Timber Framers Guild Forums Tools Timber Engineering Heavy Duty Scarf Joint Design

Hi,

Can anyone point me towards a downloadable book or paper that illustrates various options and considerations for the design of a very heavy duty scarf joint. I would imagine that this might well be included within the pages of a bridge building manual or the like. I am looking for inspiration to help establish a good timber / bolted / banded design that is capable of medium to longer term adjustment.

Regards

Ken Hume

Here is one Ken.

http://www.tfhrc.gov/structur/pubs/04098/14.htm

Will T. should have some stuff. It will be interesting to see what you come up with for this scarf.

How long is the timber you are making, 68' was it?

Tim

Hi Tim,

This is a good document and just the very thing needed to kick start the brain into action to think about the issues that need to be addressed. The composite will be 84'.

Regards

Ken Hume

what does that mean? in what context will you be 'adjusting' it?

Hey All, here is a good one.

Strongest one I know of W/O bolts. All wood, opposing keys (in the 5" slot) to knock around down the road. Precision is beneficial on this one, otherwise you might get some splitting at the abutments (sp?).





my apologies for the sloppy ink, from awhile ago. Great Scarf Joint. A little labor intensive, but in the grand scheme of things....

Happy 4th!

Hi M & M.

The wood is bound to dry in service and so it would be important to be able to tighten up any metal bolts or hoops employed so that the joint can be kept tight in service.

Regards

Ken Hume

Ken,

I don't see the point in your new thread. You have asked a question about a reasonable issue, but have given no circumstances.

I am lost in this thread.

There are papers available -

Dr. Sangree having several, some which speak to specific scarf types.

http://cedb.asce.org/cgi/WWWdisplay.cgi?0609170


This I have yet to see but it may be what you are looking for -

http://www.highbeam.com/doc/1G1-91972717.html

Funny, but when I am in need of scarf to fit some funky loading issue, I always at least initially, look to the appendix in EHC for a list of potential choices.

Hi Will,

Thanks for those links - both of which seem to require registration and paying a fee. I agree that English Historic Carpentry is also my usual start point for selecting an all timber scarf joint as found mainly in buildings. Unfortunately this scarf joint is unsupported and will have to generate the same load, moment and shear carrying capacity as a continuous timber, hence the already recognised need for metal reinforcement. The marriage of differing materials is not uncommon in bridge, mill and ship building (rope / timber mast joints) and, thinking aloud, I seem to recall that the TFG Lexington Bellifortis trebuchet mast was banded to help hold it together. I shall need to retrieve TF No 44 to see what clues and / or design considerations are detailed within.

The manual reference provided by Tim is excellent and its worthy of note that the engineering for this document was done by Dr. B Brungraber.

Mo,

Thank you for your contributions. I did say at the outset that this was to be a heavy duty joint and would need a bolted / banded design.

Please don't punish yourself (or me) - all will be revealed in due course when I am a little more confident (or not !) about being able to produce a workable design solution.

Regards

Ken Hume

Hi,

I have now retrieved TF No 44 and Colonel Neel says "some main beams appear to be made up of several pieces scarfed and laminated, held together with Dutch pins and bound with rope coils, or with iron bands".
What are Dutch pins ?

Regards

Ken Hume