[TheForge] Re: (no subject) Timber Straps

Fri Oct 25 09:25:00 2002

So far everyone has confirmed my hesitation to proceed on a photo for design. I contacted the architects and told them if I was to do anything with the project, they needed to provide a detailed drawing of exactly what they want. The builder thought I could quote them from a color copy of a magazine photo!!

We'll see.
Ray
Cincinnati

> 
> From: "Walter L. Mullett" <[email protected]>
> Date: 2002/10/25 Fri AM 07:56:40 EDT
> To: <[email protected]>
> Subject: Re: [TheForge] Re: (no subject) Timber Straps
> 
> Wood connectors are hard to design.  When I took my wood design course in
> college, we used to say wood structural design "...depended on rather or not
> it was Thursday and if it was raining". There are a lot of variables and
> then when you account for all you can think of, mother nature puts a knot
> somewhere.
> 
> If this is a commercial building, let someone else design the connectors.
> If it's a house with small spans, Ralph's rules may work.  Wood usually has
> what we call a "running" factor.  You hear it crack and you have time to run
> before it falls.  Concrete, steel and steel connectors don't give you that
> option.
> 
> BTW:  A lot of people don't understand that more is not always better.
> There are instances where more of something in one place can overload
> something else and cause a failure.  Wit connectors in bolts, more bolts
> cause less wood.  If you don't know or don't have experience, let someone
> look at the specifics who does.
> 
> Walt
> -----Original Message-----
> From: Joe Chadwick <[email protected]>
> To: [email protected] <[email protected]>
> Date: Thursday, October 24, 2002 2:43 PM
> Subject: [TheForge] Re: (no subject) Timber Straps
> 
> 
> >Ray-
> >
> >If there are engineer's design drawings, this could be a cinch. Cut, punch,
> >weld, finish.
> >
> >If the builder just gave you a couple of his own sketches beware.
> >Contemporary timber frames are frequently constructed with members having
> >higher-than optimum moisture content. As the wood shrinks, extra stress is
> >put on the bolt patterns in the wood, simple bearing sometimes goes away,
> >and lots of unintended force vectors convene at joints never designed for
> >the load. So the thickness of the gusset, the diameter of the bolt and the
> >pattern of the bolt need to be figured together. Most of the time, the
> >number of bolts needed to transmit a load to the wood will  remove so much
> >of the wood that there is no capacity left in the member. There are
> >however, a few styles of  "shear" connectors that can be bought or made
> >depending on the  look of the joint.
> >
> >When I worked on coal-breakers (collieries) in my lost youth, gussets and
> >straps usually started at 1/2". Granted, corrosion was a consideration, but
> >later in school, the math proved out. Gravity load is only part of the
> >picture, and a small part too. Wind loads, and the resulting stress
> >reversals are spooky, especially since there is little in the way of
> >redundancy in timber frames. I also don't know if your codes require
> >seismic design for houses.
> >I'm not trying to sound whiny. Like your contractor, everybody wants to
> >shed job-costs and liability. Even if you (or whomever eventually does make
> >these) hired an engineer to design the joints, that team holds more
> >liability than if one were simply fabricating.
> >
> >Jeeze. Now that I took all the fun out of that job, I better get back to
> >feeding the fire in the boiler of the bureaucracy.
> >
> >
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