Bridges

The concept of steel-concrete composite beams requiring shear studs welded to an upper steel flange to provide a shear connection to a concrete slab is no longer required. Instead, composite dowels are formed by cutting an intended shape (steel-dowel) into the steel web providing a direct connection between the steel section and reinforced concrete slab or beam. The publication of several design guides (Seidl9, EUR 253214) and a general building authority approval (Z-26.4-5610) provided the first engineering tools to design this shear connector. An Annex D has been prepared with the expectation to include it in a future revision of the Eurocode 4. A technical specification (CEN/TS) is currently drafted to reach consensus of CEN National Members on design rules for composite dowels as shear connectors for composite members.

After successfully completing a pilot bridge project in Australia in 2017 (Schwarz11) using composite dowels as shear connectors for the composite beams the concept proved its simplicity, enabling local contractors in more rural areas to install bridges without learning new skills. The second composite dowel bridge in Australia was completed in 2020 with the emphasis of reducing the time on-site to a minimum by precasting all elements and the third bridge using this technology was completed before Easter 2022. Since 2019 multiple slab bridges with short 12 m spans and beams bridges with spans close to 60 m have been designed using the composite dowel technology as an economic alternative to prestressed bridge beams. Three composite dowel bridges are currently under construction or awarded to contractors and expected to be completed mid to end 2022. This paper provides a proposal on how composite dowels can be designed to Australian Standards taking the recommendations of the published design guides into account, collates the benefits of using composite dowels and discusses the improvements that were implemented as the composite dowel bridge beams evolved from project to project.