Hysteretic cyclic response of concrete columns reinforced with smooth bars
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Hysteretic cyclic response of concrete columns reinforced with smooth bars Kamyar Karbasi Arani · Mohammad S. Marefat · Marco Di Ludovico · Andrea Prota · Gaetano Manfredi
Received: 29 November 2012 / Accepted: 26 May 2013 / Published online: 5 June 2013 © Springer Science+Business Media Dordrecht 2013
Abstract The application of smooth (plain) bars in reinforced concrete (RC) construction has been abandoned since the 1970s; however, there are many old reinforced concrete buildings in the world whose construction is based on this old style that are now in need of structural seismic rehabilitation according to the requirements of present day seismic rehabilitation codes. The focus of this study concerns the investigation of the hysteretic cyclic response of RC columns with smooth bars. The results of six column specimens having a variety of details for overlapping splices of longitudinal bars while experiencing two different levels of axial loads under cyclic loading reversals are presented. Through analysis of test observations and the obtained experimental results, it is attempted to clarify major aspects of hysteretic response for RC columns with smooth bars, from a seismic assessment point of view. The hysteretic force–drift responses of columns are deeply investigated and a new concept explaining the flag shape form of the hysteretic response is presented. Furthermore, the rocking response of columns is predicted with a new formulation that assumes an internal compression strut inside the column body as a consequence of rocking that originated from high base rotations. Finally, a simple hysteresis rule is proposed which is the result of considering the combination of two springs in parallel to provide the total hysteretic response as the summation of rocking hysteretic and bottom anchor (smooth bar) hysteretic responses. Keywords Reinforced concrete · Columns · Smooth bars · Seismic assessment · Cyclic response · Rocking · Hysteresis rule 1 Introduction The application of smooth (plain) bars in reinforced concrete (RC) construction was abandoned in the 1970s apparently because of the low bond resistance between this type of K. K. Arani (B) · M. Di Ludovico · A. Prota · G. Manfredi Department of Structural Engineering, University of Naples Federico II, Via Caludio, 21, 80125 Naples, Italy e-mail: [email protected] M. S. Marefat School of Civil Engineering, College of Engineering, University of Tehran, Enqelab Ave., Tehran, Iran
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reinforcement and concrete. However, there are many old standing reinforced concrete buildings in the world today. They were constructed based on this now antiquated style and are in need of structural seismic rehabilitation according to the requirements of present day seismic rehabilitation codes. Moreover, the old practice of reinforcement detailing usually seems strange to present day engineers; e.g. the application of 180◦ hooks at the cut locations and splices of smooth bars. The major issue associated with the applicat
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