Stinger Structural Analysis Using Fully Coupled Model for Pipelay Operations

Abstract

With the growing demands and increasing challenges in deep-water pipeline installation, it is increasingly important to optimize stinger capacity assessment procedure for higher level of accuracy and cost-efficiency as compared to the traditional approach which is highly conservative. The traditional approach combines maximum stresses from three different analyses for environmental loads, vessel motions and pipeline forces to calculate the dynamic performance of a stinger. This approach ignores the coupled behavior between stinger, vessel and pipeline leading to conservative results and over-design which significantly underestimates the operational limits of the stinger structure. The main objective of this study is to develop a simple yet optimized and accurate stinger design and analysis procedure by considering the combined effect of vessel motion, pipeline forces and environmental loading on stinger structure. This is achieved by performing a Fully Coupled Analysis (FCA) in time domain, with capability to capture the impact of stiffness and hydro-elastic properties of stinger and pipeline. The fully coupled model also allows inclusion of hydrodynamic loads on installation vessel as compared to use of vessel motion RAOs in the traditional approach. Forces from this time-history analysis are extracted and mapped onto the structural model to check for structural strength using API and AISC codes. This paper presents a comparison between structural analysis results obtained from Fully Coupled Analysis (FCA) and traditional approach. Results from the FCA procedure have shown significant improvement in the operational limits of stinger.