Seismic behavior of beam-column joints with different concrete compressive strengths

This study experimentally evaluated the seismic performance of beam-column joints with different compressive strengths. A total of three exterior beam-column joints were fabricated and tested under reversed cyclic loading. The primary test parameter was the ratio of the concrete compressive strengths of the column and beam. The crack patterns and failure mechanisms, load-displacement relationships, envelope curves, stiffness degradation, energy dissipation, behavior of longitudinal reinforcement in the beam, and transverse reinforcement in the joint were analyzed in detail. Experimental results revealed that the overall seismic performance of the beam-column joint was improved as the compressive strength of the concrete in the column increased. In particular, the specimens with the column-to-beam concrete compressive strength ratios of 2.3 and 3.2 showed over 9% greater joint shear strengths than the one with a monolithic joint. However, the strains of transverse reinforcement in the joint also increased with a high ratio of the concrete compressive strengths of the column and beam. Therefore, when the compressive strength of the column concrete is greater than that of the beam concrete, it is recommended that additional transverse reinforcements be incorporated in the joint region.