Masonry Shear Walls - ASD vs Strength Design

[SE2B]

When designing a particular masonry shear wall using Strength Design (2005 MSJC Ch. 3) I have sufficient shear and flexural capacity, but I get hung up on a check for the requirement & design of special boundary elements of MSJC Section 3.3.6.6 – 3, Mu/(Vu*lw) <= 3.0.
I am hung up because I want to avoid requiring any special boundary elements so I tried designing the wall using ASD design (2005 MSJC Ch 2). Once again, sufficient shear and flexural capacity, but I do not see a check for any special boundary elements which leads me to believe my wall design is okay. I am not the smartest person you ever met so here are perhaps my simple questions.

1. Why is there not a similar check for special boundary elements in ASD design?

2. Is there another special requirement in ASD design that I am missing?

3. If ASD design doesn’t have any special requirements I think I am going to typically use that in lieu of Strength Design, any reason not to?

Thanks in advance for any help & advice.

 

[vandede427]

I would use ASD for your every day masonry design (out-of-plane flexure, and in-plane shear) unless you get into really tall walls like a theater or big box retail, then go to a strength design.

 

[sandman21]

1. No special boundary elements in ASD design is required because in ASD design you keep the member in the elastic range, special boundary is used to account for the inelastic forces on the wall during an earthquake.

2. There is a 1.5 factor required, CBC and IBC I believe, to be applied to the seismic shear force.

3. I design lots of masonry, unless I can’t get ASD to work I never use strength for in-plane design. Out-of plane I use strenght.

 

[SteelPE]

Sandman21, I thought the 1.5 seismic factor only applied to structures in Seismic Design Category D? Unless there is something I am missing?

 

[sandman21]

That is correct D and up