cnr-m1-fatigue check.xls

7/28/2019 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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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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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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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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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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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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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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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


cnr-m1-fatigue check.xls

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