NIPPON ROCLA PIPE CO. has been producing noncylinder prestressed concrete pipes since the fall of 1961. One of the products which has 1200mm inner diameter and is designed for the inner pressure of 13.0kg/cm2 was tested hydrostatically and under the external load.
The results of test obtained are as follows:
(1) Under the hydrostatic pressure up to 12.0kg/cm2, there was no leakage on outer surface of the pipe and at rubber joints.
As the capacity of the bulkhead of the machine was not sufficiently large, the test up to 13.0kg/cm2 pressure was given up.
(2) Under the external load up to 8.25 tons per meter (total load of 33.0 tons), could no visible crack was found at any point of the pipe.
From analyses about the stress and measured strain on concrete surface at the end of the pipe, the prestress in the core concrete was supposed to be as much as the designed value, and the flexural strength of the concrete to be sufficient.