Study On The Vibration Control Of The Combined Anti-vibration Offshore Platforms

Fixed offshore platforms are the most commonly used structure for offshore oil exploration and exploitation nowadays. The problems caused by the augmentation of the platforms' cubage, such as the increase of the loads and the construction expense, the unequal weight bearing and the acute vibration under the execrable circumstance loads, hinder the platforms' usage into the blue water. The traditional vibration control methods, such as the reinforcement of the platform's stiffness and the appendage of vibration absorption system to the platform, have much limitation and can't satisfy the request of platforms' security and reliability. In this dissertation, a new type platform, named as combined anti-vibration offshore platform, is constructed, which has the ability to counteract, absorb and decrease the vibration response. The new platform is made up of two parts: mega-frame platform and METMD (Multiple Extended Tuned Mass Damper) vibration control system, which is composed of several ETMD subsystems. The mega-frame platform is constructed using the mega-frame theory that is used maturely on the construction of high-rise buildings on land. The new platform is designed for the usage in the blue water. The ETMD subsystem is constituted using the equipment, device set on the platform or partial structure of the platform. The ETMD subsystem is the extension of the TMD vibration control system. The ETMD subsystem can be used to control vibration of the platforms without appending additional mass to them. The major researches in the dissertation are shown as following:Firstly, the mega-frame platform is constructed based on the jacket platform using the mega-frame theory. Its major columns are the enlargements of vertical shafts of the traditional jacket platform by increasing their diameters. And the major beams are developed from the waling stripes and the inclined struts by collecting and newly disposing them on the major columns. The major columns and the major beams constitute the major frame, which has the great side force counteraction stiffness and can effectively bear the vertical and horizontal loads of the platform. The machines, equipment and partial platform can be joined to the mega-frame platform by springs and/or dampers and become minor frames or sub-structures. The mega-frame is the main part to counteract the side force. The sub-structures can merely transport the loads to the mega-frame and counteract some of the side force. So the huge mega-frame and...