Modeling and characteristic analysis of lightning electromagnetic transient of high-speed railway viaduct box girder
The box girder of high-speed railway viaduct is the main leakage channel of lightning current when lightning strikes the catenary.Because the box girder is a complex squirrel-cage structure com-posed of hundreds of reinforcing bars,it is difficult to accurately establish its broadband calculation model of lightning strike.Therefore,this paper establishes box girder models with different numbers of longitudinal reinforcing bars based on transmission-line matrix(TLM),and analyzes the feasibility of simplified modeling of lightning electromagnetic transient.It is found that the lightning current is mainly distributed in the outer longitudinal reinforcement when the box girder is drained,which ac-cords with the law of skin effect.Longitudinal reinforcement at the large curvature of box girder cross section is the key reinforcement in lightning transient calculation.Retaining this part of longitudinal reinforcement and appropriately reducing longitudinal reinforcement at the small curvature can simpli-fy the electromagnetic transient model of box girder lightning.Transient current will produce transi-ent electromagnetic field around box girder when it is drained,which threatens the normal operation of signal equipment and cable termination equipment beside the rail.In order to further study the in-fluence of simplified longitudinal reinforcement on transient electromagnetic environment around box girder,based on the simplified modeling method mentioned above,this paper calculates the electro-magnetic field distribution and attenuation characteristics of bridge deck with different numbers of lon-gitudinal reinforcing bars,and finds that when box girder drains lightning current with an amplitude of 100 kA,the magnetic field intensity within 30 m of lightning current injection point exceeds the magnetic field immunity of electronic equipment specified in the national standard.Bridge deck elec-tronic equipment in this range is seriously threatened.
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