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Re: UBC DRIFT VERSUS CBC DRIFT

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In 1630.9.1 It actually first says "Delta_S, a static, elastic analysis of the lateral force-resisting system shall be prepared using the design seismic forces from section 1630.2.1"

Those are the base shear equations which are already factored. Why they would then direct you to section 1612.2, which doesn't alter those computed values, is what is weird. Why place that sentence in there at all for ASD design or Drift if you are already instructed to use factored loads? Currently it reads as an exception ( i.e. for ASD and Drift) clause but doesn't contain an exception.

-g

On 1/10/07, David Topete <dtopete(--nospam--at)gfdseng.com > wrote:

Doesn't make much sense…  It tells you to use the LRFD combinations "where Allowable Stress Design is used…"

 

David A. Topete, SE

Structural Engineer


From: Gerard Madden, SE [mailto:gmse4603(--nospam--at)gmail.com]
Sent: Wednesday, January 10, 2007 10:00 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: UBC DRIFT VERSUS CBC DRIFT

 

Looks like they did switch back in the UBC.

This is the original Errata changing it to 1612.3:
http://www.iccsafe.org/cs/codes/errata/1997-ubc-p2.html

Then they came out with another one that switched it back to the original text: http://www.iccsafe.org/cs/codes/errata/1997-ubc-jan-01.pdf

For some reason, I thought it went back one more time to 1612.3....

-g




On 1/10/07, Gerard Madden, SE < gmse4603(--nospam--at)gmail.com> wrote:

Dave,

do you have the 98 CBC or 2001 CBC? I have VOl 2 of the 98 CBC, but not the 2001. Didn't think anything changed structurally so I didn't get the 2001 version of Vol II (el cheapo).

I'll re-check the UBC errata to see if they switched back. I know they flip flopped an errata but I thought that was the the EQ 30-7 thing.

-g




On 1/10/07, David Topete < dtopete(--nospam--at)gfdseng.com> wrote:

G-

Have you checked the ICC website for errata?  My copy of CBC says the same.  I would think you would use the ASD load combinations of 1612.3, and explain the issue to a plan checker, if needed.

 

David A. Topete, SE

Structural Engineer

 

GFDS Engineers

543 Howard St. , First Floor

San Francisco , CA 94105

v : (415) 512-1301 x21

f : (415) 512-1302

dtopete(--nospam--at)gfdseng.com

www.gfdseng.com

 


From: Gerard Madden, SE [mailto: gmse4603(--nospam--at)gmail.com]
Sent: Wednesday, January 10, 2007 9:30 AM
To: seaint(--nospam--at)seaint.org
Subject: UBC DRIFT VERSUS CBC DRIFT

 

Section 1630.9.1 of the UBC underwent an Errata. The section originally stated that "Where Allowable Stress Design is used and where drift is being computed, the load combinations of section 1612. 2 shall be used". The Errata changed the referenced section to 1612.3 which uses E/1.4.

In the CBC, it still says 1612.2. Did they flip flop again on this or is there an Errata out there for the CBC?

thanks,
-gm





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