Download - CNR-M1-Fatigue Check.xls
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abb FATIGUE CHECK - Rev C 6/20/2013
MODULE 1 ANCHOR JOINTS (Reference Dwg: 1072-MI20-9046-0125)
Bearing plate is provided between bottom of Deck beam and Stool and Fillet welded allround on both sides
Bearing Plate Size:
Length, L : 350 mm
Width, B : 250 mm
Thickness, t : 60 mm
Fillet Weld Leg-size, sw 16 mm
The Reactions and Stresses in Weld at Anchor Joints due to 100-year return Extreme Storm Onsite Accelerations
as per Doct.1072-MI20-00DS-0010
JOINT LOAD SHEAR(Fx) SHEAR(Fy) RESULTANT PRINCIPAL
NUMBER CASE (KN) (KN) SHEAR (Fs) STRESSES ON
(KN) WELD(N/mm )
1 I11 62 91 110 8.1I12 86 -90 124 9.2
I13 -67 93 115 8.4
I14 43 -87 97 7.1
I15 61 91 110 8.1
I16 85 -90 124 9.1
I17 -68 93 115 8.5
I18 -44 -88 98 7.2
11 I11 64 94 114 8.4
I12 41 -99 107 7.9
I13 -60 94 112 8.2I14 -83 -99 129 9.5
I15 65 94 114 8.4
I16 42 -99 108 7.9
I17 -59 94 111 8.2
I18 -82 -99 129 9.5
Maximum Nominal Stress: 9.5
RESULTANT SHEAR
STRESSES ON WELD (N/mm2)
Fs/(2(L+B)*sw*0.707)
8.1
9.1
8.5
7.2
8.4
9.2
8.4
7.1
8.1
7.9
8.2
9.5
7.9
8.29.5
8.4
250
350
Y
X
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abb FATIGUE CHECK - Rev C 6/20/2013
MODULE 1 ANCHOR JOINTS (Reference Dwg: 1072-MI20-9046-0125)
Refer to: Offshore Installations: Guidance on Design, Construction and Certification
Fourth Edition, 1990 with Amendments in 1993, 1995
Health and Safety Executive, Department of Energy, London
HOT-SPOT STRESS RANGE
The fillet weld is subjected to shear and tension.
Since the stress path between beam flange to bearing plate and bearing plate to stool is independent of plates geometry,
Geometric Stress Concentration Factor: 1.00
As per Section A21.2.12a of HSE Guidance (reference),
For fillet welds which are essentially transverse to direction of stress (with edge distance > 10mm),
Weld Classification Factor: 1.52
Since the above principal stresses are computed based on 100-year return extreme severe motions,
the Hot-Spot Cyclic Stress Range is computed as below:
Hot-Spot Cyclic Stress Range = SCFxClassification Factor x Nominal StressSB = 14.5 N/mm
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abb FATIGUE CHECK - Rev C 6/20/2013
MODULE 1 ANCHOR JOINTS (Reference Dwg: 1072-MI20-9046-0125)
ALLOWABLE NUMBER OF CYCLES
Basic S-N Curve for welded tubulars and plates in air
Log10(N) = Log10(K1) - m Log10(SB)
where,
N = Predicted number of cycles to failure
SB = Stress range
m = Inverse slope
K1 = Constant
For welded plate connections in air,
S0 = Stress range at which the slope of S-N Curve changes
= 53 N/mm2
N0 = 1.00E+07 TABLE FOR S-N CURVE FOR WELDED PLATES AS PER HSE GUIDANCE
SB (N/mm2) Log10(K1) m Log10(N) N
(a) For SB < S0 10 15.637 5 10.637 4.34E+1020 15.637 5 9.132 1.35E+09
Log10(K1) = 15.637 30 15.637 5 8.251 1.78E+08
m = 5 40 15.637 5 7.627 4.23E+07
50 15.637 5 7.142 1.39E+07
(b) For SB > S0 53 15.637 5 7.016 1.04E+07
60 12.182 3 6.848 7.04E+06
Log10(K1) = 12.182 70 12.182 3 6.647 4.43E+06
m = 3 80 12.182 3 6.473 2.97E+06
90 12.182 3 6.319 2.09E+06
For SB = 14.5 N/mm 100 12.182 3 6.182 1.52E+06
Log10(K1) = 15.637 150 12.182 3 5.654 4.51E+05
m = 5 200 12.182 3 5.279 1.90E+05
250 12.182 3 4.988 9.73E+04
Log10(N) = 9.835 300 12.182 3 4.751 5.63E+04
N = 6842966771 350 12.182 3 4.550 3.55E+04
400 12.182 3 4.376 2.38E+04
Allowable number of cycles, N = 6.8430E+09 450 12.182 3 4.222 1.67E+04
500 12.182 3 4.085 1.22E+04
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abb FATIGUE CHECK - Rev C 6/20/2013
MODULE 1 ANCHOR JOINTS (Reference Dwg: 1072-MI20-9046-0125)
ACTUAL NUMBER OF CYCLES
Fatigue Life = 20 years
Motion period = 8.9 sec
Actual Number of cycles, Nactual
= 7.0867E+07
Factor of Safety = N/Nactual
(on 20 yrs fatigue life) = 96.5601
> 1.0
Okay
1
10
100
1000
1.00E+04 1.00E+05 1.00E+06 1.00E+07 1.00E+08
StressRange(N/Sq.mm)
Endurance (Cycles)
S-N CURVE FOR WELDED PLATES
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MODULE 1 ANCHOR JOINTS (Reference Dwg: 1072-MI20-9046-0125)
Bearing plate is provided between bottom of Deck beam and Stool and Fillet welded allround on both sides
Bearing Plate Size:
Length, L : 350 mm
Width, B : 250 mm
Thickness, t : 60 mm
Fillet Weld Leg-size, sw 16 mm
The Reactions and Stresses in Weld at Anchor Joints due to 100-year return Extreme Storm Onsite Accelerations
as per Doct.1072-MI20-00DS-0010
JOINT LOAD SHEAR(Fx) SHEAR(Fy) RESULTANT PRINCIPAL
NUMBER CASE (KN) (KN) SHEAR (Fs) STRESSES ON
(KN) WELD(N/mm )
1 I11 85 125 151 11.1I12 84 -129 154 11.3
I13 -87 129 156 11.5
I14 -88 -125 153 11.3
I15 88 125 153 11.3
I16 87 -129 156 11.5
I17 -84 129 154 11.3
I18 -85 -125 151 11.1
11 I11 89 115 145 10.7
I12 90 -109 141 10.4
I13 -87 111 141 10.4I14 -86 -112 141 10.4
I15 86 112 141 10.4
I16 87 -111 141 10.4
I17 -90 109 141 10.4
I18 -89 -115 145 10.7
Maximum Nominal Stress: 11.5
10.4
10.4
10.7
10.4
10.410.4
10.4
11.3
11.3
11.5
11.3
11.1
10.7
RESULTANT SHEAR
STRESSES ON WELD (N/mm2)
Fs/(2(L+B)*sw*0.707)
11.111.3
11.5
250
350
Y
X
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abb FATIGUE CHECK - Rev C 6/20/2013
MODULE 1 ANCHOR JOINTS (Reference Dwg: 1072-MI20-9046-0125)
Refer to: Offshore Installations: Guidance on Design, Construction and Certification
Fourth Edition, 1990 with Amendments in 1993, 1995
Health and Safety Executive, Department of Energy, London
HOT-SPOT STRESS RANGE
The fillet weld is subjected to shear and tension.
Since the stress path between beam flange to bearing plate and bearing plate to stool is independent of plates geometry,
Geometric Stress Concentration Factor: 1.00
As per Section A21.2.12a of HSE Guidance (reference),
For fillet welds which are essentially transverse to direction of stress (with edge distance > 10mm),
Weld Classification Factor: 1.52
Since the above principal stresses are computed based on 100-year return extreme severe motions,
the Hot-Spot Cyclic Stress Range is computed as below:
Hot-Spot Cyclic Stress Range = SCFxClassification Factor x Nominal StressSB = 17.4 N/mm
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abb FATIGUE CHECK - Rev C 6/20/2013
MODULE 1 ANCHOR JOINTS (Reference Dwg: 1072-MI20-9046-0125)
ALLOWABLE NUMBER OF CYCLES
Basic S-N Curve for welded tubulars and plates in air
Log10(N) = Log10(K1) - m Log10(SB)
where,
N = Predicted number of cycles to failure
SB = Stress rangem = Inverse slope
K1 = Constant
For welded plate connections in air,
S0 = Stress range at which the slope of S-N Curve changes
= 53 N/mm2
N0 = 1.00E+07 TABLE FOR S-N CURVE FOR WELDED PLATES AS PER HSE GUIDANCE
SB (N/mm2) Log10(K1) m Log10(N) N
(a) For SB < S0 10 15.637 5 10.637 4.34E+1020 15.637 5 9.132 1.35E+09
Log10(K1) = 15.637 30 15.637 5 8.251 1.78E+08
m = 5 40 15.637 5 7.627 4.23E+07
50 15.637 5 7.142 1.39E+07
(b) For SB > S0 53 15.637 5 7.016 1.04E+07
60 12.182 3 6.848 7.04E+06
Log10(K1) = 12.182 70 12.182 3 6.647 4.43E+06
m = 3 80 12.182 3 6.473 2.97E+06
90 12.182 3 6.319 2.09E+06
For SB = 17.4 N/mm 100 12.182 3 6.182 1.52E+06
Log10(K1) = 15.637 150 12.182 3 5.654 4.51E+05
m = 5 200 12.182 3 5.279 1.90E+05
250 12.182 3 4.988 9.73E+04
Log10(N) = 9.431 300 12.182 3 4.751 5.63E+04
N = 2700214712 350 12.182 3 4.550 3.55E+04
400 12.182 3 4.376 2.38E+04
Allowable number of cycles, N = 2.7002E+09 450 12.182 3 4.222 1.67E+04
500 12.182 3 4.085 1.22E+04
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abb FATIGUE CHECK - Rev C 6/20/2013
MODULE 1 ANCHOR JOINTS (Reference Dwg: 1072-MI20-9046-0125)
ACTUAL NUMBER OF CYCLES
Fatigue Life = 20 years
Motion period = 8.9 sec
Actual Number of cycles, Nactual
= 7.0867E+07
Factor of Safety = N/Nactual
(on 20 yrs fatigue life) = 38.1023
> 1.0
Okay
1
10
100
1000
-1.00E+10 0.00E+00 1.00E+10 2.00E+10 3.00E+10 4.00E+10
S-N CURVE FOR WELDED PLATES
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