5_CEG 4012 Notes Fall 2011 CEG 4012 Notes Fall 2011

5_CEG 4012 Notes Fall 2011 CEG 4012 Notes Fall 2011 - = =...

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S2 Pyramid Approximation For Surface Loads: The "2:1 melhod "used for "back of Ihe envelope" solutions (seen on the PE exam). Q q = unit pressure r+--" o A=LoadedArea =BxL Q = Tolal Load = q x B x L where B = width (short sjde, alwill's) L _ length !loM-side) - tr,'p = lotarTciad in Ibs, tons, kips, kN q, P = uniform pressure in psf, tsf, kN/m' a Loaded area expands at a 2:1 (V:H) slope in o each direction. :. at depth Z, the contact area zJ2 B zJ2 L zJ2 z .'\" = qBL .. (B+zXL+z) Q d a For the fooling comparison proposed above: 10' x 10' fooling: qA 6crVA 100' x 100' footing: q. .6.crVB = 50 lI(10'xIO') = = 50/[(10+20)(10+20))
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Unformatted text preview: = = 5000 I I (1 OO'xl 00') = = 5000 V [(100'+20')(100'+20')) = a The pyramid approximation prOVides a constant ..1a. .. over the expanding contact area (B+z)(L+z), but day = 0 outside this area. A gradual distribution is more realistic. nav :I; constant vs. !J.crv = constant ~ Mv=O I I Pyramid Solulion Actual Case o The theory of elasticity will give a better pressure distribution. On any horizontal plane the sum of the vertical stresses over the pressure area equals the applied surface load. q = Q/A q=Q/A :.---r1JItD---z...
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