Bridge Maintenance Course Series Reference Manual Chapter 17 – Table of Contents Chapter 17 - Movable Bridges ................................................................................................ 17-1 17.1 Common Types of Movable Bridges .................................................................................. 17-2 17.1.1 Terminology ............................................................................................................. 17-2 17.1.2 Bascule Bridges ........................................................................................................ 17-3 17.1.3 Vertical Lift Bridges .................................................................................................. 17-9 17.1.4 Swing Bridges ......................................................................................................... 17-11 17.2 Operation of Movable Bridges ......................................................................................... 17-12 17.2.1 Counterweights ..................................................................................................... 17-15 17.2.2 Mechanical Systems .............................................................................................. 17-17 17.2.2.1 Types of Span Drives .................................................................................................... 17-30 17.2.2.2 Open and Closed Gearing ............................................................................................ 17-34 17.2.2.3 Bearings ........................................................................................................................ 17-36 17.2.3 Electrical Systems .................................................................................................. 17-40 17.2.3.1 AC and DC Motors ........................................................................................................ 17-48 17.2.3.2 Interlock System........................................................................................................... 17-51 17.3 Preventive and Basic Maintenance of Movable Bridges ................................................. 17-52 17.3.1 Open Gears ............................................................................................................ 17-55 17.3.2 Closed Gearing (Speed Reducers) ......................................................................... 17-57 17.3.3 Shafts and Couplings ............................................................................................. 17-59 17.3.4 Bearings ................................................................................................................. 17-59 17.3.5 Brakes .................................................................................................................... 17-62 17.3.6 Air Buffers .............................................................................................................. 17-63 17.3.7 Locks ...................................................................................................................... 17-63 17.3.8 Steel Counterweights and Auxiliary Counterweights ............................................ 17-64 17.3.9 Live Load Bearings and Strike Plates ..................................................................... 17-65 17.3.10 Wire Ropes .......................................................................................................... 17-66 17.3.11 Counterweight Sheaves and Operating Drums ................................................... 17-66 17.3.12 Span Guides ......................................................................................................... 17-67 17.3.13 Tread Plates and Racks ........................................................................................ 17-67 17.3.14 Traffic Barriers ..................................................................................................... 17-68 17.3.15 Electrical System .................................................................................................. 17-68 i Bridge Maintenance Course Series Reference Manual 17.3.16 Hydraulic System ................................................................................................. 17-72 17.3.17 Predictive Maintenance....................................................................................... 17-74 17.3.18 Structural Health Monitoring .............................................................................. 17-75 17.3.19 Generator Maintenance ...................................................................................... 17-75 17.3.20 Lubrication of the Gears and Bearing Mechanisms ............................................ 17-76 17.3.20.1 Types of Lubrication ................................................................................................... 17-77 17.3.20.2 Lubrication Conditions ............................................................................................... 17-79 17.3.20.3 Selecting a Lubricant .................................................................................................. 17-79 17.3.20.4 Removing Grease ....................................................................................................... 17-83 17.3.20.5 Lubricating Movable Bridge Components ................................................................. 17-84 17.3.21 Alignment ............................................................................................................ 17-89 17.3.21.1 Repair of the Pivot/Rack Assembly ............................................................................ 17-90 17.3.21.2 Balance Testing .......................................................................................................... 17-91 17.4 Chapter 17 Reference List ................................................................................................ 17-93 ii Bridge Maintenance Course Series Reference Manual Chapter 17 – List of Figures Figure 17.1 Bicentennial Bascule Bridge over the St. Joseph River ........................................... 17-1 Figure 17.2 Single Leaf Simple Trunnion Bascule ...................................................................... 17-5 Figure 17.3 Cylinder Driven Simple Trunnion Bascule ............................................................... 17-6 Figure 17.4 Types of Bascule Bridges (a) Simple Trunnion (b) Rolling Lift Bascule ................... 17-7 Figure 17.5 Rack and Pinion Gear .............................................................................................. 17-7 Figure 17.6 Hydraulic Cylinder on Trunnion Bascule Bridge ..................................................... 17-8 Figure 17.7 Through Single-Leaf Scherzer Rolling Lift Bascule .................................................. 17-9 Figure 17.8 Span Driven Vertical Lift Bridge .............................................................................. 17-9 Figure 17.9 Tower Driven Vertical Lift Bridge .......................................................................... 17-10 Figure 17.10 Vertical Lift Bridge Schematic ............................................................................. 17-10 Figure 17.11 Center Bearing Swing Span Bridge ..................................................................... 17-11 Figure 17.12 Center-Bearing Swing Bridge Schematic ............................................................ 17-11 Figure 17.13 Example of a Table of Contents of a Bridge Specific Movable Bridge ................ 17-13 Figure 17.14 Live Load Wedges and Shoes .............................................................................. 17-14 Figure 17.15 Components of a Span Drive .............................................................................. 17-14 Figure 17.16 Trunnion Bearing ................................................................................................ 17-15 Figure 17.17 Counterweight Assembly .................................................................................... 17-16 Figure 17.18 Mechanical/Electrical System of Representative Movable Bridge ..................... 17-17 Figure 17.19 Brake and Hydraulic Span Drive System ............................................................. 17-17 Figure 17.20 Open Gearing Operating Machinery................................................................... 17-18 Figure 17.21 Speed Reducer (Closed Gearing), Shaft, and Coupling ....................................... 17-18 Figure 17.22 Bearings Supporting Span Drive Shaft ................................................................ 17-19 Figure 17.23 Typical Brake Assembly ....................................................................................... 17-20 Figure 17.24 Air Buffer Schematic ........................................................................................... 17-21 Figure 17.25 Air Buffers in the Retracted (left) and Not Retracted (right) Positions .............. 17-21 Figure 17.26 Mechanically Driven Span Lock .......................................................................... 17-22 Figure 17.27 Span Lock Bars and Shim Removal (Courtesy of UCF) ........................................ 17-22 Figure 17.28 Disengaged Span Lock (Courtesy of Indiana DOT) .............................................. 17-23 Figure 17.29 Engaged Tail Lock ................................................................................................ 17-23 Figure 17.30 Tail Lock in Fully Engaged Position (left) and Disengaged