Support width
b = (2Yt)1/2
where
b = minimum (axial) saddle width. (mm)
Y = actual outside diameter of pipe. (mm)
t = nominal pipe wall thickness. (mm)
Localised stress at supports
fr = K (wL/a2) ln(Y/2a)
where
K = saddle coefficient.
w = unit load per linear metre. (N/m)
L = span length. (m)
a = minimum wall thickness of pipe. (mm)
Y = pipe outside diameter. (mm)
K = 0.03 - 0.00017(b-90o)
b = saddle angle, 90 < b
Hoop stress due to internal pressure
p = 2fa/D thus f = pD/2a
where
a = wall thickness. (mm);
D = mean pipe diameter. (mm) = (Y-a) mm
Flexural stress at centre span
fb = 1270YwL2/(Y4-d4)
where
Y = pipe outside diameter. (mm)
w = unit load per linear metre. (N/m)
L = length of span. (m)
d = Y-2a. (mm);
Beam deflection at centre span
To prevent damage to the cement mortar lining, maximum allowable midspan deflection is;
yr = 8.33L
where
yr = maximum allowable deflection at centre span. (mm)
L = length of span. (m)
Beam deflection at centre span for a uniformly distributed load on a simply supported beam
can be calculated using;
y = 265.26x106wL4/(E(Y4-d4))
where
y = deflection at centre span. (mm)
w = unit load per linear metre. (N/m)
L = length of span. (m)
Y = pipe outside diameter, (mm)
d = Y-2a. (mm)
