Why are my nonconstrained embedment depths less in the current version than in Version 5.8?

You might notice that for embedment depths greater than 12' you will get shallower calculated depths in the current version.

The difference is due to a change in the way the program calculates the allowable lateral pressure when checking for a 12-foot limit.

Please see the relevant code sections as follows:

IBC 2006 Section 1805.7.2.1

IBC 2009 Section 1807.3.2.1

IBC 2012 Section 1805.3.2.1

IBC 2015 Section 1807.3.2.1

IBC 2018 Section 1807.3.2.1

IBC 2021 Section 1807.3.2.1

The item to look at is the definition of "d":

"Depth of embedment in earth in feet (m) but not over 12 feet for the purpose of computing lateral pressure."

Also note the definition of "S1":

"Allowable lateral soil-bearing pressure......based on a depth of 1/3 embedment...."

In Version 5.8 of the SEL this was conservatively interpreted as meaning that the allowable lateral soil pressure was to be calculated based on one-third of the depth of embedment, where one-third of the depth of embedment was not to exceed 12 feet/3 = 4 feet.

However, this item was clarified in the 2006 IBC Structural Q&A Application Guide. That document clearly indicates that the intent of that provision was that the allowable lateral soil pressure was to be calculated based on one-third of the depth of embedment, where one-third of the depth of embedment was not to exceed 12 feet. In other words, the 12-foot limit was to be taken literally, not divided by a factor of three.

Depth of Embedment to be used in Nonconstrained Pole Formula

Why are my nonconstrained embedment depths less in the current version than in Version 5.8?