Research Article An Experimental Study of Structural Identification of Bridges Using the Kinetic Energy Optimization Technique and the Direct Matrix Updating Method Gwanghee Heo and Joonryong Jeon Department of Civil and Environment Engineering, Konyang University, 121 Daehak-ro, Nonsan, Chungnam 320-711, Republic of Korea Correspondence should be addressed to Joonryong Jeon; jrjeon@konyang.ac.kr Received 25 September 2015; Accepted 27 December 2015 Academic Editor: Guillermo Rus Copyright © 2016 G. Heo and J. Jeon. 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. Tis paper aims to develop an SI (structural identifcation) technique using the KEOT and the DMUM to decide on optimal location of sensors and to update FE model, respectively, which ultimately contributes to a composition of more efective SHM. Owing to the characteristic structural fexing behavior of cable bridges (e.g., cable-stayed bridges and suspension bridges), which makes them vulnerable to any vibration, systematic and continuous structural health monitoring (SHM) is pivotal for them. Since it is necessary to select optimal measurement locations with the fewest possible measurements and also to accurately assess the structural state of a bridge for the development of an efective SHM, an SI technique is as much important to accurately determine the modal parameters of the current structure based on the data optimally obtained. In this study, the kinetic energy optimization technique (KEOT) was utilized to determine the optimal measurement locations, while the direct matrix updating method (DMUM) was utilized for FE model updating. As a result of experiment, the required number of measurement locations derived from KEOT based on the target mode was reduced by approximately 80% compared to the initial number of measurement locations. Moreover, compared to the eigenvalue of the modal experiment, an improved FE model with a margin of error of less than 1% was derived from DMUM. Tus, the SI technique for cable-stayed bridges proposed in this study, which utilizes both KEOT and DMUM, is proven efective in minimizing the number of sensors while accurately determining the structural dynamic characteristics. 1. Introduction During their service period, structures are exposed not only to gradual aging but also to unspecifed harmful environmen- tal efects, such as earthquakes, strong winds, impacts, and structural instability due to external forces that can give rise to various structural defects. Tese defects can in turn lead to reduced life expectancy and unexpected serious structural damage. Tus, from a long-term perspective, continuous structural health monitoring (SHM), systematic evaluation, and maintenance eforts are pivotal, especially for structures that are vulnerable to vibration occurring during service, such as cable-stayed bridges. For these eforts, a technique for accurate structural identifcation (SI) is of utmost impor- tance. SI is defned as the process of defning a mathemat- ical model of a given structure using measured physical information acquired from the actual target structure. Since Lie and Yao (1978) [1] introduced the concept of SI into structural engineering, many experiments have been con- ducted to identify a mathematical model that can represent the behavioral characteristics (equations of motion) of a target structure [2–5]. Despite such eforts, the SI technique has been applied in everyday practice in only a few cases and with limited efectiveness. It has not been adapted to convenient everyday application in general structural design and maintenance [6–8]. Appropriate utilization of the SI technique not only allows for thorough SHM of the target structure but also reduces the amount of efort required for evaluation and maintenance of the structure and can contribute to ensuring structural safety. As explained above, to conduct SI, physical struc- tural information must be obtained from the target struc- ture through experimentation. In such experimentation, if Hindawi Publishing Corporation Shock and Vibration Volume 2016, Article ID 3287976, 13 pages http://dx.doi.org/10.1155/2016/3287976