Buckling behavior of orthotropic steel deck stiffened by slender bulb flats for large span bridges

Slender bulb flat stiffeners with a large height-to-thickness ratio were proposed for the orthotropic steel decks (OSDs) in a large span suspension bridge. The buckling behavior of the panels stiffened with bulb stiffeners under pure compression was experimentally and numerically studied in this paper. Four specimens consisting of four longitudinal stiffeners and a top deck plate were fabricated and subjected to axial compression loading tests. Finite element models were established and validated by the result tests. A parametric analysis was conducted to study the effects of residual stresses and geometric imperfections on buckling behavior. A buckling failure of overall stiffener buckling before the yielding and ductile post-buckling behavior were observed in the tests. A buckling strength of 311 similar to 337 MPa was obtained in the tests. The ratio of buckling stress to yield strength ranging from 0.80 to 0.86 was slightly lower than that of closed ribs, which shows a potential use of the slender bulb flat in large span suspension bridges. The numerical results showed that the residual stresses can decrease the load-bearing capacity by 10%. The residual stresses have a higher influence on the resistance than the regular geometrical imperfections. The standard vehicle load has negligible influence on the buckling resistance, but overload may cause a certain decrease.