In CHBDC, there are two methods available, as specified in CHBDC Art. 8.9.3.6: simplified and Art. 8.9.3.7 General method. The simplified method uses β and θ, as specified in Art. 8.9.3.6 namely θ = 42 and β as per one of the following conditions:
- For sections with at least the minimum amount of transverse reinforcement required by Clause 8.9.1.3, β shall equal 0.18.
- For sections containing no transverse reinforcement located in footings where the distance from the point of zero shear to the face of the column, pedestal, or wall is less than 3dv , β shall equal 0.18.
- For other sections not containing transverse reinforcement but having a specified nominal maximum size of coarse aggregate not less than 20 mm, β shall equal 230/(1000 + dv ).
The general method computes β and θ, as specified in CHBDC 8.9.3.7.
For shear and torsion calculations, the effective shear depth, dv, is taken as the greater of .72h or 0.9d, where d is distance taken as distance from extreme compression fiber to the centroid of longitudinal tension reinforcement in the half depth of the section containing flexural tension zone.
where
| de | = | distance from extreme compression fiber to center of tensile reinforcement |
| h | = | height of beam |
| a | = | depth of concrete rectangular fiber computed as follows |
where
| As | = | area of tension reinforcement |
| fy | = | yield strength of reinforcement |
| f'c | = | compression strength of concrete |
| b | = | width of member |
Note: The effective steel area at each section is used to compute
a.
The maximum spacing is based on Art. 5.8.2.7. Th program reports the additional required effective steel (Alx). This already accounts for excess effective steel present at that section, which is more than the required flexural.
Beam properties for torsion (Aoh and ph) consider the stirrup size, specified or chosen for Auto Design. For the calculation of Aoh, the program uses the rebar clear cover for sides to be equal to the value specified on A/D parameters dialog for cap side cover. Computed Avs/s is the required steel for shear only, 2Ats/s is the required steel for two legs of torsion, and Av/s is the total computed steel due to shear and torsion at that section. When torsion is present at a section, the program also calculates longitudinal steel.
