Input
Lever arm to tie centroid (≈0.9·d).
Results
Aspect ℓn/h (deep if ≤4)—
Strut angle θ—
Reaction at support R—
Strut force Cs—
Tie tension T—
Required tie As—
ϕ·Fns (strut capacity)—
ϕ·Fnn (node capacity)—
Method
Symmetric load at midspan — reactions R = Pu/2. Strut runs from support to load with vertical jd and horizontal ℓn/2. tan θ = jd / (ℓn/2). Strut force Cs = R / sin θ; tie T = R·cot θ = R · (ℓn/2)/jd. Strut/node strengths: ϕ·fce·Astrut where fce = 0.85·βs·f'c (strut) or 0.85·βn·f'c (node), ϕ = 0.75. Tie steel As ≥ T / (ϕ·fy).