Improved Solution for Pipe Stiffness as Measured by Parallel-Plate Load Test Method

摘要

The ring stiffness of flexible pipe specimen is usually measured in the laboratory according to the parallel-plate load test (ASTM D-2412) method. When the laboratory test equipment is not available, a theoretical solution based on the elastic curved beam theory is often used to estimate the ring stiffness of the flexible pipe. Laboratory test data accumulated by the author indicated that the classical solution has a tendency to overestimate the actual ring stiffness of thermoplastic pipe significantly. In this paper, the parallel-plate load test method is examined closely to identify the area where the classical curved beam solution deviates from the actual test conditions. Based on the finding the classical theory is modified to obtain a more realistic solution for the ring stiffness of the flexible pipe measured under the parallelplate load test condition. The revised solution expresses the ring stiffness as a function of the pipe radius, flexural rigidity of the wall section, and the extent of the flattened region appearing at the pipe’s crown and invert regions. The revised pipe stiffness formula is evaluated using the laboratory test cases presented earlier. The outcome shows that it reduces the degree of overestimation made by the classical solution.