Research Article Detection of Earthquake-Induced Damage in a Framed Structure Using a Finite Element Model Updating Procedure Eunjong Yu, 1 Seung-Nam Kim, 1 Taewon Park, 2 and Sang-Hyun Lee 2 1 Department of Architectural Engineering, Hanyang University 222, Wangsimni-ro, Seongdong-gu, Seoul 133-791, Republic of Korea 2 Department of Architectural Engineering, Dankook University, Jukjeon-dong, Yongin-si 448-701, Republic of Korea Correspondence should be addressed to Eunjong Yu; eunjongyu@hanyang.ac.kr Received 31 October 2013; Accepted 17 December 2013; Published 16 January 2014 Academic Editors: A. K. Gupta, R. Su, and Q. W. Yang Copyright © 2014 Eunjong Yu et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Damage of a 5-story framed structure was identifed from two types of measured data, which are frequency response functions (FRF) and natural frequencies, using a fnite element (FE) model updating procedure. In this study, a procedure to determine the appropriate weightings for diferent groups of observations was proposed. In addition, a modifed frame element which included rotational springs was used to construct the FE model for updating to represent concentrated damage at the member ends (a formulation for plastic hinges in framed structures subjected to strong earthquakes). Te results of the model updating and subsequent damage detection when the rotational springs (RS model) were used were compared with those obtained using the conventional frame elements (FS model). Comparisons indicated that the RS model gave more accurate results than the FS model. Tat is, the errors in the natural frequencies of the updated models were smaller, and the identifed damage showed clearer distinctions between damaged and undamaged members and was more consistent with observed damage. 1. Introduction Monitoring integrity of infrastructures without interruption of its function is the primary motivation in developing vibr- ation-based damage detection methods. Tis method relies on the fact that changes in structural properties, such as dam- age, afect the overall dynamic properties of the structure. Te general approach to detecting damage in this method is to establish analytical models which represent the reference state and damaged state of the structure and then to investig- ate the change in structural properties between the two ana- lytical models. Tus, a relevant parameter identifcation method yielding the optimal analytical model which repre- sents the observed behaviors of a structure is essential. Sev- eral approaches have been explored to solve this inverse pro- blem and are summarized by Doebling et al. [1, 2], Farrar et al. [3], Humar et al. [4], and Brownjohn [5]. Te numerical optimization procedures that can be used in the feld of damage detection are divided into two categories. One is based on pattern recognition algorithms such as artifcial neural networks, which fnd an optimal parameter set from a relationship previously established using numerous parameter-response pairs [1, 6]. Te other is the model updat- ing approach which iteratively adjusts parameters (the stif- ness, mass, and/or damping parameters) of the FE model to minimize diferences in measured dynamic properties and those of the FE model [7]. Damage of the structure is eval- uated by comparing the updated models of the reference state and damaged state. In the FE model updating method, structural properties that represent the stifness of the members in the analytical model, such as the modulus of elasticity or sectional property, are usually selected as the updating parameters. At this point, to obtain accurate results, it is important to establish a relev- ant analytical model and choose appropriate updating param- eters so that the efects of damage on the dynamic properties can be accurately replicated. For example, if the fexural stif- ness values of members were chosen as the updating param- eters when the analytical model was not sufciently discre- tized, it would be impossible to replicate the dynamic prop- erties of a framed structure that has concentrated damage at only a few joints or portions of a few beam-column members. Hindawi Publishing Corporation e Scientific World Journal Volume 2014, Article ID 410539, 11 pages http://dx.doi.org/10.1155/2014/410539