Condition Assessment/Damage Identification of an Aged, Deteriorated Steel-Stringer Bridge

The primary objective of this paper and its affiliated research is to rigorously demonstrate that modal analysis and the measure of flexibility extracted from modal test data are effective tools for the condition assessment of civil-engineered structures. The use of flexibility as a condition assessment/damage identification index is the fundamental concept, therefore two basic questions need to be resolved scientifically through the analysis and synthesis of modal test data. These are (1) Is a linear parameter such as modal flexibility reliable as an index for infrastructure condition and damage identification?; and, (2) What are the attributes of modal flexibility when obtained through modal test methods? The investigation of these fundamental questions is intended to reveal and characterize behavioral tendencies of modal flexibility (such as stationarity and accuracy). This involves determining how severely flexibility is influenced, or affected, by not only damage, but also by variations in ambient conditions and experimental errors. Consequently, a typical reinforced-concrete deck on steel girder bridge (steel-stringer bridge) will be subjected to a series of deliberately induced damages that simulate typical steel-stringer bridge deterioration and damage scenarios. Throughout this paper, the authors will summarize not only their field test efforts on this bridge, but also the results of the field tests and, in particular, the reliability, practicality, and usefulness of modal testing and flexibility as condition assessment/damage identification tools for typical steel-stringer bridges.