Chris Webster Wrote:
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> Fred T Wrote:
> --------------------------------------------------
> -----
> > These girders are not built like an I-beam.
> There
> > are an assembly consisting of a flat plate that
> > has angles riveted top and bottom with a flat
> cap
> > riveted to the top of the angles. With this
> type
> > of construction the rivets can be removed and
> the
> > angles replaced. If the web is damaged and the
> > area is not to big, it can be patched by adding
> > local doubling plates.
>
> I don't think the girders can safely be repaired
> without first bringing them down to the ground.
> That means you need to bring in cranes, which will
> be very expensive - you'll need large ones because
> of Lobato's height and span length.
>
> So you bring in a pair of cranes and lower the
> girders down to a work area. You can no longer
> get ironworkers who know how to put in rivets, so
> you need to figure out a way to weld in the
> replacement angles and/or figure out a way to use
> structural bolts. Of course, before doing any of
> that, you also need to contain and remove any lead
> paint that may be on the iron.
>
> While you're doing all the above, the cranes are
> just sitting there unused... but you're still
> having to pay daily rental charges for them.
>
> Compare that to replacing the bridge span(s) --
> you can hoist replacement girders up on the same
> day that you're lowering the old bridge girders.
> So, for the cost a couple of steel welded I-beams,
> you can save days/weeks of crane rental costs...
> large crane rentals aren't cheap, so it'll
> probbaly cost less to completely replace the iron
> instead of attempting to repair it.
>
> That'll leave you with brand new steel span(s) on
> top of 100+ year old bents. Personally, I
> wouldn't bet my license on 100+ year old bents,
> not when I could economically replace the bents
> with welded steel tubes (like the Loop's high
> bridge).
Chris,
What do you think would be the probable range of cost to remove the existing bridge, design and engineer a new one, and build it?
