Structural Ice Monitoring Systems Geir SAGVOLDEN, Dr Philos ...
Structural Ice Monitoring Systems Geir SAGVOLDEN, Dr Philos ...
Structural Ice Monitoring Systems Geir SAGVOLDEN, Dr Philos ...
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<strong>Structural</strong> <strong>Ice</strong> <strong>Monitoring</strong> <strong>Systems</strong><br />
<strong>Geir</strong> <strong>SAGVOLDEN</strong>, <strong>Dr</strong> <strong>Philos</strong>, Director of Technology
<strong>Structural</strong> <strong>Monitoring</strong> <strong>Systems</strong> Outline<br />
Hull Stress <strong>Monitoring</strong> <strong>Systems</strong><br />
<strong>Structural</strong> response<br />
<strong>Ice</strong> Load <strong>Monitoring</strong><br />
Conclusions and Outlook<br />
© Light Structures AS. All rights reserved | www.lightstructures.no
Where did it all begin – GRP hulls<br />
Skjold Series fast patrol boats about 30 sensors. Since 1999<br />
Alta class mine countermeasure vessels about 50 sensors. Since 1997<br />
Light Structures – Spinoff from Navy R&D projects in 2001<br />
© Light Structures AS. All rights reserved | www.lightstructures.no
Light Structures today<br />
World's leading supplier of fiber optic<br />
Hull Stress <strong>Monitoring</strong> <strong>Systems</strong> (HSMS)<br />
Approx. 100 solutions implemented on<br />
LNGCs, VLCCs, FPSOs, shuttle tankers,<br />
container, highspeed and Navy vsls<br />
Scientific approach and adaption to<br />
individual client needs<br />
One of only two suppliers approved and<br />
recommended by DNV<br />
© Light Structures AS. All rights reserved | www.lightstructures.no
<strong>Structural</strong> <strong>Monitoring</strong><br />
Light Structures’ <strong>Structural</strong> <strong>Monitoring</strong><br />
systems are generic and may be applied<br />
to a wide range of structures<br />
– Ships<br />
– Wind power turbines<br />
– Oil & Gas Offshore<br />
– Infrastructure<br />
– Aerospace<br />
Focus on structural measurements in a<br />
broad application context<br />
Fiber optic sensor technology<br />
© Light Structures AS. All rights reserved | www.lightstructures.no
Standard minimum HSM arrangement<br />
HMON ShipRight SEA HM MON-HULL<br />
© Light Structures AS. All rights reserved | www.lightstructures.no
Fatigue management<br />
HSMS follows every hull load cycle<br />
Processed to calculate:<br />
fatigue accumulation rate<br />
total accumulation so far<br />
Pinpoint causes<br />
Promote operational awareness<br />
Minor adjustment – major gain<br />
© Light Structures AS. All rights reserved | www.lightstructures.no
Why Monitor Fatigue Development?<br />
Wave spectra<br />
General statistical,<br />
Not vessel specific<br />
Response<br />
model<br />
Fatigue<br />
from model input<br />
HSMS:<br />
Actual hull loads<br />
Specific to vessel experience<br />
Includes “all” phenomena<br />
(whipping/springing)<br />
∆A=??<br />
F∝(A±∆A) 3<br />
∆A=”0”<br />
Fatigue model<br />
SN curves<br />
Stress Conc Factors<br />
Class calculation - general<br />
Actual calculation – Light Structures<br />
Fatigue<br />
from real loads<br />
- bypass model uncertainty<br />
- include all phenomena<br />
- vessel specific<br />
- operation/trade specific<br />
- enabling optimal decisions<br />
© Light Structures AS. All rights reserved | www.lightstructures.no
Vibration phenomena<br />
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Overload Prediction and Avoidance<br />
Loads from Cargo<br />
LNGC sloshing<br />
Operator Guidance<br />
Localized hull<br />
Loads (ILM)<br />
Global hull<br />
Loads (FPB)<br />
© Light Structures AS. All rights reserved | www.lightstructures.no
Decision Support (Norwegian Navy)<br />
Royal Norwegian Navy MCMVs<br />
Operational limits based on<br />
Predicted Loads (not seastate)<br />
Optimal utilization of strength in<br />
any condition<br />
SIGNIFICANT cost savings due<br />
to reduced damage rate<br />
Strains<br />
Predicted<br />
Loads<br />
Limits<br />
© Light Structures AS. All rights reserved | www.lightstructures.no
Risk evaluation<br />
What is the most likely maximum load in the current conditions<br />
What is the risk of an overloading situation<br />
Statistical<br />
properties<br />
Measurements<br />
Current risk level<br />
Load limits<br />
© Light Structures AS. All rights reserved | www.lightstructures.no
Risk evaluation<br />
What is the most likely maximum load in the current conditions<br />
What is the risk of an overloading situation<br />
Model<br />
Statistical<br />
properties<br />
Measurements<br />
Current risk level<br />
Positions<br />
Load limits<br />
Policy<br />
Design<br />
© Light Structures AS. All rights reserved | www.lightstructures.no
Linear <strong>Structural</strong> Response Models<br />
Calc Loads<br />
Meas Strains<br />
F =K −1 E<br />
Response factors<br />
from<br />
FE models<br />
or Calibration<br />
© Light Structures AS. All rights reserved | www.lightstructures.no
System data flow<br />
Fiber optic<br />
Strain sensors<br />
Fiber optic<br />
Temp sensors<br />
Fiber optic<br />
Accelerometer<br />
HMON system<br />
Fiber optic<br />
interrogators<br />
Data processing<br />
Data consolidation<br />
Ship systems<br />
GPS<br />
MRU/Gyro<br />
SpeedLog<br />
Rudder<br />
Propulsion<br />
Weather<br />
IAS<br />
VDR<br />
Routing....<br />
System display<br />
(separate/integrated)<br />
Decision support<br />
Hull<br />
Condition<br />
Database<br />
On-shore database<br />
Live-link capable<br />
Vessel/fleet reports<br />
Performance analysis<br />
Maintenance planning<br />
DS system data<br />
© Light Structures AS. All rights reserved | www.lightstructures.no
<strong>Ice</strong> Load <strong>Monitoring</strong> project<br />
Project partners:<br />
© Light Structures AS. All rights reserved | www.lightstructures.no
<strong>Ice</strong> Load <strong>Monitoring</strong><br />
© Light Structures AS. All rights reserved | www.lightstructures.no
<strong>Ice</strong> load monitoring system<br />
9 frames instrumented, mainly in the bow<br />
area<br />
25 locations, 2 and 3 filament rosettes, 54<br />
FBGs total<br />
© Light Structures AS. All rights reserved | www.lightstructures.no
Field test<br />
Detailed analysis of two measurement voyages (others have been carried out after<br />
project end)<br />
System operated satisfactorily throughout the project period in Arctic conditions<br />
A large number of loads detected<br />
Load magnitudes and durations within expected range<br />
Loads follow statistical models reasonably well<br />
© Light Structures AS. All rights reserved | www.lightstructures.no
Evaluation of sensor arrangement<br />
Basic instrumentation<br />
Comparison confirms: Basic instrumentation suffice for the ILM application<br />
Allows a larger instrumented area / lower system cost<br />
© Light Structures AS. All rights reserved | www.lightstructures.no
Load Models<br />
Find load position and magnitude from sensor shear stress measurement<br />
Several unknowns: Position of contact, number of contact points<br />
© Light Structures AS. All rights reserved | www.lightstructures.no
Load models, ensemble average<br />
F∝∆γ<br />
Average force acting on a frame is proportional to the shear stress difference<br />
measured by the 4 sensor filaments<br />
Proportionality factor depends on an ensemble average of all likely load cases, as well<br />
as the material parameters and geometric details of the structure<br />
Proportionality factors and structural capacity was found using nonlinear finite<br />
element models<br />
The true load in an individual load case may deviate significantly from the ensemble<br />
average<br />
© Light Structures AS. All rights reserved | www.lightstructures.no
<strong>Structural</strong> utilization<br />
Proportionality assumption allows calculating the structural utilization in percent of<br />
total capacity<br />
Key parameter for vessel operator, easily understandable<br />
Results agree well with expectations; with regard to ice type and thickness, range of<br />
levels observed, and statistical distribution of the loads<br />
© Light Structures AS. All rights reserved | www.lightstructures.no
Distribution of Loads<br />
Maximum loads registered during the test voyages:<br />
• Higher loads close to shoulder area.<br />
• Midship section sensitive for course changes.<br />
• Comparable loads between port and starboard sides<br />
Observed<br />
maxima:<br />
L1: 201 kN<br />
L2: 243 kN<br />
L3: 298 kN<br />
L4: 290 kN<br />
L5: 350 kN<br />
L6: 392 kN<br />
L7: 560 kN<br />
L8: 330 kN<br />
L9: 441 kN<br />
L9<br />
L7<br />
L5<br />
L3<br />
L1<br />
560<br />
450<br />
340<br />
220<br />
110<br />
Force [kN]<br />
L8<br />
L6<br />
L4<br />
L2<br />
0<br />
© Light Structures AS. All rights reserved | www.lightstructures.no
Load magnitude predictions<br />
PDF/CDF from distribution of magnitudes and inter-event times<br />
© Light Structures AS. All rights reserved | www.lightstructures.no
Calibration and verification<br />
Applied controlled static load at several positions of monitored frames<br />
Measured response agree well with theoretical expectations<br />
© Light Structures AS. All rights reserved | www.lightstructures.no
New ILM projects by LS<br />
2012 – Installation on S. A. Agulhas II – Polar Supply<br />
and Research Vessel<br />
2013 – Series of <strong>Ice</strong>breakers<br />
Several tenders for commercial projects<br />
© Light Structures AS. All rights reserved | www.lightstructures.no
Fiber Optic Sensor <strong>Systems</strong><br />
© Light Structures AS. All rights reserved | www.lightstructures.no
Why fiber optic sensing<br />
Safe<br />
– Completely explosionsafe technology<br />
Accurate and stable<br />
– Intrinsic calibration: Direct optical measurement of strain<br />
– No electromagnetic interference in signal path<br />
Robust<br />
– Resistant to most chemicals<br />
– Lowloss signal transfer: Well suited for large structures<br />
Flexible<br />
– Light weight cables, easy to multiplex<br />
– Mount in ballast tanks, insulation system, machine space<br />
© Light Structures AS. All rights reserved | www.lightstructures.no
Summary<br />
<strong>Structural</strong> monitoring systems have progressed far from the early hull girder overload<br />
alarm systems<br />
<strong>Systems</strong> can be tailored to provide information on fatigue development, loads and<br />
deformations on the hull or on any detail of interest<br />
The real potential emerges when measurements are combined with models.<br />
<strong>Structural</strong>, Statistical, RAOs ...<br />
Examples shown from ice load monitoring, one of many application examples<br />
Potential of providing control parameters of interest to various systems<br />
© Light Structures AS. All rights reserved | www.lightstructures.no
© Light Structures AS. All rights reserved | www.lightstructures.no<br />
Source: YouTube – Arne Bergholtz
Contact Light Structures<br />
© Light Structures AS. All rights reserved | www.lightstructures.no
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