Failure analysis of bilge keels and its design improvement

• Published in: Engineering failure analysis 2013-01, Vol.27, p.232-249
• Main Authors: Martins, Rui F., Rodrigues, Hugo, Leal das Neves, L., Pires da Silva, P.
• Format: Article
• Language: English
• Subjects: Bilge keels; Failure analysis; Finite Element Analysis; Improved design arrangement
• ISSN: 1350-6307; 1873-1961
• DOI: 10.1016/j.engfailanal.2012.06.002

► A failure analysis in a bilge keel structure was undertaken. ► Several stress concentration regions were identified in the structure. ► An improved geometry for the bilge keel was proposed and analysed. ► The influence of the internal reinforcements of the hull (stiffeners) was assessed. ► A fatigue life assessment of the new bilge keel structure was carried out. Several cracks were detected in the internal structure of the bilge keels used to enhance the transverse stability of ships, as well as on the connection of these to the hull and in some regions of the plating edges of the bilge keels. These cracks compromised the watertight integrity of the bilge keels and, in the long run, could also jeopardize the integrity of the hull. A failure analysis of the structural damages detected was carried out, in order to identify the causes of failure and to propose improvements that could avoid them. Several stress concentration regions were identified in the structure studied, which coincided with the critical areas where the structural failures were found. The influence of the internal reinforcements of the hull (stiffeners) in the increased levels of stress induced in the welded joints of the bilge keels to the hull was also assessed. Improved design geometry for the bilge keel internal structure was proposed, taking into account the longitudinal and transversal structural performance of the bilge keels.