Experimental study on condition assessment of reinforced concrete structure using a dynamics response approach Chun Pong Sing Department of Construction Management, School of Built Environment, Curtin University, Perth, Western Australia, and P.E.D. Love and P.R. Davis School of Built Environment, Curtin University, Perth, Western Australia Abstract Purpose – Condition assessment on reinforced concrete (RC) structures is one of the critical issues as a result of structure degradation due to aging in many developed countries. The purpose of this paper is to examine the sensitivity and reliability of the conventional dynamic response approaches, which are currently applied in the RC structures. The key indicators include: natural frequency and damping ratio. To deal with the non-linear characteristics of RC, the concept of random decrement is applied to analyze time domain data and a non-linear damping curve could be constructed to reflect the condition of RC structure. Design/methodology/approach – A full-scale RC structure was tested under ambient vibration and the impact from a rubber hammer. Time history data were collected to analyze dynamics parameters such as natural frequency and damping ratio. Findings – The research demonstrated that the measured natural frequency is not a good indicator for integrity assessment. Similarly, it was revealed that the traditional theory of viscous damping performed poorly for the RC with non-linear characteristics. To address this problem, a non-linear curve is constructed using random decrement and it can be used to retrieve the condition of the RC structure in a scientific manner. Originality/value – The time domain analysis using random decrement can be used to construct a non-linear damping curve. The results from this study revealed that the damage of structure can be reflected from the changes in the damping curves. The non-linear damping curve is a powerful tool for assessing the health condition of RC structures in terms of sensitivity and reliability. Keywords Condition assessment, Damping ratio, Natural frequency, Reinforced concrete structure Paper type Research paper Introduction Condition assessment for reinforced concrete (RC) has attracted a considerable amount of attention from the research community, practicing engineers and surveyors, as a result of structural degradation due to aging (e.g. Xia and Hao, 2003; Concu et al., 2011). Traditional approaches to examine dynamic response parameters have been based upon visual or localized experimental procedures such as a rebounded hammer. With such approaches the location of the damage must be known a priori and the inspection area must be accessible (Xia and Hao, 2003). Moreover, such methods are largely based on the experience of the observer who may not be able to ascertain the level of degradation or safety of the structure (Concu et al., 2011). Unlike traditional approaches, dynamics response provides an assessment of the condition for a structure with entire integrity rather than a single location. The current issue and full text archive of this journal is available at www.emeraldinsight.com/0263-080X.htm Structural Survey Vol. 32 No. 2, 2014 pp. 89-101 r Emerald Group Publishing Limited 0263-080X DOI 10.1108/SS-02-2013-0017 89 Study on condition assessment of RC structure