Estimating Bridge Remaining Service Life - Available Guidance?
Estimating Bridge Remaining Service Life - Available Guidance?
(OP)
Any guidance available for estimating the remaining service life of existing bridges? Customer wants this information to program future repair/replacement funds.
I have a 75 year old railroad bridge with steel stingers controlling the load rating in flexure, with no section loss or corrosion, and concrete bents with spalling/delaminated concrete everywhere. All the spalling is in the concrete cover only. Marine environment. Spalled areas show reinforcement has surface corrosion. Substructure rating is "Fair", Superstructure rating is "Good" by inspection report. Concrete features have had capacity's reduced for load rating do to condition factor, but are far from controlling the load rating, compared to the stringers in flexure.
I have a 75 year old railroad bridge with steel stingers controlling the load rating in flexure, with no section loss or corrosion, and concrete bents with spalling/delaminated concrete everywhere. All the spalling is in the concrete cover only. Marine environment. Spalled areas show reinforcement has surface corrosion. Substructure rating is "Fair", Superstructure rating is "Good" by inspection report. Concrete features have had capacity's reduced for load rating do to condition factor, but are far from controlling the load rating, compared to the stringers in flexure.






RE: Estimating Bridge Remaining Service Life - Available Guidance?
Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries
www.americanconcrete.com
RE: Estimating Bridge Remaining Service Life - Available Guidance?
Just my opinion, it sounds like the service life is indefinite at this point. Based on your description, I'd expect the bridge to be adequate until the spalling accelerates to begin controlling the rating (which sounds like it may be a while), some other decay begins to show, or systematic changes (heavier traffic) require a retrofit or total replacement of the bridge.
RE: Estimating Bridge Remaining Service Life - Available Guidance?
RE: Estimating Bridge Remaining Service Life - Available Guidance?
www.SlideRuleEra.net
www.VacuumTubeEra.net
RE: Estimating Bridge Remaining Service Life - Available Guidance?
RE: Estimating Bridge Remaining Service Life - Available Guidance?
You could get into the betting game of finding the expected return period of an earthquake expected to damage the structure (beyond some minimum acceptable threshold). This would be similar to the logic behind bringing down the 6th St Viaduct in LA -- currently adequate, but likely to collapse within X years under a Y size earthquake. There are probably some public documents available from that project that would give you some framework for how to discuss the risk (after your technical evaluation is done).
Of course, then you run the risk of a non-technical manager getting upset if that earthquake happens to hit in 5 years instead of 10. Hopefully they all live in the same high-seismic region as your bridge and understand the basics of earthquake magnitude and frequency.