Bridge: Superstructure Material Selection

Superstructure Material Selection

Primary Guidance Structures crossing waterways or railroads should have low maintenance superstructures that do not require painting Weathering steel should not be used in a location where it will stay wet

Discussion Low Maintenance Superstructures Structures crossing railroads should have low maintenance superstructures that do not require painting. Since it is difficult to obtain approvals from railroads to erect containment systems over their tracks, weathering steel or concrete girders are a good choice for railroad crossings. Environmental agencies require containment systems when painting structures crossing waterways. Concrete slabs, concrete girders, or steel girders that are galvanized or metallized are good choices for stream crossings since they do not require painting. For either crossing type when considering concrete girders with their deeper depths, evaluate the need to raise the roadway profile, which may create additional roadway costs. Weathering Steel Weathering steel should not be used at stream crossings or in marine environments where the girder will get wet and stay wet for long periods of time, since this prohibits the formation of the sacrificial layer of rust and the weathering steel will actually deteriorate faster than it would if it was not coated at all. If a bridge is high above a stream or waterway and the girders will be able to fully dry out, weathering steel may be considered. See Also Practical Design Implementation Guidance