The damage in a steel truss model bridge is simulated by changing its element
stiffness. The dynamic behaviors of the model bridge are analyzedwithFEMdynamic structural
analysis program before and after the model bridge is damaged. It is found that the changes in
the mode of vibration are sensitive to the damage degree of elements, and there exists a
corresponding relationship between them. A new method for weighting the changes in modes
during the structural damage is proposed, inwhich the modes of structural vibration are chosen
as weight coefficients. Element damages can be oriented effectivelywith this method.