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Title: Analysis of a doubly plated grillage under in-plane and normal loading
Author: Williams, Donald Gatherer
Awarding Body: University of London
Current Institution: Imperial College London
Date of Award: 1969
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Losses in the overall flexural and shear stiffness of plated grillages are studied with particular reference to the double-bottom structure. It is shown that in longitudinally framed ships, losses in flexural stiffness can be of the order of 15% in the longitudinal direction due primarily to shear lag, and can be in excess of 20% in the transverse direction due primarily to local panel bending. The latter effect is analysed by considering the large deflexion behaviour of initially deformed shell panels with restrained edges. Losses in shear stiffness due to perforations are shown to be of the order of 50% for hole sizes typical of the double-bottom structure. Finite difference solutions to the orthotropic plate equations including shear deformation are given to show the effect of shear deformation on the behaviour of rectangular plated grillages under transverse and in-plane load. Flexural boundary conditions varying from simple support to fully clamped are treated. Within the practical range of plate dimensions the effect of shear deformation on stresses and deflexions can be of the order of ±40% and +100% respectively. The above treatments are combined in order to analyse the results of tests conducted on a one-eighth scale steel model of a section of the double-bottom of a typical dry cargo ship. The agreement between measured and theoretical results for overall and local behaviour is satisfactory up to about 0.6 of the assumed working load. At this load non-linearity became evident in overall behaviour. Surface yielding of webs began at about 0.5 of the assumed working load and heart of plate yielding of the webs and surface yielding of shell panels began at about 0.75 of the assumed working load. The ultimate load for the model was 1.35 times the assumed working load.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available