WisDOT Bridge Manual Chapter 24 – Steel Girder Structures Table of Contents 24.1 Introduction ...................................................................................................................... 5 24.1.1 Types of Steel Girder Structures ............................................................................... 5 24.1.2 Structural Action of Steel Girder Structures .............................................................. 5 24.1.3 Fundamental Concepts of Steel I-Girders ................................................................. 5 24.2 Materials ........................................................................................................................ 11 24.2.1 Bars and Plates ...................................................................................................... 12 24.2.2 Rolled Sections ....................................................................................................... 12 24.2.3 Threaded Fasteners ............................................................................................... 12 24.2.3.1 Bolted Connections ......................................................................................... 13 24.2.4 Quantity Determination ........................................................................................... 14 24.3 Design Specification and Data ....................................................................................... 15 24.3.1 Specifications ......................................................................................................... 15 24.3.2 Resistance .............................................................................................................. 15 24.3.3 References for Horizontally Curved Structures ....................................................... 15 24.3.4 Design Considerations for Skewed Supports .......................................................... 15 24.4 Design Considerations ................................................................................................... 20 24.4.1 Design Loads ......................................................................................................... 20 24.4.1.1 Dead Load ...................................................................................................... 20 24.4.1.2 Traffic Live Load ............................................................................................. 21 24.4.1.3 Pedestrian Live Load ...................................................................................... 21 24.4.1.4 Temperature ................................................................................................... 21 24.4.1.5 Wind ............................................................................................................... 21 24.4.2 Minimum Depth-to-Span Ratio ................................................................................ 21 24.4.3 Live Load Deflections ............................................................................................. 22 24.4.4 Uplift and Pouring Diagram ..................................................................................... 22 24.4.5 Bracing ................................................................................................................... 23 24.4.5.1 Intermediate Diaphragms and Cross Frames .................................................. 23 24.4.5.2 End Diaphragms ............................................................................................. 25 24.4.5.3 Lower Lateral Bracing ..................................................................................... 25 24.4.6 Girder Selection ...................................................................................................... 26 24.4.6.1 Rolled Girders ................................................................................................. 26 24.4.6.2 Plate Girders ................................................................................................... 26 July 2021 24-1 WisDOT Bridge Manual Chapter 24 – Steel Girder Structures 24.4.7 Welding .................................................................................................................. 28 24.4.8 Dead Load Deflections, Camber and Blocking ........................................................ 32 24.4.9 Expansion Hinges ................................................................................................... 33 24.5 Repetitive Loading and Toughness Considerations ........................................................ 34 24.5.1 Fatigue Strength ..................................................................................................... 34 24.5.2 Charpy V-Notch Impact Requirements ................................................................... 35 24.5.3 Non-Redundant Type Structures ............................................................................ 35 24.6 Design Approach - Steps in Design ................................................................................ 37 24.6.1 Obtain Design Criteria ............................................................................................ 37 24.6.2 Select Trial Girder Section ...................................................................................... 38 24.6.3 Compute Section Properties ................................................................................... 39 24.6.4 Compute Dead Load Effects ................................................................................... 40 24.6.5 Compute Live Load Effects ..................................................................................... 40 24.6.6 Combine Load Effects ............................................................................................ 41 24.6.7 Check Section Property Limits ................................................................................ 41 24.6.8 Compute Plastic Moment Capacity ......................................................................... 42 24.6.9 Determine If Section is Compact or Non-compact .................................................. 42 24.6.10 Design for Flexure – Strength Limit State ............................................................. 42 24.6.11 Design for Shear ................................................................................................... 42 24.6.12 Design Transverse Intermediate Stiffeners and/or Longitudinal Stiffeners ............ 43 24.6.13 Design for Flexure – Fatigue and Fracture ............................................................ 43 24.6.14 Design for Flexure – Service Limit State ............................................................... 43 24.6.15 Design for Flexure – Constructability Check ......................................................... 43 24.6.16 Check Wind Effects on Girder Flanges ................................................................. 44 24.6.17 Draw Schematic of Final Steel Girder Design ....................................................... 44 24.6.18 Design Bolted Field Splices .................................................................................. 44 24.6.19 Design Shear Connectors ..................................................................................... 44 24.6.20 Design Bearing Stiffeners ..................................................................................... 44 24.6.21 Design Welded Connections ................................................................................. 44 24.6.22 Design Diaphragms, Cross-Frames and Lateral Bracing ...................................... 45 24.6.23 Determine Deflections, Camber, and Elevations ................................................... 45 24.7 Composite Design .......................................................................................................... 46 24.7.1 Composite Action ................................................................................................... 46 July 2021 24-2 WisDOT Bridge Manual Chapter 24 – Steel Girder Structures 24.7.2 Values of n for Composite Design........................................................................... 46 24.7.3 Composite Section Properties ................................................................................ 47 24.7.4 Computation of Stresses ........................................................................................ 47 24.7.4.1 Non-composite Stresses ................................................................................. 47 24.7.4.2 Composite Stresses ........................................................................................ 47 24.7.5 Shear Connectors ................................................................................................... 48 24.7.6 Continuity Reinforcement ....................................................................................... 49 24.8 Field Splices ................................................................................................................... 51 24.8.1 Location of Field Splices ......................................................................................... 51 24.8.2 Splice Material ........................................................................................................ 51 24.8.3 Design .................................................................................................................... 51 24.8.3.1 Obtain Design Criteria ....................................................................................