacity of the I-beam reinforced under load reduces when the failure mode of the beam is lateral-torsional buckling (LTB). On the other hand, the variation of the preload has an insignificant effect on the behavior and ultimate strength of the reinforced beam when the reinforced beam fails in flexural yielding. Also, effects of different parameters, such as residual stress patterns in the I-beam and cover plate, welding residual stress, type of welding patterns, the difference in steel grades between I-beam and reinforcing plate, on the behavior of the steel I-beams reinforced while under load are investigated numerically. Finally, the flexural capacities of reinforced I-beams with welded cover plates obtained from FE analyses are compared with the capacities predicted by the American (AISC 360-16) and Canadian (CAN/CSA-S16-19) steel design standards. FE analysis shows that AISC 360-16, when the effect of loading height is considered, can reasonably predict the capacity of I-beam reinforced with welded cover plate at the bottom flange.