Determination of monitoring parameters for fatigue behavior of steel-concrete composite bridge girders with welded full depth transverse stiffeners

In this study, parameters that should be monitored during the service life of a bridge and the relationship between the parameters and damage are investigated in order to predict the fatigue damages in steel-concrete composite bridge girders with welded full depth transverse stiffeners. In this context, static and fatigue tests are carried out on steel-concrete composite beam specimens with welded full depth transverse stiffeners. Load-deflection behavior of specimens is determined by these monotonic tests. In the fatigue tests, the specimens are subjected to cyclic loading with various stress ranges, and stress range-number of cycles (S-N) data is obtained. Fatigue crack and fatigue fracture are observed in the first two specimens with the highest stress range applied. As expected, the fatigue crack occurred at the point where the stiffener is welded to the bottom flange. During the tests, dynamic deflection and strain measurements are performed at the critical points throughout the cyclic loading. The parameters which are more critical in terms of fatigue behavior and should be monitored are determined by examining the relationship between the obtained data from these measurements and fatigue damage. Discussions and evaluations are made on the level of safety presented in the relevant code by the comparison of the obtained results from fatigue tests with the code and the important studies in the literature. Finally, the specimens without fatigue fracture were tested under monotonic loading to determine the residual strength. Accordingly, the change in the load-deflection behavior after cyclic loading is demonstrated.