Behaviour of steel reduced beam web (RBW) connections with drilled voids

The 1994 Northridge earthquake caused widespread damage to moment-resisting frames. Various brittle fractures were found in beam-to-column welded moment connections. This prompted the initiation of new research programs to investigate the causes of these fractures and to propose the necessary changes in design procedures. In recent years a variety of approaches have been proposed by researchers to improve the ductility of post-Northridge connections. The improvements are mainly based on reinforcing the connection or weakening of the beam end. These methods are intended to force the plastic hinge to form away from the face of the column, to avoid premature fractures at this region. Providing circular voids at vicinity of the beam end is one of the solutions to reach adequate ductility in post-Northridge connections in the case of using deep beams. However, in this method the presence of circular void causes a significant reduction in the beam shear capacity and initial rotational stiffness of the beam. Hence, in this study to prevent the detrimental effects of big voids, a number of drilled voids are created in the beam web. A parametric study has been done to find out the best configuration of these voids. Finite element results have shown the adequacy of this method to increase the connection ductility without significant reduction in the connection strength. This type of modification can be easily applied to existing buildings with no need to break of the concrete slab as it is the case for reduced beam section (RBS) connections.

Keywords:

Ductility , Plastic hinges , Post-Northridge connection , Reduced beam web , Strength