Laminated bridge beam (photo) · AditNow Community

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simonrl
51% (Neutral)
Administration Topic Starter

10 years ago

A brief discussion on this with Donstuart on Thursday night and I knew I'd seen one somewhere... the "how on earth did they get the beams around corners" question...

How common was it for them to be laminated or sections bolted together like this?

Photograph:

🔗99560[linkphoto]99560[/linkphoto][/link]

my orders are to sit here and watch the world go by

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Donstuart
50.2% (Neutral)
Newbie

10 years ago

I've walked along those several times & not noticed that 'construction'.

It's not clear in the photo whether each of the main sections of the beams are in two pieces, joined by the planks bolted on either side, or are the side planks just reinforcements for a one-piece main beam?

Must remember to have a look next time I'm up there.

Morlock
50.2% (Neutral)
Newbie

10 years ago

Looks like the joint is between the 4 central bolts, where the grain changes?

[photo]99623[/photo]

may be scarfed ends?

Donstuart
50.2% (Neutral)
Newbie

10 years ago

"Morlock" wrote:
Looks like the joint is between the 4 central bolts, where the grain changes?

Yes, I can see that joint line on both beams now that I've viewed the photo enlarged.

I don't fancy doing a stress analysis of those joints however!

ebgb
50.2% (Neutral)
Newbie

10 years ago

they've built boats like that for centuries, big sawn sections, jointed and nailed together... futtocks to us of a boaty disposition!

would make perfect sense to take the technology elsewhere, and also means they can use less expensive lumps of wood

probably be hard to find much that hasn't festered away though given the conditions they were mostly put to

http://bf494.co.uk

Roger L
50.2% (Neutral)
Newbie

10 years ago

There is something strange about the joint. The plates either side of the main beam taper to nothing on both of the beams.
As these are fully supported on the ground (assume from picture) it would be an acceptable method of jointing. Metal and wood plates are still used in modern construction this way. They would be better than a scarf joint.

Mine Lectures & Walks available for around Huddersfield

gNick
50.2% (Neutral)
Newbie

10 years ago

"Isabel Gott" wrote:
There is something strange about the joint. The plates either side of the main beam taper to nothing on both of the beams.
As these are fully supported on the ground (assume from picture) it would be an acceptable method of jointing. Metal and wood plates are still used in modern construction this way. They would be better than a scarf joint.

Where exactly do they taper? they look vey parallel to me...

Very normal joint, load transferred to side plates from main beam by friction from the bolt clamp force, it would work much less effectively if the bolts were acting as pins.

Don't look so embarrassed, it's a family trait...

ebgb
50.2% (Neutral)
Newbie

10 years ago

a well made scarf will be every bit as strong as any other method, including plates and bolts. The face of the joint takes the load. If the scarf is hooked or hooked with nibs it has phenomenal strength.

http://bf494.co.uk

lozz
50.2% (Neutral)
Newbie

10 years ago

"If the scarf is hooked or hooked with nibs it has phenomenal strength"

Ditto.

Lozz.

gNick
50.2% (Neutral)
Newbie

10 years ago

#10

Probably not a joint easy to make underground though...

Don't look so embarrassed, it's a family trait...

ebgb
50.2% (Neutral)
Newbie

10 years ago

#11

cut and loose assemble the components above ground, cart em in and assemble in situ I would have thought.

resembles the 'first futtock' in a wooden ship in many repsects.

personally I would trust a jointed timber like that more than any modern held together with cheap steel and screws construction

http://bf494.co.uk

Ty Gwyn
50.2% (Neutral)
Newbie

10 years ago

#12

"gNick" wrote:
Probably not a joint easy to make underground though...

Nothing really complicated with that joint that it could`nt be done in situ.

exspelio
50.2% (Neutral)
Newbie

10 years ago

#13

Would'nt be surprised if some mines employed redundant ship's carpenters, used to working in adverse conditions.

Always remember, nature is in charge, get it wrong and it is you who suffers!.

gNick
50.2% (Neutral)
Newbie

10 years ago

#14

"exspelio" wrote:
Would'nt be surprised if some mines employed redundant ship's carpenters, used to working in adverse conditions.

But they used big bolts and brace plates anyway:)

Engaging brain after the event, presumably you need the brace plates anyway to hold the scarf joint together? I can't see a glued joint going down a storm underground...

Don't look so embarrassed, it's a family trait...

ebgb
50.2% (Neutral)
Newbie

10 years ago

#15

"gNick" wrote:

"exspelio" wrote:
Would'nt be surprised if some mines employed redundant ship's carpenters, used to working in adverse conditions.

But they used big bolts and brace plates anyway:)

Engaging brain after the event, presumably you need the brace plates anyway to hold the scarf joint together? I can't see a glued joint going down a storm underground...

pretty much. the bolts plate are just for compression in the absence of glue and contribute very little towards strength in torsion.

for what it's worth, some of the ancient wood glue potions based on milk compounds are ridiculously strong. I've seen 8"x6" sawn oak frames that have broken in the clear timber, integrity of the scarfe having remained intact. Such glues work really well, in fact perform slightly better in damp conditions as well, relying on moisture to get into the timer fibres

http://bf494.co.uk