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The effective depth of cross-section is usually defined as distance of the most compressive fibre of concrete to centre of gravity of tensile reinforcement. In SCIA Engineer, the effective depth of cross-section is defined as distance the most compressive fibre of concrete to position resultant of forces in tensile reinforcement. There is calculated in SCIA Engineer the perpendicular projection of this distance to straight line perpendicular to neutral axis (slope line plane of equilibrium), called drec. The problem is how to calculate this distance if the difference between direction of resultant of bending moment and resultant of shear force is significant. In this case the effective depth for shear is calculated, than perpendicular projection of this distance is calculated from bending load to direction of shear force resultant. There are some exceptional cases when effective depth is not calculated from plane of equilibrium:
In this cases, the effective depth is calculated according to formula
d = Coeffd ∙ hl ∙ cos(|αV - αM|)2
The effective depth d calculated from plane of equilibrium or from formula above is compared with the minimal allowed effective depth. It can occur when cos(|αV - αM|)2 is lower than 0,5 (the distance between angle αM and αV is greater than 45 °). In that case is the effective depth calculated according formula
d = Coeffmin ∙ Coeffd ∙ hl
where
| hl |
The height of cross-section in the direction of shear forces resultant |
| Coeffd | The coefficient for calculation effective depth of cross-section, see "Coefficient for calculation of effective depth of cross-section" |
| Coeffmin | The coefficient for minimal effective depth of cross-section, set to 0,5 |
| αV | The angle between direction of shear resultant and y-axis of cross-section |
| αM | The angle of slope line plane of equilibrium |
