jmcquown wrote:

> When I was dating Ray he was a construction superintendant. He said
> government contracts were the *worse* because the contractor was forced to
> lowball the bid to win the contract, then try to do the work using quality
> materials and not go over cost. Obviously many contractors don't adhere to
> the original specs; rather, as Sheldon says, they use inferior and hence
> cheaper materials to get the job done. Go over cost and they're not likely
> to get another big government contract. Big catch 22 at the expense of
> safety.

Steel is usually inspected at the factory. It has to meet certain standards
and is generally stamped or tagged with the quality approval. It is usually
the type of fill on the approaches, gravel size and dust components,
compaction of fill on ramps and approaches where contractors scrimp for bi
savings. Every load of fill they bring in costs money, and because it is
wet and lumpy it needs to be compacted. Our inspectors had to watch and
ensure that they were bringing in the right type of material and that it
was being compacted properly. Otherwise, it would settle over time and the
road surfaces drops and asphalt breaks up. Then there is the asphalt and
the concrete. Our inspectors used to take a sample of every load that that
came in and test it to make sure it had the right particulate matter and
binders.


Contractors take big chances when using substandard materials, especially
in litigation prone societies like the US. The failure of a major structure
like a bridge can lead to multi million dollar law suits. Bear in mind that
the Minneapolis bridge had been standing for 40 years. I read something
about a bearing failure. Bridges are built to move on bearings. As the air
temperature rises and falls the bridge material expands and contracts quite
a bit. They also move a lot with the wind and bounce up and down with the
traffic. If you have ever been standing on a large bridge you would realize
how much they move. They are supposed to. If the bearings seize up they
cannot move and the incredible stresses can cause something to snap.

FWIW, I heard something on the news today that one section of the bridge
was displaced several meters to one side, which indicated that there was
some force twisting it.




>
> They did a news report about the bridges over the Mississippi River from
> Memphis to Arkansas shortly after the MN/St. Paul collapse. I always get
> nervous driving over the main Memphis/Arkansas bridge. The river is a lot
> deeper and a lot wider here than up in Minneapolis. The news report
> indicated they are inspected every two years. Since we are located on the
> New Madrid fault, the bridges were built (or upgraded) to withstand a level
> 8 on the Richter scale earthquake. I guess that's supposed to be comforting
> ;)
>
> Jill