Potential Flaw Found in Design of Fallen Bridge

The following is some comments I have seen from locals that are in the bridge collapse area.

I am hearing that this possible area of flawed designed was brought to the NTSB’s attention by the engineering firm hired by the State after the accident. And as the article says, these gusset plates are used in bridges and structures of all kinds and sizes all over the country.

Also pointing to the 100 or so tons of rock dumped on the bridge as part of the construction going on. Jack hammer use was also brought up.

The reports the last few days said the crew was jackhammering the concrete away, and then was applying a 2 inch layer of crushed rock that the new roadway would sit on — the reports specifically said 100 tons of crushed rock were on the bridge ready to be spread (or already spread – that point was unclear)

Now a real concern of mine is in the picture you can also see a concrete truck. Also a loaded dump truck, loads dumped on the bridge and the mini dumpers. The combined weight of the loads, the dump truck is excessive but, all that combined with the concrete truck mixing concrete in one area should have been a major concern.

A fully loaded concrete truck alone weighs anywhere between 80 to 100,000 lbs. Take into consideration with 44,000 lbs of concrete mixing, note “mixing”….. When a load of concrete gets to a job it needs to be mixed to the consistency desirable for pouring. 44,000 lbs spinning at high rpms in a confined area puts an incredible amount of torque in a small area. That alone could cause an extreme amount of movement in a bridges structure.

Of course this is just my opinion, I am not an expert. I have been contacted by people in the field concerning the Grand Island bridges because they are very similar to this bridge.

Potential Flaw Found in Design of Fallen Bridge

MINNEAPOLIS, Aug. 8 — Investigators have found what may be a design flaw in the bridge that collapsed here a week ago, in the steel parts that connect girders, raising safety concerns for other bridges around the country, federal officials said on Wednesday.

The Federal Highway Administration swiftly responded by urging all states to take extra care with how much weight they place on bridges of any design when sending construction crews to work on them. Crews were doing work on the deck of the Interstate 35W bridge here when it gave way, hurling rush-hour traffic into the Mississippi River and killing at least five people.

The National Transportation Safety Board’s investigation is months from completion, and officials in Washington said they were still working to confirm the design flaw in the so-called gusset plates and what, if any, role they had in the collapse.

Still, in making public their suspicion about a flaw, the investigators were signaling they considered it a potentially crucial discovery and also a safety concern for other bridges. Gusset plates are used in the construction of many bridges, not just those with a similar design to the one here.

“Given the questions being raised by the N.T.S.B., it is vital that states remain mindful of the extra weight construction projects place on bridges,” Secretary of Transportation Mary E. Peters said in a statement issued late Wednesday.

Since the collapse, the concern among investigators has focused on “fracture critical” bridges, which can collapse if even a single part fails. But neither the safety board nor the federal Department of Transportation on Wednesday singled out any particular design of bridge in raising its new concerns about gusset plates and the weight of construction equipment.

Concerns about the plates emerged not from the waters of the Mississippi River…

(Excerpt) Read more at nytimes.com …