The linear, wave-induced response of a 5-module, 1500 m long MOB is determined. Each module is a 2 pontoon, 8 column semi submersible, and the MOB is represented by a rigid module-flexible connector model. A parametric study is carried out to determine the impact of the connector stiffness on the motions and connector loads. Results show that the hydrodynamic interaction between modules is relatively small. Although the response is a complicated function of the connector stiffness, the maximum extreme connector loads for a number of stiffness cases are a result of horizontal bending induced by oblique waves. Also, it is shown that resonance can be a significant problem, especially for softer connectors.
There has been renewed interest in floating mobile offshore bases (MOBs) for military purposes. The general function of a MOB would be to provide logistical support where other appropriate facilities are not available. In this context, logistical support includes stationing of several thousand personnel and stockpiling supplies and materiel. Transport to and from the MOB would be via sea and air. Air support would require a MOB that is at least 1500 m long to accommodate the landing and takeoff of large cargo airplanes. There are several conceptual designs of a MOB. Mobility requirements and the possible necessity to operate in deep, unprotected waters favor a multi-module design in which the modules are joined on-site. One such design consists of relatively conventional semisubmersible modules which are joined by mechanical connectors. Because semi submersible design, analysis, and construction technologies have been well-developed and proven in the oil industry, the principle technological questions for this class of MOB relate to the connectors, including their influence on the response and the forces they must withstand. To better understand the wave-induced behavior of this class of MOB, a 5-module, 1500 m structure has been analyzed.