Lateral response evaluation of old type reinforced concrete columns with smooth bars

Currently, the seismic assessment of old reinforced concrete (RC) construction in the case of the internal reinforcement of smooth bars, as well as the decision regarding convenient rehabilitation strategies, are of major interest throughout the seismically active areas of the world. The lateral response evaluation of old type RC columns that have smooth (plain) bars is the focus of this study. The results of three monotonic tests on columns, which have been performed under two different experimental setups in two different university laboratories, are presented. Through analysis of test observations and experimental results, this paper aims at investigating the lateral behavioral aspects of RC columns with smooth bars. A new formulation is derived for predicting base shear strength in RC columns with smooth bars, considering quasirocking mode of deflections imposed by high levels of base rotations; furthermore, a new macro model for predicting the related lateral force-deflection response is consequently proposed. Finally, the macro model results are compared with the results of two types of fiber element methods. The macro model allows for prediction of the main characteristics of the response as well as simulating a real internal shear resistance mechanism accompanied with the formation of a compression strut inside the column body as a consequence of a quasi-rocking mode of deflections.