Hindawi Publishing Corporation Chinese Journal of Engineering Volume 2013, Article ID 126509, 7 pages http://dx.doi.org/10.1155/2013/126509 Research Article Fracture Formation Evaluation of Reinforced Concrete Structure Using Acoustic Emission Technique Alireza Panjsetooni, 1 Norazura Muhamad Bunnori, 1 Amir Hossein Vakili, 1 Zohreh Shirkhani, 2 and Zeinab Shirkhani 3 1 School of Civil Engineering, Engineering Campus, Universiti Sains Malaysia (USM), Seri Ampangan, Seberang Perai, Malaysia 2 Department of Biology, Payame Noor University, P.O. Box 19395-4697, Tehran, Iran 3 Governor General Ofce of Ilam, Ilam, Iran Correspondence should be addressed to Alireza Panjsetooni; alireza5civil@yahoo.com Received 7 July 2013; Accepted 7 August 2013 Academic Editors: R. Maceiras and G. Xie Copyright © 2013 Alireza Panjsetooni 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. Acoustic emission (AE) is an important nondestructive evaluation (NDE) technique used in the feld of structural engineering for both case local and global monitoring. In this study AE technique with a new approach was employed to investigate the process of fracture formation in reinforced concrete structure. A number of reinforced concrete (RC) one story frames were tested under loading cycle and were simultaneously monitored using AE. Te AE test data was analyzed using the relaxation ratio and calm and load ratio method. Also, the relaxation ratio was dominated with approaching load to 58% of the ultimate load. In addition three levels of damage using calm and load ratio were distinguished. Te trend of relaxation ratio and calm and load ratio method during loading and unloading showed that these methods are strongly sensitive with cracks growth in RC frame specimens and were able to indicate the levels of damage. Also, results showed that AE can be considered as a viable method to predict the remaining service life of reinforced concrete. In addition, with respect to the results obtained from relaxation ratio and, load and calm ratio indicated, a new chart is proposed. 1. Introduction AE testing is a useful nondestructive technique for real-time examination of the behaviour of materials deforming under stress [1]. Te main goal of the monitoring of AE phenomena is to provide a series of useful information by the correlation of AE signals with growing fracture process [2]. Te wide range for application of acoustic emission is between seismic event as the largest scale and the movement of small numbers of dislocation in material as the small scale [3]. Te primarily sources of AE are microcracking, macrocracking, compres- sion failure, yielding, fracture, debonding between materials, sliding, and friction between interfaces [4]. AE data can be evaluated by means of several methods. Relaxation ratio and calm and load ratio which are derived from events during unloading and loading are reasonable methods for evaluation of structure under cyclic load. Te relaxation ratio and calm and load ratio have been used by several researchers to evaluate structural damage. A few works found that relaxation ratio have been used for evalu- ation of concrete structure such that [5–7] have been inves- tigating several RC beams under cyclic load using relaxation ratio. Tey found that relaxation ratio is more than one when approximately 45% of the ultimate bending load was reached. In addition, several works found that calm and load ratio has been used for evaluation of concrete structure such as [5, 6, 8– 11]. Reference [11] investigated a large number of full-scale laboratory test beams similar to highway bridge structure under a cyclic load using AE technique. Tey suggested a new threshold on the load and calm ratios specifc to this class of structure and loading. Reference [10] evacuated global monitoring of concrete bridge using AE technique. Tey reported the suitability of AE to monitor large concrete structure using the values of quantifcation indices like the calm and load ratio. Te main objective of this current study was damage evaluation assessment of RC frame with a new approach and