CT4860 STRUCTURAL DESIGN OF PAVEMENTS

Extensive finite element calculations have strongly indicated that the ordinary
Westergaard-equations 25 and 26 for edge loading are not correct. On the
contrary, the new Westergaard-equations for edge loading, equations 27 to
30, are in good agreement with the finite element method (see 3.6). The
differences between a circular loading area and a semi-circular loading area
are marginal.
Corner loading
Circular loading area (15,17)
0.
6
⎪⎧
⎛ ⎪⎫
1 ⎞
= ⎨ − ⎜ ⎟
2
⎬
⎪⎩ ⎝ ⎠ ⎪⎭
1
3P
a
σ (31)
h l
P
w =
k l
2
⎪⎧
⎛ a ⎪⎫
1 ⎞
⎨1
. 1 − 0.
88 ⎜ ⎟ ⎬
(32)
⎪⎩ ⎝ l ⎠ ⎪⎭
distance from corner to point of maximum stress:
x1 1
= 2 a l
(33)
In the equations 23 to 33 is:
σ = flexural tensile stress (N/mm²)
w = deflection (mm)
P = single wheel load (N)
p = contact pressure (N/mm²)
P
a = = radius (mm) of circular loading area
π p
a2 =
2 P
π p
= radius (mm) of semi-circular loading area
E = Young’s modulus of elasticity (N/mm²) of concrete
υ = Poisson’s ratio of concrete
h = thickness (mm) of concrete layer
k = modulus of substructure reaction (N/mm 3 )
3
Eh
l = 4
2
12(1 −υ
) k
= radius (mm) of relative stiffness of concrete layer
γ = Euler’s constant (= 0.5772156649)
a1 = a √2 = distance (mm) from corner to centre of corner loading
x1 = distance (mm) from corner to point of maximum flexural tensile stress due
to corner loading
Example
Edge loading (equations 27 and 28)
34