Page 82 - Ship Construction.DJ Eyres 6Ed

P. 82

Ch08-H8070.fm Page 71 Wednesday, October 18, 2006 7:29 AM
Stresses to which a Ship is Subject 71
compression will also have a critical buckling load whose value depends on
the plate thickness, unsupported dimensions, edge support conditions and
the materials modulus of elasticity. Unlike the pillar, however, slightly
exceeding this load will not necessarily result in collapse of the plate but
only in elastic deflection of the center portion of the plate from its initial
plane. After removal of the load, the plate will return to its original unde-
formed state. The ultimate load that may be carried by a buckled plate is
--- ใช้เพื่อการศึกษาเท่านั้น---
determined by the onset of yielding (i.e. when the yield point of the mate-
rial is reached) at some point in the plate or in the stiffeners. Once begun
this yielding may propagate rapidly throughout the stiffened panel with fur-
งานห้องสมุด ศูนย์ฝกพาณิชย์นาวี
ther increase in load until failure of the plate or stiffeners occurs.
In recent years Lloyds Register has introduced for oil tankers over 150
metres in length rules that contain formulae to check the buckling capacity
of plate panels and their main supporting stiffeners. Where further buckling
assessment is required a computer based general and local stiffened plate
panel ultimate buckling strength evaluation assessment procedure is used.

Monitoring Ship Stresses at Sea
ึ
In order to enhance safety during shipboard operations real time motion
and stress monitoring information equipment can be supplied by Lloyds
Register to a ship at the owners request. This entails the fitting of strain
gauges to the deck structure, an accelerometer and a personal computer
with software that displays ship stress and motion readings on the bridge.
An alarm is activated if the safety limits are exceeded, enabling remedial
action to be taken. Where this equipment is installed the notation SEA is
assigned and if coupled to a data recorder the assigned notation is
SEA(R).