For each of these parameters, any user defined limits (as specified on the appropriate Reinforcement Settings page within Design Options) are considered in addition to any ACI code recommendations.

Minimum and maximum diameter of reinforcement

IF torsional reinforcement is required, there shall be at least one longitudinal bar in every corner of the stirrups. Longitudinal bars shall have a diameter at least 0.042 times the stirrup spacing, but not less than 9 mm (3/8 in).

The maximum diameters of reinforcement to be used in the various locations is set by the user.

Standard hooks for stirrups and ties are limited to No.8 bars, d_b=25mm (1.0in.) and smaller.

And the 90-degree hook with 6d_b extension is further limited to No. 5, d_b=16mm (0.625in.) bars and smaller.

For primary reinforcement there is no limit on bar size.

Minimum distance between bars

The minimum clear horizontal distance between individual parallel bars, s _cl,min, is given by;

s_cl,min ≥ MAX [d_b, 25 mm] metric-units

s_cl,min ≥ MAX [d_b, 1in] US-units

IF the above check fails then a Warning is displayed.

Where parallel reinforcement is placed in two or more layers, bars in the upper layers shall be placed directly above the bars in the bottom layer with clear distance between layers not less than 25mm (1in.).

Maximum spacing of tension bars

The spacing of reinforcement closest to the tension face, s is given by;¹

 ≤ 

 ≤ 

 = 

 = 

 = 

IF the above check fails then a Warning is displayed

IF torsional reinforcement is required:

the longitudinal reinforcement required for torsion shall be distributed around the perimeter of the closed stirrups with maximum spacing of 300mm (12 in.)²

Minimum area of beam reinforcement

The minimum area of longitudinal tension reinforcement, A _s,min, is given by;³

 ≥ 

 ≥ 

 = 

 = 

 = 

 = 

 = 

The above equation is used wherever reinforcement is needed, except where such reinforcement is at least one-third greater than that required by analysis, in which case A_s,min not required.

Minimum area of slab reinforcement

For ACI 318-08 and ACI 318-11⁵

For structural slabs of uniform thickness the minimum area of tensile reinforcement in the direction of the span is:

For US-units:

IF Grade 40 to 50 deformed bars are used

A_s,min,reqd ≥ b*h*0.0020

IF Grade 50 to 60 deformed bars or welted wire reinforcement are used

A_s,min,reqd ≥ b*h*0.0018

For metric units:

IF Grade 280 to 350 deformed bars are used

A_s,min,reqd ≥ b*h*0.0020

IF Grade 350 to 420 deformed bars or welted wire reinforcement are used

A_s,min,reqd ≥ b*h*0.0018

IF yield stress exceeding 420 MPa

A_s,min,reqd ≥ b*h* [MAX(0.0014 , 0.0018*420/f_y)]

Maximum area of reinforcement

Net tensile strain in extreme layer of longitudinal tension steel, ε_t should not be less than 0.004;

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