Seismic Performance of Concrete Columns Reinforced with Hot-Rolled Thermo-mechanically Treated Steel Bars

The details of experimental testing of full-scale reinforced concrete columns are presented in this paper. The columns were reinforced with hot-rolled thermo-mechanically treated bars with uncertain yield strength which influences (particularly) the splice length demand and column response to seismic loads. The testing was carried out using quasi-static cyclic or monotonic loading under a constant axial load to study the seismic behaviour of the columns. The parameters of the study included lap splices, cold joints and lateral load scenarios. The damage concentration was higher close to the end of the dowel bar (as opposed to the column base) for the lap-spliced columns subjected to cyclic loading due to larger slippage in the dowel bars. Conversely, the damage was the least in a similar column subjected to monotonic loading which also exhibited the largest lateral load capacity and highest ductility. The influence of shear distortion was insignificant on the column free-end deflection. The pre-peak stiffness and lateral load capacity were less for the lap spliced columns tested under cyclic loading as a result of deficient development length due to unintended increase in the rebar yield strength. The lateral load capacity of the column was uninfluenced by the cold joint at the column base although it reduced the column ductility by nearly 25% compared to a similar column without a cold joint.