Analisi delle normative sulle unità da diporto in vetroresina con metodi numerici e sperimentali

In this paper the scantling procedures contained in the “Rules for the Construction and Classification of Pleasure Vessels” of the Italian Classification Society RINA, relatively to GRP vessels, are assessed in detail. This work represents the continuation of a joint research performed in cooperation by AZIMUT Shipyards in Avigliana (Italy) and the Dipartimento di Ingegneria Navale of the University of Genova. In the first phase of the investigation a statistical analysis of dimensional and geometric characteristics of a number of medium size motor yachts have been performed, aiming at expressing the main scantling formulas as a function of minimum number of variables. In the second phase several versions of the same part of a 55’ motor yacht, chosen as reference vessel, have been obtained by parametrically varying the main scantling variables: for each of them the correspondent finite element model has been created by the FEM code NASTRAN. Finally the safety factors of RINA scantling formulas have been evaluated by studying the stress levels of all models and comparing them with the RINA equivalent stress level.