We all see steel bridges, and most all of them are covered with large patches of rust. Which means a gradual weakening, and lots of maintenance problems. Are there no grades of steel that are relatively rust proof and suited for this use? Even if a bit weaker and thus needing more structure?
And if so, what would be the relative price difference? My point is, would it not be cheaper in the long run to build bridges with rust proof material and reduce the maintenance costs?
A similar question revolves around the Rbar used in concrete structures.
I’m not sure that doubling the capital cost of the bridge and slashing the maintenance costs is not a good deal. Consider that a bridge should be good for 100 years, and calculate the costs over that time. But the politicians would never buy it.
I thought galvanizing didn’t last that long, as the zinc "sacrifices itself", but as it does that, it gets oxidized. When it’s all gone, no more protection.
Bill: I’m a civil/structural engineer with bridge design experience. In addition to its high cost, stainless steel is not manufactured in many of the the heavy rolled shapes commonly used in fabricate structural members for bridges. This would necessitate connecting structural (carbon) steel and stainless steel members, which poses the threat of the accelerated corrosion that can take place between dissimilar metals. Brittle fracture and weldability of stainless steel are other concerns. Finally, the American Association of State Highway and Transportation Officials bridge design code (first link below) does not address the use of stainless steel for bridge members such as girders and beams, though stainless steel is sometimes used for hangers in arch or cable bridges.
Check out the second link below for information on corrosion protection of steel bridges.
Weathering steel is a type of structural steel that forms a patina of oxidation to protect the steel in the same way that paint does. This type of steel looks rusty, which looks great in some settings, but may be too rustic in other settings. Special detailing of runoff points from the superstructure is needed to keep oxides from staining substructures. Take a look at the third link below to learn more about weathering steel.
well, the problem is not in the strength with stainless steel, its the cost. stainless steel costs a lot more to cast, and a lot more to obtain, and so its just not cost effective to build a bridge out of stainless steel. for example, if a normal bridge costs 5 million to build, the cost for stainless steel could even triple it. and the maintenance, even over 20 years wouldnt come to the 10 million or so difference. galvanizing works almost as well anyway, and is certainly much cheaper.
I See they in some states use cement to make bridges or suspended bridges Im estimating that the cost of the stainless steel is a problem, because years ago they tried making cars of stainless even a old model A ford and it still exists without a mark of rust on it ,for some reason they stopped using it?
To add on to the reason the others have said i would add stainless is not easy to work with. It’s not easy to weld or machine.So the time building would be increased. All so other than the cost of normal stainless you have to add the cost of "machinable and weldable" stainless. You couldn’t use low end stainless like you can use cheap steel.
Over all it would be hard to say. But we all know we live in a "walmart world" there is no way any city would pay one dollar more to save million.
One of the evident reason for not using stainless steel in bridges is the cost ( of producing such material and construction of bridge). The second one, which, i considered critical is stainless steel expands with heat easily and more compared to other steel. Would you like to see bridge warping in the middle of the day? It’s very dangerous!!
It is not cost effective.