Design for shear (pad and strip base:EC2)

Tekla Structural Designer
2021
Tekla Structural Designer

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
  =  
1.035k3/2fck 1/2 EC2 recommendations
vmin
  =  
1.035k3/2fck 1/2 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 4l * f ck ) 1/3 ,v min )
vRd.c,y
  =  
max(CRd.c * k * (100 N 2 /mm 4l * 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.

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