Energy-absorbing Structure For Semi-submersible Platform

Deep sea semi-submersible platform normally works in severe sea conditions. Due to improperly operating or impact of wind, wave and current when docking near a deep sea semi-submersible platform, vessels may collide to the platform. Since the location where a deep sea semi-submersible platform works is far from land, it will be quite inconvenient to perform rescue operation after a collision accident, as a result the consequences are usually much more critical. Considering from the standpoint of safety, economy and environment, it is very important to improve the collision resistibility of semi-submersible platforms.During the past few decades, ship collision was deeply researched, a series of methods to study collision character were proposed, and a lot of energy-absorbing structures for ship were designed. However, collision study aimed at semi-submersible platform is only at its early-stage. This paper studied the collision resistibility of a semi-submersible platform, and raised a kind of energy-absorbing structure suitable for semi-submersible platform based on comparison study of several kinds of energy-absorbing structures. This paper mainly focuses on the following three points:First, seven kinds of energy-absorbing structures such as honeycomb sandwich plate, triangular sandwich plate and hat stiffened plate are introduced and applied to a common panel. Collision process is simulated with ANSYS/LS-DYNA explicit dynamic analysis program and the deformation characteristics, failure modalities, stress distribution as well as energy dissipation status are observedThen, advantages of the above-mentioned seven kinds of energy-absorbing structures are summarized, and a new kind of energy-absorbing structure (grid sandwich plate) that can be applied to semi-submersible platforms is raised. The collision character of grid sandwich plate is compared with other energy-absorbing structures mentioned above.Last, grid sandwich plat and honeycomb sandwich plate are applied to the column of a semi-submersible platform, the process of a ship bow colliding the very column is simulated. The collision resistibility of grid sandwich plat is verified.Based on the previous analysis, the following conclusions can be drawn:compared with the above-mentioned seven kinds of energy-absorbing structures, grid sandwich plate has better collision resistibility under same initial collision conditions. The application of grid sandwich plate to semi-submersible platform column can decrease column structure's deformation, improve the distribution of structure stress, enhance the capability of collision energy absorption, and thus remarkably increase collision resistibility of the semi-submersible platform.