CMU Wall Anchorage

[archengineer]

I am in seismic zone 3 and am confused about the requirements for CMU wall anchorage. UBC section 1611.4 requires a minimum seismic ultimate force of 280 plf to be substituted for design force E for all concrete and masonry walls. That would indicate to me that the force acts at a location halfway up the wall. Several design manuals take that force and apply it directly to the anchorage at the top of the wall.

It seems like over kill to me.

If the force does go at the top of the wall, what about cantilever CMU partition walls?

 

[whymrg]

This load is at anchorage, if you read it one more time. (In seismic zone 4 for anchorage to flexible diaphragm you need to use 420 plf per 1633.2.8.1).
Load on cantilevered wall shall be determined according to 1632.2

 

[archengineer]

I have read through it again and it still says the same thing to me. A force of 280plf shall be substituted for E.

It would seem to me that design force E occurs at the center of mass, the mid height of the wall. The anchorage would be designed for the tributary load resulting from design force E, not the full force.