Modal Identification of Cable‐Stayed Pedestrian Bridge

Abstract

The vibrations of a cable‐stayed pedestrian bridge are measured and compared with a numerical model, and used to produce improved estimates of the structural properties. Fourteen deck modes with frequencies under 16 Hz were identified using the impact hammer technique. The damping of all but one of the modes was measured at 0.75%, in spite of a wood deck. The numerical model consisted of a three‐dimensional finite element analysis which incorporated nonlinear cable effects. The experimental and numerical results were shown to be highly correlated by visual inspection, the MAC, and the CoMAC. The primary differences were: (1) Two of the experimental mode shapes showed a slight asymmetry that was not present in the numerical modes; and (2) the measured natural frequencies were consistently higher than the numerical frequencies. Parameter estimation using eigenvalue sensitivities with changes of less than 12% in the nominal values helps reconcile the experimental and numerical differences.