Damage Assessment of Truss Diagonal Members Based on Frequency Changes in Local Higher Modes

Abstract This article examines about a possibility of the damage assessment of truss diagonal members by using local higher modes. Firstly, the local vibration characteristics of diagonal member were analyzed by FEM eigenvalue analysis. Through the analysis, the natural modes of the diagonal member were classified roughly as bending modes of in-plane and out-plane direction of the truss, torsional modes and plate modes of the flange and web. The mode dependence of frequency changes caused by a damage in the diagonal member was also confirmed in the analysis with the damage model. Secondly, healthy and corroded diagonal members with same specifications were examined by the hammering test on site. As a result, it was concluded that the decreases in the natural frequencies of higher modes are prominent enough to assess the corrosion.