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Re: 1950's era timber properties - Aren't they brittle

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Regardless of the grading method used, old DF is brittle compared to new wood (not talking about Home Depot green lumber) * you are likely to split the wood while driving nails; and if you manage to drive nails, pulling them out is a nightmare. 

It appears old wood is superior strengthwise but lack toughness - that should require modifications to R value (if used in shear walls), and phi factor (for LRFD).

Suresh Acharya, S.E.




>>> jrgrill(--nospam--at)cableone.net 2/4/2006 8:47 AM >>>
That is what I have heard also, that you should check existing structures based on the new stress values.  It's not the wood that has changed, but the methods of testing.

Joe Grill
  ----- Original Message ----- 
  From: Mlcse(--nospam--at)aol.com 
  To: seaint(--nospam--at)seaint.org 
  Sent: Friday, February 03, 2006 6:51 PM
  Subject: Re: 1950's era timber properties


  I would use the latest NDS values for checking the 8x14, assuming DF#1.  Methods of testing the properties of wood have changed over the years, and design values have changed based upon the testing. Sometimes the values go up, sometimes they go down.  In some cases, the previous testing methods were found to not be accurate, resulting in large changes in allowable design values, such as tension values for DF in the early 70's. 

  I would not evaluate a piece of lumber based upon older allowable design values given in previous building codes.

  Maybe Buddy Showalter can provide additional information, especially regarding old growth wood versus new growth wood where trees are harvested after a relatively short growing period

  Michael Cochran S.E.  SECB


  In a message dated 2/3/2006 4:59:00 PM Pacific Standard Time, elig(--nospam--at)psm-engineers.com writes:
    Can someone give me a ballpark value for bending stress in an 8x14 beam.  Assume DF#1.  Manufactured in 1950.



    thanks



    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    Eli S. Grassley, PE

    PETERSON, STREHLE, MARTINSON, INC.

    CONSULTING ENGINEERS




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