Page 346 - Practical Ship Design

Structural Design 303

should be introduced in any area where the loss of a member due to corrosion or
fatigue might be calamitous.
Classification Societies have in recent years issued some very useful guidance
on good and bad details and these should be carefully studied by all designers.

10.7 STRUCTURAL STRENGTH UNITS

Because the author learned his theory of structures many years ago, he found he
needed an aide memoire on modern units and their equivalents whilst writing and
this is included as Table 10.2.

Table 10.2
Structural strength units
~
Unit S.I. and metric equivalents Old British
~___ -.
Mass 1 tonne = 1000 kilograms I tonne = 0.9842 tons I ton = 2240 Ibs
= grams 1 ton = 1.016 tonnes

Acceleration due to 9.8 I metres per sec2 32.2 feet per sec'
gravity

Force I Newton = force to 1 Newton = 7.233 Poundals 1 Poundal = Force to
accelerate a mass of 1 kg at accelerate a mass of I Ib at
I metre per set' I ft/sec2
I tonne force = force due to 1 ton force = force due to
gravity on 1 tonne mass gravity on 1 ton mass
1 tonne (F) = 9.81 kN I ton (F) = 7.2128~10~
poundals

Stress and pressure 1 N/mm' = I MN/m' I tonne/mm2 = 635 tons/in2 tons/in'
1 tonne(F)/mm2 = 9.81~10~ ton/in2=0.00157S tons/ft2
1
N tonnes/mm2
1 todin' = 15.42 N/mm' Ibs/in'

Metric multiples:
IO^ = giga IO-' = milli
10' = mega IO-' = micro
IO3 = kilo = nano