What Is a Cantilevered Column System?
A cantilevered column system is a lateral-force-resisting system where individual columns, fixed at their bases, bend like vertical cantilevers to resist wind and seismic loads — no beams, braces, or walls needed. It is the simplest lateral system in the code and the weakest: strictly limited in height and seismic application because a single column has little redundancy and limited ductility. Typical uses: carports, shade structures, and small industrial canopies.
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How it works
Lateral load pushes the top of the column; the fixed base resists the overturning moment. The column must be designed for the full moment at the base plus P-delta effects (the axial load acting on the deflected shape amplifies the moment). Base fixity is everything — a 'fixed' base on an undersized footing rotates, and the system fails. The footing is typically much larger than gravity alone would require.
Code limits
ASCE 7 restricts cantilevered column systems to low seismic design categories and limited heights (ordinary systems capped around 35 feet, with tighter limits in higher categories). Special steel cantilevered columns get slightly more height. The R-factor is low (1.5-2.5), meaning design forces are high relative to more ductile systems. These limits exist because the system's failure mode — a plastic hinge at the column base — has no backup.
Design and detailing
The engineer designs the column for combined axial and bending with deflection limits that keep P-delta manageable, sizes the footing for the overturning moment (often with a factor of safety against uplift and soil bearing), and details the base connection for true fixity (embedded columns, base plates with multiple anchor bolts designed for the moment). In wood construction, the post-to-footing connection achieving fixity needs careful hardware selection — most post bases are pinned, not fixed.
The bottom line
Cantilevered columns resist lateral loads by base fixity alone — simple but strictly height- and seismic-limited. Size footings for overturning, detail true base fixity, and verify the application is within code limits.
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