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Re: Retaining wall footing resultant CBC

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Dear Mr. Brooks,
 
As far as I know, active pressure on a cantilevered retaining wall develops following some movement (rotation) of that wall under the pressure from the retained soil.  If we have active pressure on the retained side, we cannot physically have a simultaneous active pressure on the toe side, where the movement of the wall occurs toward the soil, i.e., in the opposite direction. 
 
The program essentially combines the active and passive pressures on the toe side to resist the active pressure on the heel side.  This does not appear physically obvious within the theories/assumptions used. 
 
Can you please comment on the physical nature behind that option?
 
Thank you,
 
V. Steve Gordin, SE
Irvine CA    
 
 
----- Original Message -----
Sent: Thursday, April 09, 2009 14:48
Subject: RE: Retaining wall footing resultant CBC

Steve   

Although a foot or two of soil over the toe would not be significant, Retain Pro allows the option since a greater height over the toe could significantly reduce overturning and sliding due to its countering effect.  It?s the designer?s option.  See page 42 of the RP user?s manual.

Hugh Brooks, SE

 

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 -----

From: Hugh Brooks

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