PSI - Issue 78

Gloria Terenzi et al. / Procedia Structural Integrity 78 (2026) 341–348

345

Table 4. BC1DN-FC dampers: Measured and computed response data from 2025 tests.

d i [mm]

Test Nr.

E D,comp (kN·mm)

d exp,max- [mm]

d exp,mean [mm]

v exp,max [mm/s]

c id kN(s/mm) 

E D,exp (kN·mm)

d exp,max+ [mm]

 [Hz] 0.01 0.01

T1 T2 T3 T4 T5 T6

5

3.98

-3.75

3.87

0.24 0.74

8.74 8.87 6.76 6.52 6.42 5.58 5.86 5.80 5.82 5.90 5.92 5.83

84.8

84.8

14 14 14 14

11.21 10.19

-12.22

11.71 10.03

746.1

794.1

0.1 0.5 1.0 2.0 2.0 4.0 4.0 5.0 5.0 8.0

-9.88 -9.34 -9.31 -1.83 -6.58 -1.72 -6.13 -1.69 -6.73 -6.54

6.3

1957.5 2255.1 2362.4

1951.0 2255.3 2361.5

9.58 9.86 2.68 5.75 2.52 5.70 2.41 5.75 5.66

9.46 9.58 2.25 6.16 2.12 5.92 2.05 6.24 6.11

29.7 60.2 28.3 77.4 53.3

5

292.5 3304 483.6

292.2

T11

10

3303.1

T7

5

483.3

T10

10

148.8

3716.9

3717.4

T8 T9

5

64.4

155.5

154.9

10 10

195.9 307.1

2396.9 3389.8

2396.8

T12

3388

By way of example of the identification analysis carried out for the tests characterized by frequencies of 0.01 Hz, 1 Hz and 5 Hz, Figs. 3 and 4 show, in superimposition, the experimental and numerical cycles obtained in the 2008 and 2025 campaigns for the BC1BN-FC (Fig. 3) and BC1DN-FC (Fig. 4) damper pairs. A satisfactory correlation is observed for all tests. Starting from these data, the possible aging effects on the two types of dampers were assessed by comparing the mechanical properties estimated from the response obtained in the two campaigns. Concerning BC1BN-FC devices, an identical k 2 value of 1.2 kN/mm was identified from the two test sets for the elastic component F e . The velocity exponent  shows a stable value of 0.2. The c id estimates derived from the identification process are plotted as a function of v exp,max in Fig. 5a, where blue “o” and red “+” symbols refer to the 2008 and 2025 tests, respectively. The first three points of the two series (tests T1-T3) are related to frequencies of 0.01 Hz ( v exp,max = 0.51 mm/s), 0.1 Hz ( v exp,max = 4.92 mm/s), and 0.5 Hz ( v exp,max = 27.9 mm/s), which correspond to quasi-static testing conditions. The c id values are very similar for the two series, reaching a maximum of 4.0 kN(s/mm)  in T1 test. Starting from the T4 tests, performed at a frequency of 1 Hz, c id appears to be stable, with mean values of 3.33 kN(s/mm)  for the 2008 tests (blue straight line), and 3.29 kN(s/mm)  (red dotted line), for the 2025 tests. These nearly coincident mean values highlight that the mechanical behaviour of BC1BN-FC spring-dampers is not affected by any appreciable aging effect. For BC1DN-FC devices an identical k 2 value of 1.4 kN/mm is found, for the two test sets. Like for BC1BN-FC dampers  shows a stable value of 0.2. The c id values plotted in Fig. 5b, are very similar for the two testing campaigns, reaching a maximum of 8.87 kN(s/mm)  in T1-T2 tests, with frequency of 0.01 Hz, and decreasing in the subsequent T3 (0.1 Hz, v exp,max = 6.2 mm/s) and T4 (0.5 Hz, v exp,max = 31 mm/s) quasi-static tests. Starting from T5 tests, carried out at a frequency of 1 Hz, c id is stable, with mean values of 6.08 kN(s/mm)  for 2008 tests (blue straight line), and 6.04 kN(s/mm)  (red dotted line), for 2025 ones. These nearly coincident mean values assess, for this second pair of dampers too, the absence of aging effects. During the 2025 campaign, additional tests were performed to check the dynamic response stability of the devices for higher numbers of consecutive cycles. To this aim, the tests with frequency of 5 Hz were replicated by applying, to both pairs of devices, sinusoidal displacement time-histories characterized by more than 100 cycles with amplitude comparable to the one imposed in T7 test for BC1BN-FC devices (results in Table 2) and T9 test for BC1DN-FC devices (results in Table 4). These supplementary tests are named T10, T13 for BC1BN-FC and B1DN FC dampers, respectively. Based on the response obtained in T10 and T13 tests, the stability of the mechanical characteristics of the devices was analysed by evaluating the deviation of relevant computed c id values, equal to 3.38 kN(s/mm)  (T10),