Oklahoma Suspension Bridge

Step 5 Bridge Raising

One of the most difficult aspects of building a suspension bridge is hanging the first pieces of deck from the catenary cable. Had I not been able to assemble the bridge substructure ahead of time and float the assembly to the site, I would have had to use another process to actually raise the bridge. Most likely, I would have installed a second, and much smaller, pair of catenary cables pulled to less that half the designed sag of the main cables. Then I would have pulled the main cables across, having preinstalled the suspenders, attaching joists as the main catenary cables were pulled. I also would have installed either the outside deck boards, or the bottom hand rail boards, or perhaps both. I don't think I would have installed the 2x8 joist end boards at all had I been forced to use this raising process.

As it was, we levered up the west end of the bridge sufficiently to attach the catenary cables to the eye bolts in the top of the tower, then, again using my compact tractor, I pulled the east end up far enough to attach the 12 ft come alongs to the slings and we began to winch away, slowing raising the bridge. The turnbuckles were very hard to turn -they got HOT! But in about 4 hours from working on the catenary to calling it a day, we hung the bridge more or less level, and called it good.

Comments

[symesy]

A little bit of grease goes a long way on thoes turnbuckles. Also if you used gal ones they can be a bit harder to work because of the galvanising on the threads, stainless ones might be more expensive but would make it a lot easier.

[Jakebutnottheone]

Both those things are true - but I wanted them to stay put once they were adjusted, so I put no grease on them, and they were expensive enough that for one adjustment, or very few over the life of the bridge, I was okay with the galvanized.

[symesy]

Fair enough. Just thought id say. Great build anyways, its really good to see people building. Good on ya.