Reinforcement Ratio Limits
This section discusses the reinforcement ratio checks that are implemented within the RAM Concrete Wall module and the assumptions made by the program when performing the necessary calculations. Table below provides a summary of the sections of ACI 318-11 covering reinforcement ratio that have been implemented within the program.
Each of the Wall Panels that intersect the Section Cut being evaluated is checked separately for these provisions using the respective Wall Panel properties and Bar Pattern information. Note that using the Bar Pattern information rather than the true reinforcing bars has two impacts:
- The nominal bar spacing is used in the calculations rather than the spacing between any two bars as placed in the wall.
- The patterned reinforcing bar size is used in the calculations rather than the sizes of individual bars. Thus if the user has edited individual bars, these changes will not be reflected in these calculations.
| Code Section | Limit Check | Referenced Code Sections |
|---|---|---|
| 14.3.1 | Minimum horiz & vert reinf | 11.9.9.2, 11.9.9.4 |
| 14.3.2 | Minimum vert reinf | - |
| 14.3.3 | Minimum horiz reinf | - |
| 21.9.2.1 | Minimum web reinf | - |
| 21.9.4.3 | Minimum long reinf | - |
The RAM Concrete Wall module checks Sections 14.3.1, 14.3.2, and 14.3.3 of ACI 318-11, which specify the horizontal and vertical reinforcement ratio limits in walls. Section 14.3.1 mandates that the minimum horizontal and vertical shear reinforcement ratios in walls comply with ACI Sections 11.9.9.2 and 11.9.9.4, respectively. When the provisions of Chapter 21.9 are considered (Special Reinforced Concrete Structural Wall), Sections 21.9.2.1 and 21.9.4.3 are also checked.
- ρl = Ratio of area of distributed longitudinal reinforcement to gross concrete area perpendicular to that reinforcement.
- ρt = Ratio of area of distributed transverse reinforcement to gross concrete area perpendicular to that reinforcement.
Despite the above definitions given by ACI, ρl is also used within ACI 318-11 to denote horizontal reinforcing (e.g., 11.9.9.2), and ρt is also used to denote vertical reinforcing (e.g., 11.9.9.4). To resolve this, the following approach is used within the RAM Concrete Wall module:
In cases where ρlis referenced and the text within the ACI code section specifically mentions "vertical" reinforcing, ρlis calculated using the area of vertical reinforcing resulting from the Bar Pattern. If "vertical" reinforcing is not specifically referenced, the area of reinforcing is calculated using the area of the reinforcing bars that intersect and are normal to the Section Cut Segment under consideration.
In cases where ρt is referenced and the text within the ACI code section specifically mentions "horizontal" reinforcing, ρt is calculated using the area of horizontal reinforcing resulting from the Bar Pattern. If "horizontal" reinforcing is not specifically referenced, the area of reinforcing is calculated using the Bar Pattern that is parallel to the Section Cut Segment under consideration.
Sections 11.9.9.3 and 11.9.9.5 both specify spacing limits that are a function of the overall length of the wall, lw. RAM uses the Section Cut Segment length for this value. The limitation of this assumption is that for very short wall segments, the limit spacing will likewise be small. Since the calculated spacing limit is compared to the nominal bar spacing and not the true bar spacing, false check failures may be reported for short wall segments.