Keywords: high-speed, orthotropic plate, fatigue, vehicle acceleration, ballast disintegration.

The three main weaknesses of orthotropic plated bridge decks (OPD) are fatigue resistance, train car acceleration and ballast liquefaction. These are discussed in this paper, based on the design and testing of this type of bridge deck, applied to ten bridges of a high-speed network. Fatigue resistance of OPD is mainly related to the various cutting and welding details, as well as to geometric discontinuities. High speed mostly contributes to fatigue damage by increasing wheel loads and in a lesser way by vibrations being introduced. The second criterion is related to passenger comfort and the acceleration of train cars. It requires that the vertical acceleration of the train car, above the suspension system, does not exceed 1 m/s squared for excellent comfort. Obviously these values do not depend on the structure itself, but also on the train car suspension and damping. The third criterion is concerned with track stability. At some particular train speed the ballast may disintegrate and behave like a liquid. This liquefaction of ballast highly affects the track stability and may lead to derailment. In the case of slab track, derailment may also occur, although there is no risk of liquefaction. For both conditions limiting values of the vertical acceleration of the subjacent structure have been established.

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