الفهرس 
INTRODUCTION AND LITERATURE REVIEWOnly 14 pages are availabe for public view
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Abstract
Plates are very important components in ship and offshore structures, and they form the backbone of most of the ship’s structure, and they are by far the most nl used element in a ship. They can be found in bottom structures, decks, side shell, and superstructures. In typlca ta er s p s ruc panels are reinforced by longitudinals (stiffeners) in the longitudinal direction and transversely supported by widely spaced transverse structures (such as transverse bulkheads, deck beams and bottom floors). The conventional longitudinals are usually Tee, angle, bulb or flat bar profiles, while the transverses are typically T¬beam sections. During the loaded condition, deck panels are subject to uniaxial compression stress in the longitudinal direction from the effect of the membrane compressive stress induced by hull girder vertical sagging bending moment, while during the ballast condition, inner and outer bottom panels are subject to uniaxial compression stress in the longitudinal direction from the effect of the membrane compressive stress induced by hull girder vertical hogging bending moment and the outer bottom panels are subject to additional lateral pressure from both sea water and double bottom ballast water.The objectives of the present thesisare: 1) Generation of equivalent conventional and new Y stiffener profiles. The conventional stiffener profile as a part of the new Y stiffener profile may be a rolled or fabricated section according to the ratios stated in IACS-CSR, while the hat part is made by a hot-rolling process with inclination angle of the two webs of the hat taken as 30, 45, 60, and 90 degree. The new Y stiffener profile is a fabricated section and the simplest production method is to weld the lower end of the web of the conventional stiffener profile to the top of the hat flange. 2) Replacement of the longitudinal conventional as-built stiffener profiles in deck and bottom panels of oil tankers with the generated equivalent conventional and ne’ ties in order to obtain more ultimate strength, safety margin (ultimate strength minus applied compression stress), ultimate strength to panel weight ratio, safety margin to panel weight ratio, panel weight reduction (saving) and section modulus of the stiffener with the effective attached plate based on the advantages of using Hat section (closed section) in Y stiffener profiles to give more torsional rigidity and effective plate allowing an increase of the stiffener spacing, hence a reduction of the number of the stiffeners. The effective plate for the new Y stiffener profiles was calculated according to Eurocode and IACS-CSR. All deterministic calculations were carried out using EES (Engineering Equation Solver) and Microsoft Excel software by applying IACS-CSR for oil tankers (Deterministic Method) based on the following failure modes: unstiffened plate buckling, stiffener beam-column buckling, and stiffener torsional/flexural buckling (tripping). 3) Comparison between the deterministic resultsof the as-built conventional. generated equivalent conventional and generated equivalent new Y stiffener profiles.4) Verifying the results from deterministic method by reliability analysis (stochastic method) using VaP (Variable Processor) software applying both approximated solution methods (FORM or SORM) and exact solution method (MCS-LHS) to calculate and compare the safety indices of the longitudinally stiffened panels in deck and bottom panels with the as-built conventional, generated equivalent conventional and generated equivalent new Y stiffener profiles along the ship lifetime. 5) Comparison between the time variant reliability safety indices of the longitudinally deck stiffened panels with the as-built conventional or generated equivalent new Y stiffener profiles and the target reliability safety indices to determine the first required thickness measurements. 6) Performing a sensitivity analysis for the longitudinally deck stiffened panels with the as-built conventional and generated equivalent new Y stiffener profiles.