Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.
Field Characterization of
Location-specific Dynamic Amplification
Factors towards Fatigue Calculations in
Ship Unloaders
T...
STRUCTURAL ELEMENTS
2
UPPER
SUBSTRUCTURE
LOWER
SUBSTRUCTURE
WATERSIDE
TIES
REAR
TIES
FRONT
BOOM
REAR
BOOM
WATERSIDE
PORTAL...
STANDARD PROCEDURE FOR ASSESSMENT
3
Ship Unloader
Modes
Measured ModesStrain Histories
Monitoring System Modal Testing
FEA...
IDEA FOR IMPROVEMENTS
3
Ship Unloader
Modes
Measured ModesStrain Histories
Monitoring System Modal Testing
FEA Model
Stres...
MONITORING SYSTEM
4
-48 channels of strain
-4 channels of temperature
transducers installed at 16 locations in
full bridge...
DATA PROCESSED
5
DATA
Strain-time histories
Dynamic Stresses
MATLAB
E=207 GPa
It can be assumed that:
• 400s the empty gra...
ESTIMATED STATIC RESPONSE
6
FILTER
A low-pass filter was applied to the dynamic recorded data to
obtain a static response:...
DYNAMIC & 1.3*STATIC RESPONSE
7
For some locations, such as the lateral bending stress in the waterside ties the
dynamic s...
LOCATION-BASED DYNAMIC AMPLIFICATION FACTOR
8
𝐷𝐴𝐹𝑠 =
𝑑𝑦𝑛𝑎𝑚𝑖𝑐 𝑟𝑒𝑐𝑜𝑟𝑑𝑒𝑑 𝑑𝑎𝑡𝑎
𝑒𝑠𝑡𝑖𝑚𝑎𝑡𝑒𝑑 𝑠𝑡𝑎𝑡𝑖𝑐 𝑠𝑡𝑟𝑒𝑠𝑠𝑒𝑠
Cut off frequency of ...
IDENTIFY LOAD CYCLES
9
In order to define these DAFs as accurately as possible, several load cycles need
to be considered:...
DAFs AXIAL STRESS
10
Referring to axial stress, the lifting boom appears to have the biggest dispersion.
In fact, it has a...
DAFs
11
• The DAF provided by the standard was not considered
representative of the real behaviour for the majority of the...
OUTER TIE
INNER TIE
LIFTING
BOOM
WATERSIDE
LEG
LANDSIDE
LEG
REAR
BOOM
REAR TIE
2D FINITE ELEMENT MODEL
12
• Primary elemen...
STATIC RESULTS
83 Load cases have been considered:
-different position of the grab and shuttle trolley along the boom
13
I...
STRESS RANGES FOR FATIGUE LIFE ASSESSMENT
14
• Axial and bending stresses were combined to evaluate the stress at each cor...
STRESS RANGES (Panamax range)
15
REMAINING LIFE
16
• The mean value of the stress ranges was evaluated for each location
• Miner’s rule was applied to eval...
CONCLUSIONS
17
• For the scenario under investigation the DAF provided by the standard was
not considered representative o...
Thank you for your attention!
Lloyd’s Register University College Dublin
This project has received funding from the Europe...
Upcoming SlideShare
Loading in …5
×

"Field characterization of location-specific dynamic amplification factors towards fatigue calculations in ship unloaders" presented at ESREL2017 by Giulia Milana

285 views

Published on

Abstract: This paper highlights the impact of dynamic amplification factors in remaining fatigue life assessment of ship unloaders. In practice, the widely accepted procedure for these structures is to carry out a fatigue life assessment envisages: (1) carrying out static analysis, (2) taking into account dynamics via the application of dynamic amplification factors, and (3) applying Miner’s rule. This factor, provided by the standard, is applied to the structure as a whole without considering the vibration of each structural member individually. This paper characterizes the dynamic behavior of each element using location-based dynamic amplification factors estimated from measurements. This caters for a more accurate assessment of the structure, whilst maintaining the simplicity of the standard procedure.

Published in: Engineering
  • Be the first to comment

  • Be the first to like this

"Field characterization of location-specific dynamic amplification factors towards fatigue calculations in ship unloaders" presented at ESREL2017 by Giulia Milana

  1. 1. Field Characterization of Location-specific Dynamic Amplification Factors towards Fatigue Calculations in Ship Unloaders This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 642453 ESREL2017 21st June 2017 G. Milana, K. Banisoleiman, A. Gonzalez Lloyd’s Register/University College Dublin
  2. 2. STRUCTURAL ELEMENTS 2 UPPER SUBSTRUCTURE LOWER SUBSTRUCTURE WATERSIDE TIES REAR TIES FRONT BOOM REAR BOOM WATERSIDE PORTAL LANDSIDE PORTAL
  3. 3. STANDARD PROCEDURE FOR ASSESSMENT 3 Ship Unloader Modes Measured ModesStrain Histories Monitoring System Modal Testing FEA Model Stress Modal Analysis Stress Ranges + Number Cycles Cumulative Damage Rainflow Counting Method Miner’s Rule Reconciled Model Critical Areas Assessment Static Analysis
  4. 4. IDEA FOR IMPROVEMENTS 3 Ship Unloader Modes Measured ModesStrain Histories Monitoring System Modal Testing FEA Model Stress Modal Analysis Stress Ranges + Number Cycles Cumulative Damage Rainflow Counting Method Miner’s Rule Reconciled Model Critical Areas Assessment Static Analysis Location-based DAFs
  5. 5. MONITORING SYSTEM 4 -48 channels of strain -4 channels of temperature transducers installed at 16 locations in full bridge configuration A1 L1 A2 L2 Axial EX+ AI- AI+ EX- L2 -vε A2 +ε L1 -vε A1 +ε T1 T2 C1 C2 Bending EX+ AI- AI + EX- C2 -ε T2 +ε C1 -ε T1 +ε
  6. 6. DATA PROCESSED 5 DATA Strain-time histories Dynamic Stresses MATLAB E=207 GPa It can be assumed that: • 400s the empty grab starts moving from the hopper to the boom • 425s the grab starts to lift the coal • then it starts to return to the hopper and drops the coal at 455s Static Stresses Cut off frequency
  7. 7. ESTIMATED STATIC RESPONSE 6 FILTER A low-pass filter was applied to the dynamic recorded data to obtain a static response: 8th order Chebyshev Type I with cut-off frequency (0.8*(Fs/2)/R) *where fs is the sampling frequency (125 Hz) and R is the factor use for filtering DYNAMIC AMPLIFICATION FACTOR The estimated static stresses were then multiplied by a dynamic amplification factor provided by the FEM 1.001 A: Overhead travelling cranes B: Jib cranes Y=1.3
  8. 8. DYNAMIC & 1.3*STATIC RESPONSE 7 For some locations, such as the lateral bending stress in the waterside ties the dynamic stress is underestimated by the pseudo-static stress*, while for some others, such as the vertical bending stress in the lifting boom, the pseudo-static stress* turns out to be conservative. *pseudo-static stress=DAF*estimated static stress
  9. 9. LOCATION-BASED DYNAMIC AMPLIFICATION FACTOR 8 𝐷𝐴𝐹𝑠 = 𝑑𝑦𝑛𝑎𝑚𝑖𝑐 𝑟𝑒𝑐𝑜𝑟𝑑𝑒𝑑 𝑑𝑎𝑡𝑎 𝑒𝑠𝑡𝑖𝑚𝑎𝑡𝑒𝑑 𝑠𝑡𝑎𝑡𝑖𝑐 𝑠𝑡𝑟𝑒𝑠𝑠𝑒𝑠 Cut off frequency of 10 Hz to remove noise from the measured signal Cut off frequency of 0.4 Hz to remove dynamics
  10. 10. IDENTIFY LOAD CYCLES 9 In order to define these DAFs as accurately as possible, several load cycles need to be considered: based on axial stress of the Inner ties and vertical bending stresses of the lifting boom and lateral ties, 11 other files with dynamic recorded data have been selected to identify a number of hoisting cycles.
  11. 11. DAFs AXIAL STRESS 10 Referring to axial stress, the lifting boom appears to have the biggest dispersion. In fact, it has a wide range of values between 1.3 and 3.2.
  12. 12. DAFs 11 • The DAF provided by the standard was not considered representative of the real behaviour for the majority of the structural elements considered • Some locations are more prone to dynamic amplification than others. For example, the lifting boom and the waterside ties.
  13. 13. OUTER TIE INNER TIE LIFTING BOOM WATERSIDE LEG LANDSIDE LEG REAR BOOM REAR TIE 2D FINITE ELEMENT MODEL 12 • Primary elements modelled by beam elements • Equivalent section for each member with ANSYS Workbench • Modified densities to take into account non-structural members
  14. 14. STATIC RESULTS 83 Load cases have been considered: -different position of the grab and shuttle trolley along the boom 13 INNER TIES LIFTING BOOM
  15. 15. STRESS RANGES FOR FATIGUE LIFE ASSESSMENT 14 • Axial and bending stresses were combined to evaluate the stress at each corner • The maximum amplitude was evaluated to establish the stress range • Location-based DAFs were applied to each component of stress
  16. 16. STRESS RANGES (Panamax range) 15
  17. 17. REMAINING LIFE 16 • The mean value of the stress ranges was evaluated for each location • Miner’s rule was applied to evaluate the cumulative damage corresponding to a single cycle at that stress range • Remaining life for each location was evaluated
  18. 18. CONCLUSIONS 17 • For the scenario under investigation the DAF provided by the standard was not considered representative of the real behaviour for the majority of the structural elements considered. • The remaining number of cycles can be extended or decreased with respect to the standard by considering the unique dynamic features of each section CONCLUSIONS IMPROVEMENTS • A more accurate 3D FE model will be built to model lateral bending stresses and the characteristic behaviour of the waterside ties • The FE model would need to be calibrated to gather DAF and remaining number of cycles before fatigue failure, for locations with or without available measurements. • More sample will be taken into account, considering also different kind of vessels unloaded
  19. 19. Thank you for your attention! Lloyd’s Register University College Dublin This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 642453

×