Evaluation of Bending Stresses in Pipelines by Using Hole-drilling Measurements Combined with Interferometry

Abstract

Pipelines are usually designed to withstand stresses generated by the internal pressure of the fluid being transported. Nonetheless, internal pressure is only one stress component of the real complex state of stresses acting on their walls. Usually, pipelines are buried running throughout populated and rural areas. Soil movements act as unpredictable loadings which can impose mainly bending and axial loadings on pipelines. The application of the hole-drilling technique combined with digital speckle pattern interferometry is presented in this work in order to compute stress fields acting in angular spaced points distributed on a pipe cross-section. By using a proposed methodology, these stresses can be combined to evaluate the bending stresses presented into the cross-section of interest. A test bench formed by a pipe with a length of 12 m and a diameter of about 200 mm is also presented, which was used as pure-bending reference to experimentally assess the performance of the proposed methodology. Results have shown that the methodology is able to determine bending stresses with a relative deviation of ±10 % of the larger bending stress magnitude measured in the proposed bench.