Blue Book Article 4.02.031
Cantilever column systems are defined in ASCE 7-05 as “a seismic force-resisting system in which lateral forces are resisted entirelyby columns acting as cantilevers from the base.” The code does not explicitly acknowledge the fact that many applications of cantilever columns elements are within mixed systems, especially in light-frame construction. A strict reading of the code indicates that a structural system where lateral forces are only partially resisted by columns acting as cantilevers from the base is not technically a Cantilever Column System. However, in general the provisions for Cantilever Column Systems can be applied to cantilever columns elements in mixed systems, since it will lead to conservative results regarding system strength. One caution however is that the system strength provided by the Cantilever Column System provisions may lead to stiffness incompatibilities with surrounding elements of the lateral force-resisting system. Therefore, in mixed systems, designers should consider introducing a ductile grade beam to the base of the column and perform a stiffness analysis to ensure deformation compatibility with the other surrounding lateral force-resisting elements.