Dynamic behaviors of bridges on high-speed railway are often the main criteria in bridges design. It has a huge impact on the technical choices and thus on the building cost. In the European Union, civil engineers rely on the Eurocode standards which defines the dynamic constitutive law for bridge designing. Those laws were based on the results of the European research program ERRI with few experimental test results. Therefore, to guarantee the structural safety, the design rules are disadvantageous that implies the design of oversized bridges and thus extra building costs. In the interest of improving the safety of the infrastructure and optimizing the cost, SNCF Réseau realized a research program in a two-step approach. Firstly, it has carried out a great monitoring campaign of its bridges on the high-speed railway network. This experimental campaign consists of measuring the acceleration and the dynamic displacement of the deck under train traffic. Secondly, we create a digital twin of measured bridges by modeling them with an in-house software for dynamic solution. An important number of measurement data were used to correct the simulation of the digital twin. In the end, through the digital twin of bridges, we were able to refine the dynamic constitutive law of bridges by extracting the adjusted values like the damping coefficient or the structural stiffness from the numeric model.