Estimation of modal parameters ofcivil structures from frequency response function

This paper focuses on estimating the modal parameters of the dynamic system that constitutes the pedestrian footbridge of the Science Museum of the city of Valladolid (Spain). The work consists not only of calculating natural frequencies and damping factors associated to each of the estimated modes, as many commercial software provide from acceleration measurements of tests OMA (Operational Modal Analysis) and/or EMA (Experimental modal Analysis), but the aim of this paper is to calculate the generalized masses corresponding to each of the estimated modes of the structure. For this purpose, firstly a representation of the dynamic system is obtained in the state space by SSI technique (Stochastic Subspace Identification), and secondly, vibration modes are scaled from the estimation of the residues of the decomposition in partial fractions of the frequency response function (FRF) measurements. This method gets accurate estimations in the results whose vibration modes are excited, allowing the simulation of the dynamic response of the structure without the need for updating a finite element model of the structure under study