Home / Reinforced Concrete / Column pre-sizing C · v1.0

TS 500 Column Pre-Sizing (Axial, Square Section)

Estimates the square column depth needed to carry a factored axial load at a target reinforcement ratio, ignoring moment and buckling. For concept/pre-design only — always follow with a full P-M interaction check.

Inputs

Factored axial load N_ud kN

Column width b (assume square: h will be found) mm

Target reinforcement ratio ρ %

Concrete f_ck MPa

Steel f_yk MPa

Results

Required depth h—

Total steel area A_st—

Round-trip check: N₀ at this section—

This tool solves the axial-capacity equation algebraically for h, then calls the same tested columnAxialCapacity() function forward with the result — the "round-trip" N₀ above should equal your input N_ud almost exactly. No new formula is introduced; this is the same equation used (and verified) elsewhere on this platform, applied in reverse.

Citations

TS 500N₀ = 0.85·fcd·b·h + fyd·Ast (pure axial capacity, no eccentricity/buckling). Solved for h given a target ρ = Ast/(b·h).

VERIFYEngine: engine/rc-tr.js columnAxialCapacity(), exact-match tested in tests/rc-tr.test.js.

Engine: rc-tr.js · Code pack: TR-TS500-2000.v1 ·

Pre-design tool only — pure axial capacity, no moment/buckling/slenderness check. A final column must be verified with a full P-M interaction analysis (see the Column Interaction Curve tool) before use in construction documents.