DETERMINATION OF THE FREQUENCY IN CABLE STRUCTURE OF CABLE-STAYED BRIDGE USING ACCELEROMETER DATA

The cable is a tensile element which has the property of providing tension rigidity to the bridge structure. The dimension and stiffness of the cable is determined by the magnitude of the force that occurs in the cable. In determining the cable force under service conditions, it is necessary to carry out a dynamic testing on the bridge. Dynamic testing provides prediction of modal parameter values such as natural frequency, mode shape and damping at service conditions in cable structure. The test equipment used in obtaining the modal parameter values is the accelerometer. The accelerometer is installed on a bridge cable to capture the acceleration on cable structure. Then, it is converted by Fast Fourier Transform (FFT) to get the frequency value of the cable structure. Previous study has been done using this method, the results of cable force values still have a high difference, when it is compared with the results of numerical modeling using finite element method and measurements with other equipment such as Electromagnets (EM). The method proposed in this study is to use wavelet transform in additional method in reducing noise in signal processing. The results for the sample frequency, fs = 32 Hz is suitable to be used to analyze the signal for accelerometer data recording on the Cable SC2 Jembatan Merah Putih, the number of sample frequencies (fs) is twice the frequency of the structure (fn). Another result, the frequency value in the first mode shape (f1) from the data accelerometer shows the value is in the minimum and maximum range when it compared with the measurement results of the frequency value with an Electromagnetic (EM) instrument.