**3. Experimental test**

An experimental bridge structure was built at a reduced scale to which a composed isolation system, also built on a small scale, was added. The isolated structure assembly equipped with the dissipation system is schematically shown in Figure 2. The rolling friction device is composed of two main rolling plates (a flat and a spherical surface), a central spherical part positioned between the two main rolling surfaces which moves by rolling ensuring relative movement of the two main surfaces. Thus, a specific movement undertaken by the foundation ground along with the bridge pier is filtered through the rolling friction and the elastomeric isolation system, so that the request is not fully transmitted on vertical direction to the superstructure which tends to remain in equilibrium position during any dynamic action.

**Figure 2.** Schematic representation for the isolation system model assembly [3].

The bridge model has four isolation systems positioned at the ends of the beam or superstruc‐ ture. Tri-axial accelerometers have been mounted in the bridge pier and beam. The excitation

is provided with a special device that provides a set of random vibrations at the pier level. Because of the excitation force of random value, at the isolation system level, the spherical steel parts are rolling on the main steel spherical surface, while the friction coefficient is in the range of 0.15–0.18 (Coulomb friction without lubrication) [4, 5].

The experimental results recorded are presented for the main transversal and longitudinal directions of movement at the level of support pier and the isolated superstructure. Figure 3 presents the values recorded at the pier support on the transversal direction of motion.

**Figure 3.** Experimental results obtained for pier transversal direction of motion. (a) Acceleration values vs. time. (b) Acceleration amplitude values vs. time. (c) Spectrogram of frequency values vs. time.

is provided with a special device that provides a set of random vibrations at the pier level. Because of the excitation force of random value, at the isolation system level, the spherical steel parts are rolling on the main steel spherical surface, while the friction coefficient is in the range

Proceedings of the International Conference on Interdisciplinary Studies (ICIS 2016) - Interdisciplinarity and Creativity

The experimental results recorded are presented for the main transversal and longitudinal directions of movement at the level of support pier and the isolated superstructure. Figure 3 presents the values recorded at the pier support on the transversal direction of motion.

(a)

(b)

(c)

**Figure 3.** Experimental results obtained for pier transversal direction of motion. (a) Acceleration values vs. time. (b)

Acceleration amplitude values vs. time. (c) Spectrogram of frequency values vs. time.

of 0.15–0.18 (Coulomb friction without lubrication) [4, 5].

in the Knowledge Society

114

**Figure 4.** Experimental results obtained for superstructure transversal direction of motion. (a) Acceleration values vs. time. (b) Acceleration amplitude vs. frequency. (c) Spectrogram of frequency vs. time values.

The results obtained are presented in order to highlight the differences between the values obtained at the support pier and at the superstructure level. Figure 4 presents the recorded values at the superstructure level on the transversal direction of motion. Figure 5 presents the values obtained at the support pier for the longitudinal direction of movement.

**Figure 5.** Experimental results obtained for pier longitudinal direction of motion. (a) Acceleration values vs. time. (b) Acceleration amplitude vs. frequency values. (c) Spectrogram of frequency values vs. time.

Figure 6 presents the obtained result values at the superstructure level for the longitudinal direction of movement.

(a)

Proceedings of the International Conference on Interdisciplinary Studies (ICIS 2016) - Interdisciplinarity and Creativity

(b)

(c)

**Figure 5.** Experimental results obtained for pier longitudinal direction of motion. (a) Acceleration values vs. time. (b)

Figure 6 presents the obtained result values at the superstructure level for the longitudinal

Acceleration amplitude vs. frequency values. (c) Spectrogram of frequency values vs. time.

direction of movement.

in the Knowledge Society

116

**Figure 6.** Experimental values obtained for superstructure longitudinal direction of motion. (a) Acceleration values vs. time. (b) Acceleration amplitude values vs. frequency. (c) Spectrogram of frequency values vs. time.

The values obtained for acceleration amplitude at the level of pier and superstructure are presented in Table 1 for both transversal and longitudinal directions. The differences between the values obtained at the support pier and the superstructure for both directions of movement can be observed due to isolation system action.


**Table 1.** Numerical values obtained for both transversal and longitudinal directions of movement

**Figure 7.** Graphical representation for the recorded values on the transversal and longitudinal directions of motion. (a) Transversal direction of motion. (b) Longitudinal direction of motion.

Figure 7 presents the graphical representation of numerical results obtained on transversal and longitudinal directions of movement.

On the graphs, representations of the values obtained and the motion mitigation trend at the isolated superstructure level can be observed due to action of the hybrid isolation system mounted.
