Impact factor estimation of railway masonry arch bridges subjected to the Pardis high-speed train

Currently, the Pardis high-speed train with a speed of 150 (km/h) is known as the only high-speed train in service in Iran. Impact factor or dynamic load allowance are the most important parameters that can express the dynamic behavior of the bridge under a train. These parameters are used in bridge design codes instead of exhaustive dynamic analyses. Although the use of impact coefficients in some cases provides conservative answers, the use of these coefficients and the possible relationships derived from them can be a good alternative to dynamic analyses due to time and computational cost savings. Masonry arch bridges are geometrically and behaviorally complex structures and it is impossible to prepare an accurate numerical model and to conduct dynamic analyses due to their multiplicity; Therefore, calculating the impact factor due to the passage of high-speed trains can determine the initial behavior of masonry arch bridges. For this purpose, in the present study, first the finite element model of two masonry arch bridges was prepared which are completely different in terms of geometric and mechanical characteristics, and then by performing 52 dynamic analyzes, the time history of impact factor and dynamic load allowance has been calculated. The results show that the behavior of masonry arch bridges is appropriate in different conditions under the Pardis high-speed train and all the calculated impact coefficients are in the rational range.