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RE: 3000 psi for LA DBS Requirements

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Dennis:  There is an exception to the required 3000 psi in Sec. 1921.2.4.1 (2001 CBC) that says:  "Footings of buildings three storeis or less may have concrete with f'c of not less than 2500 psi".  This would allow most small buildings with grade beams to use only 2500 psi if the design warrents.  I don't know if City of LA has removed/modified this exception in the Code or not...it does'nt look like they allude to the exception in their standard correction list as you have copied below.
 
Steve Widmayer, PE
-----Original Message-----
From: Dennis Wish [mailto:dennis.wish(--nospam--at)verizon.net]
Sent: Sunday, October 10, 2004 11:22 AM
To: seaint(--nospam--at)seaint.org
Subject: 3000 psi for LA DBS Requirements

The closest I could get to the 3000 psi requirement for grade beams is still written in the City of Los Angeles (which I have always used as a standard) LARUCP R-1 Occupancy Plan Review List:

http://netinfo.ladbs.org/ladbsec.nsf/0/5b134e7ca1950f8a882569cf0066a669/$FILE/R-1RESIDENTIAL0603.pdf

 

Number 115 on sheet 22 of 23 states:

“Add the following material specifications and/or notes to plans;”………

“Concrete: Standard 2500 psi concrete. 3000 psi minimum for grade beams and caissons.” (1905.1, 91.1921.2.4.1)

“Continuous inspection by a deputy inspector is required for all concrete designed with f’c greater than 2500 psi.”

 

Gosh, I knew I wasn’t going nuts here. While it is required for R-1 Occupancy, I believe it was the standard of practice for moment frame grade beams during the era of RGA 1-91 but this may have changed between 1993 and the present since I have not done much retrofit of existing buildings during this era. I have, however, designed grade beams for custom homes and have required 3000 psi concrete in my general notes without exception.

 

Respectfully,

Dennis

Dennis S. Wish, PE

California Professional Engineer

Structural Engineering Consultant

dennis.wish(--nospam--at)verizon.net

http://www.structuralist.net

 


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