[TheForge] Re: (no subject) Timber Straps

Fri Oct 25 18:33:00 2002

I might give an estimate off the photo but explain that exact price will 
follow the Architect's drawings ;-) Leave the design to someone with an 
engineering degree (Let it be someone elses' fault)
Larry Brown

At 09:15 AM 10/25/2002 -0400, you wrote:
>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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