Question

Problem 3: (45 points) A square foundation was decided to be constructed to support the load of a column in a residential building construction project located in Claremont, CA. During the site investigation, only sandy soil (c'=0) was encountered. The ground water was observed at the depth 1.2m from ground level. Obtained samples were tested in the lab and the internal friction angle of the soil was found to be equal to 30°. The unit weight of the soil above and below of the ground water table were found to be equal to 16kN/m and 19kN/mº respectively. Due to some construction limitations, the bottom of the foundation must be place 1.2m below the ground level. The column loads on this foundation will be a vertical load equal of 450kN and a one-way moment equal to 70kN-m. Determine the appropriate size of the foundation in respect to the bearing capacity of soil. Consider a safety factor of FS-6. (Use Meyerhof method). 450 kN 70 kN•m y = 16 kN/m3 c' = 0 d'= 30° 1.21 BXB Water table You - 19 kN/m c' = 0 d' = 30°

Answer 1

am N=16 C=0 2-30 P = 450KN M = 70 KN.mo Df = 1.2 m. Let, rw = 10 kN/m² . BXB NY=19 C-o = 30 For, last term in du formula, 8=8= rsat-tw = 19-10=9 kN/m3 FS = 6. [Meyerhof method.7 Forr, p= 30 S Nc=37.16 19.13 - 22.46 Nr= NA for square and footing, sets and footing, du= 1.38Nc+qNq +0.4 MB Afy q=rof 16x1.2) - = 19.2 kN/m2 r=r = 9 kN/m² -. du = (19.2% 22.46) +0.4+9xBX 19.13) D + 68.7 B 4 31.2 to 0.156 m P 450 6x0.1562 450 B a may Q BL [1+ Goren 82114 B2 450 421.2 + B2 B3 CSScanned with CamScanner

Now, & max .FS. FS- qu a max =) du= 450 421.2 + 4213) (131.2 + 68.7B ) B2 ) = 6C 2700 + 2527.2 7 431.2 + 68.fB B2 B3 4 431.2 B & 68.7 B 2700 B + 2527.2 3 2527.2=0. => 68.734 + 431.2 B-2700 B By trial & erron method, 1 B = 2-5 m. Ans CSScanned with CamScanner