Seismic Behavior of Reinforced Concrete Beam-Column Subassemblages Reinforced with Multiple Composite Central Reinforcements

Three RC beam-column subassemblages, in which the concrete columns were reinforced by multiple composite central reinforcements and multiple-steel stirrups, were tested under reversed cyclic loading. The test results show that the increase in axial compression ratio (increased from 0.2 to 0.35) had little effect on the energy dissipation, but increased the peak load by 60.5% and decreased the ultimate deformation by 34.4%. The increase in shear span ratio of the column (increased from 2.6 to 3.7) improved the energy dissipation and deformation capacity, but decreased the peak load by 17.6%. In addition, the stress-strain relationships of the concrete confined by multiple stirrups were represented by functions with different levels of confinement, and an equivalent coefficient was proposed to simplify the computation. Finally, the analytical methods to predict the yielding response and deformation constitution of the specimen were developed.