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Damage assessment of reinforced concrete flat slabs through modal tests using impact excitation

Gabriel S. Ferreira (Department of Civil and Environmental Engineering, Universidade Federal da Paraíba, João Pessoa, Brazil)
Tulio O. Guedes (Department of Civil and Environmental Engineering, Universidade Federal da Paraíba, João Pessoa, Brazil)
Lucas F. Melo (Department of Civil and Environmental Engineering, Universidade Federal da Paraíba, João Pessoa, Brazil)
Márcio S. Gonçalves (Department of Civil and Environmental Engineering, Universidade Federal da Paraíba, João Pessoa, Brazil)
Roberto Pimentel (Department of Civil and Environmental Engineering, Universidade Federal da Paraíba, João Pessoa, Brazil)

International Journal of Structural Integrity

ISSN: 1757-9864

Article publication date: 7 February 2019

Issue publication date: 3 April 2019

265

Abstract

Purpose

In reinforced concrete (RC) structures, an evidence of damage is the presence of cracking. In order to evaluate the effect of damage on cracking pattern and natural frequency in RC slabs, two of such structures with different dimensions and reinforcement ratios were tested, in which cracks were induced through application of static load, followed by modal tests using impact excitation. The paper aims to discuss this issue.

Design/methodology/approach

The gradient of the fundamental natural frequency along the decay, the crack opening rate and also a global damage index based on changes of the fundamental natural frequency were evaluated.

Findings

The behaviour of the aforementioned gradient was distinct for both slabs, increasing monotonically with the cracking level for the slab with lowest reinforcement ratio, and increasing until 33 per cent of the collapse load and then decreasing afterwards for the slab with the highest ratio. Changes of the gradient were consistent with changes of the crack opening rate. Both results of gradient changes and cracking pattern brought evidence that the balance between open (old) and breathing (new) cracks differed between the slabs, and may be responsible for such differences.

Originality/value

Damage assessment in RC structures using vibration tests is mostly concentrated on beams. In this work, an advance is made by investigating slabs. The lack of a unique pattern of changes of the gradient implies that its absolute value is not generally suitable for the association with the damage level. However, the impact tests can be effectively used to detect early damage on slabs using this proposed parameter.

Keywords

Acknowledgements

Conflict of interest: the authors declare that there are no conflicts of interest regarding the publication of this paper.

Financial support from Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Capes) is acknowledged. Thanks are due to R. Finotti, C. Theodoro, G. Medeiros, L. Silva, J. Carvalho and L. Pereira for their help during the tests. The data sets generated and/or analysed during the current study are available from the corresponding author on reasonable request.

Citation

Ferreira, G.S., Guedes, T.O., Melo, L.F., Gonçalves, M.S. and Pimentel, R. (2019), "Damage assessment of reinforced concrete flat slabs through modal tests using impact excitation", International Journal of Structural Integrity, Vol. 10 No. 2, pp. 265-275. https://doi.org/10.1108/IJSI-08-2018-0049

Publisher

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Emerald Publishing Limited

Copyright © 2019, Emerald Publishing Limited

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