Suspension bridge

[Darren]

I'm looking for ideas on how to renovate a 150' long suspension bridge. One of the lower wire ropes gave way as I was crossing. I used a piece of regular wire rope to reattach it to the anchor. To replace the lower rope, I'll also have to replace the hangers that suspend the two lower ropes from the two upper ropes.

The original hangers are metal rods which had hooks formed in the ends and were heated and bent around the ropes. They'll have to be cut to remove the old rope. I can always strip the deck, and cut the old ropes loose which will drop them and the hangers.

Hanging new rope won't be a big deal. However installing new hangers with nothing to stand on with a 40' drop is going to be interesting. I've considered renting a manlift, but because of access on either bank and the length of the span, nothing will reach out over the creek like I need.

I read someplace that the Army Corps of Engineers builds these. I've looked on the internet for some sort of directions but nothing came up.

Other than a skyhook, anyone got any ideas?

 

[MarkV]

Darren,

I am no help at all, but you sure caught my attention when you used the words <font color=blue> One of the lower wire ropes gave way as I was crossing.</font color=blue> and then said <font color=blue> nothing to stand on with a 40' drop</font color=blue>. Geez, I’d be changing my shorts after that rope broke.

MarkV

 

[TonyC]

Hmmm...complicated question. I think you'd get better help if you could post some pictures of it showing the problem.

 

[dgizmo1]

Have you thought about completely removing it from across the creek and the rebuilding it and then streching it back across the creek using a tractor or somthing?

 

[Darren]

When it let go I was almost to the farm side end and the deck sagged to the right. When the creek's up high, the footbridge is the only way into the place. I was using a wheel barrow to carry feed. I was more puzzled than anything.

I remember looking at the deck while it was sagging thinking why is it doing that? At that point I was about 6' off the ground.

The bridge is hung on two truncated "A" pipe frame towers made out of 6 or 8" pipe. Each tower stands about twenty feet tall and has three horizontals. The top one caps the "A", is about 4' wide and has two eyes welded on top for the top ropes to pass through. The next lowest cross member is below the deck and the two lower ropes pass over it. The deck is made out of 2x6 treated lumber cross pieces spaced about 3' apart which set on top of the two lower ropes and are fastened to each rope with 2 J bolts. The oak deck planks run the length of the bridge and are nailed on the 2x6s.

Because of the way everything is intertwined including the top ropes passing through welded eyes on top of the towers so they can't shift, the bridge can't be assembled on the ground. The ropes have to be pulled and tensioned. There's four large turnbuckles on the highway side anchorage for that purpose. After the ropes are up. The lower ropes have to be suspended from the top ropes by vertical stays. the current stays are made out of 5/8" rod.

The length of each stay changes depending on its position on the bridge since the distance between any top rope and the rope below it varies across the bridge. I think the deck cross pieces and the stays have to be attached at the same time. The problem is without the stay the lower ropes will sag under any weight. They should be somewhat level all the way across.

Writing this out has helped. I need to figure out a way of clamping something onto both the top and bottom rope that's adjustable to fix the distance so the lower rope stays level after attaching a cross piece and temporary planks. I could then heat and bend the new stays and secure them, remove the adjustible pieces, move farther out and repeat the process.

 

[MarkV]

Darren, sure would enjoy a photo. It sounds like a real interesting piece of property and the bridge sounds fascinating.

MarkV

 

[Scott_in_WVA]

I cannot help you any(at the moment),but when you said suspension bridge,I thought to myself where is this guy from?And then I looked at your profile.What part of the mountain state are you from?/w3tcompact/icons/smile.gif

 

[RobS]

Sounds like a fascinating project Darren. I can't offer any direct help but here's a possible lead for you. There is a suspension bridge (foot traffic) in Turkey Run State Park here in Indiana. A couple of years ago it was renovated. We were bummed as we went down there for some camping and hiking but couldn't access the best trails as they are on the other side of the creek /w3tcompact/icons/sad.gif

Anyway, perhaps a call to the park would put you in touch with the folks who did that work. I have no idea if it was done by the park, the DNR, the army corp, or an independant contractor.

A search for "Turkey Run State Park" should get you a web-site with a phone number. Good luck with your project /w3tcompact/icons/smile.gif

 

[rcpaul]

Darren, have you thought about a bucket type trolley that you could suspend from the top cables and work from one side to the other attaching the stays as you go. then go back and attach the decking.

Rusty

 

[Darren]

Sorry guys, I have no way of posting pictures. I guess it's possible to get a picture scanned and put in the right format. I'll have to think about that.

Around here, central WV, bridges like this aren't unusual. A lot of folks live on the wrong side of the creek so to speak.

The problem with using a trolley is that the ropes initially aren't level and the upper ropes never are since between the towers they assume a catenary shape. What that means is that any trolley (with wheels) attached to the upper ropes is going to run downhill and end up in the center of the bridge. I need something that will grip the rope that can be applied and loosened easily without using tools.

A trolley without wheels consisting of a few cross planks utilizing something to keep it from coming off the lower ropes might work if it could be fastened so it didn't move unless you wanted it to. I could use come-alongs attached to the upper ropes to pull the lower ropes up level. Again I need some way of attaching them to the ropes so they don't slide.