Concrete · Special elements

Corbel (strut-and-tie) calculator

Single strut-and-tie model: tie force including horizontal restraint, tie steel, strut angle and strut stress with βs.

Standard: AS 3600 Ch 7 (strut-and-tie), Cl 12.? corbel detailing (simplified)

Inputs in the worked example

The live calculator starts with these values; change any of them and every result, check and diagram updates instantly.

Input	Value	Unit
Vertical load V*	400	kN
Horizontal restraint (≥ 0.2V)	80	kN
Load to column face av	200	mm
Effective depth at face	500	mm
Corbel width	400	mm
Bearing plate width (strut width basis)	150	mm
f′c	N40	MPa
fsy	500	MPa
Tie steel provided	1200	mm²

Result	Value	Unit
Lever arm ≈ 0.8 d	400.0	mm
Strut angle atan(z/av)	63.43	°
Tie force V av/z + H	280.0	kN
Tie steel T/(0.8 fsy)	700.0	mm²
Strut force V/sin θ	447.2	kN
βs = 1/(1 + 0.66 cot²θ) (0.3 … 1.0)	0.858
φ strut capacity 0.6·βs·0.9f′c·b·wb sinθ	995.0	kN

Diagram for the worked example

Lever arm ≈ 0.8 d = 0.8*500 = 400 mm
Strut angle atan(z/av) = DEGREES(ATAN(400/200)) = 63.435 °
Tie force V av/z + H = 400*200/400+80 = 280 kN
Tie steel T/(0.8 fsy) = 280*1000/(0.8*500) = 700 mm²
Strut force V/sin θ = 400/SIN(RADIANS(63.435)) = 447.21 kN
βs = 1/(1 + 0.66 cot²θ) (0.3 … 1.0) = MIN(1,MAX(0.3,1/(1+0.66/TAN(RADIANS(63.435))^2))) = 0.85837
φ strut capacity 0.6·βs·0.9f′c·b·wb sinθ = 0.6*0.85837*0.9*40*400*150*SIN(RADIANS(63.435))/1000 = 995 kN

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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.