Buckling and ultimate strength of stiffened panels

Γεωργίου, Δεσποινα; Georgiou, Despina

dc.contributor.author	Γεωργίου, Δεσποινα	el
dc.contributor.author	Georgiou, Despina	en
dc.date.accessioned	2020-01-21T09:39:52Z
dc.date.available	2020-01-21T09:39:52Z
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/49700
dc.identifier.uri	http://dx.doi.org/10.26240/heal.ntua.17398
dc.description	Εθνικό Μετσόβιο Πολυτεχνείο--Μεταπτυχιακή Εργασία. Διεπιστημονικό-Διατμηματικό Πρόγραμμα Μεταπτυχιακών Σπουδών (Δ.Π.Μ.Σ.) “Ναυτική και Θαλάσσια Τεχνολογία και Επιστήμη”	el
dc.rights	Αναφορά Δημιουργού-Όχι Παράγωγα Έργα 3.0 Ελλάδα	*
dc.rights.uri	http://creativecommons.org/licenses/by-nd/3.0/gr/	*
dc.subject	Buckling	en
dc.subject	Torsion	en
dc.subject	Finete element analysis	en
dc.subject	Stiffeners	en
dc.subject	Aabaqus	en
dc.title	Buckling and ultimate strength of stiffened panels	en
dc.contributor.department	Marine Technology	el
heal.type	masterThesis
heal.generalDescription	Present Rules given by Classification Societies (IACS) give rational criteria for dimensioning the hull structure ensuring sufficient strength for safe operations. However, the ship designers/yards are in fierce competition and by offering reduced steel weight, possible increased cargo capacity and reduce fuel consumption can be achieved. This business pressure leads to creative thinking among designers and more optimal and thinner structures are the result. For extreme loads this again will challenge the structural capacity limits and unwanted “overload” damages and permanent sets may be the result. Safe Rule scantlings are mainly determined by stress and buckling criteria such as given in DNV GL Ship Rules. They are typically based on text book formulas (Euler, etc.) modified to take into consideration different buckling modes, interactions between elements, non-linear behaviour, combined bi-axial/shear loads acting, etc. These types of Rule models are termed Closed Form Method (CFM) and covers basically all relevant failure modes. Though, some of these CFM models have limitations, and improvements/extensions are needed to provide for more consistent dimensioning for some designs. The most advanced approach is to use non-linear FE tools (Abaqus or equivalent). Such models are expensive and time consuming to analyse and not much used in normal ship design work unless the case requires special documentation. However, such models are very valuable for benchmarking simpler buckling models. The task of the master thesis work is to assess existing buckling models of stiffened plate as proposed by DNV GL and develop new and improved models where found necessary. The buckling/failure modes to be considered are torsional buckling of different types of stiffener sections and global (overall) buckling of stiffened panels. The approach used for solving the overall task will constitute a combination of analytical work and numerical analyses using non-linear FE tool. Analytical work will be needed in relation to derivation of closed formed buckling models and proposal of approximations while numerical buckling analyses (Abaqus) will be used for validating the simpler formulas (CFM) The work rreviews and summarizes the DNV GL (IACS) Rules, as relevant for the two buckling modes to be considered. Additionally, numerical comparison studies (Abaqus) were carried out for validating the CFM predictions given above. Two levels of validation achieved. The first refers to the comparison of eigenvalues and the second, on ultimate capacity over a relevant parameter span as typical for ship designs (vary stiffener lengths, plate thickness, etc.). Finally, alternative models were improved or developed for eigenvalues for torsional and overall buckling strength.	en
heal.classification	Structural Analysis	en
heal.language	en
heal.access	free
heal.recordProvider	ntua	el
heal.publicationDate	2019-09-13
heal.abstract	Thin plates are structural elements that are widely used in many engineering fields, such as aerospace, shipbuilding and civil engineering. Ribbed and stiffened ship plates, offshore, and aerospace panels are commonly utilized and always subjected to partial edge traction on their own plane. This type of loading can induce buckling, which negatively affects the function of the structural elements concerned. Plate instability is generated globally or locally through in plane compression and lateral loading. The corrugations resulting from plate instability may cause permanent deformations and reduce the efficiency of the entire structure. The project focuses on buckling and ultimate strength of stiffened panels. Torsional buckling of the stiffeners, plate local buckling as well as overall buckling of stiffened panels will be examined. During the assessment of their structural responses, both numerical and analytical methods will be implemented.	en
heal.sponsor	6-month Erasmus project	en
heal.advisorName	Σαμουηλίδης, Μανώλης	en
heal.advisorName	Jorgen, Amdahl	el
heal.committeeMemberName	Σαμουηλίδης, Μανώλης	en
heal.committeeMemberName	Jorgen, Amdahl	el
heal.committeeMemberName	Ανιφαντής, Κωνσταντίνος	el
heal.academicPublisher	Εθνικό Μετσόβιο Πολυτεχνείο. Σχολή Ναυπηγών Μηχανολόγων Μηχανικών	el
heal.academicPublisherID	ntua
heal.numberOfPages	81 σ.	el
heal.fullTextAvailability	true