Experimental and analytical investigation of fatigue life on trapezoidal longitudinal ribbed on steel bridge decks

The system of Orthotropic decks was used in the long span bridges in the world because of many recognized properties like light weight, high resistance, fast installing in the bridge structure and life cycle economy. The fatigue issue in orthotropic decks started clearly during the two last decades ago after watching the fatigue failure. During these periods of detection of the fatigue problem, there are plenty of studies implemented and lead to good results. These studies gave results that most of the fatigue crack were watched at the weld connections rib-to-deck plate, rib-to-diaphragm, and rib-to-diaphragm-to-deck plate. The reason of this is that the area of the weld is sensitive to the fatigue crack relative to highly concentrated stress and residual stress at welded connections This study includes one closed longitudinal rib which has a trapezoidal cross-section. Laboratory tests were carried out for the specimen including two types of tests which are static calibration and dynamic. In static calibration test, strain gages were installed on the specimen and strain values were obtained for all of the tests to compare the results of strain values obtaining by using finite element simulation (ABAQUS PROGRAM) and hand calculations.Dynamic tests were carried out to assess the fatigue life for specimen by observing the initiation of cracks and propagation by accounting in which a number of cycles the specimen will fail.Crack lengths were measured versus a number of cycles until fatigue. The specimen was classified according to S-N curve to determine in which category lies to estimate its strength. Also, this study includes two parametric studies for the same model by using finite element simulation (ABAQUS PROGRAM).The first study includes the effect of using different lengths of connection pieces between the weld zones along the depth of longitudinal ribs on displacements and stresses under applied loads. The second study includes the effect of different lengths of cracks in the weld zones on the stresses under applied loads.The stresses of the ribs were evaluated due to applied loading using finite element analysis (FEM) and the results were compared to each other