بررسی تأثیر گسیختگی کابل بر رفتار لرزه ‏‏ای پل ‏های کابلی خودایستا در حوزه فرکانس

Cables, as load-bearing elements, play a critical role in cable-stayed bridges. Past evidence suggests that damage and rupture in these cables are inevitable during the service life of such structures. Given that some of these bridges are located in seismic zones, this study investigates the effect of consecutive cable failures on the ultimate seismic capacity of cable-stayed bridges in the frequency domain. For this purpose, the Bill Emerson Memorial Bridge was selected to develop a numerical model using OpenSees software. After validating the numerical model and assuming various defective cable scenarios, the structure was subjected to nonlinear dynamic analysis under different earthquake intensities from the Superstition Hills records until total failure of structure. The acceleration response at the deck midpoint in all three directions and the acceleration response at the top of the pylon in the longitudinal and transverse directions were extracted to analysis of results. Using Fourier Transform, the results were transformed into the frequency domain, and significant frequency peaks were identified through power spectral density (PSD) analysis. The results were then compared to the primary structural frequencies to evaluate the bridge's behavior. The findings reveal that, despite the rupture of two deficient cables, the bridge's capacity does not significantly decrease. However, the rupture of three defective cables by changing the frequency content reduces the seismic capacity and causes frequency peaks at the bridge's natural vibration frequencies. If four defective cables rupture during an earthquake, progressive collapse leads to the total failure of the bridge. It was also observed that the transverse response of the deck is more sensitive compared to other directions, highlighting the need to account for this in deck design in guidelines.