船舶英语外文翻译 Longitudinal strength of ships with accidental

外文翻译

Longitudinal strength of ships with accidental

damages

Ge Wang*, Yongjun Chen, Hanqing Zhang, Hua Peng

This paper presents an investigation of the longitudinal strength of ships with damages due to grounding or collision accidents. Analytical equations are derived for the residual hull girder strength and verified with direct calculations of sample commercial ships for a broad spectrum of accidents. Hull girder ultimate strengths of these sample vessels under sagging and hogging conditions are also calculated, based on which correlation equations are proposed. To evaluate a grounded ship, using the section modulus to the deck would be optimistic, while using the section modulus to the bottom would be conservative. On the contrary, to evaluate a collided ship, using the section modulus to the deck would be conservative, while using the section modulus to the bottom would be optimistic. The derived analytical formulae are then applied to a fleet of 67 commercial ships, including 21 double hull tankers, 18 bulk carriers, 22 single hull tankers and six container carriers. The mean values, standard deviations and coefficients of variation for the coefficients in these new analytical formulae are obtained. The ship length exhibits little influence on these coefficients because they are close to the mean values although ship length spans from 150 to 400 m. The ship type shows some influence on the residual strength. Uniform equations are proposed for commercial ships which do not depend on a ship’s principal dim ensions. These formulae provide very handy tools for predicting the residual strength in seconds, without performing step-by-step detailed calculations, an obvious advantage in cases of emergency or salvage operation. r 2002 Elsevier Science Ltd. All rights reserved.

Keywords: Residual strength; Hull girder ultimate strength; Section modulus; Damage; Collision;Grounding

1. Introduction

Traditionally, ships have been designed to resist all loads expected to arise in their seagoing environment. The objective in structural design has been to maintain a ship’s structural integrity for normal operating conditions. A combination of the most severe loads is usually selected as the nominal design load.

Protection of a ship and the cargo it carries from damages incurred by accidents, though an essential issue in the design of watercraft, has been focused on subdividing a ship into compartments. National and international standards (Load Line,MARPOL, SOLAS, Classification Societies’ Rules) have established requi rements or watertight bulkheads and subdivision. Structural strength in collision, grounding or internal accidents (such as an explosion) has attracted very little attention.

Public sensation increases each time there is a major loss of ships, cargo and life atsea, or when there is oil pollution from damaged ships. This motivates the development of design procedures and related analysis methods for accidental loads, in particular, the loads due to ship collision or grounding accidents.