Lateral pressure effect on average compressive strength of stiffened panels for in-service vessels

Abstract

This paper presents the estimation of the average compressive strengths of three types of stiffened panels under axial compression and lateral pressure based on simplified formulae in the CSR for tankers (common structural rules for double hull oil tankers) and nonlinear finite element analyses (FEAs). Basic scenarios are determined based on the slenderness ratios of the stiffened panels used for in-service ships. Secondary scenarios are subdivided by external pressures that are applied to finite element model by increasing 1 bar, assuming 30 m water height. The total number of FEAs for flat bar (FB)-, angle bar (AB)- and tee bar (TB)-stiffened panels is 189. FEA results show that the existence of pressure can cause a significant reduction of ultimate strength, while CSR formulae do not take into account the effect of lateral pressure. The lateral pressure is more detrimental to the ultimate strength of stiffened panels with a higher column slenderness ratio than those with a smaller column slenderness ratio. A new concept of the relative average compressive strain energy, instead of the ultimate strength, is introduced in order to rationally compare the average compressive strength through a complete compressive straining history. The differences in the ultimate strengths between CSR formulae and FEA results are relatively small for FB- and AB-stiffened panels, but larger discrepancies of relative average compressive strain energies are obtained.

Keywords:

• stiffened panel
• average compressive strength
• ultimate strength
• slenderness ratio
• relative average compressive strain energy
• lateral pressure

Acknowledgements

This work is the outcome of a Manpower Development Program for Marine Energy by the Ministry of Land, Transport and Maritime Affairs (MLTM). This work was also supported by the New & Renewable Energy of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea government, Ministry of Knowledge Economy. The authors are grateful to INHA University for funding research grant. This research was also supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2012R1A1A1002897).