The dynamic amplification factor (DAF) is one of the most important parameters to express the dynamic behavior of bridges under moving loads. This parameter is used in bridge design codes instead of exhaustive dynamic analyses. Therefore, the DAF and the possible derived relationships can be good alternatives to dynamic analyses because of time and computational cost savings. Masonry arch bridges are complex infrastructures due to their geometry and structural behavior, and it is troublesome to prepare an accurate numerical model. To conduct dynamic analyses, due to their multiplicity, calculating the DAF of the bridges imposed by high-speed trains can lead to a rapid assessment of these old railway arch bridges. For this purpose, in the present study, the finite element models of two concrete and masonry arch bridges with small fill material heights, which are completely different in terms of geometric and mechanical characteristics, were prepared. In the next step, by performing 378 dynamic analyses based on the 27 different train models, the DAF has been computed. The results show that the calculated DAFs are in the rational range, and bogies interval, axles interval, and span length are recognized as the most important parameters in the DAF changes.
