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RE: Retaining wall footing resultant CBC

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I don't see any commentary either. However, Page 19 of the 7th edition Basics of Retaining wall design book has one sentence that states that soil above footing on the toe side will oppose the heal side active pressure with a net reduction in overturning and lateral force for sliding. It make sense to me that if you have alot of soil above the toe you would get some active pressure in addition to the passive resistance. But checking a wall with 2 feet of soil over the toe barely has an effect. Seems to me that would be the call of the soils engineer. I see soils reports that don't allow the upper foot of soil for any passive resistance. The only way I know of  to model this in retain pro is to take a percentage of passive under the Footing>Key dimensions tab.

From: SGE Structural [mailto:sgordin(--nospam--at)sgeconsulting.com]
Sent: Thursday, April 09, 2009 10:22 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: Retaining wall footing resultant CBC

Dear Mr. Brooks,
 
Could you please comment on the rationale behind the available input of "active soil pressure on the toe side"? 
 
I cannot come up with any physical justification for the use of that option. To the best of my knowledge, the RetainPro and Enercalc manuals are silent on the issue.  
 
Thanks,
 
V. Steve Gordin, SE
Irvine CA
 
 
----- Original Message -----
Sent: Thursday, April 09, 2009 09:49
Subject: RE: Retaining wall footing resultant CBC

This is an arguable issue, but I accept the design if outside middle third if soil pressure OK and stability >1,5.

Hugh

 

From: Jeff Smith [mailto:jeffsmith7(--nospam--at)comcast.net]
Sent: Thursday, April 09, 2009 9:44 AM
To: seaint(--nospam--at)seaint.org
Subject: Retaining wall footing resultant CBC

 

California Building Code section 1806A.1 requires the resultant must be in the middle half using 1605A.3 load combinations. I don't see this requirement in chapter 1806. For non essential facilities are there any requirements for the retaining wall resultant, or do we just need a 1.5 safety factor?

 

Jeff