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Echinodome response to dynamic loading

The response of an Echinodome to static and dynamic point loads, and explosive type loadings was examined both theoretically and experimentally. The finite element method of analysis was employed in the theoretical investigation. Semi-loof thin shell elements were used to model a GRP prototype on which the experiments were performed. The stress distribution of the Echinodome under a static symmetric point load were investigated both experimentally and theoretically. Then the Southwell technique was employed in estimating the critical buckling load from deflection measurements. Experimental estimates were then compared with the numerical predictions in the form of non-linear collapse and non-linearbifurcation buckling loads. A free vibration was performed to determine the structural natural frequencies and typify the mode shapes. The shock response spectra of several pulse shapes were determined using the finite element method. The most severe loading function was established to be a step loading with infinite duration and zero ramping time and was then employed as the load-time history in an axisymmetric and symmetric non-linear dynamic buckling analysis. The dynamic collapse buckling loads were found to be smaller in magnitude than their static correspondents. A modal testing was then carried out on the Echinodome prototype to determine the experimental modal parameters (natural frequencies, damping values and mode shapes). Newly developed correlation techniques were adopted in the comparison of the experimentally derived parameters with those predicted and poorly modelled regions were identified. Great improvement was achieved by correcting the experimental data and updating the finite element model's boundary conditions. A set of underwater free field experiments was performed to determine the pulse characteristics for a specific explosive charge, followed by another set while the prototype was in a floating submerged state and acting as the target for the same explosive charge. A theoretical simulation was accomplished by employing a finite element-boundary element approximation for the modelling of the structure and infinite fluid media respectively. Measured responses were compared with the numerical predictions and means of acquiring better theoretical approximations are mentioned. The loading conditions to be experienced by an underwater LNG Echinodome vessel are reviewed with emphasis on accidental dynamic loads (impact and explosion). A state of the art storing configuration is proposed for the Echinodome in order to limit the extent of damage and hence minimise risk during upset conditions. Finally, appropriate design, construction and prestressing procedures were recommended.
Date January 1990
CreatorsEl-Deeb, Khaled Mohamed Mahmoud
PublisherUniversity of Edinburgh
Source SetsEthos UK
Detected LanguageEnglish
TypeElectronic Thesis or Dissertation

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