A thesis submitted in partial fulfilment of the requirements for the degree of Master of Engineering in Structural Engineering, School of Engineering and Technology

Thesis (M.Eng.) - Asian Institute of Technology, 2008

The offshore concrete gravity base structure (CGBS) is the structure placed on seabed against the loadings without any piles. The advantages of CGBS compared to typical jacket platform are the ability to storage crude oil, ability to decommission after the use, more capacity to carry payloads, less time for onsite installation, and more durable. The objective of the research is to optimize the geometrical dimensions of CGBS to satisfy both of floating case and in-place case especially in Gulf of Thailand whose water depth is less than 85 meters. The parametric study of geometrical dimensions is conducted for 3 water depths, 20, 28, and 41 meters, and then the parameters consisting of payload, wave height, and soil conditions are varied to observe the structural behavior of mini CGBS. The four mini CGBS per water depth are modeled using SAP2000, after that the quasi»static analysis is conducted and shell thicknesses are obtained. The results are interpreted in term of floatability and stability at any geometrical dimensions. Then the three varied parameters of each loading and soil conditions are applied to observe the behavior of mini CGBS for in-place case. The results are presented as the topsides displacement and the soil settlement. The results of two cases are quite clear that the geometrical dimensions affect significantly both floating case and in-place case.