Evaluation of Liquid Dynamic Loads in Slack Lng Cargo Tanks
摘要
This report provides an evaluation of dynamic sloshing loads in slack LNG cargo tanks. A comprehensive review of worldwide scale model sloshing data is presented. The data are reduced to a common format for the purposes of defining design load coefficients. LNG tank structural details are reviewed with emphasis placed on defining unique design features which must be considered in designing LNG tanks to withstand dynamic sloshing loads. Additional scale model laboratory experiments are conducted to supplement the available model sloshing data. Experiments are conducted in combined degrees of freedom to establish the potential for multi-degree of freedom excitation for augmenting dynamic sloshing loads. Experiments are also conducted to establish the sloshing dynamic pressure-time histories which are necessary for structural response analysis. Experiments are also conducted on representative segments of a full-scale LNG ship tank structure which is loaded with a typical full-scale dynamic sloshing pressure as predicted from the model results. Analytical studies are undertaken to provide techniques for determining wall structural response to dynamic slosh loads. Finally, design methodology is presented for membrane and semi-membrane tanks, gravity tanks, and pressure tanks whereby the design procedures sequences from comparing resonant sloshing periods to ship periods, defining the design loads, and designing the tank structures affected by dynamic slosh loads by delineated procedures which vary with tank type.