This International Standard provides methodology for the evaluation of results from dynamic tests and investigations on bridges and viaducts. It complements the procedure for conducting the tests as given in ISO 14963 and considers — the objectives of the dynamic tests, — the techniques for data analysis and system identification, — the modelling of the bridge, and — evaluation of the measured data. NOTE 1 The evaluation may seek to define all of the dynamic characteristics of each mode of vibration examined, i.e. frequency, stiffness, mode shape and damping, and their non-linear variation with amplitude of motion. These can supply information on the dynamic characteristics of a structure for comparison with those assumed in design, or as a basis for condition monitoring or system identification. The dynamic tests considered in this International Standard do not replace static tests. This International Standard gives guidance on the assessment of measurements carried out over the life cycle of the bridge. The stages of the life cycle that are considered are a) during construction and prior to commissioning ,b) during commissioning trials, c) during specified periods throughout the life of the bridge, and d) immediately prior to decommissioning the bridge. This International Standard is applicable to road, rail and pedestrian bridges and viaducts (both during construction and operation) and also to other works, provided that they justify its application. The application of this International Standard to special structures (cable-stayed or suspension bridges) requires specific tests that take into account the particular characteristics of the work. NOTE 2 Throughout this International Standard, “bridges and viaducts” are called “bridges”. The term “viaduct” is used only when it is necessary to distinguish between these.