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Concrete Column Design

The scope of this calculation module is to analyse and design a concrete column section for the given axial load, biaxial moment and shear force. Axial load can be either tensile or compressive in nature. The section can be designed using rectangular or circular geometry and also as a short or slender type where, the additional moment due to slenderness will be calculated by the program.

Standards: British.

Slenderness Moment

ECPLUS DESIGN adopts biaxial interaction curve for design of column:

Deflection of column,
au = βa * K * h
βa = 1 / 2000 * (le / b')2

Reduction factor,
K = (Nuz - N) / (Nuz - Nbal) ≤ 1

Additional moment,
Madd = N * au

Features

  • The module adopts a superior biaxial neutral axis search algorithm for safe and economical design of the section.
  • The column can be analysed and designed using one of the following options:
  • Check reinforcement adequacy
  • The moment capacity interaction ratio and shear reinforcement spacing is checked by the calculation module.
  • Find required reinforcement
  • The area for reinforcement required for design moment and shear is computed by the calculation module.
  • Additionally, the program provides an option to the user to distribute the main bars as:
  • Equally distributed
  • Proportionately distributed
  • The column slenderness check is analysed via two options:
  • Short column
  • The calculation module ignores the slenderness effect thus, considering the section as a short column.
  • Long column
  • The module checks the slenderness effect based on the fixity conditions defined and computes the additional moment due to slenderness.
  • The design module also provides an option to check the moment due to minimum eccentricity.
  • User is allowed to specify the column section reinforcement with additional bars for both width as well as depth side.

Design Considerations

  • Ultimate axial load, moment and shear shall be specified for the analysis and design of the section.
  • Effective height of the column is computed based on the fixity condition of the section at top and bottom.
  • The section is analysed and designed independently at three different positions of column height (top, bottom and middle).
  • Section design moment is considered by comparing the moments in the section height (initial moment, minimum eccentricity moment and slenderness moment), at respective directions.
  • For circular sections, resultant moment and shear is considered for the design.
  • For shear check, half of the corner bar area is considered for the effective tension steel consideration.
  • For reinforcement adequacy check, the program provides the moment capacity ratio and shear reinforcement spacing for the design moment and shear.

National Standards Available

British Standard

References

  • BS 8110-1:1997 - Structural use of concrete - Part 1: Code of practice for design and construction.

Revision

  • Ver 1.0 - Original version