Application of EMD to modal parameter identification of a bridge

According to the fact that the responses of a bridge under ambient excitation trend to be non-stationary, a method to identify the modal parameter of the bridge is presented by using empirical mode decomposition (EMD) and random decrement technique (RDT) simultaneously. The responses of the bridge are decomposed into a series of intrinsic mode functions (IMFs) by carrying out EMD, and the responses of free vibration are separated from those IMFs by using RDT. The free vibration responses are then expressed as an analytic form in which modal parameters of the bridge are included. In addition, parameter identification theories and optimum estimate theories are used in obtaining modal parameters of the bridge. The modal parameters of the Nanjing Yangtze River Bridge (NYRB) identified from the measured vibration responses of the NYRB are compared with those provided by finite element analysis and related measured value. The results demonstrate that the method is effective and practical to modal parameter identification for large civil structures such as bridges.