Abstract:
This paper describes an investigation of the applicability of changes in modal properties of a
bridge to structural health monitoring. Vibration measurements were conducted at an existing Warren
truss bridge for road traffic in-service for more than 40 years. Experimental modal analysis applied to the
measured data identified global vibration mode of a bridge span and local vibration modes dominated by
vibrations of diagonal members. There were a partial fracture, cracks and pitting corrosions in diagonal
members of the truss bridge detected during recent visual inspections and some of those damages were
repaired during the investigation described in this paper. The effects of those structural changes on the
modal properties identified were discussed with the results of finite element analysis so as to investigate
the applicability of modal properties changes in global and local vibration modes to the identification of
structural changes in truss bridges.
