Design for shear (pad and strip base:EC2)
Pad base shear design check
Calculate tension reinforcement ratio (cl 6.2.2(1)):
| ρl |
|
min(Asl / (L*d), 0.02) |
where
| Asl |
|
area of tension reinforcement |
| L |
|
unit width of foundation in which A sl is provided |
| d |
|
effective depth of reinforcement in direction considered |
| Fy,sup |
|
Horizontal force acting on support Y-direction in STR/GEO limit states - from analysis |
Calculate k (cl. 6.2.2(1)):
| k |
|
min(1 + (200mm/d)1/2, 2.0) |
Calc min shear strength (NDP) (cl. 6.2.2(1)):
| vmin |
|
1.035k3/2fck1/2 | EC2 recommendations |
| vmin |
|
1.035k3/2fck1/2 | for UK, Irish, Malaysian and Singapore NA |
Calculate resistance without shear reinforcement for X and Y directions (cl. 6.2.2(1)):
| vRd.c,x |
|
max(CRd.c * k * (100 N 2 /mm 4 *ρ l * f ck ) 1/3 ,v min ) |
| vRd.c,y |
|
max(CRd.c * k * (100 N 2 /mm 4 *ρ l * f ck ) 1/3 ,v min ) |
Maximum allowable shear resistance (cl. 6.2.2(6));
| vRd,max |
|
1.5 *v * fcd |
where
| fcd |
|
concrete design compressive strength |
| v |
|
cracked concrete reduction factor |
If applied design shear force is less than or equal to the shear resistance i.e vEd ≤ vRd = min (vRd,c , vRd,max) the foundation thickness is adequate for beam shear.
Strip base shear design check
The principle of the strip base shear design check is similar to that for the pad base. Only the direction X is checked (around Y-axis) using segment widths.