TRANSPORTATION

Issue

FDOT spends $25-$30 million each year repainting existing bridges in addition to the initial painting costs associated with new steel bridges.  The use of weathering steel can eliminate the initial and maintenance costs of painting structures with no reduction in service life when there are no valid reasons for not allowing weathering steel.  The use of weathering steel should be consistently evaluated as primary choice for structural steel girders unless there are environmental conditions or overriding aesthetic considerations.  A more consistent approach in evaluating when steel bridges should be painted will save money, reduce inconveniences and delays to the traveling public, reduce a hazardous work condition and eliminate environmental monitoring and hazardous waste disposal.

Recommendation

Use weathering steel for new steel bridges in suitable environments.  Use a single coat of inorganic zinc paint system for extremely aggressive environments.  Where higher aesthetics are required, use a 3 coat inorganic zinc paint system with clear coat finish.  The use of the 3 coat system with clear coat finish should be an exception, requiring justification and approval from the Chief Engineer.  For multi girder bridges where the use of higher level aesthetics has been approved:

• Use a 3 coat inorganic zinc paint system with clear coat finish on fascia girders. Depending upon environment, use weathering steel or a 1 coat inorganic zinc paint system on interior girders.

• For box girder bridges where the use of higher level aesthetics has been approved, use a 3 coat inorganic zinc paint system with clear coat finish.

Guidance on the justification for painting and approval from the Chief Engineer for higher aesthetic considerations was developed in Structures Design Bulletin C12-02/Roadway Design Bulletin 12-04 which can be accessed here. Subsequently, this recommendation has been further clarified with Structures Design Bulletin 12-08 which can be accessed here. For questions on the suitability and use of weathering steel, contact Robert Robertson, State Structures Engineer at (850)414-4267.  For question on structural steel painting and paint systems, contact Jeff Pouliotte, State Structures Maintenance Engineer at (850)410-5691.