Dynamic Elastic-Plastic Response of Frame Structures under Collision

Abstract

Offshore structures are exposed to higher probability of collision with ships or icebergs because of their limited mobility. In general, the consequence of the collision is disastrous. It is important to study the behavior of offshore structures under collision to ensure their safety.In this paper, dynamic elastic-plastic response of frame structures carrying heavy mass on the top is investigated to provide better understandings of the dynamic response. For this purpose, the Plastic Node Method, which is superior to ordinary Finite Element Methods for elastic-plastic problems, is employed. The numerical results show a clear transition in plastic deformation modes. It is also found that these deformation modes can be correlated with equivalent static deformation modes. Considering these characteristics of the phenomena, a simple method based on a modified rigid-plastic model is proposed to estimate the plastic deformation due to collision. Further, it is applied to classify the dynamic response with respect to the mass and the initial velocity of the colliding body.