Friday, September 2, 2011

Re: CMU wall and footing interface shear

In the Seismic Design Guide for Masonry Buildings it uses the normal force on the plan (dead load plus tension force in reinforcing) times a friction factor of 0.7 for masonry on smooth concrete for shear walls.


On Sep 2, 2011, at 1:35 PM, David Topete <> wrote:

I have always looked at shear friction for providing shear transfer in these conditions.  While the building code says that friction may not be used for shear resistance, like in the "anchorage" of (rooftop) equipment, and must have positive anchorage, I check for shear friction and neglect the friction between the masonry or concrete walls and foundations.

On Wed, Aug 31, 2011 at 8:47 AM, William Haynes <> wrote:
What is the correct way to quantify the shear resistance at the interface at the base of a cmu wall and footing? This is for out-of-plane shear on the wall but it should apply for in-plane shear as well. We have always provided dowels matching the vertical bar size and spacing but I was thinking that since the interface is between masonry and concrete (and not concrete and concrete), that shear friction may not be appropriate.
Will Haynes

David Topete, SE