Design Principles
Columns are designed for axial force and bi-axial end moments, as well as bi-axial shear. Torsion moments are not included. Reinforcement is designed by the program based on the forces generated in the Analysis mode and the code clauses outlined below.
All selected load combinations are used to calculate the required reinforcement. The combination which produces the maximum required reinforcement area is called the "Guiding Load Case", and the bar arrangement is chosen based on that combination. Detailed printout of the design calculations is also for that combination.
The main reinforcing bars may be modified to allow for other bars passing through the section and then re-checked to ensure that the design requirements are satisfied.
Design Moments
For each load combination (and skip pattern) the program uses the largest of the end moments about each axis to design the column. Where the column is required per code to be designed as a biaxial column the final design moment is calculated per 3.8.4.5. Also, where a column is slender the moments considered for the design are potentially increased according to the requirements of 3.8.3. Note that these modified moments are the magnitudes that will display in the view update list box for the particular load combination and may not therefore be equal in magnitude to the applied forces.
Load Capacity Ratio
For each column, for each load combination (and skip pattern if live load) the program calculates a single load capacity ratio. This capacity ratio is based on the largest of the design moment divided by the moment capacity of the cross section (which includes the affect of axial load on the section) and the axial force divided by the pure axial column capacity.
Code Clauses Implemented
| Clause | Description | Note |
|---|---|---|
| 3.8.1 | General | Program Conforms |
| 3.8.1.1 | Symbols | Program Conforms |
| 3.8.1.2 | Size of columns | N/A |
| 3.8.1.3 | Short and slender columns | Program Conforms |
| 3.8.1.4 | Plain concrete columns | N/A |
| 3.8.1.5 | Braced and unbraced columns | Program Conforms |
| 3.8.1.6 Effective height of a column | ||
| 3.8.1.6.1 | General | Program Conforms with Beta as a user input |
| 3.8.1.6.2 | End conditions | Program Conforms with Beta as a user input |
| 3.8.1.7 | Slenderness limits for columns | Program conforms |
| 3.8.1.8 | Slenderness of unbraced columns | Program conforms |
| 3.8.2 Moments and forces in columns | ||
| 3.8.2.1 | Columns in monolithic frames designed to resist lateral forces | User decision |
| 3.8.2.2 | Additional forces induced by deflection at ULS | Program Conforms for column being designed, not for members connected |
| 3.8.2.3 | Columns in column and beam construction or in monolithic braced structural frames | Forces to be designed for are determined by the users own model. |
| 3.8.2.4 | Minimum eccentricity | Program conforms |
| 3.8.3 Deflection induced moments in solid slender column | ||
| 3.8.3.1 | Design | |
| 3.8.3.2 | Design moments in braced columns bent about a single axis | Program Conforms |
| 3.8.3.3 | Slender columns bend about a single axis( major or minor) | Program Conforms |
| 3.8.3.4 | Columns where le/h exceeds 29, bent about their major axis | Program Conforms |
| 3.8.3.5 | Columns bent about their major axis | Program Conforms |
| 3.8.3.6 | Slender columns bent about both axes | Program Conforms |
| 3.8.3.7 | Unbraced structures | Program Conforms |
| 3.8.3.8 | Deflection of unbraced column | N/A |
| 3.8.3.9 | Additional moments on members attached to a slender column | N/A |
| 3.8.4 Design of column section for ULS | ||
| 3.8.4.1 | Analysis of sections | Program Conforms |
| 3.8.4.2 | Design charts for symmetrically-reinforced columns | N/A |
| 3.8.4.3 | Nominal eccentricity of short columns resisting moments and axial loads | N/A |
| 3.8.4.4 | Short braced columns supporting an approximately symmetrical arrangement of beams | N/A |
| 3.8.4.5 | Biaxial bending | Program Conforms |
| 3.8.4.6 | Shear in columns | Program Conforms |
| 3.8.5 | Deflection of columns | N/A |
| 3.8.6 | Crack control in columns | The clause states that "if crack check is required, then the member should be checked as a beam" |
N/A is to be interpreted as either not application or not implemented. Clauses that do not appear in the list are deemed not to be considered by the program.