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Antique Timber Testing #7975 06/22/99 12:33 AM
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Wood source Offline OP
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I have a client who wants to purchase an antique timber frame, ash timber,but wants the timbers tested for strenghth. For example, he wants to know what size timber to use for particular spans. My quandrie is where can I get this done near Ottawa, Canada? Can anyone direct me, please.

Re: Antique Timber Testing #7976 06/22/99 08:23 AM
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Ed Levin Offline
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Check the Guild Roster for members near Ottawa. They should be able to recommend engineers with timber experience whom your client could consult. One candidate is Dave Trudell of Markdale, Ontario who was the engineer of record on the Speed River Covered Bridge in Guelph.

By the way, it's no big deal to check timbers for stiffness. You can do it by simply supporting the ends, carefully measuring the span and resulting sag with a known weight suspended from midspan, then plugging the values back into the appropriate formula (see below) solved for modulus of elasticity.

Here is the formula for midspan deflection under a single concentrated load at midspan (metric units can be substituted as desired):

delta = PL^3/(48EI) where

delta is the deflection (inches)
P the load (pounds)
L the span (inches)
E the modulus of elasticity (pounds per square inch)
I the moment of inertia (inches to the fourth power)

For rectangular beams, I = bd^3/12

Solving the equation for E, you get

E = P x L^3 / (48 x I x delta)

Good Luck!


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