Fatigue tests and optimization for a new rib-to-diaphragm joint in orthotropic steel deck

Abstract

The rib-to-diaphragm (RTD) joint in the orthotropic steel deck (OSD) of steel bridge under traffic flow is prone to fatigue damage due to the complex geometry-induced difficulties of welding and defects. To avoid the complex geometry-induced stress concentration and the low weld quality-induced defects at the RTD joint, a new RTD joint with a smiley cut-out under the bottom of U-rib was applied to reduce the stress concentration and defects. The fatigue tests including the traditional and new RTD joints were conducted by using the full-scale segment models, and the fatigue performances of the traditional and new RTD joints were experimentally compared. Moreover, the Kriging metamodel-based multi-objective evolutionary algorithm (MOEA) was established to optimize the geometric parameters of the smiley cut-out of diaphragm. The results indicate that the fatigue life of full-scale model including the new RTD joints is over 700 million cycles, which is over 5 times as large as that including the traditional the RTD joint. After optimization, Von Mises stress, the first principal stress and tangential stress amplitude of the smiley cut-out of diaphragm respectively jump by 9%, 33% and 34%, resulting in a remarkable improvement in fatigue performance.