Reliability analysis of offshore structures under earthquake excitation

• Main Author: Tan, Qing Hong.
• Other Authors: Liu Yu
• Format: Final Year Project
• Language: English
• Published: 2009
• Subjects: DRNTU::Engineering::Civil engineering::Water resources
• Online Access: http://hdl.handle.net/10356/16098
• Institution: Nanyang Technological University

Our world today depends heavily on oil and gas for energy needs. Without them, our society would grind to a standstill. We would not be able to produce electricity and there would be no cars travelling on the roads. Therefore, it is only natural that vast resources are dedicated to the art of extracting these commodities from their sources. In order to keep the oil extraction process running like clockwork, it is imperative that the reliability of the structures is sufficient to prevent a catastrophic collapse. This is especially true for offshore platforms as it is essentially “on its own” during operations, far away from immediate assistance. We are particularly interested in analysing the reliability of offshore oil-extraction platforms in withstanding earthquakes. Due to the highly excitable nature of earthquake loads, we must employ dynamic analysis to acquire accurate results. As predicting earthquakes are stochastic in manner, we will employ the Monte Carlo method to simulate their occurrences. We are heavily reliant on pseudo-random reproductions of potential earthquake loads, thus, historical data are primarily essential. In this report, the procedures to map out our sequential analysis will be outlined. Key to our work is the use of popular computer-aid design software like GT STRUDL and MATLAB. GT STRUDL is the “brain” behind the structural analysis runs. In a short period, it can calculate the behaviour of the structure under dynamic loads, i.e., deflection, reaction forces, member forces, etc. MATLAB will be the indispensable tool in formulating the Monte Carlo simulation results. The primary objective of this project is to attain a reliability analysis with regards to dynamic earthquake loads. However, due to time constraints, the methods used involve a fair bit of assumptions. As such, the secondary objective would be to recommend refinements in the analysis to include improved calculations in place of the assumptions.