Short and long term structural response to irregular seas of a 112 m length tanker

Published in: Proceedings of the 13th Latin American and Caribbean Conference for Engineering and Technology: Engineering Education Facing the Grand Challenges, What Are We Doing?
Date of Conference: July 29 - 31, 2015
Location of Conference: Santo Domingo, Dominican Republic
Authors: José R. Marín L.
Lissette P. Salazar L.
Refereed Paper: #238

Abstract:

In this work, structural response (Vertical Shear Force, SFZ, and Lateral Bending Moment, BMY) to irregular seas for a 7440 DWT and 112-m lbp tanker is calculated for three loading conditions, traveling at constant speed. SCORES computer program was used to linearly calculate the response on regular waves, obtaining the Response Amplitude Operators (RAO) of the Internal forces for different wave lengths and angles of incidence. To calculate Internal Forces at irregular waves, Short and Long Term load prediction methods were implemented. In both cases Spectra of the internal forces were calculated using Bretschneider formulation to represent the surfave elevation. For the first approach, navigation was considered in stationary conditions in three sea states: 5, 6 and 7 of the Beaufort scale, and with probabilities of exceedance of 10-7, 10-8 and 10-9. For the Long term approach, it was considered 20 years of navigation for a constant route between South America and Western Europe, and calculations were performed with a probability of exceedence of 10- 8 and 10-9. These calculations were performed using Weibull distribution, including a simple process to estimate its parameters. Finally, these results from probabilistic Short and Long Term approaches were compared with formulas from DNV classification society, and with results from classic quasistatic approach, obtaining acceptable differences.

Keywords—Structural Random response, Small tanker, irregular seas.