E5.2 Basis of Design
ASCE/SEI 7 (ASCE, 2022) includes two types of cantilever column systems: ordinary and special. The ordinary cantilever column system (OCCS) is intended to provide a minimal level of inelastic rotation capability at the base of the column. This system is permitted in seismic design categories B and C only and to heights not exceeding 35 ft (11 m). A low seismic response modification coefficient, , of 1.25 is assigned due to the system's limited inelastic capacity and lack of redundancy. The OCCS has no requirements beyond those in the Specification, except as noted in Sections E5.4a and E5.6.
E5.4 System Requirements
E5.4a Columns
The required axial strength of columns in these systems under the load combinations including the overstrength seismic load is limited to 15% of the axial yield strength. Because axial load can negatively impact the inelastic rotation capacity in columns, this requirement is to ensure that cantilever columns can still develop plastic hinges similar to flexural members.
E5.4b Stability Bracing of Columns
Bracing at the top of the column or along the length of the column is not required to accommodate the expected inelastic rotation of the columns.
E5.6 Connections
In OCCS, the column base must be capable of developing the moment capacity of the column, including overstrength and strain hardening. Detailed requirements are provided in Section D2.6 and are discussed in the corresponding commentary section.