NAFID - A Grid Tool for output only modal analysis

In this paper, we propose a technique to enhance and facilitate the output only modal analysis of systems and structures by using the vector autoregressive (VAR) model. As we have witnessed, the VAR model with its robustness, accuracy and noise - excitation resistance is beneficial for output only modal analysis. However, the VAR model and others parameters models have to deal with the variation of the model orders such as the frequency stabilization diagram. A grid technique is introduced to classify the natural frequencies and damping ratios in order to automatically evaluate its stabilization. The combination of the grid technique and the stabilization diagram will allow to users to have a better perspective of the modal parameters and a more accurate modes. The method is implemented and built in Matlab as the NAFID-tool which is users friendly and interactive. Examples on simulations of a MDOF system and on a real structure the applicability of the technique.