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RE: Historic Wood Structure; How to Dete

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Roger,

I appreciate your input.....let me ask you about a couple of your
comments.....

I always thought grade & species were equally important with regard to
member strength....just the allowable bending stress on a Mixed Oak can
range from 725 psi (for a No. 2) to 1350 psi (Select Structural) per the
1997 NDS supplement.....and I'm still a little confuse.......if I just
assume this value, what is my engineering basis for this assumption ?

I do like the idea regarding the increment borer.....and no, they did
not use one.....they mainly "looked" and "tapped" and did some drilling
with 1/8" bit & a portable drill....

Thanks
Robert 

-----Original Message-----
From: Roger Turk [mailto:73527.1356(--nospam--at)compuserve.com] 
Sent: Friday, April 25, 2003 10:27 AM
To: seaint(--nospam--at)seaint.org
Subject: RE: Historic Wood Structure; How to Dete


Considering the size of the members you described, I assumed that it was

probably a pre-1930's industrial building.  Yes, I would still use the
No. 1 
grade stress values in the 1997 NDS to evaluate the structural adequacy
of 
the members.  Since the species is identified, that is the most critical
in 
determining member strength.

As far as evaluating the effect of weather/exposure damage, that would
have 
to be done on an individual basis.  If the various specialists did not 
examine some of the more damaged members using an increment borer, I
would 
request that they do so.  (I would also want to be there to make sure
that 
they would not be taking a core at a critical location/direction.)

HTH

A. Roger Turk, P.E.(Structural)
Tucson, Arizona

Robert Rogers wrote:

. > Did I mention the building was constructed around 1918 ?....would
you . > still use the same approach ?

. > Additionally, how would you take into account possible weathering /
. > exposure damage ?

. > Robert

-----Original Messages-----
From: Roger Turk [mailto:73527.1356(--nospam--at)compuserve.com] 
Sent: Friday, April 25, 2003 8:37 AM
To: seaint(--nospam--at)seaint.org
Subject: Historic Wood Structure; How to Determin


Robert,

Prior to 1970's, the lowest grade of structural wood was "Construction 
Grade."  Comparing the visual grading rules of 1960's "Construction
Grade" to 
today's grading rules, these are equivalent to today's No. 1 grade,
therefor, 
I would use the allowable stresses for today's No. 1 Grade to evaluate
the 
structural capacities of the existing members.  (Also, I believe that
the 
UCBC states that No. 1 grade stresses be used.)

HTH

A. Roger Turk, P.E.(Structural)
Tucson, Arizona

Robert Rogers wrote:

. > A question for all of my colleagues.......looking at an existing
brick . > masonry shell & interior wood joist, timber girder, timber
column . > 4-story structure......roof was off top of structure for 3~4
year time . > frame and some water damage has occurred.  Joists are 3x14
@ 14" o.c. . > and timber girders are range from 10x12 to 14 x16 and the
columns range . > from 10x10 to 14x14.  Floor dead loads are increasing
but live load is . > decreasing (used to be an old light-industrial
building; being converted . > to "lofts"; loads added to roof).  Joists
span ~19 feet, girders span . > ~14 ft. and column height ~12-13 feet.
 
. > Material testing company performed visual / sounding of wood members
and . > provided recommendation on replacement of specific members but
refused . > to provide any allowable stresses for the wood members.
Material . > testing company provided species type but would not
identify grade . > (thereby "locking-in" allowable stresses per NDS
supplement for use in . > structural analysis).
 
. > How would any of you approach this situation to try and get a handle
on . > the amount of strength of the existing wood joists, wood girders,
and . > wood columns (i.e, pin-down the allowable wood stresses) ?  I've
spoke . > to a few "experts" and have their recommendation......what
would the . > everyday structural practitioner do ?
 
. > Robert Rogers, PE

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