SBO formulations¶

What the program calculates, with which assumptions and within which range of validity.

This section applies in full to SBX, which shares the same core — it only adds section optimisation.

The calculation chain¶

Materials — fck, fyk, Es and the partial factors define fcd, fyd and the stress-block parameters

Simple bending — longitudinal reinforcement consumes: materials, geometry and Mk

Shear and torsion — transverse reinforcement consumes: materials, geometry, Vk and Tk

Strut interaction — the criterion that can fail the section consumes: shear and torsion together

Detailing — bar sizes, number of bars, provided As consumes: the calculated reinforcement

Moment-curvature — stiffness and ductility consumes: geometry and provided reinforcement

Simple bending

Rectangular and T sections, tension-only and compression reinforcement, the parabola-rectangle diagram parameters and the minimum reinforcement.
Shear and torsion

Model I, equivalent hollow section and the interaction check — the point at which the two compete for the same strut.
Moment-curvature

The non-linear analysis with the real constitutive relationship, and what it shows about stiffness and ductility.

Each one ends with the limits of validity, in its own coloured block:

Range of application

It delimits where the method holds. Read it as part of the result, not as a footnote.