China Ocean Eng., Vol. 25, No. 3, pp. 519 − 530 © 2011 Chinese Ocean Engineering Society and Springer-Verlag Berlin Heidelberg DOI 10.1007/s13344-011-0042-5, ISSN 0890-5487 Configuration Analysis of Deepwater S-Lay Pipeline * GONG Shun-feng (龚顺风) a, 1 , CHEN Kai (陈 凯) a , CHEN Yuan (陈 源) a JIN Wei-liang (金伟良) a , LI Zhi-gang (李志刚) b and ZHAO Dong-yan (赵冬岩) b a Institute of Structural Engineering, Zhejiang University, Hangzhou 310058, China b Offshore Oil Engineering Co. Ltd., Tianjin 300452, China (Received 22 April 2010; received revised form 14 April 2011; accepted 8 June 2011) ABSTRACT The safety of offshore pipeline has drawn a great deal of attention during deepwater installation due to the combined actions of high external pressure, axial tension, and bending moment. Meanwhile, the pipeline configuration has a remarkable effect on the structural behaviour of the tube. The special studies focus on the deepwater S-lay technique in the present paper. The stiffened catenary theory is applied to establish the static equilibrium governing differential equation of a pipe element, and the solution equations of the total pipeline configuration from a lay-barge over a stinger to the seabed are derived. The numerical iteration method for solving pipeline configuration is described in detail, and the corresponding program is developed to conduct the analysis of effects of various parameters such as laying water depth, pipe diameter, thickness of concrete weighted coating layer, stinger length, control strain, and axial tension on pipeline configuration. The results show that the laying water depth, the submerged weight of the pipe, and the axial tension are the critical factors influencing pipeline configuration. In addition, geometrical parameters of the stinger such as length, radius, and shape have an important effect on the pipe-laying capacity of the vessel. The validity of the program is further verified by means of a comparison with results obtained from the commercial finite element software OFFPIPE. Key words: offshore pipeline; S-lay; stiffened catenary theory; stinger; configuration 1. Introduction S-lay method, as a conventional pipe-laying technique, still occupies an important position in the market for offshore pipeline installation in deep waters. The pipeline is usually subjected to the combined actions of high external pressure, axial tension, and bending moment during deepwater installation, thus its safety becomes an important concern. In the past few decades, great efforts have been devoted to the analysis of S-lay pipeline. Li et al. (2008) compared S-lay method with other laying techniques and outlined the characteristics of each pipe-laying method. Dixon and Rutledge (1968) introduced the stiffened catenary theory to solve the pipeline laying problem. Palmer et al. (1974) emphasized the importance of pipeline configuration in the distribution of stress, and solved the equations governing the configuration by use of the finite difference method. Gu (1989) expanded the stiffened catenary method, which usually can only be used to determine the pipeline configuration in the sag-bend, to solve the total configuration of pipeline from the lay-barge to the seabed in the conventional water depth. Guarracino * The work was financially supported by the National Natural Science Foundation of China (Grant No. 51009122), the Fundamental Research Funds for the Central Universities (Grant No. 2010QNA4030), and the National High Technology Research and Development Program of China (863 Program, Grant No. 2006AA09A105) 1 Corresponding author. E-mail: sfgong@zju.edu.cn