Pedestrians strike back!
I remember one bridge being built they figured out someone forgot to turn on a layer with reinforcement something or other when printing out the plans.
I have no idea what that is supposed to mean but somehow it just seems like an unnecessary statement.
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Well I think he means that in computer blue prints, there are various layers of detail. One for plumbing, electrical, mechanical and so on. Might be one for rebar etc. A mechanical engineer told me that usually they will use a stress factor of 2-3 in critical designs, so that if it is supposed to support 1000#, they’ll engineer it to 2 or 3000#. We don’t know yet if it was the structure or the supports at either end that gave way and probably won’t for a while until the forensic engineers get done with it. Either way, I think the company is toast and should change their name and the University isn’t looking much better.
The irony. One kid got killed crossing the street so now they have managed to kill a few more in the process of being safe. Those safe pedestrian ramps we were talking about a while ago?
Bridges collapse for a number of reasons. Of the ones I’m familiar with:
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Design flaws due to ignorance: the Tacoma Narrows Bridge developed harmonic vibrations in a storm. Lessons were learned
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Under design in an effort to save money. Structure can fail just after completion or have a shorter life span.
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Design is Ok, but the lowest bid contractor cuts corners and/or bribes the inspector. This happens often
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The design is adequate but for the particular location corrosion and temperature variation cause it to fail. The Montreal Olympic Stadium built for the 1976 Olympics was to a French design that did not address the severe climate. Many pieces broke off and the roof also collapsed.
Many highway overpasses have collapsed in North America; although the design was often adequate, the construction and materials selection and overall quality control was lacking.
I was a pipeline inspector on new construction for 3 years in he 50s and not a foot of the lines I signed off on ever developed a leak.
Don’t forget the collapse of the pedestrian walkway in that Kansas City Hyatt Regency (1981). That was due to the contractor taking a short cut with the design.
edit, and the engineering firm was also culpable as they approved the changes over the phone without any calculations or drawings.
Remember this accident next time you jack up a car and don’t bother to carefully place jack stands.
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One of the more spectacular INDOOR collapses was at the MGM Grand in Las Vegas. The large mezzanine balcony was not designed to accommodate a full complement of people. Such oversights are inexcusable!
I suppose the contractor became so complacent that he regarded the load test as a formality that had to be gone through.
I think it come out that the design was flawed to begin with. It was labeled as a suspension bridge and it had a lot of cables going through it. It looked to me that the cables run from an anchor on the ground, up to a pulley, then down at a very slight angle to a low point in the center of the bridge, then back up to the pulley on the other side and down to another anchor. By putting a lot of tension on the cables, the center of the bridge is suspended.
That has been used successfully to keep floors from sagging in high rise buildings and was used to stabilize the patio that juts out over the water in Frank Lloyd Wright’s Falling Waters. It was featured on an episode of This Old House.
I think it was those cables they were tightening. The problem I see is that this would be the longest and heaviest span that that technology has been used on that I know of. The tension on those cables would be in the millions of pounds, and they would all have to be equally tight or the other cables would be under too much tension to hold.
Could be. It sure looked from the pictures that the thing collapsed somewhere in the middle. I wouldn’t rule out a poor concrete mix either or substandard steel or connections. Inspectors are a little irritating sometimes needing concrete samples for testing and I wonder if they ever had a chance to actually test the concrete samples, it went up so quick.
I don’t think this is something you can joke about in good taste. People are dead. 
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