Dynamic Analysis of the Ampelmann G25 Gangway.

The Ampelmann system is an active motion compensation system that can compensate the vessel motions in six degrees of freedom. The Ampelmann, together with the attached gangway, makes it possible for people to transfer between a vessel and offshore structures safely. The Ampelmann system has been designed in the early stages based on a set of static load cases. For design and analysis related to fatigue life estimation, system operability and control improvements, it is necessary to obtain more insights in the structural dynamics of the system. With the earliest system approaching a lifetime of 10 years, fatigue lifetime is of high importance and forms the main goal of this study The main function of the Ampelmann gangway is to serve as a bridge for people transfer between the ship, where the Ampelmann system is placed on board, and the offshore structure. Ampelann utilize various types of gangway in the market. This will be focus primarily on the most widely used gangway (G25), which consist of a Main Boom and a telescoping T-boom. The transfer deck in which gangway is attached to is assumed to be rigid. To asses G25 for fatigue, first dynamic behavior under certain loading must be determined. In general the gangway in operation experiences various load conditions, which have to be taken into account. However, in this only the load condition under steady wind velocity, base excitation and rotation of the gangway under applied torque is considered. The T-boom cross section, dimension as well as weight are different to the main boom. The gangway as a whole consist of three parts: the main boom, overlapping T-boom in the main boom and the T-boom. The gangway is modeled as a step or segmented Euler-Bernoulli beam to describe the dynamic characteristic. The dynamic characteristics are the mode shape and natural frequency in its vibrating plane. Since the gangway is a ’U shape’ like beam, the offset of the shear center will cause coupled effect between bending and torsio
Mechanical, Maritime and Materials Engineering
Offshore & Dredging Engineering