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D1.F.3.1 ACI 318-2011 Design Parameters

The following outlines the parameters that are available to control the design of members as beams or columns per the ACI 318-11 code. The commands that initiate the design of these is outlined in TR.53.3 Concrete Design Command. If any parameter is not specified and its value is required in the design, then it will use that specified as the default value in the tables below.
Note: Not all the parameters are used in all versions of the ACI 318 code. Ensure that all the necessary parameters for the version of the code are properly specified. Where practical, parameters used in earlier versions of the code will be supported in the newer versions. Some old parameters are not supported in newer versions of the code and new parameters have been added in newer versions of the code that provide greater flexibility in the design.
Table 1. ACI 318 2011 Design Parameters
Parameter Name Default Value Description
ALPHA 1.5 for rectangular sections, 2.0 for square sections Exponent for Bresler Load Contour Method for Bixaial Interaction.
Note: The value should in theory be specified differently for each load case. This can be done by performing multiple designs with different load cases and choosing a value that is appropriate for all those cases.
BDY 1.0 Column stiffness reduction factor for bending about the local Y axis.
Note: Not used if parameter MMAG > 0
Note: Only used with ACI 318-11 and ACI 318-14.
BDZ 1.0 Column stiffness reduction factor for bending about the local Z axis.
Note: Not used if parameter MMAG > 0
Note: Only used with ACI 318-11 and ACI 318-14.
CLB

1.5 in. (38 mm) for beams*

0.75 in. (19 mm) for plate elements*

Minimum cover from the base of the section to the bottom longitudinal reinforcement.

See Note c below.

CLS 1.5 in. (38 mm)* Minimum cover from the sides of the section to the side longitudinal reinforcement.

See Note a and Note c below.

CLT

1.5 in. (38 mm) for beams*

0.75 in. (19 mm) for plate elements*

Minimum cover from the top of the section to the top longitudinal reinforcement.

See Note c below.

DEPTH YD* Depth of the member measured in the local Y axis.
Note: This parameter is not used with ACI 318-14.
EFACE 0.0*

Face of support location at end of beam. If specified, the shear force at end is computed at a distance of EFACE + d from the end joint of the member.

Note: See D1.F.4.3 Shear and Torsion Design for additional information.
Note: This parameter is not used with ACI 318-14.
FC 4,000 psi (28 N/mm2)* Compressive strength of concrete.
FYMAIN 60,000 psi (420 N/mm2)* Yield stress for main longitudinal reinforcing steel.
FYSEC 60,000 psi (420 N/mm2)* Yield stress for transverse reinforcing steel.
LWF 1.0 Modification factor, λ, for lightweight concrete as specified in ACI i318-08, cl. 8.6.1. Valid entries are between 0.75 and 1.0, inclusive. Used as a reduction factor for the mechanical properties of lightweight concrete.
Note: This parameter is used in ACI 318-2008, 2001, and 2014 only.
MAXMAIN #18 bar (57 mm)

Maximum size of reinforcing bar to be used for longitudinal reinforcement.

Note: When using ACI 318-14, the maximum size used in specific positions can be individually set. See detailing parameters below.
Note: See Note b below.
MINMAIN #4 bar (13 mm)

Minimum size of reinforcing bar to be used for longitudinal reinforcement.

Note: When using ACI 318-14, the minimum size used in specific positions can be individually set. See detailing parameters below.
Note: See Note b below.
MINSEC #4 bar (13 mm)

Minimum size of reinforcing bar to be used for transverse reinforcement.

Note: When using ACI 318-14, the minimum size used in specific positions can be individually set. See detailing parameters below.
Note: See Note b below.
MMAG 1.0 Factor to magnify the analysis moments used for column design.
Note: For ACI 318-14, if this is set to 0, then the moments for the local Y and Z axis will be calculated independently using the parameters BDY and BDZ.
NSECTION 12

Number of equally spaced sections to be considered in finding critical moments for beam design. The valid range is from 12 to 20.

This parameter applies to the design process rather than individual members and thus should not have any assigned member list. If more than one NSECTION parameter is defined, then highest value will be used.

REINF 0

Column transverse reinforcement type.

  • 0) links (tied column)
  • 1) spiral reinforcement
RHOMIN 0.01 Minimum reinforcement required in a concrete column. Enter a value between 0.0 and 0.08, where 0.08 = 8% reinforcement; the maximum allowed by the ACI code.
Note: This parameter is not used with ACI 318-14.
SFACE 0.0*

Face of support location at start of beam. If specified, the shear force at start is computed at a distance of SFACE + d from the start joint of the member.

Note: See D1.F.4.3 Shear and Torsion Design for additional information.
Note: This parameter is not used with ACI 318-14.
SKY 1.0 Effective length factor for moment magnification procedure calculations for columns, in the local Y direction. When the SWY parameter is 0 (i.e., not braced), then SKY ≥ 1.0. When SWY is 1 (i.e., braced), then 0.5 ≤ SKY ≤ 1.0.
Note: Only used with ACI 318-11 and ACI 318-14.
SKZ 1.0 Effective length factor for moment magnification procedure calculations for columns, in the local Z direction. When the SWY parameter is 0 (i.e., not braced), then SKZ ≥ 1.0. When SWY is 1 (i.e., braced), then 0.5 ≤ SKZ ≤ 1.0.
Note: Only used with ACI 318-11 and ACI 318-14.
SLY n/a

Number of the load case that applies sidesway load in the local Y axis for column design.

The moments from this case are used to magnify the local Y axis moments for all design load cases as per the sway or non sway requirements. Calculations are dependent on the SWY parameter setting.

Note: This parameter is not used if MMAG has been specified.
Note: Only used with ACI 318-11 and ACI 318-14.
SLZ n/a

Number of the load case that applies sidesway load in the local z axis for column design.

The moments from this case are used to magnify the local Z axis moments for all design load cases as per the sway or non sway requirements. Calculations are dependent on the SWY parameter setting.

Note: This parameter is not used if MMAG has been specified.
Note: Only used with ACI 318-11 and ACI 318-14.
SQY 0.2

Stability index, Q, in the local Y axis as defined in ACI 318 section 6.6.4.3(b).

Note: Only used with ACI 318-11 and ACI 318-14.
SQZ 0.2

Stability index, Q, in the local Z axis as defined in ACI 318 section 6.6.4.3(b).

Note: Only used with ACI 318-11 and ACI 318-14.
SWY 0

Braced against sidesway:

  • 0) Not braced
  • 1) Braced
Note: Use only when MMAG parameter is equal 0.
Note: Only used with ACI 318-11 and ACI 318-14.
TRACK 0.0
Specify the level of detail in the output:
  • 0) Beam and Column Design - Minimum details
  • 1) Beam Design - Intermediate level details; Column Design - TRACK 0 detail and column interaction
  • 2) Beam Design - TRACK 1 detail and steel required at 1/12th sections; Column Design - TRACK 1 detail and interaction diagram
TRN 0

Transverse loads between supports

  • 0 - False
  • 1 - True
Note: Only used with ACI 318-14.
WIDTH ZD* Width of the member measured in the local Z axis.
Note: This parameter is not used with ACI 318-14.
Note: * These values must be provided in the current unit system being used.

Notes

  1. The value used when specifying the CLS parameter for column design is taken to be the clear cover for the longitudinal bars in a column. It is not taken as the clear cover for the tie bars. Therefore, the distance from the edge of the column to the centerline of the first row of longitudinal bars is CLS plus half the diameter of the main bar.
  2. When using metric units for ACI design, provide values for these parameters in actual 'mm' units instead of the bar number. The following metric bar sizes are available: 6 mm, 8 mm, 10 mm, 12 mm, 16 mm, 20 mm, 25 mm, 32 mm, 40 mm, 50 mm, and 60 mm. 
  3. Clear cover values are set for the concrete Not exposed to weather or in contact with ground. Plates or slabs are assumed to be reinforced with bar number 11(in imperial units) or smaller.
  4. Required for bar detailing in a physical member which might contain intermediate members along with cantilevers.

    For internal members both STRS and EDSP should be set to 0.

  5. In ACI 318-14, members are always designed with 5 sections. The parameter NSECTION used with older editions of the code has no effect.
Parent topic: D1.F.3 Design Parameters