Journal of Scientific & Industrial Research Vol. 77, June 2018, pp. 337-341 Damage Identification of Reinforced Concrete Beam Using Modal Curvature Approach A Chaurasia, S K Panigrahi* and S S Patel CSIR-Central Building Research Institute, Roorkee-247667, India Received 03 April 2017; revised 22 December 2017; accepted 16 January 2018 Reinforced concrete (RC) beams are one of the main load bearing structural elements in buildings. These elements suffer from distress, primarily cracks, due to many reasons resulting into degradation of stiffness and strength. The modal curvature approach is a very good technique in damage identification in steel and RC beams. This study provides a critical review on the different approaches for damage prediction. The current state of the knowledge is presented and the different models which have been proposed in the past for damage identification on structural systems are discussed. In this paper, a technique for damage identification and assessment of RC beams is proposed which makes use of vibration data to compute the Curvature Damage Factor (CDF). To detect damage progression, simply-supported RC beams were subjected to an incrementally increasing static four point loading in steps till ultimate failure. After each load step, vibration measurements were performed using wireless sensors mounted at critical locations. The experimental crack pattern and results of modal curvature were compared. The results show that this approach is efficient for damage identification of reinforced concrete beams which exhibit high non-linear behavior. Keywords: RC Beam, Modal Curvature, Frequency, Crack Pattern, CDF Value, Vibration Measurement, Damage Identification Introduction The performance of a structure is affected due to permanent unfavorable change in its physical properties, which is referred as damage. The causes of damage may be due to excessive vibration, harsh environment, ageing, overloading, fatigue, corrosion of reinforcing bars in concrete etc. Consequently, it is important to know damage progression for estimation of residual service life. Structural Health Monitoring is the implementation of damage identification process, classified into four levels: Level 1: Damage detection, Level 2: Damage location, Level 3: Damage quantification and Level 4: Remaining life prediction. Structural damage is a local perturbation of its physical characteristics, i.e. its stiffness, mass and/or damping, which produces change in the vibration characteristics of the structure. This forms the basis for vibration based structural health monitoring techniques. Extensive efforts have been made to detect and ascertain the cause of damage in global scenario. Fan & Qiao 1 presented a comprehensive review on vibration based approaches for structural damage identification. Panigrahi et al. 2 proposed a method for identifying damage in a multi storeyed shear building using minimum number of modal parameters of the structure. The proposed methodology requires experimentally determined sparse modal data of any particular mode as input to detect the location and extent of damage in the structure. Patel et al. 3 used acceleration-time histories from reinforced concrete building to detect the change in physical properties of the building. Frequency spectra have been widely used for fault identification in mechanical and civil structures 4 . An alternative approach, based on modal curvature was demonstrated to enhance the sensitivity of damage identification 5 . Further, Wahab 6 studied the use of modal curvature for damage identification. Based on measurements of Eigen vector curvatures and Eigen frequencies. Ciambella et al. 7 proposed a technique for damage detection and assessment. The proposed technique was illustrated with reference to a cantilever Euler beam endowed with a set of piezoelectric transducers. The result shows that the modal curvature difference method is an effective damage detection technique for 1D beams but not very effective for 2D structures. Therefore, Zhang 8 improved this method by introducing coordinate transformation technique so as to settle the calculation —————— *Author for Correspondence E-mail: skpanigrahi@cbri.res.in