SHEAR STRENGTH OF BEAM-COLUMN JOINTS UNDER SEISMIC LOADING – FIBER EFFECTIVENESS

International Codes, to avoid collapse of the reinforce concrete (RC) structures under seismic loads, recommend a high transverse reinforcement percentage into the joint, to guarantee a sufficient shear resistance. Practical application are often restrained because of the cost of steel and installation, and because of the difficulties due to the steel congestion into the joint core. Tests results reported by other authors from 1977 have illustrated that when fiber reinforced concrete (FRC) is used in the beam-column region, there is an increase in the joints shear capacity, ductility, bond between steel and concrete, and energy-dissipation capacities. This indicates that a reduction of the transverse reinforcement percentage could be obtain by increasing the hoop spacing, and by compensating the required shear strength by fibers in the reinforced concrete. In this paper it will be considered if fiber shear resisting contribution can be correlate to the stirrup one, or to the concrete one, or both. Hence an expression for calculating the shear strength of FRC beam-column joints with stirrups will be obtained. From the comparison on the experimental studies done by other researchers on RC and FRC beam-column joints, the reliability of the proposed expression will be evaluated.