STRENGTHENING JOINTS OF RC FRAMES WITH STIFFENED STEEL PLATES

In this paper, stiffened steel plates are used as a practical repair and strengthening scheme for damaged 3D, RC beam-column joints. The objective of the proposed scheme is to enhance damaged joint seismic performance by means of enlarging the joint area and relocating the plastic hinge away from the damaged region. In this scheme, the joint is strengthened by installing stiffened steel plates at the corners of the beam–column joint, both above and below the beam. This retrofitting scheme is relatively simple to implement and unlike many other proposed retrofitting techniques does not need cutting through the slab except for some small holes to pass the connecting bars through. A full scale external beam-column joint is designed and constructed as an ordinary moment resisting frame. The structure is then subjected to progressive quasi-static cyclic loading to failure. The damaged joint is then repaired to its former configuration using pressurized epoxy resin, then retrofitted by stiffened steel plates. The repaired and retrofitted joint was subjected to the same cyclic loading protocol to failure. Seismic performance parameters such as strength, stiffness, ductility and energy dissipation capacity of the original joint and the repaired and retrofitted joint are then extracted from their capacity backbone curves and compared. Results show that the proposed repair and retrofit technique not only regenerated the original capacity but also increased capacity and improved the joint performance by relocating the plastic hinge beyond the repaired region.

Keywords:

Seismic retrofitting , Beam-column joint , RC structures , Stiffened steel plates