ANALISIS RESONANSI GETARAN JEMBATAN TERHADAPKEJADIAN GEMPABUMI YOGYAKARTA(STUDI KASUS JEMBATAN BANTAR III BANTUL YOGYAKARTA)

A vibration resonance studies were performed at Bantar III Bridge Kali Progo Sedayu Sub-district of Bantul. The study aims to determine the natural frequency of the bridge and compare it with the frequency of earthquakes to determine the possibility of resonance. Furthermore, a particle motion and displacement of the bridge were also analysed. Spectral analysis of the earthquake and the bridge using the FFT to obtain the dominant frequency of the bridge and the frequency of earthquakes. The natural frequency of the bridge obtained about 3,5 Hz � 5Hz. This is apropriate with the analytical calculation based on the construction of the bridge that showed the natural frequency about 3.51 Hz - 5.18 Hz. The frequency survace wave of the Yogyakarta earthquake which took place within the periode 2009 � 2010 is 1,1 Hz � 3,3 Hz. Comparison of natural frequency experimentally and the frequency of earthquakes indicated very small possibility of resonance amplification occured in the Bantar III bridge Kali Progo Yogyakarta. Displacement value due to vehicles loaded experimentally is range from 8,5 mm � 29,2 mm whereas a theoretical value range from 127,5 mm � 170 mm. The experimental value is smaller than it obtained from theoritically. That means that the structure of the bridge is able to withstand the external load moment the bridge. The movement direction of particle passed on bridges due to vehicle are generally parallel and perpendicular to the direction of the bridge.