Hmmm. Remember that post on resilience from the other day? Might be even more important than we know….
the whole post linked to is well worth a read for great examples of the dangers of electing Republican officials, too.
The Next Hurrah: Minnesota’s “Mess Across the River”
What they seem to be telling us is that this “style” of Bridge has no real redundancy in it — if one critical member fails, the whole thing falls down. This was understood with the Silver Bridge Failure over the Ohio River a few years after the I-35W bridge was constructed, and design criteria were modified requiring more redundency — but it was too late for this one, and about 700 others, mostly built for the Interstate System, around the country. Apparently they no longer build this style bridge.
So understanding the problem probably will require going back into the mists of the early 1960’s when the design contracts were let, and taking a good critical look at the assumptions of that period. I seriously doubt if they comprehended traffic volume, truck weights, and all the rest that apply today at the time of design, and I suspect we’ll find many modifications have been made over the years that did not go back and look at those assumptions before adding traffic, weight, and all the rest, and modifications — such as adding extra lanes further stressed the structure.
One Response
Oddly enough, lack of redundancy may have saved lives on the bridge. Because the middle just fell out and straight down into the river, the people on the span over the water were spared most of the crushing and piling up that killed the people on the north end.
Obviously, the heart of the problem is that the bridge failed at all – but when it did, it broke as it was made to break.
But you lost me on one point…extra lanes? When was that? And how?