Shear Strength of Shear-Controlled Columns under Cyclic Loading

Code-based design equations for estimating the shear strength of new and existing reinforced concrete (RC) columns do not account for the nature and rate of cyclic loading, even though columns in earthquake-prone areas are subjected to cyclic load reversals during earthquakes. The influence of initial loading cycles on the strength of shear-controlled columns is investigated in this study using data on 498 RC column specimens compiled by ACI Committee 369. It is observed that the number of initial loading cycles does not evidently affect the shear strength of the columns. This study also evaluates the shear strength limits prescribed by ACI design codes. For more than 90% of the shear-controlled column specimens examined, the measured shear strength was found to be within one to two times the shear strength calculated ACI 318-19.