Seismic Strengthening of Beam-Column Joints with Steel Bars

It is well-known that beam-column connections are subjected to high stresses during earthquakes. Therefore, design of these connections play an important role in designing an earthquake resistant structure. Stirrup spacing on beam-column connections should be smaller in order allow for safety in carrying the stresses. Since the placement of ties required by the code in this region is rather difficult, this condition is fulfilled with difficulty. As a result of this difficulty, beam-column joints are in a very unfavorable state in terms of seismic behavior. In a beam-column connection which has no sufficient shear reinforcement, it is thought that additional reinforcement which is arranged by placing steel bars into inclined holes drilled from outside and anchored by epoxy can carry principal tensile stresses on beam-column connections. This experimental study was carried out at the METU Structural Mechanics Laboratory by using T-shaped test specimens reflecting an exterior joint region of a frame having normal dimensions to a scale of 2/3. In total, eleven elements were tested, four of which are reference specimens, while the others are strengthened at their joint regions with diagonal steel bars.