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  • 21 Aug, 2019

  • By, Wikipedia

Taxiway Bridge
Aircraft bridges, including taxiway bridges and runway bridges, bring aircraft traffic over motorways, railways, and waterways.

Construction

Aircraft bridges must be designed to support the heaviest aircraft that may cross them, or that will cross them in the future. In 1963, a taxiway bridge at O'Hare International Airport, one of the busiest airports in the world, was planned to handle future aircraft weighing 365,000 pounds (166,000 kg), but aircraft weights doubled within two years of its construction. Currently, the largest passenger aircraft in the world, the Airbus A380, has a maximum take-off weight (MTOW) of 575 t (1,268,000 lb).

The largest Boeing planes, i.e. the current "Project Ozark" versions of the Boeing 747-8, are approaching MTOW of greater than 1,000,000 lb (450,000 kg). Aircraft bridges must be designed for the substantial forces exerted by aircraft braking, affecting the lateral load in substructure design. Braking force of 70 percent of the live load is assumed in two recent taxiway bridge designs. And "deck design is more apt to be controlled by punching shear than flexure due to the heavy wheel loads."

Taxiway bridges are unusually wide relative to their length, and aircraft loading cannot be assumed to be distributed evenly to a bridge superstructure's web, so different modeling is required in these bridges' structural design. In cold climates, provisions for anti-icing must be made. In the U.S., regulations of the Federal Aviation Administration must be met. And there are various other differences versus typical bridges covered by AASHTO standards.

A major issue is that closing an airport for construction even temporarily is impossible.

Major alternatives considered for construction of a taxiway bridge in 2008 were:

  • use of precast, prestressed concrete I-girders
  • use of precast, prestressed concrete box girders
  • use of steel girders
  • cast-in-place, post-tensioned concrete box girder bridge.

Finite Element Analysis has been advocated for, or applied in, taxiway bridge design since at least 1963.

List of taxiway bridges, runway bridges, and related tunnels

Kai Tak Tunnel east entrance, near the old Kai Tak airport

Taxiway bridges and runway bridges are bridges at airports to bring airplane taxiways and runways across motorways, railroads, or waterways. A taxiway bridge must be designed to carry the weight of the maximum size airplanes crossing and perhaps stopping directly upon it. A runway bridge is similar but may have different stresses. Alternatively, a motorway may be brought by tunnel underneath one or more runways and taxiways.

Examples include: