Guide for Heat-Straightening of Damaged Steel Bridge Members
Table of Contents
- 1. Introduction
- 2. Heat Straightening Basics
- 2.1 What is Heat Strightening?
- 2.2 Why Heat Straightening Works
- 2.3 Fundamental Heating Patterns
- 2.4 Defining Basic Damage Patterns and Yield Zones
- 2.5 Basic Heating Patterns
- 2.5.1 Flat Plate Bent About the Major Axis (Category S)
- 2.5.2 Structural Members Bent About Their Strong (Major) Axis (Category S)
- 2.5.3 Structural Members Bent About Their Weak (Minor) Axes (Category W)
- 2.5.4 Structural Members Subject to Twisting Damage (Category T)
- 2.5.5 Flanges and Webs with Local Buckles (Category L)
- 2.5.6 Angles
- 2.6 Complex Damage
- 2.7 Equipment and Its Use
- 2.8 Safety Considerations
- 2.9 Temperature Control
- 2.10 Restraining Forces
- 2.11 Practical Considerations
- 3. Assessing, Planning and Conducting Successful Repairs
- 3.1 Role of Engineer, Inspector and Contractor
- 3.2 Keys to a Successful Repair
- 3.3 Steps in the Assessment Process
- 3.4 Steps in the Planning and Design Process
- 3.4.1 Analysis of Degree of Damage and Determination of the Maximum Strain due to Damage
- 3.4.2. Conduct a Structural Analysis of the System
- 3.4.3. Select Regions Where Heat Straightening is Applicable
- 3.4.4. Select Heating Patterns and Parameters
- 3.4.5. Develop a Constraint Plan
- 3.4.6 Estimate the Heats Required to Straighten the Members
- 3.4.7 Repair Plans and Specifications
- 3.5 Supervision of Repairs
- 4. Effects of Heat Straightening on the Material Properties of Steel
- 5. Heat Straightening of Flat Plates
- 6. Heat Straightening Rolled Shapes
- 7. Heat Straightening Repair of Localized Damage
- Appendix I: Specifications for the Selection of Contractors and the Conduct of Heat-Straightening Repairs
- Appendix II: Nomenclature
- Appendix III: References and Other Sources of Information
Figures
- Figure 1: Graphic illustration of Category S damage.
- Figure 2: Examples of Category W damage.
- Figure 3: Examples of Category T damage.
- Figure 4: Category L damage showing flange buckles on wind bracing on Mississippi River Bridge in Greenville, MS.
- Figure 5: Conceptual example of shortening a steel bar.
- Figure 6: Stages of movement during vee heat.
- Figure 7: Schematic diagram of edge heats used to heat–curve a beam.
- Figure 8: Line heat in progress on the web of a wide flange beam.
- Figure 9: Schematic of line heat mechanism.
- Figure 10: Strip heat in progress with a completed strip heat in the foreground.
- Figure 11: Schematic of strip heat on the flange of a rolled beam.
- Figure 12: Yield zones for basic damage patterns.
- Figure 13: Yield zone and vee/strip heat layout for a category S damage to a rolled beam.
- Figure 14: Plate vee heat pattern over yield zone.
- Figure 15: Heating patterns for wide flange beams and channels bent about their major axes (Category S).
- Figure 16: Heating patterns for wide flanges and channels bent about their minor axes (Category W).
- Figure 17: Wide flanges and channels with twisting damage (Category T).
- Figure 18: Typical heating patterns for local damage.
- Figure 19: Heating patterns for angles.
- Figure 20: Characteristics of plastic flow and restraint during heat straightening.
- Figure 21: Brittle fracture during heat straightening.
- Figure 22: Offset measurements to calculate degree of damage and radius of curvature.
- Figure 23: Radius of curvature for a damaged beam of curvature and cord length.
- Figure 24: Diaphragm damage due to vehicle impact on girder.
- Figure 25: Jacking arrangements for global and local damage on a composite girder bridge.
- Figure 26: Temperature sensing crayons.
- Figure 27: Jacks in place on a Wisconsin bridge.
- Figure 28: Iron–carbon equilibrium diagram.
- Figure 29: Residual stress distribution for plates damaged and then vee heated
- Figure 30: Typical residual stress distribution for a heat straightened angle
- Figure 31: Typical residual stress distribution for a heat straightened angle
- Figure 32: Typical residual stress distribution for a heat straightened channel
- Figure 33: Typical residual stress distribution for a Category S wide flange beam
- Figure 34: Typical residual stress distribution for a Category W heat straightened wide flange beam
- Figure 35: Yield stress versus number of damage/repair cycles for heat straightened beam.
- Figure 36: Tensile stress versus number of damage/repair cycles for heat straightened beam.
- Figure 37: Percent elongation versus number of damage/repair cycles for heat straightened beam.
- Figure 38: Influence of heating temperature on plastic rotation for 3/4 depth vee heats and a jacking ratio of 0.16.
- Figure 39: Influence of jacking ratio on average plastic rotation for 650°C (1200°F) heating temperatures
- Figure 40: Primary and stiffening plate elements for a channel bent about its major axis (Category S damage).
- Figure 41: Weak axis bending resulting in a yield line in the plate element.
- Figure 42: Typical deformed shape and yield zones in damaged composite girders.
- Figure 43: Heating patterns for composite girder.
- Figure 44: Diaphram stiffened composite girder.
- Figure 45: Dead load conditions on a simply supported beam.
- Figure 46: PΔ effect on an axially loaded column.
- Figure 47: Plastic rotation versus jacking ratio for axially loaded Category W column.
- Figure 48: Typical localized damage classified as Category L.
- Figure 49: Typical Category L/U damage.
- Figure 50: Heat straightening local flange damage (Category L/U).
- Figure 51: Arrangement of restraining forces during various stages of repair.
- Figure 52: Arrangement of vee and line heats.
- Figure 53: Curvature and line heating patterns for category L/S damage.
Tables