Re: Post-Fire Pictures of Lobato Bridge **PICS**

Fred T Wrote:
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> 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).

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Chris Webster