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Finite element method in crane structural failure analysis & rectification (TOC Europe 2011)

A presentation by Portek International at the TOC Asia 2011, March 15-17 Tianjin, covering: - Reasons for increasing crane structural failure - Types of failure - Finite Element Method (FEM) solutions

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Premature Crane Structure Failure & Finite Element
       Method Analysis and Rectification




By SC Tok & Larry Lam / Portek Group
                                                 1
2
Overviews

   Introduction of Portek
       • About Portek
       • Our Experience
   Premature crane failures
   Application of FEM
       • Crane Repair
       • Crane modification
       • Crane life assessment
   Conclusions
   Q&A Session




                                 3
Company History

  • Established in 1988
  • Turnkey provider of equipment, services and solutions to the
    global port industry.
  • Expanded into port operations in 1999.
  • Listed on the Mainboard of Singapore Stock Exchange in
    2002.
  • Headquartered in Singapore, with offices in locations across
    Asia, Europe and Africa employing over 1600 employees.




                                                                   4
Core Businesses & Competencies
   Port Operations and Management
    •   Operate and manage 8 terminals globally

   Equipment Engineering
    •   Equipment sale and leasing
    •   Mobilization, modification & modernization
    •   Maintenance, diagnostics & repairs
    •   Distribution of components and spares

   Port IT Solutions
    •   Container Terminal Management System (CTMS)
    •   Equipment Maintenance System
    •   Terminal Planning & Simulation
    •   Radio Data Terminal System (RDTS)
    •   Positioning Determining Systems (PDS)
    •   Optical Character Recognition (OCR)
                                                      5
Terminal Ops & Management

   Bejaia Mediterranean Terminal, Algeria
   Valletta Gateway Terminals, Malta
   Terminal 009, Jakarta
   Terminal 300, Jakarta
   Port D’Owendo, Libreville, Gabon
   Port Gentil, Gabon
   Banten Multipurpose Terminal, Java
   Dry port in Kigali, Rwanda




                                            6
Introduction
Premature failures of crane structure are becoming more common!




             About 1.2m crack found at boom web plate



                                                                  7
Introduction
Premature failures of crane structure are becoming more common!




                  Crack found at boom-girder
                  hinge



                                                                  8
Introduction
Premature failures of crane structure are becoming more common!




    Incident of trolley wheel truck
                                      Serious wear on trolley rail
    due to crack




                                                                     9
Introduction
Premature failures of crane structure are becoming more common!




Cracks at girder end           Repair of forestay gusset plate:
                               wear and cracks



                                                                  10
Introduction
Why do crane structures fail prematurely?

Although modern design software and manufacturing process have
helped crane manufacturers to optimize their design, there is still
some degree of trial and error in any new crane design.

• Crane sizes have increased significantly. Weight of the crane has
  increased to 2000 ton versus 800 ton. Outreach of 65m versus 34 m.
• Crane speeds have also increased substantially.
• Crane lift capacity increased from 40 ton to now 65 ton
• Twinlift and tandem lift operation




                                                                       11
Introduction
Why do crane structures fail prematurely?

• We are venturing into new territories which only time will tell as to
  how well crane structures can withstand heavier duties they are
  subject to
• Most crane designs are based on experiences and data gathered.
   • Static + dynamic factor
   • Not enough study on the dynamic characterization of super
     sized crane. In some design cases, 1 loading cycle actually
     generate 20 oscillations, hence causing the fatigue cycles to
     be reached well before intended life cycle.


• Need to determine if manufacturing quality problem or inherent
  design problem.


                                                                          12
Premature crane failure

 Manufacturing Quality – a major factor

  •   Low cost country with cheaper labour


  •   Even within the same country, there was a case of an established
      manufacturer who suffered quality problems after transferring crane
      manufacturing to different factory using sub-contract labour.


  •   Employing 3rd party inspection helps, but cannot eliminate all problems




                                                                                13
Procurement considerations

 •   Procurement decision increasingly governed by short term financial
     considerations – pennywise, pound foolish

 •   True cost of a crane is life cycle cost : depreciation plus
     maintenance plus performance consideration.

 •   Examples: cranes are scrapped after 10 years of problematic
     service life. These are the most expensive cranes, no matter how
     cheap they are in beginning.




                                                                          14
Purchase considerations

 • With raw materials and energy cost rising, days of cheap cranes will
   soon be over. Inflationary pressures and rising labour cost in low
   cost countries are putting upward pressures on crane prices.

 • Port Operators will have to squeeze productivity and make assets
   sweat for them

 • Life cycle factors such as reliability, availability, energy consumption,
   maintenance cost, will feature more prominently in purchaser
   consideration.

 • Safety of crane operation has been largely overlooked, and not
   accorded enough consideration. Reputational damage.




                                                                               15
Practical difficulties with crane shutdown for
repairs and upgrade


  •   Operational needs always take priority over engineering
      tasks. Frequent delays to project execution

  •   Operationally difficult to isolate cranes in between other
      cranes. Skidding back and pushing it to end of the quay
      may be only solution.

  •   “Boom down” position could be achieved owing to vessel
      movements




                                                                   16
Introduction
What are the common types of crane structure failures?

    •   Trolley structures
    •   Boom-girder joints
    •   Trolley rail
    •   Crane leg structure
    •   Gusset plate of forestay
    •   Main equalizer beam
    •   Rope sheave supports
    •   others

Many failures caused by premature fatigue well before
reaching design lifecycle!




                                                         17
Solutions for Crane Failures
Conventional approach of repairing cracks

    •   gouging out the cracks and filling up with welds is no longer
        sufficient, and in fact dangerous. Often the root cause of certain
        cracks may originate from points remote from the cracks

    •   Due to added design complexity and load, terminals should study
        and approach each case scientifically and get to the root cause of
        failure



 The Finite Element Method (FEM) should be a standard tool in
 analyzing the cause of failure, and in recommending proper
 repair procedures !




                                                                             18
What is FEA

Finite Element Analysis (FEA) is a way to simulate loading conditions on a
design and determine the design’s response to those conditions.

The design is modeled using discrete building blocks called elements.

     •   Each element has exact equations that describe how it responds to a
         certain load.
     •   The “sum” of the response of all elements in the model gives the total
         response of the design.
     •   The elements have a finite number of unknowns, hence the name
         finite elements.




                                                                                  19
Why is FEA Needed

To help find the root cause of failure
    •  Computer simulation allows multiple “what-if” scenarios to be
       tested quickly and effectively.

To help make right decision for the repair at beginning
    •  Computer simulation allows comparing the different designs
       Virtually.

The bottom line:
   •   Cost savings
   •   Time savings
   •   Create more reliable, better-quality designs




                                                                       20
Application of FEM in Portek

   •   Transportation
          • Sea fastening design
          • Deck strength
          • Quay strength
   •   Crane modification
   •   Crane repair
   •   Crane life assessment




                                   21
Sample 1: Top Girder Support
Beam Crack Repair




                               22
Modeling of the affected areas Using FEM




                                           23
Loading and Boundary Conditions




                                  24
Simulation Results for Original Design




                                         25
Proposed Solution 1: Internal Reinforcement




                                              26
Proposed Solution 2: to Remove Sharp Edges



                             Very High Stress




Improper design caused
stress migration!



                                                27
Proposed Solution 3: Smooth Curve w/o Sharp
Edges




 Selected Solution Using Finite Element Method!


                                                  28
Interpretation of Results
     Maximum stresses found on the hanger plates and stress
          reduction as compared to the original design
                  Stresses      Stress value   Stress reduction
                                   (MPa)
   Landside left top                102             44%

   Landside left bottom             132             29%

   Landside right top               88              37%

   Landside right bottom            98              23%

   Seaside left top                 125             52%

   Seaside left bottom              168             29%

   Seaside right top                115             46%

   Seaside right bottom             142             15%




                                                                  29
Site Execution of Repair




                           30
Sample 2: Trolley Structure
          Recovery and Repair




                                31
Trolley Structure Recovery


             William Rod




                             32
Investigation of Stress in Trolley Truck




     Geometry model
      - quarter platform
                                  Finite element model



                                                         33
Investigation of Stress in Trolley Truck




    Load and boundary conditions




                                           34
Investigation of Stress in Trolley Truck




            Different boundary conditions to
            investigate the reason of failure




                                                35
Investigation of Stress in Trolley Truck




structure under uniform constrain       structure under wheel truck bend
                                    Conclusions:
                                    1. Major cause is the wheel truck bend
                                       along the rail direction
                                    2. Boom-girder joint maintenance is very
                                       important
                                    3. Trolley truck with equalizer pin is the
                                       efficient way to avoid this kind failure
One of the proposed modification
 under uniform constrain--worse
                                                                                  36
Sample 3: Structure Repair of RTG
                                      Designed centreline of leg

                                      Measured centreline of leg




Angle of                                               Angle of
misalignment                                           misalignment

= 0°20’11”                                             = 0°25’30”




  Off by 53mm                                         Off by 109mm
  at 0m                                                   at 0m




                                                                   37
Sample 3: Structure Repair of RTG
Normal Gantry Tyre Position




             Far side                   Near side


 Gantry Tyre Position for damaged RTG




               Far side             Near side


                                                    38
Finite Element Analysis




• At least 27ton pulling force to cause this
  failure
• Plastic deformation occurred at corner
• Conner reinforcement can prevent this failure
  efficiently


                                                  39
Repair Procedure




                   40
Structure Repair




                   41
Boom Extension
Modification required
 1. Extend boom 4.5 m
 2. Expensive to use Floating Crane
 3. Design method




                                      42
FE Simulation

Solver: ANSYS/Mechanical

Elements:     Plate
              Beam
              Bar
              Joint
Models:
      1. Original boom
      2. Extended boom without moving lug
      3. Extended boom by moving lug




                                            43
Simulation results & Comparison




                                  44
Real World




             45
Height Extension Using Synchronise
Jacking System


Modifications

 1. Increase height 5.0 m

 2. Strength & stability of
    jacking tower

 3. Design method




                                     46
FE Simulation

Solver: LS_DYNA

Model: Inner tower & Jacking components

Key point: Multi-surface contact

Loads:
               1. Overall crane weight
               2. Lateral wind




                                          47
Simulation Results




                     48
Simulation results




                     49
Facing the Real World




                 Components to equipment




Jack up 5 m
      &
 Insert new
     leg                                   Jack up 1 m




                                                         50
Simulation vs. Design
     The jacking procedure is safe despite contact stresses are high;
     The stress on the pin is quite low;
     Local modification of the jacking section is suggested.




                                                                         51
Useful Life Assessment


  1. Structural Condition Survey

  2. Useful Life Estimate Before Inspection

  3. Structural Inspection

  4. Useful Life Estimate After Inspection




                                              52
Crane Structural Inspection, Why?


   • Many Cranes are at the end of their designed life cycle

   • Fatigue cracks will occur and can be catastrophic if not
     repaired

   • Crack repairs are often inexpensive and cracking can be
     controlled by proper analysis, design, workmanship, quality
     control and maintenance

   • It is prudent to perform structural inspection prior to
     spending huge amount of money on refurbishment and
     drive retrofitting




                                                                   53
Structural Condition Survey


  •   Look for:

         •   High stress areas
         •   Suspect details
         •   Attachments

  •   Make photo record for the NDT inspection.




                                                  54
Useful Life Estimate Before Inspection

   •   Perform finite element analysis
   •   Calculate relative cumulative damage
   •   Estimate remaining useful life




Forestay failure analysis using ANSYS

                                              55
Structural Inspection

 •   Inspect and compare with                                              
                                                                               N-6

     predictions

 •   Non-Destructive Test (NDT)
                                                                                                            
                                                                                                                N-5
 •   Repair procedures
                                                                                                                   
                                                                                                   Leg #1               Leg #2




                                                                                                                
                                                                 
                                                                     N-4                                            N-8

                                                            
                                                               N-10                                        
                                          N-2                                                                    N-9
                                                                                     
                                                                                         N-7
                                          
                                              Leg #3

                                                      
                                N-3                        Leg #4




                                                                                                                                 56
Useful Life Estimate After Inspection


  • Review inspection reports

  • Identify fatigue cracks

  • Compare identified cracks with prediction

  • Re-evaluate the reliability and useful life




                                                  57
Conclusions

• Finite Element Analysis is an essential tool for helping us in
  determining the cause of the problems and recommending the
  solutions.
• FEM analysis of structural failure should be adopted as standard
  tool in failure analysis
• With a trained engineer, FEM is quick and easy to deploy.
• With the exponential increase in computing power, FEM is
  economical to carry out.




                                                                     58
Thank you




            59

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Finite element method in crane structural failure analysis & rectification (TOC Europe 2011)

  • 1. Premature Crane Structure Failure & Finite Element Method Analysis and Rectification By SC Tok & Larry Lam / Portek Group 1
  • 2. 2
  • 3. Overviews Introduction of Portek • About Portek • Our Experience Premature crane failures Application of FEM • Crane Repair • Crane modification • Crane life assessment Conclusions Q&A Session 3
  • 4. Company History • Established in 1988 • Turnkey provider of equipment, services and solutions to the global port industry. • Expanded into port operations in 1999. • Listed on the Mainboard of Singapore Stock Exchange in 2002. • Headquartered in Singapore, with offices in locations across Asia, Europe and Africa employing over 1600 employees. 4
  • 5. Core Businesses & Competencies Port Operations and Management • Operate and manage 8 terminals globally Equipment Engineering • Equipment sale and leasing • Mobilization, modification & modernization • Maintenance, diagnostics & repairs • Distribution of components and spares Port IT Solutions • Container Terminal Management System (CTMS) • Equipment Maintenance System • Terminal Planning & Simulation • Radio Data Terminal System (RDTS) • Positioning Determining Systems (PDS) • Optical Character Recognition (OCR) 5
  • 6. Terminal Ops & Management Bejaia Mediterranean Terminal, Algeria Valletta Gateway Terminals, Malta Terminal 009, Jakarta Terminal 300, Jakarta Port D’Owendo, Libreville, Gabon Port Gentil, Gabon Banten Multipurpose Terminal, Java Dry port in Kigali, Rwanda 6
  • 7. Introduction Premature failures of crane structure are becoming more common! About 1.2m crack found at boom web plate 7
  • 8. Introduction Premature failures of crane structure are becoming more common! Crack found at boom-girder hinge 8
  • 9. Introduction Premature failures of crane structure are becoming more common! Incident of trolley wheel truck Serious wear on trolley rail due to crack 9
  • 10. Introduction Premature failures of crane structure are becoming more common! Cracks at girder end Repair of forestay gusset plate: wear and cracks 10
  • 11. Introduction Why do crane structures fail prematurely? Although modern design software and manufacturing process have helped crane manufacturers to optimize their design, there is still some degree of trial and error in any new crane design. • Crane sizes have increased significantly. Weight of the crane has increased to 2000 ton versus 800 ton. Outreach of 65m versus 34 m. • Crane speeds have also increased substantially. • Crane lift capacity increased from 40 ton to now 65 ton • Twinlift and tandem lift operation 11
  • 12. Introduction Why do crane structures fail prematurely? • We are venturing into new territories which only time will tell as to how well crane structures can withstand heavier duties they are subject to • Most crane designs are based on experiences and data gathered. • Static + dynamic factor • Not enough study on the dynamic characterization of super sized crane. In some design cases, 1 loading cycle actually generate 20 oscillations, hence causing the fatigue cycles to be reached well before intended life cycle. • Need to determine if manufacturing quality problem or inherent design problem. 12
  • 13. Premature crane failure Manufacturing Quality – a major factor • Low cost country with cheaper labour • Even within the same country, there was a case of an established manufacturer who suffered quality problems after transferring crane manufacturing to different factory using sub-contract labour. • Employing 3rd party inspection helps, but cannot eliminate all problems 13
  • 14. Procurement considerations • Procurement decision increasingly governed by short term financial considerations – pennywise, pound foolish • True cost of a crane is life cycle cost : depreciation plus maintenance plus performance consideration. • Examples: cranes are scrapped after 10 years of problematic service life. These are the most expensive cranes, no matter how cheap they are in beginning. 14
  • 15. Purchase considerations • With raw materials and energy cost rising, days of cheap cranes will soon be over. Inflationary pressures and rising labour cost in low cost countries are putting upward pressures on crane prices. • Port Operators will have to squeeze productivity and make assets sweat for them • Life cycle factors such as reliability, availability, energy consumption, maintenance cost, will feature more prominently in purchaser consideration. • Safety of crane operation has been largely overlooked, and not accorded enough consideration. Reputational damage. 15
  • 16. Practical difficulties with crane shutdown for repairs and upgrade • Operational needs always take priority over engineering tasks. Frequent delays to project execution • Operationally difficult to isolate cranes in between other cranes. Skidding back and pushing it to end of the quay may be only solution. • “Boom down” position could be achieved owing to vessel movements 16
  • 17. Introduction What are the common types of crane structure failures? • Trolley structures • Boom-girder joints • Trolley rail • Crane leg structure • Gusset plate of forestay • Main equalizer beam • Rope sheave supports • others Many failures caused by premature fatigue well before reaching design lifecycle! 17
  • 18. Solutions for Crane Failures Conventional approach of repairing cracks • gouging out the cracks and filling up with welds is no longer sufficient, and in fact dangerous. Often the root cause of certain cracks may originate from points remote from the cracks • Due to added design complexity and load, terminals should study and approach each case scientifically and get to the root cause of failure The Finite Element Method (FEM) should be a standard tool in analyzing the cause of failure, and in recommending proper repair procedures ! 18
  • 19. What is FEA Finite Element Analysis (FEA) is a way to simulate loading conditions on a design and determine the design’s response to those conditions. The design is modeled using discrete building blocks called elements. • Each element has exact equations that describe how it responds to a certain load. • The “sum” of the response of all elements in the model gives the total response of the design. • The elements have a finite number of unknowns, hence the name finite elements. 19
  • 20. Why is FEA Needed To help find the root cause of failure • Computer simulation allows multiple “what-if” scenarios to be tested quickly and effectively. To help make right decision for the repair at beginning • Computer simulation allows comparing the different designs Virtually. The bottom line: • Cost savings • Time savings • Create more reliable, better-quality designs 20
  • 21. Application of FEM in Portek • Transportation • Sea fastening design • Deck strength • Quay strength • Crane modification • Crane repair • Crane life assessment 21
  • 22. Sample 1: Top Girder Support Beam Crack Repair 22
  • 23. Modeling of the affected areas Using FEM 23
  • 24. Loading and Boundary Conditions 24
  • 25. Simulation Results for Original Design 25
  • 26. Proposed Solution 1: Internal Reinforcement 26
  • 27. Proposed Solution 2: to Remove Sharp Edges Very High Stress Improper design caused stress migration! 27
  • 28. Proposed Solution 3: Smooth Curve w/o Sharp Edges Selected Solution Using Finite Element Method! 28
  • 29. Interpretation of Results Maximum stresses found on the hanger plates and stress reduction as compared to the original design Stresses Stress value Stress reduction (MPa) Landside left top 102 44% Landside left bottom 132 29% Landside right top 88 37% Landside right bottom 98 23% Seaside left top 125 52% Seaside left bottom 168 29% Seaside right top 115 46% Seaside right bottom 142 15% 29
  • 30. Site Execution of Repair 30
  • 31. Sample 2: Trolley Structure Recovery and Repair 31
  • 32. Trolley Structure Recovery William Rod 32
  • 33. Investigation of Stress in Trolley Truck Geometry model - quarter platform Finite element model 33
  • 34. Investigation of Stress in Trolley Truck Load and boundary conditions 34
  • 35. Investigation of Stress in Trolley Truck Different boundary conditions to investigate the reason of failure 35
  • 36. Investigation of Stress in Trolley Truck structure under uniform constrain structure under wheel truck bend Conclusions: 1. Major cause is the wheel truck bend along the rail direction 2. Boom-girder joint maintenance is very important 3. Trolley truck with equalizer pin is the efficient way to avoid this kind failure One of the proposed modification under uniform constrain--worse 36
  • 37. Sample 3: Structure Repair of RTG Designed centreline of leg Measured centreline of leg Angle of Angle of misalignment misalignment = 0°20’11” = 0°25’30” Off by 53mm Off by 109mm at 0m at 0m 37
  • 38. Sample 3: Structure Repair of RTG Normal Gantry Tyre Position Far side Near side Gantry Tyre Position for damaged RTG Far side Near side 38
  • 39. Finite Element Analysis • At least 27ton pulling force to cause this failure • Plastic deformation occurred at corner • Conner reinforcement can prevent this failure efficiently 39
  • 42. Boom Extension Modification required 1. Extend boom 4.5 m 2. Expensive to use Floating Crane 3. Design method 42
  • 43. FE Simulation Solver: ANSYS/Mechanical Elements: Plate Beam Bar Joint Models: 1. Original boom 2. Extended boom without moving lug 3. Extended boom by moving lug 43
  • 44. Simulation results & Comparison 44
  • 46. Height Extension Using Synchronise Jacking System Modifications 1. Increase height 5.0 m 2. Strength & stability of jacking tower 3. Design method 46
  • 47. FE Simulation Solver: LS_DYNA Model: Inner tower & Jacking components Key point: Multi-surface contact Loads: 1. Overall crane weight 2. Lateral wind 47
  • 50. Facing the Real World Components to equipment Jack up 5 m & Insert new leg Jack up 1 m 50
  • 51. Simulation vs. Design  The jacking procedure is safe despite contact stresses are high;  The stress on the pin is quite low;  Local modification of the jacking section is suggested. 51
  • 52. Useful Life Assessment 1. Structural Condition Survey 2. Useful Life Estimate Before Inspection 3. Structural Inspection 4. Useful Life Estimate After Inspection 52
  • 53. Crane Structural Inspection, Why? • Many Cranes are at the end of their designed life cycle • Fatigue cracks will occur and can be catastrophic if not repaired • Crack repairs are often inexpensive and cracking can be controlled by proper analysis, design, workmanship, quality control and maintenance • It is prudent to perform structural inspection prior to spending huge amount of money on refurbishment and drive retrofitting 53
  • 54. Structural Condition Survey • Look for: • High stress areas • Suspect details • Attachments • Make photo record for the NDT inspection. 54
  • 55. Useful Life Estimate Before Inspection • Perform finite element analysis • Calculate relative cumulative damage • Estimate remaining useful life Forestay failure analysis using ANSYS 55
  • 56. Structural Inspection • Inspect and compare with  N-6 predictions • Non-Destructive Test (NDT)  N-5 • Repair procedures   Leg #1 Leg #2   N-4 N-8   N-10  N-2 N-9  N-7  Leg #3   N-3 Leg #4 56
  • 57. Useful Life Estimate After Inspection • Review inspection reports • Identify fatigue cracks • Compare identified cracks with prediction • Re-evaluate the reliability and useful life 57
  • 58. Conclusions • Finite Element Analysis is an essential tool for helping us in determining the cause of the problems and recommending the solutions. • FEM analysis of structural failure should be adopted as standard tool in failure analysis • With a trained engineer, FEM is quick and easy to deploy. • With the exponential increase in computing power, FEM is economical to carry out. 58
  • 59. Thank you 59