New proposal for dynamic factors for en 1991-2 ultimate and serviceability states verifications on highspeed railway bridges

Abstract eng:
The actual EN 1991-2 recommendations for a quasi-static (Φ) analysis of highspeed railway bridges do not take in consideration the type of traffic of the bridge, defined in the Annex 0 of the TSI L245. Therefore, for railway bridges specially built for highspeed traffic (Category I), amplification of LM71 model by the dynamic factor Φ may be at a certain point overconservative and unrepresentative of the real traffic. The authors propose new expressions for amplification of the HSLM models featured in EN 1991-2. These expressions also take in consideration several effects, such as material damping (plus additional damping for vehicle/track interaction) and track irregularities, and apply to reinforced concrete, prestressed concrete and steel bridges. The static and dynamic displacements, accelerations, shear forces and bending moments are obtained through Fryba’s solution for a moving load series in a simply supported beam and DER Method. The mass and fundamental frequency are defined as a function of the span length, based on a confidence interval for extensive experimental results for existing railway bridges and previous research. The dynamic factor expressions are, thus, developed for vertical displacements, shear forces and bending moments, leading to an accurate quasi-static verification of the bending and shear at ULS and maximum vertical displacement at SLS. Finally, for the maximum vertical acceleration at SLS, the authors develop a critical 3d surface for the maximum acceleration permitted on a ballast track (3.5m/s2), as a function of span length, mass and fundamental frequency.

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