Page 294 - Buried Pipe Design

Rigid Pipe Products 265

Cement-Mortar Coating
Prestressed Steel Wire
Mortared in Field
Bell Ring

Spigot Ring
Rubber Gasket Steel Cylinder
Inside Diameter Cement-Mortar Coating Mortared in Field
Figure 5.9 Wall cross section of pretensioned shot-cote concrete
cylinder pipe. (Reprinted,by permission, from Bulletin No. 200,
United Concrete Pipe Corporation.)

Pretensioned concrete cylinder pipe
In the manufacture of pretensioned concrete cylinder pipe, one starts
with steel cylinders made from steel coils and spirally welded or made
from steel sheet and welded longitudinally. End rings are welded to the
steel cylinder, and then it is hydrostatically tested to 75 percent of yield
strength of the steel. A cement mortar lining is applied centrifugally.
After curing, the cement mortar-lined steel cylinder is pretensioned by
helically winding steel rod under a small tension to the outside of the
steel cylinder. The pitch of the winding is controlled by specific design
requirements. A cement-mortar coating is then applied to the exterior
surface of the rod-wrapped cylinder, and the completed pipe is cured
(Fig. 5.9). This pipe is normally available in diameters of 10 through 42
in. The design of this pipe is based on an analysis of both internal pres-
sure and external loads acting separately but not in combination. This
design method is usually used for flexible pipe, which pretensioned con-
crete is not. The pipe must be installed in such a manner that the
deflection is less than D 2 /4000 (see AWWA C303, App. A).

AWWA Design of Reinforced Concrete
Pressure Pipe
The following is an abbreviated design procedure for concrete pressure
pipes as given in AWWA M9. Additional details are found in the fol-
lowing AWWA standards:

Standards for the reinforced types:
■ AWWA C300
■ AWWA C302
■ AWWA C303