Timber Bridge

I would imagine that you are going to be looking at an arch shaped bridge if you can't use RSJs.

I've done a couple of bridges over ponds one of which was over 10 metres long, we used RSJs clad in timber, you would never have known.

Just cause customer doesn't want RSJs, doesn't mean they are right, you have to be sure its safe and will be for years to come

 

Anthony, your work says everything about you. The customer pays for your professional ability and safety is the first consideration. Using rsj's is a no brainer. As Phil says you can clad them and I defy anyone to tell that they're covered rsj's.

The only alternative is to make an arched structure. I would get a structural engineer involved to help. They will have access to cad programmes and you will then have a completed set of drawings. You'll then need to make a template out of plywood.

Make the structure in sections and bolt and glue on site. Using the template ensures you get a faithful copy for both sides of the bridge. Putting a deck on creates a platform to work on so I would get that done asap in the erection process.

The bridge must have a balustrade for safety and aesthetic reasons.

Make sure you locate the bridge structure onto 2 concrete pads using 12mm studs located in the pad and anchoring angle irons.

You will need access to a Manitou for lifting into position. Lift with straps not chains or rope otherwise you will have some terrible marks in the timber.

Ooops, didn't notice the width. 1.8m that's wide! Will it have wheeled traffic using it? Golf buggies are heavy and I would be concerned about making something entirely in wood if that's the intention. Afraid my advice is insist on rsj's or walk away.

Good luck Anthony.

 

or if your clever, you can say you need RSJ's and have them covered in timber so then from the outside it looks like timber but on the inside it is steel.

 

As has been said if you're covering that span in timber it will probably need to be arched and so the base will need to be massive, why do the clients not want to use steel?

 

Found this spec from Hampshire County Council, it's a maximum 6 Metre span and 1.2 Metres wide, you could add an extra base beam to go 1.8 Metres.

Components for 6m timber footbridge: •Some companies produce kit bridges which meet these specifications. 3 x Main Beams 300mm x 100mm x 6m, 10 x handrail uprights 100mm x 100mm x 1.5m (centres spaced at 1.5m intervals) 3 x cross beams 100mm x 100mm x 1.8m 4 x Handrails 100mm x 50mm x 6m 30 x Deck boards 1.2m x 200mm x 50mm 2 x toe boards 100mm x 50mm x 6m Corrosion-resistant screws and bolts

This is for foot traffic only, not speced even for horse riders, on their web page it states that any bigger/heavier requires still beams.