Okay so i have an old railroad bridge on my property (we own the old abandoned rail road bed. The rail road ties are pretty much all rotted and need to be removed. I was looking to replace with pressure treated lumber. There are two 24" high I-beams that are in great shape, they span 36, and have a 13" wide flange and are spaced 6'-1" from inside flange. I need to know what I could use for the new joist size and spacing to replace the old railroad ties. Most I would have on this bridge would be 5000 pounds (compact tractor). So it wont be as heavy as what use to be on it- +200 tons. Also will be adding a 2x10 decking since it will also be used as a foot bridge and by ATV's.
I know you said the tractor would weigh about 5K. I would feel better if you designed the bridge to support double that. You could be carrying something with the tractor, pull a trailer with weight, etc.
Here's some reading material for ya. It should allow you to correctly calculate the wood needed. Just remember to pay attention to the species of wood - I believe they reference different species of wood in the links. You might have to call the company that makes the specific treated lumber that you are planning on using to see what species of wood they use for treated lumber.
I have read the joist span charts and all but I just don't know if the Live load would be the same as say a house LL. The tractor only weighs 3200 pounds I just round it up to 5000# for safety. Of course there will be railings on the bridge, that's a must with kids! Most pressure treated lumber around here is SYP #2 or better.
You may check and see if you have a local sawmill. You may be able to find some rough cut stuff. Some types of oak will long outlive the pressure treated stuff.
Give a man a fish, and he will eat for a day. Teach a man to fish and he will sit in a boat and drink beer.
Cool bridge! Looks like a lot of hard work to make it trustworthy though. Have you considered replacing the old ties with newer, grade #1 used ties? They're available retail for about $12 apiece. Probably cheaper if bought in bulk. They are a bear to handle. I hope your tractor has a front end loader. Large ice tongs can also be handy when handling the ties. You might also consider using steel components instead of wood.
I have looked at used railroad ties and all the ones i found are not any more trustworthy-I want this to last another 50 years +. I do have a front loader but will mostly be renting a material lift so i can reach across the Bridge without driving on it until the decking is on. I have contacted a rail road tie manf. and they will only sell non treated ties to private individuals. I would go the saw mill route but still need to know the joist size and spacing to support the 5000 pounds.
As for using more steal it would be too expensive.
I will try to contact an architect friend and see what he might say. He will want to know the type of wood you are using? And the decking on top will be solid and right angles to the joists? thickness?
Does the spacing of the beams match the track of the tractor? or is the wood decking taking the load? This is also dynamic loading as opposed to static which is a little more critical. NEED MORE INPUT!
He has followed up with an email after I sent him your pic and told him that my tractors were between 5 and 6 feet wide at the wheels. Here's what he said:
Yeh! those beams and their foundations could carry a whole caravan of tractors. Just run 4" t&g southern yellow pine decking across the steel beams. At a 10' span they will carry over 200 lbs/ sq. ft. Another option is to use 4X6 treated SYP layed flat. They could be spaced 1/2" apart to save some cost.
Here are a few thoughts from my viewpoint. I have run a sawmill for close to 30 years. I would not use oak, for it does not last as long as most think. Under certain circumstances it is great, but there are to many variables that can cause troubles.
I would go with the 4x6 pressure treated SYP. Make sure it is the good stuff, not the cheaper PT that is sold off the shelf in most places now. The good PT will say for use below ground. The cheap stuff will say above ground and will be PT to about .05pcf. There are tags on the wood that will say this.
You could check to see if locust is available from a sawmill in a 4x6x8' solid/sound size.
Use all this info at your own risk. Your safety is involved, and it would be best to confirm and double check with other sources.
P.S. What brought you to the PondBoss Forum? Have you been sitting on the sidelines for awhile, or did this site come up when you were searching for bridge repair?
Fish n chips, if locust wasn't available, what about osage orange?
Yes, that would be a very good choice too. Didn't even occur to me because around here it is unlikely to get of any size, but that's not to say it can't somewhere else.
Another one that is good for outdoor use and grows large is Catalpa. However, it is not as strong as osage. We have a lot of that around here compared to the other two. You would want to go heavier in thickness with it. I would go with any of these 3 types before oak.
I asked my buddy about all these, and he said he can't recommend them because they are not commercially available choices. And like I eluded to, there are a lot of variables that can change quality. No real "building standards/codes" for these, just opinions of the quality from one mill to the next of what you might get (there are grade rules, but these types are so uncommon it rarely would be sorted to grade). Just like fish, one person will see it as a trophy, and the next will say it's a forage fish.
Guess I was wrong. I assumed that since White Oak was used to build ships,barrel staves, railroad ties and also bridge planks. that white oak would have been a good choice on a bridge! My bad! But I did stay at a Holiday Inn once!
Give a man a fish, and he will eat for a day. Teach a man to fish and he will sit in a boat and drink beer.
JB you are right, but there are a lot of "it depends" at work.
As RR ties they are treated before they are put in place. So, between the type of wood and the treatment, they will outlast any PT material from the big box stores. Ships get regular preventative maintenance, which is probably why some old oak bridges last longer than others. I believe they use white oak barrels because it doesn't impart(or does and they want that?) or take on food flavors or some kind of benefit like that, not because it's rot proof.
White oak as far as rot proof is up there, it just would follow behind the others I mentioned. As far as a bridge decking, I would not want to worry about doing a routine maintenance on it, whether it be a coating or replacing some of the timbers every five years or so.
If the regular Joe goes to a sawmill and says I need 4x6's for a bridge deck, most mills will just start taking logs (of type wanted) and cutting them up to size. They will just fill that order as fast as they can for 100 pieces of 4x6's. That leaves it up to the builder to know whether it is and will still be of sound material in 10 years. Its different than 100 years ago when wood was being used for that purpose and mills understood what matters. Seeing how far up this bridge is, I sure wouldn't want problems.
Going back to Osage Orange. It is hard, strong stuff. You probably could get by with 2" to 3" thick stock. However, you have to weigh in the inconvenience of using it compared to a good PT SYP. My experience with the real hard hardwoods is that you need to pre-drill a hole to drive a nail/spike thru. To me that is a real hassle. For me, when I need wood, I will usually cut what I need because I can. If you were laying out cash anyway, consider spending a little more and making it easier/better.
Another option may be a cedar of some type, but since we don't have them around here and I primarily use hardwoods, I can't say much about it.
My neighbor works for the railroad, and says that #1 ties are available (used) and are in a LOT better condition than the ones from Lowes/Menards/Home Depot
Does the spacing of the beams match the track of the tractor? or is the wood decking taking the load? This is also dynamic loading as opposed to static which is a little more critical. NEED MORE INPUT!
the beams are wider than the tractor (4'-0" ctr to ctr. tires) I am attaching a photo showing the dimensions of the beams and what i would like to do. What I have now is the 2x10 rough cut decking made out of hemlock (already cut and paid for). I do have a person to get rough cut lumber from but he does not have any larch anymore, just Hemlock and White pine.
Sorry about the delayed response but i don't get e-mails when i get a new post. I found this forum by doing a google search and looking around found a lot of good info, plus this summer we will be putting in a pond.
My neighbor works for the railroad, and says that #1 ties are available (used) and are in a LOT better condition than the ones from Lowes/Menards/Home Depot
That's probably why the RR won't sell him any treated ones. I have been trying real hard not to mention preservatives for wood, because it is a real sore spot with me and the regulations that have been changing over the past 10 years. They want us all to reuse/ recycle, and go green but then we can't preserve a natural resource which leads the market to use more plastics, etc.
He'll just have to go visit esshup's neighbor in IN... Who would know if he changed a RR tie once in a while on that bridge, eh.
I have been doing a little bit of research on hemlock. I don't know anything about it, because it is not often found here. I have cut it up for firewood once in a great while, and was not that impressed with it. I have found two sources on it's rot resistance. They are conflicting....
From what i have heard- its a harder wood but not as hard as larch. If I can I will get larch for the main joist I am sure someone around here has to have some, I will also be applying some type of water seal to the deck, most likely year to help keep it good as new.
