Thesis Defense of JAI PRAKASH PAUL Graduate Student Mechanical Engineering

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Thesis Defense of JAI PRAKASH PAULGraduate
StudentMechanical Engineering
Sensitivity Analysis of Design Parameters for
Trunnion-Hub Assemblies of Bascule Bridges using
Finite Element Methods
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Outline

• Introduction
• Previous work done (at USF)
• Objective of Thesis
• Response Variables Properties of materials used
• Tests for Different Analyses
• Results of 5 Variation Analysis
• Results of AASHTO Analysis
• Conclusions
• Questions

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AP1
AP2

• Assembly Procedure 1 (AP1)
• Trunnion is cooled in liquid nitrogen
• Trunnion is fitted into Hub
• Trunnion-Hub is cooled in liquid nitrogen
• Trunnion-Hub is fitted into Girder

• Assembly Procedure 2 (AP2)
• Hub is cooled in liquid nitrogen
• Hub is fitted into Girder
• Trunnion is cooled in liquid nitrogen
• Trunnion is fitted into Hub-Girder

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Bascule Bridge Design Tools -Michael
Denninger (2000)

• Calculate steady state interference stresses
  radial displacements
• Steady state stresses are well under maximum
  stresses
• Transient stresses are to be calculated

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Parametric Finite Element Analysis
-Badri Ratnam (2000)

• Transient Stresses using ANSYS
• Hoop Stress Critical Crack Length
• AP1 and AP2 for 3 different bridges
• CCL AP2 is better than AP1
• Hoop Stress below maximum yield strength

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Experimental Analysis -Sanjeev
Nichani (2001)

• To measure the stresses during each step of the
  actual assembly procedures
• To compare the stresses during the 2 assembly
  procedures
• To validate the previous 2 studies

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Experimental Analysis

• Steady state stresses equal for AP1 AP2
• AP2 is a better alternative than AP1
• Higher critical crack length (CCL)
• Lower transient (thermal) stresses
• Quicker, but possibly costlier
• FEA versus Experiment
• Excellent agreement at steady state
• Good agreement during transient

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Observations Recommendations

• Thermal shock was a common problem in both
  processes
• Consider staged cooling
• Consider warming one component while cooling the
  other
• Consider heating the outer component
• Study the effect of THG geometry

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AASHTO Standards

• American Association of State Highway and
  Transportation Officials (AASHTO) call for hub
  radial thickness of 0.4 times the trunnion outer
  diameter
• Presently a hub radial thickness of 0.1 to 0.2
  times the trunnion outer diameter is used

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Objective

• Analyze the effect of geometric parameters such
  as hub radial thickness, trunnion bore to outer
  diameter ratio and variances in interference fits
  on critical crack lengths and critical stresses

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Response Variables

• Critical Crack Length
• Stress Ratio,

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Finite Element Model
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Test for Interference Stress
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Test for Interference Stress
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Test for Interference Stress
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Test for Interference Stress
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Test for Interference Stress
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Test for Cooling
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Test for Cooling
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Test for Cooling
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Test for Thermal Stress
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Test for Entire Process
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Data Analysis
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2k Factorial Method
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Geometric Parameters
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Geometric Parameters
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5 Variation Analysis

• 33 27 Experiments
• To study the effect of parameters on critical
  values
• To verify the analyses

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5 Variation Analysis
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5 Variation Analysis
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5 Variation Analysis

• 8 values from the 5 variation analysis to
  find percentage contributions for CCL

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5 Variation Analysis

• Percentage contributions for CCL

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5 Variation Analysis

• 8 values from the 5 variation analysis to
  find percentage contributions for SR

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5 Variation Analysis

• Percentage contributions for SR

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5 Variation Analysis

• For Critical Crack Length
• Interference has most effect (84)
• Hub thickness follows with 8
• For Stress Ratio
• Interference has most effect (94)
• Interaction of interference hub thickness (5.4)

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AASHTO Analysis

• 23 8 Experiments
• To study the effect of parameters on critical
  values
• To check if AASHTO standards are better

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AASHTO Analysis

• 8 values from the AASHTO analysis to find
  percentage contributions for CCL

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AASHTO Analysis

• Percentage contributions for CCL

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AASHTO Analysis

• 8 values from the AASHTO analysis to find
  percentage contributions for SR

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AASHTO Analysis

• Percentage contributions for SR

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AASHTO Analysis

• For Critical Crack Length
• Hub thickness has most effect (90)
• Interference follows with 8.67
• For Stress Ratio
• Hub Thickness has most effect (74)
• Interference follows with 25

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AASHTO Analysis

• AASHTO standards yielded crack lengths more than
  2 times the presently used standards

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AASHTO Analysis

• AASHTO standards yielded stress ratios up to 30
  for min interference and up to 40 for max
  interference more than the present standards

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Conclusions

• AASHTO standards are safer
• Higher Critical Crack Length
• Higher Stress Ratio
• Could be more economical as failures can be
  avoided
• 5 analysis and AASHTO analysis gave different
  results
• Percentage variations do not determine final
  results
• Physics of the problem plays major role

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ACKNOWLEDGEMENTS

• QUESTIONS ???