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Re: Using Wood-Framed Conventional Construction as a Lateral Shear Resisting ...

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The shake test I'm familiar with (built in a warehouse by skilled people...ymmv with real construction) yielded a result very close to the theoretical total shear if you counted every sliver of wall, no matter how small.  The implication is that it called into question whether the limitations on shear panel size were realistic, but building a house without environmental considerations or a bottom-dollar crew may be unrealistic as well.

I have scaled back and will take a "where required only" approach to residential lateral, and here's why:

If the wall in question met the prescriptive code, I would not be involved. Although we all know prescriptive is below the calculated force resistance necessary by engineering calcs, it has been decided that these systems perform adequately. That kind of performance criteria is the basis of engineering - those requiring three significant digits should be physicists.  By engineering a single wall, I'm providing more strength than is required by prescriptive code, but most likely less stiff than if the wall had been built of a solid sheet of sheathing from corner to corner. Since I am stronger than minimum, and more flexible than the maximum that could be built (for those worried about creating an unexpected collector), the design that goes out my door exceeds the requirements of the prescriptive code, and I sleep well.

I try not to get wrapped up in the detailed mechanics, especially on wood construction, as it only gets you in trouble when looking at a real structure. We ignore many items in buildings which add stiffness and strength, and the loads we use probably apply to less than 30% of the structures built due to various environmental, topographical, and other localized effects.

Jordan


Joseph R. Grill wrote:

I recently attended a seminar regarding the conventional provisions.  In the past I didn’t even want to hear about them, but in order to compete I may have to consider.  Anyway, the triggers mentioned by Joe are correct as Joe mentioned.  The speaker, evidently from the way he spoke, uses the conventional provisions quite a bit and he is located in California (for what it’s worth to the discussion).  The speaker said he designs partially to engineered provisions of a wall if it doesn’t conform to the conventional provisions.  I was shaking my head for most of the two days, but that is the way the code is written.  The speaker also said that as more of the residence does not conform to the conventional provisions then the engineer has to use judgement as to if the entire structure requires an engineered design.  He showed shake table tests of a structure constructed per the conventional provisions and looked as if it performed well.  What can I say?

Joe Grill 

 

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