Dynamic spectral fatigue behavior of a fixed offshore jacket structure

Abstract

The need for energy to run the wheels of technology is increasing day by day. Apart from non-renewable energy which cannot fulfil the today’s requirements. Henceforth the need for oil to run today’s technology is tremendous. The oil fields in Gulf countries face so many problems related to the structural life of various components of the field. This report discuss one major thing of these kind which is the fatigue analysis to evaluate the fatigue life of the weld connections pertaining to Jacket tubular joints under the cumulative actions of cyclic loads induced by waves. The jacket structure is a four-legged type, lift installed steel jacket with two vertical faces and two battered faces. Following are the key details jacket. The dimension at Work Point is 21.40 m × 10.70 m. The work point EL (+) 8.230 m. The depth of the water is at 41.30 m from LAT (Lowest Astronomical Tide). The Top of Jacket is at EL (+) 7.010 m. The bottom of Jacket level is EL (+) 41.000m. The foundation is 42” piles with leg pile annulus. The codes used are as per the International standards API RP 2A – WSD 22ND Edition & AISC – WSD – 9th Edition (Manual of Steel Construction – Allowable Stress Design). Analysis is carried out using SACS 5.7 V8i SELECT Series 4.