Structural Revision of an Independent Cargo Tank: Investigation of Ultimate Limit State and Fatigue Limit State
Typ
Examensarbete för masterexamen
Program
Naval architecture and ocean engineering (MPNAV), MSc
Publicerad
2022
Författare
Mumberg, Felix
Templin, Johan
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
This thesis is dealing with Ultimate Limit State and Fatigue Limit State of an independent
cargo tank for bitumen carriers. The cargo tank has been investigated with main focus on
the upper and lower edge of the longitudinal watertight tank bulkhead. The main question
is how can the stress concentrations in those specific connections be lowered. Additionally
the fatigue life has to be above 25 years. This can in theory archieved by decreasing the
stiffness in the connection allowing more deformation as the bulkhead hinges instead of
transferring moments in the stiff connections. Thus mainly going from a fixed connection
to a simply supported. To assess and improve the performance of the design, FE-analysis
in MSC APEX is used. For FLS the FE-analysis was used as input in the hotspot method
to be able to calculate fatigue life. All methods used are in accordance to the classification
rules of Bureau Veritas. The results show that the stress concentrations can be lowered
through a change of the position of the top tank transverse stiffener and the bottom tank
transverse stiffener as well as through the removal of a bracket and the relocation of the
anti flotation device. Further changes had to be made to meet the requirement for fatigue
life of 25 years. This was done by increasing the thickness of the bottom plate.
Beskrivning
Ämne/nyckelord
Fatigue , FEA , Design , Hot Spot Method , Classification Rules