Investigation on structure damage equivalence of hull girders with different scales subjected to near-field underwater explosion

Over the years, numerous experiments and numerical simulations have been performed to investigate the damage of marine structures subjected to near-field underwater explosions. These studies, therefore, hold immense significance as they provide identified damage pattern of structure. Despite this, it is essential to further explore the connection among various damage patterns of existing work to help predicting the damage of real structure by employing the test results of small-scale structures. To address this gap, this study proposed an equivalent design method for hull girder model based on scaled-down similarity criteria and reversed design idea, which is for investigating the equivalent damage of structures with different scale subjected to near-field underwater explosion. Different from the traditional scaling method, in which both the structure and blast load are scaled-down accordingly for small size test model, the present method concentrates on the damage equivalence between two structures with different size subjected to the same blast loading from underwater explosions. This equivalent design methodology ensures compliance with fundamental blast principles during the structural equivalence process of both overall and local damage. In order to verify the method presented in this paper, two hull girder models were designed and manufactured, and underwater explosion tests were implemented to investigate the degree of damage between models. A comparative analysis of the overall damage and local damage of the central cabin between different scale models reveals that the damage patterns exhibit a high degree of consistency under identical conditions, simultaneously the similarity ratio errors pertaining to the extent of structural damage are within a 15 % margin. The results show that the presented design method is capable of predicting the structural damage of large-scale hull girder structure under the same load condition based on the results of small-scale model tests.