Modal identification of damaged frames

What is it about?

The paper investigates the possibility of identifying localized damages in multi-span and multi-floor linear elastic frames using only natural frequencies measured in the undamaged and damaged configurations. Due to the small sensitivity of global modes of this kind of frames on localised damages, an approach is proposed that explores one by one their significant substructures (i.e. multi-span beams, floor by floor), where local modes can be detected provided that local excitations are applied. Namely, the error function to be minimised is defined through the differences between measured frequencies and those corresponding to a FEM data-base of damaged models, including only the natural frequencies of the local modes of each substructure. The performances and limits of the procedure are discussed by means of numerical simulations on steel frames of increasing complexity.

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Why is it important?

the proposed procedure, which only requires the knowledge of natural frequencies in the undamaged and damaged states, looks for the location and severity of the damage in a multi-span and multi-floor frame by exploring one by one its substructures, by means of an error function defined in a data-base of FE damaged models that only includes the local modes of the selected substructure. The effectiveness of the procedure is investigated by means of a wide numerical simulation performed on frames of increasing complexity.

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