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Step 4Bridge sections and catenary cable assembly, plus launch and towing to bridge site
The catenary cable is 1/2 in galvanized wire rope with a working load of 5300 lbs at a 5 to 1 safety factor. The cable length is calculated in the spreadsheet at approximately 80 ft 7 in. I used 12 in jaw/eye turnbuckles at each end. Each suspender location, also calculated in the spreadsheet, was marked along the cable prior to installation.
The joists were assembled in four 16 ft sections and one 14 ft section (the middle section). And the trucked (tractored) over to the final assembly area. Assembly consisted of two 2x8x16 plates screwed into each joist with three 3 in deck screws, having first marked vertical on each plate at a 2 ft spacing.
At the assembly area (more on that later), the sections were dropped onto rollers and then bolted together with 2x8 plates at each joint. The two end sections were designed to hinge, while the other connections were as rigid as possible.
Once the sections were assembled, the catenary cable was affixed to the suspenders at the marked location. The connection consisted of 1/2 in clips with the closed part of the "u" down and threaded through the thimble on the tip end of the suspender.
I built 4 ft slings which were attached to the east end of the catenary cables for pulling the bridge up to height. The slings were essentially a loop of 1/2 in wire rope attached the catenary cable with two clips. The bridge will be raised into place using come-alongs attached to the slings.
One the catenary cable and slings were installed and all bolts tightened down, the bridge was pushed into the pond (I used round treated fence posts as rollers) using my compact tractor. Once in the pond, the bridge was towed to the site.
The joists were assembled in four 16 ft sections and one 14 ft section (the middle section). And the trucked (tractored) over to the final assembly area. Assembly consisted of two 2x8x16 plates screwed into each joist with three 3 in deck screws, having first marked vertical on each plate at a 2 ft spacing.
At the assembly area (more on that later), the sections were dropped onto rollers and then bolted together with 2x8 plates at each joint. The two end sections were designed to hinge, while the other connections were as rigid as possible.
Once the sections were assembled, the catenary cable was affixed to the suspenders at the marked location. The connection consisted of 1/2 in clips with the closed part of the "u" down and threaded through the thimble on the tip end of the suspender.
I built 4 ft slings which were attached to the east end of the catenary cables for pulling the bridge up to height. The slings were essentially a loop of 1/2 in wire rope attached the catenary cable with two clips. The bridge will be raised into place using come-alongs attached to the slings.
One the catenary cable and slings were installed and all bolts tightened down, the bridge was pushed into the pond (I used round treated fence posts as rollers) using my compact tractor. Once in the pond, the bridge was towed to the site.
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