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RE: Spec needed for 3000 psi concrete

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Steve, Stan and others:

Without spending the time to search for this information, it was my experience on all seismic retrofits done in the 80’s and early 90’s within the city of Los Angeles that f’c=3,000 psi concrete was to be used for all moment frame grade beams in order to force deputy inspection. I don’t recall if that is in the City of L.A. Building code (which I used as a standard in the past) or if it is in the UCBC Appendix Chapter 1 for URM buildings or if it is specified in the Existing Building Code.

 

Inasmuch as the requirement is conservative and will only enhance the protection of my design, it is worth the cost of the deputy inspection. The building is owned by the City who has no problems with securing as much evidence that the grade beam was installed as designed and probably reduces my potential liability if you wish to look at it like this.

 

Steve, I believe the code requires deputy inspection on all concrete with f’c> 2,500 psi. I’m not sure where the 4KSI limit comes into the code either.

 

Maybe someone who is doing this work more often now (it’s been almost ten years since my last retrofit) can clarify the strength requirements.

 

Dennis

 

Dennis S. Wish, PE

California Professional Engineer

Structural Engineering Consultant

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

http://www.structuralist.net

 

-----Original Message-----
From: S. Gordin [mailto:scgordin(--nospam--at)hotmail.com]
Sent: Saturday, October 09, 2004 7:55 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: Spec needed for 3000 psi concrete

 

Stan,

 

Your point is not quite clear to me.

 

At least in our (UBC) country, without the deputy, you will not be able to utilize the actual 4,000 strength.

 

The design would have to be based upon 2,500 psi concrete. 

 

For "smaller" jobs, it is almost always sufficient anyway...

 

Steve Gordin

Irvine CA 

----- Original Message -----

Sent: Friday, October 08, 2004 5:24 PM

Subject: Re: Spec needed for 3000 psi concrete

 

Why use "3000 psi" concrete which then requires a Deputy inspector at a cost of about $75/hr?

Instead specify 5.5 or 6 sack mix, limit the water and you will end up with about 4000 psi but won't have to pay for the inspector.

 

This is especially important for smaller jobs.

 

Stan Scholl, P.E.

Laguna Beach, CA


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