Steels_ Metallurgy and Applications, Third Edition

Low-carbon structural steels 177

Figure 2.19 Types of steel for North Sea structures (After Billingham 21)

have been produced which take account of the various stress concentration factors
induced by different node geometries and plate thicknesses.
The Guidance Notes state that the calculated tensile stress in various members
should not exceed 60% of yield stress under normal operating conditions and
80% of yield stress under extreme loading conditions.

Steel selection

Steels for tubular frame platforms can be grouped into three classes, depending
on their location and duty:

1. Special structural steel.


2. Primary steel.


3. Secondary steel.