Numerical evaluation of modal indices for damage identification in steel footbridges

Resumo

Among several damage detection methodologies, the vibration-based damage identification methods
(VBDI) are remarkable since the deterioration in structural elements reflects directly on both global and local
dynamic response of the structure leading to changes in modal parameters. Different approaches focus mainly on
one-dimensional structures, which, in turn, may not represent the actual dynamic behavior of bold structures such
as bridges and footbridges. Some modal indices, namely mode shape curvature, modal flexibility, and modal strain
energy were evaluated considering a finite element model of a real curved steel footbridge and three-dimensional

vibration modes. Moreover, a recently proposed modal index called resultant vector which incorporate three-
dimensional modal coordinates is also compared to the aforementioned indices. Results show that the accuracy of

the indices is correlated with the region of the structure where damage is found. The influence of damage presence
on adjacent girders and how it is reflected in these indices is also discussed.