Minneapolis bridge collapse report

[mgb_phys]

The preliminary report is out on the bridge in Minneapolis that collapsed last year,
The BBC claims they found that some of the gusset plates that failed were only half the thickness of the rest and are calling it a design error.
Although they cannot find the original design so it's not clear if the thin plates were wrongly designed or the wrong plates were fitted.

 

[KennyCivE]

You can read the full report here:
http://www.dot.state.mn.us/i35wbridge/pdfs/ntsb_design_adequacy_report.pdf

 

[FredGarvin]

I still wonder if it is a proper conclusion to call it a design flaw when the design stood the test of time. If anything I think it should still be called a failure to use the bridge within the design limitations.

I look forward to reading this report. Thanks for posting it.

 

[mgb_phys]

I thought it was a bit unfair to call it a design fault if the bridge had worked perfectly for 40 years. Yes it was under-designed (or underbuilt) but it did quite well upto then.

 

[KennyCivE]

In a separate letter, the NTSB recommended that bridge and structure designs be checked thoroughly when modifications are made to the structure, or if traffic operations change. Because of that, I'm wondering if they suspect this was the case on the I-35W, even though it wasn't mentioned in the report. But that's just pure speculation on my part.

The calculations don't support the gusset plate sizes, so what do you call it besides a design error? They were able to retrieve plans, and these showed the incorrect thicknesses, but they were unable to find the original calcs to back this up.

NTSB safety recommendation: http://www.dot.state.mn.us/i35wbridge/pdfs/ntsb_safety_recommendation.pdf

 

[russ_watters]

I was thinking the same thing, Fred, & mgb. I was also surprised that they said corrosion played no role at all, after all the initial speculation and the previous condition report on the bridge.