Experimental Study of Fatigue Behaviors of Orthotropic Steel Bridge Decks Enhanced by the Ultra-High Performance Concrete Layer

Abstract:

In order to validate the fatigue behavior enhancement as derived from ultra-high performance concrete（UHPC） reinforcement， typical welded details of rib-to-deck-to-floor beam （RDF） connections in orthotropic steel decks were tested by employing single- and double-wheel loading conditions. Static loading was first conducted to investigate the local stress distributions at critical areas. High-cycle constant amplitude cyclic tests were then conducted to obtain the fatigue behaviors including crack initiation and propagation， fatigue failure mode， rigidity degradation， and fatigue life of RDF connections. The results show that， by introducing the UHPC reinforcement layer， the hot spot stresses at weld toes of specimens weresignificantly reduced by up to 58 %. When compared to the specimens without the UHPC layer， the numbers of fatigue cracks of steel-UHPC composite connections were found to be reduced， and the fatigue crack growth rates and the rigidity degradation speeds were also observed to be significantly depressed during the whole process of test. The S-N curve of category FAT 90 and FAT 100 as provided in international institute of welding （IIW） fatigue design recommendations can be used to predict the fatigue lives of the steel bridge decks before and after UHPC paving.