Next the experimental tests, carried out according to the international reference standards, are illustrated: starting from specifying all the electric gauges considered for the measurements. Then the test bench layout and the arrangement to apply the forces are explained. These consist of hydraulic cylinders acting at the secondary suspension housing and in a leverage system designed to apply transversal force.

Although many more tests have been completed on the bogie, here the attention is on four static load cases (exactly responding to the requirements of the standards) since the aim of the paper is to demonstrate a new general computational procedure and not to report all experimental results. The experimental section ends with a table schematically reporting all load conditions considered and with the reference for detailed deformations registered by all the gauges.

The central part concerns the general computational procedure to obtain the elastic reactions of primary suspensions on condition that the geometry and the structure of the bogie would be known. Effectively the actual layout is reduced to an equivalent "two-axle" bogie with four primary springs, defined by a stiffness resulting from parallel composition of the original primary suspensions; then imposing the stationarity principle on the deformation energy expression, we get the first Castigliano's theorem formulation which provides the final algebraic linear system. The results of the procedure are the four equivalent reactions, from which it is possible to calculate the elastic forces from all the primary suspensions.

The numerical analysis of the LDE2100-1668 bogie is the final part of this work since this enables the validation of the computational methodology described. All the experimental conditions considered are simulated with a parametric model of the whole chassis, mainly composed of four node shell elements and characterized with the actual plates thickness, this being the most important parameter for the global stiffness. Applying the reactions under the primary suspension pivots and constraining nodes where the actuators were during the bench test. It is simulated as an inversion between loads and constraints passing from the experimental to the numerical environment. This is possible only by means of the new computational procedure proposed, which provides numerical results very close to laboratory data.

The proposed implementation is a new methodology for the preliminary static test that has to be carried out before the fatigue test, saving time and consequently decreasing the total cost of the tests requested.

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