Page 279 - Buried Pipe Design

250 Chapter Five

Safety factor 1.5

safety factor
Required strength (design load)
load factor
1.5
SF
W d 11,172 8200 lb/ft
1.9
LF
Contact the manufacturer to see if this strength or higher is available.
4. Determine the strength of pipe required for C bedding, with 7-ft trench
width,

Load factor (LF) for C bedding 1.5 (see Table 3.2)

Safety factor 1.5
SF 1.5
Required strength W d 11,172
LF 1.5
11,172 lb/ft

Again, contact the manufacturer for the availability of this strength.
Although this is a nonpressure application, a pressure pipe with the
required crush strength may be used.
5. Determine the strength of pipe required if the transition width is reached
or exceeded, with class C bedding. From item 2 above,

Load W d 14,592 lb/ft
1.5
SF
Required strength W d 14,592 14,592 lb/ft
LF
1.5
This strength or higher may not be available from the manufacturer.
Asbestos-cement pressure pipes are designed using a combined load-
ing theory (Schlick formula) as discussed in Chap. 4. Equations (4.12)
and (4.13) are repeated here for convenience as Eqs. (5.1) and (5.2),
respectively.

p
w W 1 (5.1)
P

w
2
p P 1 (5.2)
W
Maximum bending stress in a pipe subjected to three-edge loading can
be calculated as follows: