Damage evaluation of a timber beam using a modal-based method

In Australia, many timber bridges are old and increasingly experience deterioration, aging and traffic overloading problems. These have attracted attention of researchers to evaluate the current state of such bridges. Whilst proof-load testing and traditional nondestructive evaluation (NDE) provide valuable tools, such procedures are often time consuming and costly. For bridge structures, to develop effective NDE at global level viz damage identification and structural health monitoring using modal-based damage identification methods have engrossed recent worldwide research efforts. However, to date there are few works reported on timber bridges using modal-based damage identification methods to evaluate their state of health. In this paper, modal-based damage identification methods for localization of damage in timber bridges are presented based on finite element analysis (FEA) and test results of a timber beam. Two algorithms of global NDE for identifying local damage and decay in timber structures are investigated. The methods employ modal parameters that monitor changes in modal strain energy (MSE) based on curvature mode shapes of a damaged beam with respect to the undamaged one. The aim of the study is to investigate the capability and limitations of the proposed algorithms for detecting damage with multiple damage scenarios in timber structures. Between the two proposed modal based damage identification algorithms, the modified method has shown better results in solving multiple damage problems.