An automated computational tool for offshore supply vessels’ structural preliminary design

Abstract

This work presents the application of the rules of the Classification Society American Bureau of Shipping (ABS) for steel vessels in a development of an Excel computational tool that allows to speed up the preliminary structural design calculation process, from several days to minutes, with no precision loss, based on the main particulars and a few structural characteristics, automating everything that does not depend on decision-making. This tool is intended to be a first of a few to perform the required calculations for the preliminary structural design, in this case, applied to Offshore Support Vessels. Once the frame type, the selection of the commercial steel type, and manufacturer are prescribed by the user, all the rules are automatically calculated, all the thicknesses are computed and presented, and rounded up to the commercial values and which reinforcements need to be dimensioned are defined. The user then should dimension these structural elements by selecting the profile type, thickness and height of the web, and thickness and length of the flange, such as stiffeners and/or girders of the bottom, double bottom, sides, double sides, decks, and bulkheads; solid and open floor, side stringers, frames, bottom and deck girders, deck transverses, bulkhead girders, and webs. Besides verifying if the structural strength values are in accordance with the classification society rules in each and every step of the dimensioning process, the program also shows a sketch of the Midship Section that is redrawn at each decision change of the user. The program also verifies the global structural resistance; calculates the steel area, the hull girder section modulus, and moment of inertia; compares these values with the minimum rules requirements; and analyzes if the ship fulfills the longitudinal resistance. Soon after, based on the midship section, the sectional area and the transverse bulkheads positions, the program estimates the steel weight, and center of gravity of the ship. Finally, the user can generate a detailed Report that contains all the information produced by the program, as well as the calculation memory. An application example is presented.