1874-8368/23 Send Orders for Reprints to reprints@benthamscience.net 1 DOI: 10.2174/18748368-v17-230223-2022-18, 2023, 17, e187483682302070 The Open Construction & Building Technology Journal Content list available at: https://openconstructionandbuildingtechnologyjournal.com RESEARCH ARTICLE Damage Identification in Plane Multi-storey Reinforced Concrete Frame Triantafyllos K. Makarios 1,* 1 Institute of Structural Analysis and Dynamics of Structures, School of Civil Engineering, Faculty Engineering, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece Abstract: Objective: In this paper, a new method for damage detection in reinforced concrete multi-storey frames is presented. Methods: The proposed new methodology is a hybrid technique consisting of two parts. The first step involves determining the seismic pushover capacity curve of the structure, and the second step includes formulating the diagram of the instantaneous eigenfequencies of the structure in the nonlinear regime. With reference to this diagram, more details are given in the text. To estimate the equivalent target displacement defined at the top of the structure, which corresponds to the instantaneous eigenfrequencies of a structure with damage, the diagram of these eigenfrequencies is combined with the seismic pushover capacity curve of the structure. Thus, the target displacement at the top of the frame is calculated. Result: The advantage of the proposed methodology is that using this target displacement, the final picture of the damage in the structure is estimated from the two pushover analyses, with positive and negative signs of the floor lateral forces corresponding to triangular distribution in elevation. For clarification, an example of a three-storey R/C frame is presented as a paradigm. Conclusion: Using the proposed methodology, the locations of damage in the structure are successfully identified, as well as the Damage Stiffness Matrix is estimated with high accuracy. Keywords: Damage identification, Diagram of instantaneous eigenfrequencies, Pushover capacity curve, Identification of dynamic characteristics, Seismic target displacement, Nonlinear analysis of reinforced concrete frames, Plastic mechanism. Article History Received: October 16, 2022 Revised: January 20, 2023 Accepted: January 24, 2023 1. INTRODUCTION It is well-known that identification of the dynamic characteristics of reinforced concrete (R/C) structures contributes to the removal of uncertainties in the structure models so as to perform advanced non-linear analyses on the inherent building seismic capacity. Additionally, the identification of eigenfrequencies (and mode shapes) of the structure supports the simple monitoring of a building’s ‘structural integrity’. For this purpose, the main target is to identify the dynamic characteristics of the structure through analytic processing of the measured response, and for this * Address correspondence to this author at the Institute of Structural Analysis and Dynamics of Structures, School of Civil Engineering, Faculty Engineering, Aristotle University of Thessaloniki 54124, Greece; E-mail: makariostr@civil.auth.gr reason, in the past, various stochastic and deterministic procedures have been presented. For example, ‘operational modal analysis’ [ 1 - 4], which uses the ‘frequency domain decomposition’ technique was developed. Furthermore, with reference to ambient vibration monitoring, much information is found in the Wenzel and Pichler book [5]. Using the ‘stochastic subspace identification’, various techniques have been proposed, which are based on the classical books by Overschee and De Moor [ 6], where the measured responses directly harmonize with the parametric models. Three distinct algorithms (principal component, canonical variate analysis algorithms, and the unweighted principal component) have been used in stochastic subspace techniques. In each case, the analysis of random data and operational modal analysis is the base field of analysis of the recorded accelerograms [ 7 - 9]. Having known the abovementioned techniques, the “modal