## 2 Experimental Scale Demonstrator for Carbody with Anti-Bending Bar System  
This section presents the physical realization of the experimental scale demonstrator for carbodies to test the effectiveness of the anti-bending bar system to reduce vertical vibration. Figure 4 shows the experimental scale demonstrator in which the scale model of the carbody is without the anti-bending bar system (Figure 4a) and with the anti-bending bar system (Figure 4b). The scale model of the carbody is made of an aluminium plate 14 mm thick and corresponds to the carbody of a passenger coach reduced to the scale of 1:10 in terms of length (2600 mm). For reasons of static stability, the width of the scale model of the carbody was chosen to be 400 mm, and it should be emphasized that this dimension has no influence on the frequencies of its bending eigenmodes. The mass of the scale model of the carbody is 39.3 kg. Figure 3: Sketch of experimental demonstrator system for the carbody with anti-bending bar system (after [24]). Each anti-bending bar is made of steel with a diameter of 8 mm and is fixed by tightening into two T-shaped steel supports that are secured to the scale model of the carbody by 4 screws (Figure 5a). The steel support leg is 15 mm thick, and its sole is a square plate 80 mm wide and 6 mm thick. The anti-bending bars are mounted in a plane 60 mm below the plane of the neutral fibre of the scale model of the carbody, and the working length of the anti-bending bars is 900 mm. The total mass of the anti-bending bar system is 4.4 kg. The scale model of the carbody rested on 4 rubber supports placed at distance of 1900 mm, corresponding to the vehicle wheelbase reduced to 1:10 scale. Each rubber support was cylindrical in shape with an outer diameter of 50 mm, an inner diameter of 17 and a height of 40 mm. Rubber supports were placed on 2 rigid sheet metal supports fixed to the laboratory floor. For the experimental determination of the frequency response function of the scale model of the carbody, the impact hammer method was used, which has the advantage of being expedient over other methods such as harmonic excitation by means of a vibrator. A Bruel&Kjaer (Narum, Denmark) accelerometer type 4514 and an N.I. impact hammer, type PCB Modally Tuned(r) (PCB Piezotronics, Depew, NY, USA), model 086C03 were utilized (Figure 6). For the acquisition and processing of experimental data, a NI cDAQ-9174 (Emerson, Austin, TX, USA) chassis equipped with a specialized NI 9234 module was used (Figure 6). Figure 4: Experimental scale demonstrator system: (**a**) carbody scale model without anti-bending bar system; (**b**) carbody scale model with anti-bending bar system. Figure 5: Details of the experimental scale demonstrator system: (**a**) support of the anti-bending bar; (**b**) rubber support. Figure 7 shows the assembly for the experimental determination of the frequency response function of a rail coupon E49 [29], 820 mm long, placed on the 4 rubber supports used in the experimental scale demonstration model. With the help of the frequency response function, the stiffness of the rubber supports was obtained for use in numerical simulations performed with the finite element model. The mass of the rail coupon was 40.4 kg, very close to the mass of the scale model of the carbody. In this way, the stiffness of the rubber supports was determined when they worked in practically the same conditions as when supporting the scale model of the carbody. The advantage lies in the fact that the rigid vibration mode of the rail coupon has a much lower frequency than the frequency of its first natural bending mode, which allows a more accurate determination of the stiffness of the rubber supports. Finite Element Model of Experimental Scale Demonstrator for Carbody without/with Anti-Bending Bar System  
In this section is presented the finite element model elaborated for the theoretical substantiation of research results.