RC and FRC Beam-Column Joints under Seismic Loading Shear Strength

To ensure the structural integrity of a building during earthquake, the structural elements must be able to dissipate enormous amounts of energy to prevent the building from collapsing. One of the most critical areas of a framed structure is the beam-column joint region, where failure is often initiated because of high shearing forces. Reinforced Concrete (RC) beam-column joints are currently designed to withstanding large shearing forces by decreasing the spacing of the joint stirrups, to have a high percentage of transverse reinforcement in the joint core. However, with a reduced spacing of the joint hoops, the concrete may not flow properly around the reinforcing bars during construction, causing steel congestion and also construction difficulties. A lot of researches 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. On the basis of the studies previously conducted by the author on beam-column joints, it is here proposed a formula simpler than the previous one that predicts the shear strength of RC and FRC beam-column joints. The shear strength values obtained with this formula have been compared to those derived by the experimental tests. It has been found that the here proposed expression, even if very simple is able to give an accurate and uniform prediction of the shear resistance, has it properly estimates the tests results.