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Alternatives to Steel Grid Decks - Phase II

A. Mirmiran / K. Mackie / M. A. Saleem / J. Xia / P. Zohrevand

The primary objective of the research project was to investigate alternatives to open grid steel decks. Three alternative deck systems, including aluminum deck, ultra-high performance concrete (UHPC) high-strength steel (HSS) deck, and UHPC-fiber reinforced polymer (FRP) tube deck, were developed and studied in the first phase of the research project. The UHPC-HSS deck showed a great potential to serve as a viable alternative. However, more studies were needed on its components and system design before it was deemed ready to be implemented. Accordingly, this phase of the project covered all the studies needed for the design and implementation of the UHPC-HSS deck system. Also, suitability of an FRP bridge deck system as an alternative to open grid steel decks was evaluated. The UHPC-HSS deck was experimentally investigated at both the component and system levels. Studies included the deck-to-girder connection test for shear and uplift forces, deck-to-deck connection test, multi-unit specimen tests to determine the lateral distribution of live loads, full-scale test for fatigue loading and residual strength, and pullout and beam tests to evaluate the development length. The deck-to-girder and the deck-to-deck connections both proved to be adequate for the loading conditions expected from the HS20 truck and wind forces. Tests for the live load distribution showed that most of the load is taken by the ribs under or immediately next to the load. The deck panels and connections successfully endured two million cycles of repeated loading and had a residual strength beyond their target design load. It was shown that the development length of HSS rebars in UHPC can be reasonably predicted by ACI 408R-03. The dowel action of longitudinal steel reinforcement in UHPC and the uniaxial fatigue behavior of UHPC specimens were also evaluated through both experimental and analytical studies. It was shown that the dowel action would contribute considerably to the shear resistance in reinforced UHPC structures. In another part of the research, an FRP deck system was tested under static and fatigue loading. The FRP deck withstood two million cycles of AASHTO-specified repeated loading with no sign of damage or failure, while its deflection under service load significantly exceeded the deflection limit suggested by AASHTO LRFD.