Step by Step Analysis and Design of Cantilever Retaining Wall
Required to retain earth 187 inch high above the ground level. Backfill surface is inclined at an angle of 15 degree with horizontal. Unit weight of soil 116 pcf and angle of friction is 30. Soil bearing capacity is 3 ksf. Coefficient of friction between soil and concrete is 0.5. Use normal weight concrete for the design of the retaining wall. f’c = 3000 psi, fy = 60 ksi.
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Step 1: Depth and dimension calculation:
Step 2: calculate force and moment acting on the wall considering 1 ft. length of the wall.
Step
3: calculation of earth pressure
Step 4: check for stability
Step 5: calculation of soil pressure below footing
Step
6: Design of toe slab
Self-weight of slab = 0.15 x 1.67 = 0.25 kip/ft2
Downward distributed load of soil acting on heel= 0.116x(18.1+1.67/2)
= 2.2 kip/ft2
Total distributed load on heel = 0.25+2.2 = 2.45
kip/ft2
Effective depth of footing, d = 20-3-6/(2x8) = 16.625
in
Using load factor 1.6, shear at d distance from the
face of stem
Vu =
1.6 [((2+1.97)/2)x(4.58-1.4)] = 10.1 kip
Vc = 0.75x2x1√(3000)x12x1.4x12 = 16.6 kip
>
Vu
Moment at face of the stem
Mu = 1.6*[(1.71 x 4.58 x 4.58/2)+0.5 x (2.56-1.71)
x 4.58 x 4.58 x 2/3] = 38
kip-ft
As = 0.53 in2
As min = 0.7 in2 /ft , spacing =
0.44*12/0.7 = 7 in c/c
The bar should extend a distance of
Ld= 44 x dia of bar =44 x 0.75 = 33 in from toe to heel.
Distribution steel = 0.0018x12x20 = 0.432 in2 = 0.44x12/0.432 = 12 in c/c
Step
7: Design of Heel slab
Distribution
steel = 0.0018x12x20 = 0.432 in2 = 0.44x12/0.432 = 12 in c/c
Step
8: Design of stem
Step
9: Check for shear:
Step 10: Detailing
