ABSTRACT
In order to investigate the fatigue perfor mance of cutouts in the diaphragm of steel box girder and decide the optimal structure of the cutout, finite element models of block-shell mixed elements were established to calculate the fatigue stresses of several fatigue vulnerable details. The fatigue lives were calculated based on Palmgren-Miner linear damage accumulation criteria and the S-N curves in Eurocode 3. And the comparison of fatigue perform ance and design optim ization of several typical cutouts at hom e and abroad were carried out. The results show that obvious com pressive and tensile stress concentration zones (Zone A and B, respectively) exist at the cutout under local wheel loads. Fatigue cracks usually initiate at Zone A, and the direction of crack propagation is alm ost perpendicular to the direction of the principal stress. The shapes of the cutouts have significant influences on the fatigue performance of vulnerable details, especially on that of Zone A. The shape of arc-strai ght line (Cutout 4) is the best shape for the rigid diaphragm s among the commonly used cutouts at home and abroad. The fatigue life of the cutout will be improved by appropriately increasing the radius of the cutout a nd the thickness of diaphragm, but the effect of increasing the radius of the cutout is better than increasing the thickness of diaphragm.
