Structural health monitoring of steel bridge model

Civil engineering structures are exposed to various dynamic effects such as earthquakes, storms, traffic loads, blast etc during their lifetime. So Structural Health Monitoring techniques are used on structures to determine how to behave against these effects , to evaluate the current condition of structures right now and to detect damage if there is any. In this M. Sc. thesis, system identification of a model steel bridge has been performed and calibrated finite element model of the bridge is obtained. Although there are many different system identification types, in this study only NExT-ERA and ERA methods are used. Methods are programmed using Matlab. As a result of this study, modal parameters (mode shapes, natural frequencies, damping ratios) of the structure has been estimated. On the other hand, modal assurance criteria is calculated to mode shapes between NExT-ERA, ERA results and SAP2000 analysis results. It has been shown that mode shapes are in good agreement with each other. Natural frequencies, obtained from NExT-ERA and ERA, are also in good agreement. In addition to these methods, mode shapes and natural frequencies have been estimated by using Cross Power Spectrum method. Besides NExT-ERA and ERA methods, to further estimate damping ratios half-power bandwidth, logarithmic decrement methods are used. Damping results estimated using different methods are found to be different from each other. In spite of this, estimated damping ratio results are reasonable.