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Re: Existing Buildings

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Jordan,

I realize that you live and work in a location where Canadian codes do not apply, however, I thought you might be interested in the following as information of interest or as a guideline in some area where you may have no other guideline.

Canadian Code Considerations

The Alberta Building Code in force is a derivation of the 1995 Canadian National Building Code. Section 4 is virtually (or actually) identical, and the 1995 Structural Commentaries are specifically made mandatory. The following two paragraphs are an excerpt from one of these commentaries.

Commentary K

Evaluation Based on Satisfactory Past Performance

18. Buildings or components designed and built to earlier codes than the benchmark codes or standards, or designed and build in accordance with good construction practice when no codes applied may be considered to have demonstrated satisfactory capacity to resist loads other than earthquake, provided: a.. careful examination by a professional engineer does not expose any evidence of significant damage, distress, or deterioration; b.. the structural system is reviewed, including examinations of critical details and checking them for load transfer; c.. the building has demonstrated satisfactory performance for 30 years or more; d.. there have been no changes within the past 30 years that could significantly increase the loads on the building or affect its durability, and no such changes are contemplated.
Serviceability

44. The serviceability criteria contained in Part 4 and referenced standards are intended for the design of new buildings. For existing buildings, in many cases demonstration of satisfactory performance eliminates the need to apply the serviceability criteria given in Part 4 and referenced structural standards for structural evaluation. Unacceptable deformation, settlement, vibration or local damage will usually be evident within a period of 10 to 30 years from construction. Examples where serviceability evaluations may be required include change of use, or alteration of building components affecting the properties of the structure.

Regards,

H. Daryl Richardson

----- Original Message ----- From: "Jordan Truesdell, PE" <seaint1(--nospam--at)truesdellengineering.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Friday, January 12, 2007 6:21 AM
Subject: Re: Existing Buildings


If something goes wrong in the building after I have certified that it is okay, I'll find myself in court - and not getting paid for it.

I do a lot of residential->commercial reviews, and some commercial capacity upgrade reviews. We apply the current code loads and most of the code provisions. Where detailing conventions have changed, we do a (fairly) rigorous analysis that shows on paper that the connections are sound, or we beef them up. I have bent the rules on occasion where, in my professional opinion, the condition was not critical to the safety of the building. An example would be a wood floor, finished top and bottom (upper floor) that had an fb/Fb of about 0.6, but a maximum live deflection of L/345. I'm comfortable with that. Occasionally I may also give a pass to local roof structures which are original, have been in service for more than 75 years, and the members are in good condition, but which don't meet the letter of code - even for capacity checks. Of course, I happen to know that there was a 100+ year snow event 50 years ago, and anything that's original and still in good condition has been proof loaded to my comfort level.

So, in answer to your question, yes - I will use engineering judgment in place of strict code adherence in some cases, but for the most part I try to conform to the current code release.

Jordan



... Does anyone here have experience in checking the capacity of existing designs in this manner, with total disregard to the building codes? Is this typical practice when substantial verifications of the existing construction can be accomplished?
 Will Haynes, P.E

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