Flexural capacity by strain compatibility with the rectangular stress block — rectangular or T-section, optional compression steel, variable φ per 5.5.4.2 — plus the required steel for a target moment, the 5.6.3.3 minimum-reinforcement check, and simplified-method shear (β = 2, θ = 45°) with stirrup spacing limits.
d = h − bar-centroid offset. For a T-section, take be from the effective flange width rules of 4.6.2.6 — it is an input here, not a computed value.
Bars are placed automatically: side/bottom clear cover + stirrup + half-bar, clear spacing ≥ max(1.5db, 38 mm) per 5.10.3.1.1. When a row fills up, the next bars stack into a second layer with ≥ max(25 mm, db) clear between layers — and d is recomputed from the real bar centroid, layer by layer.
Two habits keep this check honest. First, watch εt, not just the pass/fail: a section that only clears demand in the transition zone (φ sliding below 0.9) is telling you it wants more depth or compression steel — tension-controlled behaviour is a ductility statement, not a formality. Second, the simplified shear method (β = 2, θ = 45°) is deliberately conservative for members with decent longitudinal steel; if shear is the thing failing by a whisker, the general MCFT procedure of 5.7.3.4.2 often finds another 10–20% legitimately. The T-section flange width is an input here because 4.6.2.6 owns that decision — centre-to-centre spacing usually governs on multi-girder decks. What this screen leaves out on purpose: torsion, interface shear at composite joints, crack-control spacing under Service I, and deflections — the last two frequently size the member before strength does on shallow bridge caps.