Clarification on the Removal of the Chapter 9 Min Reinforcement Option in the Wall and Combined Footing Modules |
  
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Clarification on the Removal of the Chapter 9 Min Reinforcement Option in the Wall and Combined Footing Modules |
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What happened to the option to "Consider ACI 9.6.1.2 & 9.6.1.3 as min reinforcing" within the Wall and Combined Footing Modules?
According to ACI 13.3.2.1, the design of one-way shallow foundations—including strip footings, combined footings, and grade beams—must follow the “applicable provisions” of Chapter 7 (One-Way Slabs) and Chapter 9 (Beams). More information regarding ENERCALC's interpretation of the "applicable provisions" phrasing can be found within Shallow Foundation "Applicable Provisions".
This ambiguous phrasing led to uncertainty about which provisions from those chapters apply to the various foundation elements and associated modules within SEL. To provide more design flexibility in earlier versions of SEL, the Wall Footing and Combined Footing modules included an option to "Consider ACI 9.6.1.2 & 9.6.1.3 as min reinforcing." This allowed engineers to apply reinforcement limits typical for beam-like elements for wall footings and combined footings. However, this flexibility introduced added complexity and sometimes resulted in the feature being used inappropriately.
After further review of ACI 13.3.2, it was concluded that the reference to Chapter 9 appears to be specific to grade beams, and that sections 9.6.1.2 and 9.6.1.3 were not intended for one-way shallow foundations like wall (strip) footings and combined footings. Instead, these elements are more slab-like and are better suited to the scope of Chapter 7 provisions.
Therefore, the option to "Consider ACI 9.6.1.2 & 9.6.1.3 as min reinforcing" has been removed from the Wall Footing and Combined Footing modules, which now follow ACI 7.6.1.1 for minimum flexural reinforcement:
"7.6.1.1 A minimum area of flexural reinforcement, As,min, of 0.0018Ag shall be provided."
For designs that involve beam-like behavior, the Beam on Elastic Foundation (BoEF) module is more suitable. It remains the engineer’s responsibility to choose the appropriate module for their specific design needs.
What about the General Footing module?
For two-way isolated footings, ACI 13.3.3.1 requires adherence to the “applicable provisions” of Chapter 7 (One-Way Slabs) and Chapter 8 (Two-Way Slabs). Because Chapter 9 provisions are not relevant for two-way isolated footings, the General Footing module has never included the option to "Consider ACI 9.6.1.2 & 9.6.1.3 as min reinforcing." Instead, the General Footing module follows ACI 8.6.1.1 for minimum flexural reinforcement:
"8.6.1.1 A minimum area of flexural reinforcement, As,min of 0.0018Ag [...] shall be provided near the tension face of the slab in the direction of the span under consideration."
The removal of the option to "Consider ACI 9.6.1.2 & 9.6.1.3 as min reinforcing" from the Wall Footing and Combined Footing modules aligns their behavior with the General Footing module, creating a more consistent design approach across all footing modules.
