One of my truss bridges (wood) needs replacing but my other bridges are strong enough to be walked on.
Re: Marc's "mistakes" bridge, I saw on the history channel last week mention that rebar can expand up to 3 times its volume when rusty and that this happens on real bridges as well. One solution is electroplating the rusty metal with continuous hi-voltage and nickel. I cannot recall exactly how the procedure works but it was kinda interesting. I think it was on their modern marvels (bridges) piece.
The Home of Articulated Ugliness
Ah,
This is a good topic, as we do not want any Garden Railroad versions of the Minneapolis Bridge collapse (Which collapsed on a NS Unit Grain Train and crushed a few hoppers, btw)
Cheese
Nick! :)
I THINK my bridge is structurally sound this bridge is also concreted in the ground . BEN
One way to keep rebar from rusting out quickly is to paint it a phosphour rust converter Which converts the rust to an inert oxide,(generally available at the home improvement stores) and then prime it and cover it with a good paint before setting it in the concrete.
I set some pipe in concrete for fencing that crosses a stock pond and prepped it like that almost 8 years ago and they are just now showing some rust after being in and out of water over the years and then completely submerged for over 5 months.
Still they will rust eventually even if galvanized or plated if the plating gets nicked.
Mark
As rust has a higher volume than the originating mass of iron, its buildup may force apart adjacent parts - a phenomenon known as rust smacking.
A way to slow the rust is to make sure that none of the rebar have outside air contact. Meaning that the rebar is covered entirely of concreate. And also you are using new rebar and not stuff you find lying around.
Another thing that will affect rust is location. Because those who live near water, will have a higher amount of rust than those in drier climates. Since rust is just the steel corroding, it will happen, but it will happen faster with the addition of water.
Just my worth.......
Snoq. Pass
Good advice. Apparently, rust and cracking had an effect on the Minn. bridge collapse. For our garden RRs as well as for the big bridges, why do they insist on using steel rebar that rusts. Can't some nickel or something be mixed into the steel to prevent this from happening????
It sure would seem to save $$$ in the long run
I'm going to be doing some concrete projects and now I'm having doubts about rebar
Thats because rich lazy americans don't care about the long term, all they care about is how much money they can save here and now.
Using Maytag as an examaple, when my brother worked there, Maytag started building thier electronics in mexico, because the parts could be made cheaper. Maytag didn't take in account that nearly 80% of the parts that were tested shorted out or just plain didn't work, but they didn't care about that because they still made money, at the cost of product quality. There was a software program they used to predict the life span of a product, which means they could build a product that would function just long enough to make it out of warrenty before it would break.
Maytag did that to everything they made, all becuse it made them(and stock holders) money in the short term.... and what was the long term result? Several hundred former maytag employees lost their jobs and in the case of my brother lost his house as well. The long term results costs everyone more money and suffering than the money that was saved in the begining.Thats why this country(the u.s.) is so screwed up and no one gives a damn.
I would have to say no. Two are pressure treated 1X6 boards you could probably stand on but there are three smaller "bridges" that are held up by the rail itself. The longer one has a stick holding up the center so it does not sag. These bridges are to be projects later in the year when the weather is a little cooler and I decide what style bridge I want.
The best, strongest bridge is only as strong as its footings or piers.
JimC
Well -- I believe my bridges are structurally sound... in that I haven't installed them yet!!
They are sitting on the floor of my sun room waiting for me to get the rest of the dirt work and the piers and abutments set.
Icepuck,
It's not just corporate and shareholder greed, it's also the American consumer who's to blame. We seem to be driven to buy only the lowest priced items. Therefore we buy Korean and Japanese (and soon, Chinese) cars and products. And we encouarage retailers like Wal-Mart to keep hammering away on their suppliers for ever lower prices. American manufacturers cannot compete with cheap foriegn labor so we continue to hear sad stories like your brother's.
If we all "bought American" there would soon be many more good paying jobs for Americans. But, even though we now would be earning more, we couldn't buy nearly as much "stuff" as we can now because everything would cost a lot more. And besides, that kind of isolationism would probably throw the global economy into a tailspin that would last a decade.
So, I guess there are no easy answers to the problems caused by the new global economy. And it just seems to get more and more complicated everyday.
Walt
whiterab wrote:I am a retired engineer so all my bridges have to pass the "Engineer's Test". I sit on them. If they support my weight they have passed the Engineer's Test. None have failed yet.
That's a nice 'Philosophy', JOE
I dare not say 'Tecnical approach'
Byron
It's true that some higher end jobs that require more education and unique skill-sets may eventually be coming back. But with regard to low and moderate skilled manufacturing jobs, it appears that it will be a very long time, if ever, that American workers will be able (or will be willing) to compete with off-shore labor. Fact is that China is already looking around for ways that it can off-shore some of it's low end work. There are still a lot of poor countries with large and willing labor pools just waiting for the opportunity.
Clinton said it almost 20 years ago, America's "muscle jobs" are quickly disappearing. American workers have to get and stay better educated and trained than the rest of the world if we want to compete for good jobs.
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