[TheForge] Timber Straps

Thu Oct 24 15:11:00 2002

Joe,
You expressed all my concerns perfectly!!!

Ray
> 
> From: Joe Chadwick <[email protected]>
> Date: 2002/10/24 Thu PM 02:41:27 EDT
> To: [email protected]
> 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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