IBC Table 1805.5(5) Foundation Wall Reinforcing Conflicts with ACI-318 Requirements

[soul plate]

IBC Table 1805.5(5) indicates various vertical steel requirements for foundation walls, based of various wall height and unbalanced fill height combinations.

For a vertical steel spacing conflict example, a 7' wall with 7' unbalanced fill height @ 45pcf suggests a minimum of #5 bars @ 46" spacing, for a 7.5" wall thickness, which yields a steel/gross concrete area ratio of 0.08. Per ACI318, section 14.3.5, vertical steel shall not be spaced farther apart than three times the wall thickness (3x7.5" = 22.5"), nor farther apart than 18 in. A 46" spacing does not comply.

Are there perhaps some other code sections that justify or allow these discrepencies?

 

[Mark K]

From a technical perspective I am much more comfortable with the ACI 318 provisions. My perception is that when IBC Table 1805.5(5) is used there will likely be more cracks and the building will be more sensitive to the impact of differential ground settlement. Apparently it is believed that the added costs associated with the ACI provisions was not justified. I do not expect that this relaxation will result in safety problems.

From a code perspective the applicant is allowed to use the IBC Table 1805.5(5) when it is in a legaly adopted regulation.. The jurisdiction that adopts the code doesn't have to justify the decision.

 

[peach]

The Code is the minimum.. not necessarily best practice. Table 1805.5(5) still send you back to chapter 16 for the soil classification/lateral loads.