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Re: Acceptable Level of Overstress

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Gerard:

When we check existing wood beams we use the allowable stresses at the time the building was designed/built.  Our office standard is 5% overstress due to the variability in the material and how likely the member will see the full load.  If it's 6% or higher then we might come in and sister on a member at mid-span to bump up the section.  There are other solutions too if it's exposed.

I'm assuming it is bending stress that is controlling.  Make sure you are using all allowable stress increases.  If it's shear stress then you could use the newer NDS which allows a higher shear stress.  The reason for this was discussed in previous threads.

Seth

At 03:22 PM 12/3/2003, you wrote:
What is the general practice on acceptable level of overstress when checking an existing member for capacity?
 
I have an existing wood beam that is 6% overstressed with new loads. I am prepared to deem that ?Acceptable?. I was always taught that 10% or less overstressed is okay. I have a plan checker wanting to cut the limit at 5%. Is this somewhere in the code???
 
Tia,
-gm
 
Gerard Madden, SE, PE
California Licensed Structural and Civil Engineer
 
Madden Engineering
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