IBC 2009 1807.2.1 Retaining Wall Keyway

[FixedEarth]

I noticed IBC 2009 is requiring active earth pressure be applied to the keyway in addition to passive resistance (last sentence of 1807.2.1). Any thoughts from retaining wall designers on this topic? This was not in IBC 2006 or 2003.

 

[TDIengineer]

Personally, I try to avoid the use of key and make the footing larger / thicker. Contractors hate digging them, the key is usually rounded..
If you can dowel into a permanent slab, that helps the sliding. If its a site wall, then make it bigger. The added concrete for the footing may be cheaper then hand digging the key and install those bars from my experience. IF it's a large wall, you have no choice to make the sliding work but use a key.

Carry the active to the key depth, that's conservative.

 

[LonnieP]

I just love it when we engineers start sharpening our pencils on something. Very educational indeed. But i have a question.

Now that we're Oh so much better at calculating than the old slide rule dudes, does that mean we can do away with the 1.5 safety factor against overturning and sliding? My opinion is the "old dudes" knew all these issues and agreed, among themselves, the 1.5 factor would cover them. Now, if you really, really want to stir up an issue, why take OTM moments around the toe of the footing and NOT include the effects of the upward soil pressure. If you don't include it then the 1.5 is absolutely needed.

More food for thought?

LonnieP