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10_CEG 4012 Notes Fall 2011 CEG 4012 Notes Fall 2011

10_CEG 4012 Notes Fall 2011 CEG 4012 Notes Fall 2011 - for...

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S11 ~ ~trlp and Square Footings Strips footings have fixed width and infinite (or relatively long) length and are often used for smaller buildings (1-2 story) and walls. Square footings are a special case of the rectangular footing. B q z Influence charts are available for both Boussinesq and Westergaard solutions: x 1. Express vertical distance from footing bottom relative to (as fraction of) the footing width B (i.e. zlB) Express lateral distance from footing center relative to (as fraction of) the footing width B (i.e. xlB) 3. In chart use zlB on vertical axis and xlB on horizontal axis to find stress contour as a fraction of the uniform footing pressure, I1CJ v = I x q. (Also can approximate, with some error, a rectangular footing by using the chart for a square footing with an equivalent footing width B'= .JLxB) Find and compare location of 10% contour (0.1 q) for square vs. strip footing and
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Unformatted text preview: for Boussinesq vs. Westergaard solutions. Boussinesq is conservative (greater stress) at centerline. Westergaard was developed for stratified deposits (alternating layers of soil). a Example 1: 5 ft x 5 ft square footing, 30 ton load => q = 30/(5x5) = 1.2 tsf tJ Find Boussinesq I1crv at a depth of 10ft, on the centerline and 15 ft from it. ( ,\ c.. I-lM:r o ( I) I ') ~i+-} 1 xl-oJ.--) t1o;=().f[ q ~ 6. I .. (l,t,ll atC.L. ":fIe = I/)/S=':L 8 -/5"--I = o.,~kC at x=15 ft A<1v ': ><h: ,s/s: 1, 6 .:=;> 0, ONe/ ': (j. /)l~ (,.1)-: .o. ..0r:!J. .!./ "t/ f> ~ f0lr: 2 ,. /a: aIr:. A~-: o'3~f : o. D. (1.1.) ~ o. 3i t~/ (~). yrttkr) at C.L. a Example 2: 5 ft wide strip footing, 6 ton/ft load => q = 6/5 = 1.2 tsf (same as ex.1) Find Boussinesq I1crv at a depth of 10ft, on the centerline and 15 ft from it. at x=15 ft ~ /6 ; 'o/s ~ '1...
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