RE: S.O.G. for resisting basement wall lateral force[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: <seaint(--nospam--at)seaint.org>
- Subject: RE: S.O.G. for resisting basement wall lateral force
- From: "Haan, Scott M POA" <Scott.M.Haan(--nospam--at)poa02.usace.army.mil>
- Date: Tue, 3 May 2005 15:10:12 -0800
I was hoping someone else would respond, because this is a perplexing problem. I have seen a bunch of people assume a slab on grade resists forces at the bottom of a basement wall and not many people design it. I have had to look at a similar 24’ tall situation. It is going to need buttresses, dead men or a reinforced earth retaining wall behind the wall or something.
For a 8’ floor to floor height no problem. For 20’ retained height with a 45 psf at rest pressure how does it work [especially if the building is only buried on one or two sides]? 20’*20’*45/2*2/3=9000 lb/ft at the slab on grade and another 4500 lb/ft at a restraint at the top of a wall. For 4” 2500 psi concrete .85*2*sqrt(2500)*4”*12”/1.7=2400 lb/ft allowable shear. Slab steel is going to be required for shear. For friction to take out the lateral thrust at the base you need 13500/.35=38571 lb of gravity load for friction for each foot of building width. Each foot of building width would require a h=sqrt(13500/(.5*300))=9.5 ft high one foot width of lateral bearing. This is in addition to the friction and lateral bearing resistance for lateral forces. For tall buildings no problem but for a low light small foot print building buried on only two sides not an easy solution?
For a slab on grade to work as a diaphragm you would need to have steel through control joints and dowel to side walls with no isolation joints and have enough friction from gravity loads and lateral bearing at interior footings and side walls for it to work. If it is a vault kind of configuration, you could use wall formulas to check the slab on grade for compression between footings at opposite sides or to interior footings with enough friction and bearing. If there is a vapor retarder under the slab it may be hard to get friction into soil underneath the slab on grade.
From: Bruce Holcomb
In this particular case, it is 20’-0” tall. But I am interested in ‘how’ to analyze the slab-on-grade to resist the lateral earth pressure so I can use for other walls on future projects.
How tall is the wall?
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