Contents lists available at ScienceDirect Engineering Structures journal homepage: www.elsevier.com/locate/engstruct Evaluation and comparison of ultimate deformation limits for RC columns Muhammed Alperen Özdemir a , İlker Kazaz b, ⁎ , Suat Gökhan Özkaya c a Dept. of Civil Engineering, Iğdır University, 76000 Iğdır, Turkey b Dept. of Civil Engineering, Erzurum Technical University, 25050 Erzurum, Turkey c Dept. of Civil Engineering, Ardahan University, 75000 Ardahan, Turkey ARTICLE INFO Keywords: RC column Performance limit Strain limit Rotation limit Ultimate deformation Performance assessment ABSTRACT The ultimate deformation capacity assigned to structural elements of reinforced concrete structures is an es- sential parameter in the determination of their structural performance especially under seismic attack. Various ultimate deformation capacity limits were proposed for RC columns in the previous studies and were accom- modated in the current building codes. However, the reliability of the existing deformation limits is still a matter of considerable debate. This study mainly focuses on the evaluation of the accuracy of the existing damage limits and aims to develop a new definition with a higher reliability in comparison to the existing limits. In this purpose, the study was composed of four major steps. Firstly, the existing building codes, standards, regulations and previous studies were reviewed and evaluated in terms of ultimate deformation criteria for RC columns. Secondly, actually tested sixty-nine RC columns were selected from PEER Structural Performance Database and were numerically modelled by using finite element method. The selected RC columns have different dimensions, aspect ratios, concrete and steel strength, longitudinal and transverse reinforcement amounts and axial load ratio. Third stage includes the comparison of the results obtained from the experimentally verified numerical models with the existing ultimate deformation limits to reveal the shortcomings of existing criteria. The nu- merical modelling facilitated the consistent comparison of strains and curvatures that are rarely available and difficult to measure in tests. A new concrete compressive strain prediction equation was proposed to determine the ultimate deformation capacity of rectangular RC columns. It was concluded that there is need for further comprehensive analytical and experimental studies on deformation limits of reinforced concrete columns. 1. Introduction Predicting the deformation capacity of reinforced concrete beams, columns and walls is vital for a thorough seismic evaluation of existing or new buildings in performance based earthquake engineering. The ability to remain without significant loss of load-carrying capacity of reinforced concrete (RC) structural members under seismic loads is a necessary criteria for life safety. Understanding the behavior of col- umns, which are the primary components of structure, is important for the evaluation of entire structural system. Although behavior of RC columns is well understood and researched, the problem of determi- nation of the ultimate deformation capacity of RC columns under seismic loads is not fully resolved. There are code and performance based expressions that are re- commended for estimating the ultimate deformation capacity of RC columns. Codes and previous studies specifies deformation limits for RC columns in terms of rotation angle (θ) [1–4], strain (ε) [5–7] and drift ratio at shear failure (δ) [8]. The local strains are convenient deformation measures when fiber models are used to estimate inelastic seismic deformation demands in concrete members in nonlinear ana- lysis. However, a limited number of column test results were used for verifying these expressions and limit states specified at the codes, especially which are based on strain criteria. Acun and Sucuoğlu [9] conducted twelve full-scale column tests to evaluate performance limits and they found that proposed deformation limits in Eurocode-8 [1] and ASCE/SEI 41 [2] are very conservative. Bae and Bayrak [10] found similar results for drift capacity of RC columns. Due to the effort, time spent and limitations of the test set-ups, limited tests were conducted on large-scale RC columns with different design parameters, such as con- finement, concrete strength, longitudinal reinforcement ratio, axial load ratio and cross sectional dimensions. In addition, test results of columns with similar properties tested by different researchers indicate different drift capacities. Therefore, proposed expressions and accep- tance criteria in seismic action for RC columns need a deeper in- vestigation using more extensive and consistent column databases to improve limit state definitions and their corresponding values. http://dx.doi.org/10.1016/j.engstruct.2017.10.050 Received 15 June 2017; Received in revised form 17 September 2017; Accepted 18 October 2017 ⁎ Corresponding author. E-mail addresses: m.alperen.ozdemir@igdir.edu.tr (M.A. Özdemir), ilkerkazaz@erzurum.edu.tr (İ. Kazaz), suatgokhanozkaya@ardahan.edu.tr (S.G. Özkaya). Engineering Structures 153 (2017) 569–581 0141-0296/ © 2017 Elsevier Ltd. All rights reserved. MARK