Structural design for large seismic events must explicitly consider the effects of response beyond the elastic range.
Structural design for large seismic events must explicitly consider the effects of response beyond the elastic range. The moment resisting seismic frame is designed to form beam plastic hinges near the face of the column. After the discovery of brittle fractures in steel moment frame welded connections in the 1994 Northridge earthquake in California, the reduced beam section (RBS) moment connection was developed and is now extensively used throughout North America and other parts of the world. The intent of the RBS is to move the plastic hinge region away from the face of the column (figure 2). This is accomplished by reducing the beam’s actual plastic moment by removing part of the beam flange as shown in figure 1. This reduced section creates a weaker location where yielding and plastic hinge formation is expected to occur, and results in a reduced moment that develops at the face of the column. By reducing moment demands at the column face the beam-column connections and the column panel zone requirements are reduced. Further more, the use of RBS may also lead to smaller column sizes.