A new approach to estimate damage in concrete beams using non-linearity Muhammad Usman Hanif ⇑ , Zainah Ibrahim ⇑ , Mohammed Jameel, Khaled Ghaedi, Muhammad Aslam Department of Civil Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia highlights  Lack of globally applicable damage detection method in RC beams.  Constitutive relations for damage in concrete beams.  Method proposed for damage detection without requiring undamaged state.  Nonlinear damage detection in RC beams through simulations.  This model is capable of detecting damage in inverse problem solving. article info Article history: Received 13 May 2016 Received in revised form 17 July 2016 Accepted 28 August 2016 Available online 3 September 2016 Keywords: Damage Concrete Nonlinear analysis Inverse problem Implicit dynamic analysis abstract Damage detection in concrete structures has become a serious problem for engineers. Despite spanning almost half a century, the research on this subject has proven a lack of globally applicable damage detec- tion methodology that can detect damage without the use of parameters from the undamaged state. Therefore, there is a vital need to detect damage without the use of data from the undamaged state of the structure. This research focuses on integrating the power of commercial finite element software using modal dynamic analysis to detect damage in concrete structures. To achieve this goal, a simulation based damage detection method is used that incorporates the Concrete Damaged Plasticity model. The linear and non-linear dynamic analysis are compared and then the sensitivity of the nonlinear dynamic analysis is discussed. The results show good agreement with the previous research using different approaches. In addition, the proposed method shows significant sensitivity to estimate damage and that it can be inte- grated with modal testing to assess the current condition of the structure without the need for baseline data. The mesh size effect on crack formation is also investigated. Ó 2016 Elsevier Ltd. All rights reserved. 1. Introduction Concrete as a construction material has certain advantages over other materials. It is more durable, requires less maintenance, and has simpler and cheaper constituents. In terms of durability, differ- ent design codes specify the design life of concrete structures, as shown in Table 1. Most concrete structural failures are either during the construc- tion phase or due to heavy environmental calamities [1]. The fail- ure or collapse during construction can be due to substandard construction practices. Also, the influence of environmental effects is generally not incorporated during the design of a structure. That is why environmental influences magnify the deterioration process and the structures start deteriorating before their design life [2]. Structures are most affected by dynamic loads, which are frequent in bridges and high rise buildings. A survey in 2002 by the US Department of transportation showed that out of 5,91,707 bridges a total of 1,62,869 (28%) were structurally deficient [3]. Significant financial and human resources are required to deal with this immense inventory of structures. This huge amount of structural inadequacy calls for effective and efficient damage detection meth- ods that are easier, more convenient and applicable to a variety of structures. In addition, concrete is the most popular material in civil infrastructure and has certain merits due to self-weight, econ- omy and maintenance free construction. The currently employed damage detection methods consist of biennial inspection by tech- nical staff who use visual aids, which requires a lot of resources and staff. Usually, a consultancy firm is hired to do the detailed analysis and produce a report based on which economic rehabilita- tion measures are taken [4,5]. http://dx.doi.org/10.1016/j.conbuildmat.2016.08.139 0950-0618/Ó 2016 Elsevier Ltd. All rights reserved. ⇑ Corresponding authors. E-mail addresses: usmanhnf@gmail.com (M.U. Hanif), zainah@um.edu.my (Z. Ibrahim). Construction and Building Materials 124 (2016) 1081–1089 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat