Tubular joints are 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.
Table 11.1—Structural Steel Plates
Group Class ASTM Specification and Grade
Yield Strength Tensile Strength MPa ksi MPa ksi
I C
ASTM A36 [to 51 mm (2 in.) thick] 250 36 400–550 58–80 ASTM A131, Grade A [to 13.0 mm (1/2 in.) thick] 235 34 400–490 58–71 ASTM A285, Grade C [to 19.0 mm (3/4 in.) thick] 205 30 380–515 55–75
I B
ASTM A131, Grades B, D 235 34 400–490 58–71
ASTM A516, Grade 65 240 35 450–585 65–85
ASTM A573, Grade 65 240 35 450–530 65–77
ASTM A709, Grade 36T2 250 36 400–550 58–80
I A ASTM A131, Grades CS, E 235 34 400–490 58–71
II C
ASTM A572, Grade 42 [to 51 mm (2 in.) thicka] 290 42 415 min. 60 min.
ASTM A572, Grade 50 [to 51 mm (2 in.) thick];
345 50 450 min. 65 min.
[ASTM A6 [S29 required over 13.0 mm (1/2 in.) a]]
II B
API 2MT1 345 50 483–620 70–90
ASTM A709, Grades 50T2, 50T3 345 50 450 min. 65 min.
ASTM A131, Grade AH32 315 45.5 470–585 68–85
ASTM A131, Grade AH36 350 51 490–620 71–90
II A
API 2H, Grade 42 290 42 430–550 62–80
API 2H, Grade 50 [to 64 mm (2 1/2 in. thick)] 345 50 483–620 70–90 API 2H, Grade 50 [over 64 mm (2 1/2 in. thick)] 325 47 483–620 70–90 II A API 2W ,Grade 50 [to 25 mm (1 in.) thick] 345–483 50–70 448 min. 65 min.
API 2W,Grade 50 [over 25 mm (1 in.) thick] 345–552 50–80 483 min. 70 min.
Table 11.1—Structural Steel Plates (Continued)
Group Class ASTM Specification and Grade
Yield Strength Tensile Strength MPa ksi MPa ksi
II A
API 2Y, Grade 50 [to 25 mm (1 in.) thick] 345–517 50–75 448 min. 65 min.
API 2Y, Grade 50 [over 25 mm (1 in.) thick] 345–483 50–70 448 min. 65 min.
ASTM A131, Grades DH32, EH32 315 45.5 470–585 68–85 ASTM A131 Grades DH36, EH36 350 51 490–620 71–90 ASTM A537 Class I [to 64 mm (2 1/2 in.) thick] 345 50 485–620 70–90
ASTM A633, Grade A 290 42 435–570 63–83
ASTM A633 Grades C, D 345 50 485–620 70–90
ASTM A678 Grade A 345 50 485–620 70–90
III A
ASTM A537, Class II [to 64 mm (2 1/2 in.) thick] 415 60 550–690 80–100
ASTM A678, Grade B 415 60 550–690 80–100
API 2W, Grade 60 [to 25 mm (1 in.) thick] 414–621 60–90 517 min. 75 min.
API 2W, Grade 60 [over 25 mm (1 in.) thick] 414–586 60–85 517 min. 75 min.
API 2Y, Grade 60 [to 25 mm (1 in.) thick] 414–621 60–90 517 min. 75 min.
API 2Y, Grade 60 [over 25 mm (1 in.) thick] 414–586 60–85 517 min. 75 min.
ASTM A710, Grade A Class 3 (quenched and precipitation heat treated)
[Through 51 mm (2 in.)] 515 75 585 85
[51 mm (2 in.) to 102 mm (4 in.)] 450 65 515 75
[Over 102 mm (4 in.)] 415 60 485 70
a Maximum vanadium level permitted = 0.10 % V.
Table 11.2—Structural Steel Shapes
Group Class ASTM Specification and Grade
Yield Strength Tensile Strength MPa ksi MPa ksi I C ASTM A36 to 51 mm (2 in.) thick 250 36 400–550 58–80
ASTM A131, Grade A to 13 mm (1/2 in.) thick 235 34 400–550 58–80
I B ASTM A709, Grade 36T2 250 36 400–550 58–80
II C
API 2MT2, Class C 345 50 450–620 65–90
ASTM A572, Grade 42 [to 51 mm (2 in.) thick] a 290 42 415 min. 60 min.
ASTM A572, Grade 50 [to 51 mm (2 in.) thick;]
[ASTM A6 S29 required over 13.0 mm (1/2 in.) ] a 345 50 450 min. 65 min.
ASTM A992 345–450 50–65 450 min. 65 min.
II B
API 2MT2 Class B 345 50 450–620 65–90
ASTM A709 Grades 50T2, 50T3 345 50 450 min. 65 min.
ASTM A131 Grade AH32 315 45.5 470–585 68–85
ASTM A131 Grade AH36 350 51 490–620 71–90
II A
API 2MT2 Class A 345 50 450–620 65–90
ASTM A913 Grade 50
with CVN at –20 °C (–4 °F) 345 50 450 min. 65 min.
a Maximum vanadium level permitted = 0.10 % V.
11.3.2 Underwater Joints
For underwater portions of redundant template-type platforms, steel for joint cans (such as jacket leg joint cans, chords in major X- and K-joints, and through-members in joints designed as overlapping) should meet one of the following notch toughness criteria at the temperature given in Table 11.4:
— NRL drop-weight test no-break performance;
— Charpy V-notch energy: 20 joules (15 ft-lb) for Group I steels and 34 joules (25 ft-lb) for Group II steels, and 47 joules (35 ft-lb) for Group III steels (transverse test).
For water temperature of 4 °C (40 °F) or higher, these requirements may normally be met by using the Class A steels listed in Table 11.1.
11.3.3 Above-water Joints
For above-water joints exposed to lower temperatures and possible impact from boats, or for critical connections at any location in which it is desired to prevent all brittle fractures, the tougher Class A steels should be considered, for example, API 2H [5], Grade 42 or Grade 50. For 345 MPa (50 ksi) yield and higher strength steels, special attention should be given to welding procedures.
Table 11.3—Structural Steel Pipe
Group Class
ASTM Specification and Grade Yield Strength Tensile Strength MPa ksi MPa ksi
I C
API 5L, Grade B a 240 35 415 min. 60 min.
ASTM A53, Grade B 240 35 415 min. 60 min.
ASTM A135, Grade B 240 35 415 min. 60 min.
ASTM A139, Grade B 240 35 415 min. 60 min.
ASTM A500, Grade A (round) 230 33 310 min. 45 min.
ASTM A500, Grade A (shaped) 270 39 310 min. 45 min.
ASTM A501 250 36 400 min. 58 min.
I B
ASTM A106, Grade B (normalized) 240 35 415 min. 60 min.
ASTM A524, Grade I [through 10 mm (3/8 in.) w.t.] 240 35 415 min. 60 min.
ASTM A524, Grade II [over 10 mm (3/8 in.) w.t.] 205 30 380–550 55–80
I A ASTM A333, Grade 6 240 35 415 min. 60 min.
ASTM A334, Grade 6 240 35 415 min. 60 min.
II C
API 5L, Grade X42 2 % max. cold expansion 290 42 415 min. 60 min.
API 5L, Grade X52 2 % max. cold expansion 360 52 455 min. 66 min.
ASTM A500, Grade B (round) 290 42 400 min. 58 min.
ASTM A500, Grade B (shaped) 320 46 400 min. 58 min.
ASTM A618 345 50 485 min. 70 min.
II B API 5L, Grade X52 PSL 2 with SR5 or SR6 360 52 455 min. 66 min.
II A See 11.2.2
a Seamless or with longitudinal seam welds.
Table 11.4—Input Testing Conditions D/t Test Temperature Test
Condition Over 30 20 °C (36 °F) below LAST a Flat plate 20 to 30 30 °C (54 °F) below LAST Flat plate Under 20 10 °C (18 °F) below LAST As fabricated
a LAST means lowest anticipated service temperature.
11.3.4 Critical Joints
For critical connections involving high restraint (including adverse geometry, high yield strength, and/or thick sections), through-thickness shrinkage strains, and subsequent through-thickness tensile loads in service, consideration should be given to the use of steel having improved through-thickness (Z-direction) properties, for example, API 2H [5], Supplements S4 and S5.
11.3.5 Brace Ends
Although the brace ends at tubular connections are also subject to stress concentration, the conditions of service are not quite as severe as for joint cans. For critical braces, for which brittle fracture would be catastrophic, consideration should be given to the use of stub ends in the braces having the same class as the joint can, or one class lower. This provision need not apply to the body of braces (between joints).