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8 meter bridge project - HELP!

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mahking51

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Hi
I have just been asked to make two foot bridges to go from the shore of a pond to the central island. The quality needed is 'workmanlike' not cabinetry grade.
The span from base to base is 8m and the under bridge height is 1m.
Width is 1m. I am thinking along the lines of doing the section as a semi ellipse as I have worked with ellipses before on my floating table project.

The ends of the bridge will rest on concrete plinths with angle iron stops to fully anchor the ends and stop any spreading.

I cannot quite visualise the sizes of the timber I will need for this, something like 8x2 joist material comes to mind.
All and any advice on this is welcomed.
Regards
Martin
 

tim

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FWIW I wonder whether there are regs that govern this kind of thing. It could be great fun to do or it could go badly wrong. Its a fairly big span!

It may be worth consulting a structural engineer (unless you are one) because I would have thought that the concrete pads may well need to be reinforced and over water there could also be an increased effect of windage which may add torsion stresses that aren't obvious on paper.

Cheers

Tim
 

JFC

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8m is a big span and for a bridge i would want to use continuous timber from point to point or at least have some kind of continuous 8m support . How about making a box beam up or using a steel to support any kind of fancy work . In other words putting 2 beams across your span and then supporting the arch of the bridge off it , and hiding it with some nice joinery .
 

PowerTool

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Is this a private job ? i.e. the landowners being the only people who will use it.
If open to public use,does this mean you need Public Liability Insurance ?
(I don't know,I'm just thinking out loud :? )
 

Freetochat

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I previously built an ornamental bridge over a Japanese Koi Pond, but the span for me was only 5 metres. I would use some steel RSJ beams and build up of them for that span.
 

Howjoe

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Wow, that's quite big! Is that 8m per bridge or across the two of them?

PowerTool":1z8jgnrn said:
Is this a private job ? i.e. the landowners being the only people who will use it.
If open to public use,does this mean you need Public Liability Insurance ?
(I don't know,I'm just thinking out loud :? )
I was just thinking the same thing. IIRC, it doesn't matter whether it's open to the public or not. It covers your liability to a third party (exception being your own household familiy members) - so even if a private commission and only used for private purposes and an incident occurred then this cover would come into play, provided the policy holder was proved negligent. Not sure how long your liability to the owner/ third party is open for though once it's completed e.g,. poor materials / bad design caused injury etc 1 month, 1 year or 5 years down tte line.

Cheers

Howard
 

JFC

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You could get over the whole public liability issue by agreeing with the customer that its for light use only or an ornamental bridge , if thats what it is . If its in your quote as an ornamental bridge then its for ornamental use and light foot traffic . I think :-k
 

jasonB

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Find a local mill that does green oak, the one I usecan cut upto 9.5m lengths, longer than you will find any softwood. Just a bit weighty :D

Jason
 

mahking51

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Howjoe
That is two x 8m spans

Felderman
That is just the sort of thing I have in mind but perhaps a bit bigger!
can you elaborate on size and construction please?
There will not be an insurance issue with this project, its for private use and ornamental appeal.

Regards
martin
 

JFC

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Looks like 3 timbers laminated together then cut into an arch and held together with cross members .
 

Gill

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Please can I have the Bessey clamp that's been left behind?



Gill
 

martyn2

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Hi Martin
One of my other interests is garden railways( with boating, fishing) and we build bridges across ponds etc not that it has to carry a lot of wait but they are normally trestle bridges with A frames I have a kit at the moment ( I tend to pick bits up as i go along ) set at 1/19 scale that is base on the real thing it in wood if you would like to borrow the kit to give you some ideas on construction you would be more than welcome .

Martyn :D
 

dedee

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Martin,
Can't wait to see the project pics

Andy who is struggling to remember why I had that link in my favourites.
 

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