Offshore Structure Loads and Strength - Offshore Structures: Design, Construction and Maintenance - page 88

TABLE 2.36 Mechanical Properties for Structural Steel Shapes

Yield
Strength,
MPa

Tensile
Strength, MPa Group Class Specifications and Grade

I H

ASTM A36, to 50 mm thick 250 400 - 550

ASTM A131 Grade A, to 12 mm
thick

235 400 - 550

I N ASTM A709 Grade 36T2 250 400 - 550

II H

API Spec 2 MT2 Class C 345 450 - 620

ASTM A572 Grade 42, to 50 mm
thick

290 415 min

ASTM A572 Grade 50, to 50 mm
thick (S91 required over 12 mm
thick)

345 450 min

ASTM A992 345 - 450 450 min

II N API Spec 2 MT2 Class B 345 450 - 620

ASTM A709 Grades 50T2, 50T3 345 450 min

ASTM A131 Grade AH32 315 470 - 585

ASTM Grade AH36 350 490 - 620

II C API Spec 2MT2 Class A 345 450 - 620

ASTM A913 Grade 50 345 450 min

Selections for Conditions of Service
Consideration should be given to the selection of steels with toughness char-
acteristics suitable for the conditions of service. For tubes cold-formed to D/t
less than 30, and not subsequently heat-treated, due allowance should be
made for possible degradation of notch toughness, for example, by specifying
a higher class of steel or by specifying notch-toughness tests run at reduced
temperature.
Steel for tubular joints is subject to local stress concentrations that may lead
to local yielding and plastic strains at the design load. During the service life,
cyclic loading may initiate fatigue cracks, making additional demands on the
ductility of the steel, particularly under dynamic load. These demands are
particularly severe in heavy wall joint-cans designed for punching shear.
For the underwater portion of offshore fixed platforms, the steel members or
joint cans (e.g., jacket leg joint cans, chords in major X and K joints and