STRESS ANALYSIS OF OFFSHORE PIPELINE DURING LIFTING FOR JOINTING AND REPAIR

Abstract

The analytical stress analysis of a pipeline lifted for jointing and repair is presented. The loading considered in the analysis are the lifting forces F and P and the self weight of the pipeline q. The behaviour of the raised part of the pipeline is governed by ordinary beam theory in the absence of axial loads. However, the analysis is complicated because the total length of the pipeline lifted is very long compared to the lifted length, thus introducing a free boundary into the problem and rendering the solution difficult. Two examples of practical significance are considered. In the first case, the line is lifted by a single lift to obtain a specific height at the end of the pipe. In the second case the line is supported at two points giving a specified height and zero end slope. Computed results which are normalized in terms a particular known case for which a close form of solution exists are presented for the two cases considered. The results for the analyses are presented in normalized form and can be used as design charts to aid repairs of damaged pipelines carrying crude oil from the seabed to the shore.