Issue 29

L. Facchini et alii, Frattura ed Integrità Strutturale, 29 (2014) 139-149; DOI: 10.3221/IGF-ESIS.29.13

It can be seen that the replacement of the signum function with   s x causes the cycle of the BW oscillator to enlarge (Fig. 6), thus missing the match with the reference response (Fig. 1); on the other hand, it was seen that the re introduction of the condition upon the unloading stiffness brought back the cycle of the BW system to match the reference response again ((Fig. 7). A final check was made taking into account the dynamic response of this modified version of BW system to the El Centro 1940 earthquake, and the comparison with the FE results is shown in Fig. 8.

Figure 7: Comparison of the identified BW model with the ANSYS results.

Figure 8: Displacement time history: comparison between BW identified model and ANSYS results (El Centro 1940 earthquake).

Taking into account the proposed approximation for the signum function, Eq. (8)-(9) can be written as follows:                         1 2 1 2 1 2 2 1 2 , α 1 α 1 , where :    , , β γ n mx t cx t kg f t g x x x x z t x t h x z h x x x s x s x x z                       ⛂ ⛂ (10)

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