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RE: Shear Key in Basement walls

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Gautam
you might have more of an issue with expansive soils or hyrostatic pressure
acting as an uplift force depending on your local soils condition.  For the
slab, it will resist sliding, minimum shrinkage reinforcement  will do just
fine, any way I have not seen that to be a problem in our area.  It is
unlikely for the slab to buckle upward just due to the bottom reaction
given by your analysis.  Just remember, you have to fail the soil
supporting the footing, passive pressure for confined earth     before
realizing axial loads on the slab if you watch construction sequencing.
That is, it is likely that the slab will be installed last.  Dowels between
the slab and the wall are a good idea and do restraint the slab at the cold
joint.
that's my 0.02 cents on it.
Samir Y. Ghosn, P.E>
Harris & Associates
At 04:54 PM 7/11/2003 +0000, you wrote:
>Jake:
>
>I am kinda confused on the shear friction concept.  I agree that one can use 
>shear friction to transfer the active soil pressure from the stem wall to 
>the base slab.  Part of that load can be transferred to the foundation 
>through friction between the base slab and the foundation.  But what about 
>the base slab itself - what do you design that for ?   I would appreciate a 
>clarification on process you use - especially the  base slab design.
>
>PS: The retained earth is 9 feet.  This is a residence.   I do not have the 
>building dimensions off hand - the building is at least 40 feet wide x 100 
>feet long.
>
>Gautam
>
>
>>From: "Jake Watson" <jwatson(--nospam--at)utahisp.com>
>>Reply-To: <seaint(--nospam--at)seaint.org>
>>To: seaint(--nospam--at)seaint.org
>>Subject: RE: Shear Key in Basement walls
>>Date: Fri, 11 Jul 2003 08:24:05 -0600
>>
>>If this a standard house and you have reinforced the walls, shear friction
>>should do the trick.  Then you won't have to worry about a fancy analysis 
>>to
>>justify it.
>>
>>Jake Watson, P.E.
>>Salt Lake City, UT
>>   -----Original Message-----
>>   From: Tripp Howard [mailto:tripphoward(--nospam--at)yahoo.com]
>>   Sent: Friday, July 11, 2003 6:45 AM
>>   To: seaint(--nospam--at)seaint.org
>>   Subject: Re: Shear Key in Basement walls
>>
>>
>>   Just curious how many people use shear keys.  I've moved away from them
>>since they can be hard to form and make installing waterstops difficult.  I
>>typically just roughen the surface between the wall and the footing and
>>check it with the shear friction provisions.  What do others think about
>>doing it this way?
>>
>>   On another note, I've gone away from using the traditional rubber
>>waterstops due to the difficulty in installing them properly.  If I need a
>>waterstop, I've been using a swellable hydrophilic waterstop such as
>>Volclay's Waterstop RX.  You can adhere it to roughened surfaces and to 
>>join
>>ends you just but them together.  No welding or special glues required.
>>What are others opinions on these alternate types of waterstops?
>>
>>   G M <newabhaju(--nospam--at)hotmail.com> wrote:
>>     To all:
>>
>>     I recently designed a basement wall as a cantilever retaining wall 
>>with
>>a
>>     shear key. The slab within the two ends of the retaining walls is a 5
>>inch
>>     slab on grade. Due to field condition, the contractor does not want to
>>     intstall the shear keys.
>>
>>     One way to reduce the shear demand at the base of the retaining wall 
>>is
>>to
>>     account for the fact that the first floor provides some lateral 
>>support.
>>     However, because the first floor consists of wood construction, I am
>>     hesitant to do this and prefer to be conservative. ( I do reinforce 
>>the
>>wall
>>     stem for this condition,though).
>>
>>     The second alternative is to assume that the active force on the
>>retaining
>>     wallls at the opposite ends of the basement cancells each other out -
>>     therefore, a shear key is not necessary. This condition should hold 
>>true
>>no
>>     matter how far the two retaining walls are located - in finite terms,
>>thoguh
>>     - provided they are of the same height and have simillar backfill. The
>>     slab-on-grade will be subjected to compressive forces from the 
>>retaining
>>     wall and should act as a plate with compressive forces on all four 
>>sides
>>(
>>     four sides of the basement).
>>
>>     My question to you all is - how do you design the slab? I am thinking 
>>of
>>     taking a unit width of slab and finding the allowable compressive load
>>based
>>     on Euler's formula with a factor of safety. Since water will be
>>drainded,
>>     moment due to water pressure should not be an issue.
>>
>>     If the wall design were to include seismic forces - (Mononobe-Okabe
>>     equation)- how would one dissipate the shear for the worst case 
>>scenario
>>for
>>     seismic forces acting in the same direction for the two opposite 
>>walls.
>>
>>     Your comments would be highly appreciated.
>>
>>     Gautam
>>
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>>   Tripp Howard
>>
>>
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