Really the assessment and evaluation of the existing offshore structures and FPSO is very complicated and need a sense from the consultant rather than theoretical calculation. Really for any old system even your body, when you are youth you can go to any doctor for medical care but when you go old you need many checks and professional doctors.
Deal with the old structure very carefully as wrong treatment may result to death?!!!
The problem for the offshore structure and marine vessel like FPSO, it is now mature all over the world and the challenge now is how we can calculate its life time or in another meaning can we extend its life time. I want to conclude that the answer is under investigations and researches until now. The main problem is the fatigue effect as its calculations have a high uncertainty and the expected life time requires a sort of probability calculation. In general, until now the structure engineer can not precise and guarantee the life extension.
The below graph present the percentage of reduction in steel plate capacity due to bending moment and reduction in thickness due to corrosion. So it is clear from this figure that reduction of 30% in thickness corresponding in reduction around 50% in the capacity and the capacity is reduced gradually until reduction 70% as in this time it shall be risky to operate i this condition, but if you reduce the load dramatically you will be in a good condition is the capacity will be reduce slowlyPages: