71 replies to this topic

[Bill Z]

Bill, I only said "in theory", because there have been problems with it in the past when used in particularly corrosive environs, like near the ocean or chemical plants. Sorry, but you're wrong on this one (I've been designing bridges for 25 years, starting in the Mecca of steel bridges, Pittsburgh, PA). Weathering steel (Most commonly ASTM A588, also known by its US Steel trade name, "Corten") has been around for about 45 years. It has a chemical composition that does, indeed, result in a uniform protective coating of rust that forms on the surface, preventing moisture from reaching the rest of the material so that it prevents the typical "packing" and flaking associated with typical steel corrosion. Some states (notably Michigan) started using it in the 1960s and had bad experiences because many of their bridges were in heavily industrial areas, and so stopped using it. So it was controversial in the industry for a few years, until the industry came up with better guidelines on where not to use it.

But, if you don't believe me, here's what the American Iron and Steel Institute says about it (granted, it's a little like reading BP's page on oil spills cleanup, but for purposes of this thread, they are the experts): AISI

Maybe Kerri would like to chime in on this one, since corrosion is her specialty.

OK, You're right, I learn something new everyday. Never heard of that type of steel before. Sounds like it still isn't a perfect solution to the problem though.

But does it meet DFARS 252.225-7014 Preference for Domestic Specialty Metals Alt 1. Clause?

[tony]

OK, You're right, learn something new everyday. Never heard of that type of steel before. Sounds like it still isn't a perfect solution to the problem though.

Not perfect. But it's the steel industry's answer to prestressed concrete (although usually only competitive with concrete in CA on pedestrian bridges), which is nearly maintenance free (that doesn't include the riding surface, which is never maintenance free). Painting and repainting can be the difference between steel being competitive or not. Weathering steel offers a good solution, when used appropriately. And, generally, for trail bridges the brown color is considered acceptably "rustic". In this case, I'm not too thrilled with the combination of painted and weathering steel, but it did save some money (and will whenever the green bridge needs to be repainted).

[tony]

But does it meet DFARS 252.225-7014 Preference for Domestic Specialty Metals Alt 1. Clause?

Uh, not sure about that one. It might. I think the nearest domestic producer (of larger structural steel shapes used in bridges) is in Utah, which is one reason why it's not usually competitive in CA.

[Bill Z]

Uh, not sure about that one. It might. I think the nearest domestic producer (of larger structural steel shapes used in bridges) is in Utah, which is one reason why it's not usually competitive in CA.

That DFARS clause used to be a pet peeve of mine, but now the clause has been deleted from the DFARS. I'm in electronics and do you know how hard it is to find little 0-80 stainless steel screws that aren't made in China et al. I used to have to argue with companies when they put that clause on their PO's.

[legofamily]

I drove under it this morning. I thought it looked really nice. I actually really like the green color.

[Bill Z]

I drove under it this morning. I thought it looked really nice. I actually really like the green color.

I think they chose a green bright enough so it would be visible to low flying aircraft.

That's the last thing we need is one of those commercial cargo jets flying into Mather hitting it because they couldn't see it.

[mylo]

Maybe Kerri would like to chime in on this one, since corrosion is her specialty.

[folsom500]

Both, although there may been other reasons associated with the HOV lane project (Like vertical clearance under the bridges). In addition to not meeting ADA, both were very narrow and unpleasant at best to use.

It was my understanding that the main reason for the replacement was due to the angle of the entrances on both sides were too steep for ADA compliance. But as you said the additional need might have been the need to get them higher in the slow lanes on the widened road once they added the HOV lanes.

[Bill Z]

It was my understanding that the main reason for the replacement was due to the angle of the entrances on both sides were too steep for ADA compliance. But as you said the additional need might have been the need to get them higher in the slow lanes on the widened road once they added the HOV lanes.

Hard to know which factor was the motivation to do it now, my guess would be the road modifications, but no doubt, the ramps are now much longer to make the slope ADA compliant.

[ScionBox]

It would be funny if the city's street signage department forgets to post clearance signs on it. Nothing like a semi truck stuck under a brand-new bridge.

[tony]

It would be funny if the city's street signage department forgets to post clearance signs on it. Nothing like a semi truck stuck under a brand-new bridge.

It would have to be a very high semi, as the clearance under the bridge should be 17', 3.5' higher than the legal limit. I don't think you'll see a clearance sign; they are only used when the bridge has substandard clearance.

[FolsomParks]

Link to video of the nighttime installation of the East Bidwell Bike / Ped Overcrossing Bridge.