Optimization – based methodology for fatigue life extension of ship steel structural connections

Καπνοπούλου, Βάσω; Kapnopoulou, Vaso

dc.contributor.author	Καπνοπούλου, Βάσω	el
dc.contributor.author	Kapnopoulou, Vaso	en
dc.date.accessioned	2025-09-22T09:42:12Z
dc.date.available	2025-09-22T09:42:12Z
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/62514
dc.identifier.uri	http://dx.doi.org/10.26240/heal.ntua.30210
dc.rights	Default License
dc.subject	Fatigue life; Lower hopper knuckle connection; End bracket connection; Structural optimization; Size optimization; Fatigue-induce stress value minimization; Coupling of finite element software with optimization algorithm; Parametric finite element model	en
dc.title	Optimization – based methodology for fatigue life extension of ship steel structural connections	en
dc.contributor.department	Θαλασσίων Κατασκευών	el
heal.type	doctoralThesis
heal.classification	Ship structural analysis	en
heal.language	en
heal.access	free
heal.recordProvider	ntua	el
heal.publicationDate	2025-06-27
heal.abstract	Extension of fatigue life in ship steel structural connections is commonly attained by interfering with the weldment or by affecting local parameters of the detail. In this study, structural details are approached macroscopically and a methodology is proposed that aims in minimizing the fatigue-induce stress values developed at hot spot locations in order to maximize the fatigue life of the detail studied. This is attained by developing and solving a structural optimization problem. The methodology is implemented into three separate ship structural details at a Bulk Carrier; the lower hopper knuckle connection, the lower side frame bracket toe and the side framing bracket to upper sloping connection of a Bulk Carrier. The steps of the methodology proposed include: (a) establishing of the direction of fatigue-induce stress component, (b) identification of the structural member(s) affecting this stress component, (c) setting up and solving a size optimization problem, and (d) setting up and solving a structural optimization problem. The proposed methodology is first implemented at the lower hopper knuckle connection of a Bulk Carrier. The methodology resulted in a two-objective structural optimization problem where the objective functions were the stress values at two hot spot locations and the design variables were geometry characteristics of the detail. The solution of the optimization problem resulted in a differentiated configuration of the lower hopper knuckle connection, compared to the original configuration. The resulting fatigue life of the modified configuration is extended by 12.87 years. Next, the proposed methodology is applied at the lower side frame bracket toe. The methodology resulted in setting-up and solving a single-objective structural optimization problem which resulted in a differentiated end bracket configuration and in fatigue life extension of the detail by 13.37 years. Finally, the proposed methodology was implemented at the side framing bracket to upper sloping connection. The methodology resulted in a single objective size optimization problem which altered plate thickness parameters of the detail and extended the fatigue life of the detail by 10.83 years. The development and implementation of the proposed methodology has led to useful conclusions regarding the fatigue and strength characteristics of these specific details as well as details with similar configuration.	en
heal.advisorName	Σαμουηλίδης, Εμμανούήλ
heal.committeeMemberName	Σαμουηλίδης, Εμμανουήλ
heal.committeeMemberName	Ανυφαντής, Κωνσταντίνος
heal.committeeMemberName	Ζαραφωνίτης, Γεώργιος
heal.committeeMemberName	Παπαδόπουλος, Χρήστος
heal.committeeMemberName	Παπαλάμπρου, Γεώργιος
heal.committeeMemberName	Θεοδουλίδης, Αλέξανδρος
heal.committeeMemberName	Γιαννάκογλου, Κυριάκος
heal.academicPublisher	Εθνικό Μετσόβιο Πολυτεχνείο. Σχολή Ναυπηγών Μηχανολόγων Μηχανικών	el
heal.academicPublisherID	ntua
heal.numberOfPages	201
heal.fullTextAvailability	false