The paper presents a study related to fatigue performance of a structure, called ‘stinger’, being used as a support for offshore pipeline during installation from the board of a specialized vessel. Real-time strain measurements were set up on one of the tubular joints of the stinger. The measured data was processed and statistically analyzed after an appropriate filtering technique was developed. The measured nominal and local strain ranges at certain probability of the exceedance were used to derive the strain concentration factors (SNCF's) along the weld toe of the joint. Finite element (FE) models of the tubular joint were built using shell and solid elements, the latter comprising also the weld material. The SNCF values resulted from finite element analysis (FEA) were compared with those derived from measurements. Fatigue damage estimated based on histograms constructed on measured strain during a pipeline installation operation is discussed.

In offshore oil and gas pipeline installation, specialized vessels are used. There is a number of ways to install the pipelines (Palmer and King, 2008). In this paper, the so called S-lay type of installation process is considered when a pipeline is assembled horizontally on board of a pipe lay vessel and guided to the seabed. During the installation, pipeline is supported by ‘stinger’, usually a space frame structure attached to the pipe lay vessel at bow or stern. The stinger overall configuration is adjustable and could contain different number of sections and have different radii depending on the pipe lay project. Though the pipeline installation is limited to certain weather conditions it is performed at different sea states characterized by a combination of sea wave height (H_S), wave period (T_Z) and wave approach angle (or wave heading, θ). Stochastic nature of the environment has an effect on loads experienced by the stinger and hence on fatigue damage accumulation in stinger welded joints.