ABSTRACT
Railway bridges, due to the high intensity moving loads to which they are subjected, are structures where the dynamic effects may reach significant values, which must be considered in the design. These effects are being given greater importance at present, in consequence of the increment on the circulation speed both in existing and new railways, as is the case for those intended for the highspeed trains. In high-speed railways, the dynamic effects tend to increase even more considerably, essentially as a result of the so-called resonance effects, which occur due to the passage of trains composed by several groups of regularly spaced axles. The knowledge of these dynamic effects is ofmajor importance for the case of railway bridges for
the following reasons: i) the vibrations induced by the passage of the trains over the bridge originate, in general, displacements or internal efforts in the structures, greater than those produced when the loading is statically applied; ii) the excessive vibrations of the structure may lead to a magnification of the fatigue phenomena; iii) the deformations and accelerations of the bridge should be controlled and kept within certain limit values, in order to ensure the stability of the track and of the contact wheel-rail at all times; iv) the accelerations in the vehicles should be limited so that the passengers comfort can be guaranteed.
