# Design procedure for column with Biaxial moments

A column is a special case of a compression member that is vertical. A reinforced concrete column is basically a vertical structural member, which helps to transfer the load from top to bottom in a framed structure. Specifically, columns transfer the compressive load from the top floor to foundations.

The design procedure for the design of columns subjected to factored axial load Pu and biaxial moments Mux and Muy consists of the following steps:

1. Assume cross-sectional dimensions and the area of steel and its distribution.
2. Compute concentric load capacity Pnz as per the below equation. $$P_{nz} = 0.45 f_{ck} A_c + 0.75 f_y A_{sc}$$ and Pu/Pnz. Use chart 63 of SP 16 to evaluate the value of Pnz.
3. Determine the uniaxial capacities Mnx and Mny of the section combined with the given axial load Pu , with the use of interaction curves for axial load and uniaxial moment.
4. Determine the adequacy of the column section using the below equations $$(\frac{M_{ux}}{M_{nx}})^{\alpha} + (\frac{M_{uy}}{M_{ny}})^{\alpha} <= 1$$ $$\alpha = \frac{2}{3} + \frac{5}{3}\frac{P_{u}}{P_{nz}} for \, 0.2 < \frac{P_{u}}{P_{nz}} < 0.8$$
5. When the above equation’s value is greater than 1.0. The selected section is unsafe. When it is much lower than 1.0, the section is not economical. In such cases, the section should be modified, and steps 1-4 are to be repeated again until the resulting value of equation is nearly equal to 1.0.

Check this post to read about the detailing specification for a column section.

## Column design

• RCC Column Design is a free app for designing reinforced concrete columns as per Indian Standards.
• RCC Design and detailing could be performed for uniaxial and biaxial bending conditions specified in IS456:2000
• Option to save the design projects in local storage.
• Detailed calculation steps presented for verification and validation.