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⚠️ Short Column Killer

Someone builds a partial-height infill wall against your column after the structural drawings are done. Nothing on paper changes. But the clear height collapses, and the shear needed to develop the same flexural capacity rises as 1/Lₙ — until the column snaps in brittle shear before it can ever form a ductile hinge. Slide the infill up and find the height where your column dies.

The Infill Wall

Remaining clear height L_n 3000 mm

Full storey height is 3000 mm. Dragging left simulates a taller infill wall restraining more of the column.

Your Column

Flexural capacity M_p (each end) 200 kNm

Stirrup spacing s 100 mm

Axial load N_d 0 kN

Live Result

—

Shear demand V_e = 2M_p/L_n—

Shear capacity V_r—

Utilization V_e/V_r—

Critical clear height—

Shear span ratio L_n/2d—

Powered by capacity-design shear against TS 500 / TBDY-style shear capacity (engine/short-column.js). Verified before publishing: halving the clear height is confirmed to exactly double the shear demand, the critical clear length is round-trip verified (evaluating the demand at L_n,crit returns exactly V_r), and the ductile-to-brittle transition is confirmed to occur precisely at that length. The axial enhancement of V_c is applied but capped at 1.5 — an uncapped enhancement would be unconservative at high axial load, where behaviour is actually more brittle.

Method

Capacity designV_e = (M_p,top + M_p,bot)/L_n — the 1/L_n dependence is the entire short-column problem.

TS 500 / TBDY 2018V_r = V_c + V_s; TBDY 2018 addresses the "kısa kolon" condition explicitly — partial-height infills must be isolated from the frame or designed for.

Scope: single column, symmetric double-curvature, monotonic capacity-design shear. Does not model infill-frame interaction forces, bidirectional loading, or the cyclic degradation of V_c under load reversals — which in reality reduces the concrete contribution substantially, making the real situation worse than shown here.

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