bridge engineering handbook桥梁工程手册-23轨道桥梁.pdf

23 Railroad Bridges 23.1 Introduction Railroad Network • Basic Differences between Railroad and Highway Bridges • Manual for Railway Engineering, AREMA 23.2 Railroad Bridge Philosophy 23.3 Railroad Bridge Types 23.4 Bridge Deck General • Open Deck • Ballast Deck • Direct Fixation • Deck Details 23.5 Design Criteria Geometric Considerations • Proportioning • Bridge Donald F. Sorgenfrei Design Loads • Load Combinations • Serviceability Modjeski and Masters, Inc. Considerations W. N. Marianos, Jr. 23.6 Capacity Rating Modjeski and Masters, Inc. General • Normal Rating • Maximum Rating 23.1 Introduction 23.1.1 Railroad Network The U.S. railroad network consists predominantly of privately owned freight railroad systems classified according to operating revenue, the government-owned National Railroad Passenger Cor- poration (Amtrak), and numerous transit systems owned by local agencies and municipalities. Since the deregulation of the railroad industry brought about by the 1980 Staggers Act, there have been numerous railway system mergers. By 1997 there remained 10 Class I (major) Railroads, 32 Regional Railroads, and 511 Local Railroads operating over approximately