Stochastic evaluation of offshore carbon fibre reinforced concrete platforms on aluminum girders

Thesis Abstract

A stochastic evaluation of the performance of Carbon Fibre Offshore Plastics (CFRP) offshore platform consideringsubmerged and partially submerged environmental conditions wasanalyzed usingSwedish code,Boverket (2004). A Probability-based analysis using First Order Reliability Method (FORM) was used to determine the safety index of the deck considering varied load ratios, effective depths of the deck, and ultimate strength of Fibre Reinforced Plastics (FRP) tendons. The results generated from FORM indicates that the theoretical framework for risk assessment based on the Joint Committee for Structural Safety JCSS (2003) showed that the maximum safety index of the CFRP deck was shown to be 3.49 which is higher than the limit set by the JCSS (2003) code. Hence the deck can adequately transmit the given loading conditions when designed in accordance with Boverket (2004). Also the resultsof the Finite Elementanalysis carried out on the deck showed that the von-Mises stress was within acceptable limits, implying that the resisting moment of the CFRP deck was adequate. Hence, it is shown that the CFRP deck can be used in marine environment with increasing tidal loading as the CFRP wasalso able to resist failure due to compression. The flexural as well as shearing resistance are also within safety limits; and is about 500% greater than that of a steel reinforced concrete platform.However considering the serviceability limit state of deflection, the CFRP platforms did not show noticeable deformation in the geometry of the deck from the finite element analysis. The imposed load that can be sustained on a 150mm thick CFRP deck is 20kN/m2; while that of 200mm thick CFRP deck is 30kN/m2.