A heavy duty riveted steel grating is an open grid deck system used in movable bridge construction and rehabilitation projects. They are lightweight and easy to install when compared to conventional slab systems and is thus preferred when the load carrying capacity of an existing bridge needs to be increased. Empirical methods have been used in the past due to limited information about their design and behavior. Open grid decks have been used in a number of bridges with the majority being welded decks. A major problem encountered with these decks is the development of fatigue cracks resulting in increased maintenance cost. Observations in the field when heavy duty riveted steel gratings are used and results from experiments indicate better fatigue performance than welded decks. The fatigue characterization of the heavy duty riveted grating has not been established and there are no provisions to govern the design in the AASHTO LRFD Specifications.;The current research examines the fatigue behavior of heavy duty riveted steel decks under AASHTO H20 truck loading and also establishes an effective width to be considered during design. Preliminary tests were conducted on two large panels of 37R5 lite to investigate the static behavior and the nature of stress distribution on major components of the grating. A 3D finite element model was calibrated to laboratory data to simulate experimental tests and used for parametric studies in estimating stresses in various components. Fatigue testing of six structural panels with simulated H20 design truck tire loads and of 26 smaller panels at stress ranges of 20ksi, 25ksi, 30ksi and 35ksi was performed. A fracture mechanics approach was used to estimate the fatigue life of the gratings. Results showed that the primary strip width provided in the AASHTO LRFD specifications for the design of open grid decks under predicted the stresses on main bearing bars. An effective width is proposed and involves the length or width of the tire patch perpendicular to the direction of main bars plus twice the spacing of the main bearing bars. The intermediate bars, if present, contribute towards the load carrying properties of the heavy duty riveted gratings but not the connecting bars. Results from smaller panel specimens correlated well with that of the large panels during fatigue testing. The mean fatigue S-N curve for test data was close to that of a category B with a constant amplitude fatigue limit of 16ksi. The heavy duty riveted steel grating can conservatively be designed as a category D detail but with a constant amplitude fatigue limit of 12ksi. Results from the research were used to develop a guide towards the design of heavy duty riveted steel gratings.
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