Optimization of Türk Loydu Rules Part C chapter 35 tentative rules for ships less than 500 GT chapter 35-A hull – July 2015

Classification Societies develop and publicly publish rules, standards, guidelines, circulars and additional rules to be applied by designers and shipbuilders during design, construction and maintenance of a ship and also to be employed by plan approval engineers and surveyors during assessment of compliance of the ships with shipbuilding practice, engineering principles and engineering, physical and scientific limits. Optimisation, which may basicly and practically defined as finding the most appropriate solution within predefined limits and adhering to required criteria, is a major concern in almost every engineering disciplines and also a significant tool in development and updating of Classification Society Rules. Reason for this is that there is always a conflict between financial concerns and safety during design stages of ships. The purpose of this thesis is therefore in brief is to find a way to update Türk Loydu Rules Part C Chapter 35 Tentative Rules for Ships Less than 500 GT – Chapter 35-A Hull – July 2015 (hereinafter referred to "the Rule" in this thesis) so that this Rule converges to its optimum form both satisfying financial and structural safety concerns in a method that ships designed according to this Rule become both strong and economical by never exceeding limit engineering values. For this purpose, five ships within the application scope of the Rule are modelled and dimensioned according to the Rule and a number of equivalent rules of other Classification Societies' Rules. To find a basis or start point for optimisation of Chapter 35, the Rule is compared with other equivalent classification societies' rules based on five aforementioned ship models. A comprehensive comparison study is performed to assess internal and external load values, plating and main and secondary structural members' scantlings obtained by those five classification societies' rules plus the Chapter 35-A which is the object of this optimisation study. A detailed "disadvantages" and "what should be done?" list is obtained after close examination and evaluation of the comparison study. Subsequently rule revision recommendations are made according to that list. Many precious findings are obtained according to the comparison study each one of which might be a subject for another commercial or academic study for updating or development of ship structural requirements. However as to focus on the most significant aspects or findings relating the rule are handled as to yield a much more concentrated study. The chosen findings are evaluated, revision requests are made, new models are generated with those rule revision recommendations and after that scantling, and weight analyses are made. Finally stress and deformation analyses are performed to see as if the change stays within the engineering limits. As the nature of practical optimisation suggests, validity of a change in a design is only acceptable if it satisfies predefined criteria and stays within accepted limits. Changes should be redesiged until reaching the criteria and staying within the limits. Similarly in this study, the basic principle for a change in the rule is only after acceptance whether the rule revision both satisfies financial and structural concerns by staying within safe engineering margins. If not, process is taken back to revision recommendation stage.