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D. ACI 318 - 99 Column Design Principles

The ACI Column Design Brief is for prismatic, rectangular solid or circular shaped members. Members may be built up from multiple elements, but only the member end moments are considered, so only single height columns are recommended.

Design Principles

Columns are designed for axial force and biaxial end moments, as well as biaxial shear.  Torsional moments are also included if specified in the design brief.  Reinforcement is provided by the program based on the forces generated in the Analysis mode and the code clauses outlined below.

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.

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.

Code Clauses Implemented

The following lists the code clauses used from ACI 318-99.

Chapter 3 - Materials

  • 2.1
  • 3.3.2.(a)
  • 3.3.2.(c)

Chapter 7 - Details of Reinforcement

  • 7.1.1
  • 7.1.2
  • 7.1.3.(a)
  • 7.1.3.(b)
  • 7.2.1
  • 7.2.2
  • 7.6.1
  • 7.6.2
  • 7.6.3
  • 7.6.6.1
  • 7.6.6.2
  • 7.6.6.3
  • 7.6.6.4
  • 7.6.6.5
  • 7.10.4.1 - 9
  • 7.10.5.1 - 5
  • 7.10.5.1
  • 7.10.5.3
  • 7.11.1
  • 7.11.2

Chapter 8 - Analysis and Design - General Considerations

  • 8.5.1
  • 8.5.2
  • 8.10.2
  • 8.10.3
  • 8.10.4

Chapter 9 - Strength and Serviceability Requirements

  • 9.1.1
  • 9.3.1
  • 9.3.2.1
  • 9.3.2.2
  • 9.3.2.3
  • 9.3.3
  • 9.4
  • 9.5.2.1

Chapter 10 - Flexure and Axial Loads

  • 10.2.2 but not deep flexural members
  • 10.2.3
  • 10.2.4
  • 10.2.5
  • 10.2.6 parabolic stress block assumed except for T and L-sections
  • 10.2.7 for T and L-sections only
  • 10.3.1
  • 10.3.2
  • 10.3.3
  • 10.3.4
  • 10.3.5
  • 10.3.6
  • 10.4.1
  • 10.5.1
  • 10.5.2
  • 10.5.3
  • 10.6.3
  • 10.6.4
  • 10.6.7
  • 10.8
  • 10.9.1
  • 10.9.2
  • 10.9.3
  • 10.10.2
  • 10.11.1
  • 10.11.2 r always computed
  • 10.11.4
  • 10.11.5
  • 10.11.6
  • 10.12.1 k controlled by brief
  • 10.12.2
  • 10.12.3
  • 10.12.3.1
  • 10.12.3.2
  • 10.13.1
  • 10.13.2
  • 10.13.3
  • 10.13.4.2
  • 10.13.5

Chapter 11 Shear and Torsion

  • 11.1.1
  • 11.1.2
  • 11.1.2.1
  • 11.1.3.1
  • 11.2.1.1
  • 11.2.1.2
  • 11.3.1.1
  • 11.3.1.2
  • 11.3.2.2
  • 11.3.2.3
  • 11.5.2
  • 11.5.3
  • 11.5.4.1
  • 11.5.4.3
  • 11.5.5.1 minimum shear rft always provided
  • 11.5.5.2
  • 11.5.6.1
  • 11.5.6.2
  • 11.5.6.8
  • 11.6.1
  • 11.6.2.1
  • 11.6.2.4
  • 11.6.3.1
  • 11.6.3.4
  • 11.6.3.5
  • 11.6.3.6
  • 11.6.3.7
  • 11.6.3.8
  • 11.6.3.9
  • 11.6.4.3
  • 11.6.5.1
  • 11.6.5.2
  • 11.6.5.3
  • 11.6.6.1
  • 11.6.6.2
  • 11.6.6.3

Chapter 12 - Development and Splices for Reinforcement.

  • 12.1.1
  • 12.1.2
  • 12.2.2
  • 12.2.3
  • 12.2.4
  • 12.2.5
  • 12.3.1
  • 12.3.2
  • 12.3.3
  • 12.3.3.1
  • 12.3.3.2
  • 12.4.1
  • 12.4.2
  • 12.5.1
  • 12.5.2
  • 12.5.3
  • 12.5.3.1
  • 12.5.3.2
  • 12.5.3.3
  • 12.5.3.4
  • 12.5.3.5
  • 12.5.3.6
  • 12.5.4
  • 12.5.5
  • 12.10.2
  • 12.10.3
  • 12.10.4
  • 12.10.5
  • 12.10.5.1
  • 12.10.5.2
  • 12.10.5.3
  • 12.11.1
  • 12.11.2
  • 12.11.3
  • 12.12.2
  • 12.12.3
Notes: The following settings should be checked in the design brief:
  • beta d factor.
  • whether or not there is transverse loading.
  • stability index Q (must be > 0.05 and ≤ 0.6).
  • load case number that causes appreciable sidesway.  If columns require different loadcases for sidesway, then they should be designed in separate design groups.
  • beta factor for biaxial bending (default 0.65).