Office of Citizen
Rest in Peace,
I90 strengthening gusset plates
Submitted by Jeff Buster on Fri, 08/28/2009 - 16:50.
Why does the entire bridge need replacement if it can be repaired/strengthened in the manner in which ODOT has already implemented (image August 09 of north westerly truss over Cuyahoga River from behind the Cold Storage building).
Karen Farkas, Plain Dealer reporter does not make clear in her August 27 report whether the highest stress (red color in simulation) is a result of a flaw in the original design (they didn’t have computer stress analysis when the bridge was built over 5 decades ago) or whether the high stress is the result of corrosion thinning, fatigue, or other damage.
Below the image Daussalt Systemes uses the word “damage” while in Ms. Farkas’ copy reference is made to “extreme stress”. Daussalt is French – anything lost in translation?
And just because there is red in the visualization doesn’t mean that the truss is too weak – or that the entire bridge needs to be replaced. Every element of every structure has high and low stress areas…that is fine as long as the high stress areas don’t exceed certain margins of safety factors.
It would be important to know what the inputs were for the million dollar finite element analysis of the 7000 bridge elements. Was radiography involved, ultrasound, magnafluxing (probably not)?. Was the alloy, thickness, rivet patterns, etc. of every element analyzed against its structural load?
Every bit of this data should be on the internet – Then ODOT might be less subject to the accusation that they are spending 200 million for a new bridge, when the existing bridge could be repaired/strengthened for much, much less.
Of course, there may be other reasons, besides its (lack of) structural integrety, to replace the bridge. For example, seismic codes have changed.