 |
|
|
|
|
|
|
|
|
|
|
|
Build a Bridge | Bridge Photos |
|
||||||
|
|
Pick a Bridge |
 |
Bridge Models |
|
|||||
| Home |
 |
Contact | |||||||
|
|
|
||||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
Build a Bridge | Bridge Photos |
|
||||||
|
|
Pick a Bridge |
|
Bridge Models |
|
|||||
| Home |
|
Contact | |||||||
|
|
|
||||||||
Exlpoded diagram - larger picture
|
• Lay out the arch pieces symetrically. |
|
|
• Insert 5-1/2" bolt through the end pieces at the arch foot
and slide the cross-beam under the short piece. Push the cross-beam past the bolt hole above it. Separate the arches so the X (for the railing post) on the cross-beam is just outside the arches. |
|
|
• Lift a long piece and |
|
|
• add the next (full length) piece by putting a 4-1/2" bolt through the crossing
and mate the lap joint over the cross-beam. |
|
|
• Add the other 2 pieces • Tap the cross-beam to center under the peak so that the lap joint fits. Everything is shaky while you're adding pieces. Try to have someone hold the arch to keep it from tipping while you're completing the arch assembly. |
|
|
• add the next piece by putting a 4-1/2" bolt through the crossing
and mate the lap joint over the cross-beam. |
|
|
• Carry on adding arch pieces. |
|
|
• For longer, heavier bridges you can take a scrap 2x4 and make a stand, as in the picture,
and use a hanger to hold the lifted arch piece at a suitable height,
while you're adding the next piece. If you have a six-pack for a helper or two, you can forget the hangers. |
|
|
• Detail of the hanger.
|
|
|
• Position the "jacks" as required to raise the arch assembly. |
|
|
• Whack the arches into line so they line up with the marks on the cross-beams and stand vertical. |
|
|
• All joists point in the same direction except at one end,
where the end ramp and joist are fastened to the same arch peak with one longer bolt. |
|
|
• Attach railing posts and the end post braces at one end only. • Attach railings and side post braces. • After everything, including decking, is screwed down, attach the end post brace at the other end. |
|
A final consideration:
During erection, do not tighten nuts.
• You see on the right that 2 bamboo slivers don't work as a beam bridge.
• In the middle, fixed as an arch between two "footings", they look promising but will obviously tip sideways, even with the lightest load.
• On the left, with only some plain paper for a "deck" as lateral bracing, they support over 4 lbs with no problem.
After the arch assembly is completely erected, and railing posts are attached, snug up the nuts. Don't overtighten them as it will only crush the wood unneccessarily. Bolts carry no load and merely act as clamps to keep the wood lined up.
Bolts through the arch peaks can be temporarily removed, with no great difficulty, after the arch assembly is standing.
If you have difficulty inserting a bolt through an arch peak, despite cross beam & lap joint seemingly aligned for a reasonable fit, just ream out the misaligned bolt holes with a drill bit of your bolt size.
Before the arch is shoe-horned into the footings, it may seem longer and flatter than design so, depending on how you are holding or lifting it, the fit of the lapjoint may seem off. Once in place, you should be able to wiggle the arch in its proper shape.
This design has tremendous strength and load capacity, but only as long as the arches remain vertical.
For maximum strength and load capacity:
- Set up the arches symetrically, a mirror image of each other.
- Make sure the arches stand plumb on your footings.
- Consider fastening the cross-beams directly to the arches, especially if the cross-beams are a loose fit.
- Fasten your deck securely and ensure that several deck screws fix the pointy part of the joists well to the arch. This forms a curved truss for maximum arch efficiency.
- A well fastened deck is required to assist the cross-beams in maintaing the structure in a vertical position, even with lateral stress under load.
In the US 84Lumber can have
The longer the bridge and the heavier the load, the more important this becomes. On smaller bridges you might guarantee lateral stability by gluing and screwing the deck for each section in panels before laying those on the arch assembly with a few screws.
On larger bridges an easy way to guarantee lateral stability and erecting a straight arch assembly, is 16ga galvanized X-strap across each section before screwing down the deck planks.
You can also use this strap for easy arch foot protection & isolation
Simpson Strong-Tie
drop ship you a roll of
CS16Z-150 16ga 1¼" galvanized coiled strap
USPconnectors.com
is another supplier
RS150 CS16
In Canada Home Hardware can supply either one.
