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RE: Acceptable Level of Overstress

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Michael:
 
I obviously did a poor job crafting my post, because you seem to have missed my key point.  It's not a matter of your professional judgment or that of other structural engineers, it's a matter of what the nontechnical jury believes after the plaintiffs lawyer repeatedly reads them the text of the code, word for word.  In this instance, your professional opinion that you "wouldn’t see a problem allowing a 10% overstress or maybe even higher" will be cited at direct evidence of gross negligence ... even if your opinion is perfectly reasonable!
 
Stan
 
-----Original Message-----
From: Michael Bryson [mailto:mbryson(--nospam--at)NYASE.com]
Sent: Thursday, December 04, 2003 3:41 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: Acceptable Level of Overstress

For evaluating an existing structure that is in good condition and has essentially proven itself for 20 or 30 years, I wouldn’t see a problem allowing a 10% overstress or maybe even higher.  I think you could do a very detailed mathematical/statistical study that would show you have the same or less probability of failure as with new construction.

 

Now adding a new loading condition to an existing structure, I would only probably allow an overstress of 5%.

 

-----Original Message-----
From: Caldwell, Stan [mailto:scaldwell(--nospam--at)halff.com]
Sent:
Thursday, December 04, 2003 12:59 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: Acceptable Level of Overstress

 

Gerard, and everyone else:

 

As the years pass, I am increasingly involved as an expert witness defending fellow design professionals.  I find that an engineer learns more from failures than from successes, and it is always preferable to learn from the mistakes of others.  One thing that I have learned is that some plaintiffs attorneys are very skilled in convincing nontechnical juries of the absolute sanctity of the exact wording in applicable building codes and standards.  For example, I know of one current case where a multi-million dollar judgment hinges on a discrepancy of less than 2 psf net roof uplift, even though there is a residual factor of safety in the uplift design of at least 1.25.

 

Imagine the situation you might find yourself in if one of your projects experiences a failure and it is determined that you intentionally approved a 10% overstress in some member, even if this member is unrelated to the failure.  The plaintiffs would have a "field day" at your expense.  When I entered the profession in 1970, I was taught that the various codes allowed an overstress of 3%.  I have used that value for the past 33+ years.  If I can convince myself that IBC and other current codes now allow 5% overstress, I will adjust accordingly.  However, I would never consider approving an overstress above this amount.  In today's litigious world, such practice would be foolhardy.

 

HTH,

 

Stan R. Caldwell, P.E.

Dallas, Texas

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Beat LA!!    Beat LA!!

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