Recently it was found that a large wheel load exceeding twice of static one occurred by high speed train passage. This study is aiming to grasp the mechanism of large wheel loads by using measured data obtained by the examination train. Then, the effects of the large wheel load on steel bridges were evaluated by using field measurement data. Statistical method revealed that the frequency of larger wheel load increases by train speed and that the track type has less effect. Two scenarios of large wheel load were found. Rail joints may cause high frequency vibration and it results large wheel load, but it has no effect on steel bridges because it dissipates rapidly. Uplift of sleeper produces large wheel load with low frequency and it could increase stress range at the upper flange of girder bridges by 10-20%.
