Relation between changes in the modal properties and structural changes in an existing steel truss bridge

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.