Carlon External Load Calculation for Buried Conduit - Manual (Page 6)

EXTERNAL LOAD CALCULATIONS FOR DIRECT BURIED CONDUIT
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PS = E*I/(0.149*r
3
) = [500,000 lb/in
2
*0.001 in
3
]/[0.149*(2.132 in)
3
] = 346.3 lb/in
2
4. CALCULATE THE MAXIMUM LOAD FOR 5% DEFLECTION (W)
W = [∆ ∆ ∆ ∆X*(0.149*PS + 0.061*E
1
)]/(D*K) = [0.05*(0.149*346.3 lb/in
2
+0.061*2000
lb/in
2
)]/(1.5*0.1) = 57.87 lb/in
2
5. CALCULATE THE DEAD LOAD (DL)
DL = γγγγ * H/144 = 120 lb/ft
3
*20 ft/144 = 16.67 lb/in
2
6. DETERMINE THE LIVE LOAD (LL) USING THE TABLE
LL = 2.08 lb/in
2
7. CALCULATE THE TOTAL LOAD (TL)
TL = DL + LL = 16.67 lb/in
2
+ 2.08 lb/in
2
= 18.75 lb/in
2
SINCE THE TOTAL LOAD OF 18.75 lb/in
2
IS LESS THAN THE MAXIMUM
LOAD OF 57.87 lb/in
2
THE 4” SCHEDULE 40 CONDUIT WOULD DEFLECT
LESS THAN 5%.
4” SDR 13.5 CONDUIT WILL BE BURIED 4 FEET BELOW A HIGHWAY IN
TYPE II SOIL. 4” SDE 13.5 HAS AN OUTSIDE DIAMETER OF 4.500” AND A
MINIMUM WALL THICKNESS OF 0.333”.
1. CALCULATE THE MEAN RADIUS (r)
r = (O.D. -t)/2 = (4.500 in - 0.333 in)/2 = 2.084 in
2. CALCULATE THE MOMENT OF INERTIA (I)
I = t
3
/12 = (0.333 in)
3
/12 = 0.003 in
3
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