%0 Journal Article %T Damage detection of multi-girder bridge superstructure based on the modal strain approaches %J Journal of Theoretical and Applied Vibration and Acoustics %I Iranian Society of Acoustics and Vibration and Avecina %Z 2423-4761 %A Baghiee, Neda %A Esfahani, Mohamad Reza %A Moslem, Kazem %D 2019 %\ 01/01/2019 %V 5 %N 1 %P 21-42 %! Damage detection of multi-girder bridge superstructure based on the modal strain approaches %K Damage %K FRC deck %K Invariant stress %K Modal strains %K spurious diagnosis %R 10.22064/tava.2019.97819.1123 %X The research described in this paper focuses on the application of modal strain techniques on a multi-girder bridge superstructure with the objectives of identifying the presence of damage and detecting false damage diagnosis for such structures. The case study is a one-third scale model of a slab-on-girder composite bridge superstructure, comprised of a steel-free concrete deck with FRP rebars supported by four steel girders, similar to North Perimeter Red River Bridge in Winnipeg, Manitoba. The modal test data of the slab-on-girder specimen are analyzed by two mathematical methods and Mindlin approach. The Mindlin approach uses a small number of sensors and only the fundamental mode of vibration to obtain the modal strains. The unit-area normalization method produces a more precise damage patternbased on the Mindlin approach than the widely used unit-norm method and is thus a superior method for locating damage in multi-girder bridge structures. A new method is proposed to distinguish the false damage diagnosis that is common in multi-girder systems. Based on the invariant stress resultant theory and direct stiffness assumptions, a level III damage detection process is applied successfully to indicate damage localization and severity estimation of the damaged girder. %U https://tava.isav.ir/article_37292_41d6ca6be680010cf3cf40bf81ed7a1c.pdf