Seismic Load Resisting System 1

[LowLax]

I have a building that is essentially a rectangle. There are masonry walls on two adjacent sides and the other two sides have moment frames. I know it's not an ideal layout, but the architect won't give me braced frames.

My question is what type of lateral system is this considered? It's not a dual system is it? Do I have two different systems and therefore two different R factors? The building is only in seismic category A, and it's only two stories tall. I'd like to use R=3 (not specifically detailed for seismic) for the moment frames.

 

[frv]

I believe that for seismic design category A, you simply need to use increased loads, but do not need to use seismic detailing.

If I had to guess, I'd assume you would consider each direction separately.

 

[JAE]

For SDC A you would probably end up using a seismic load of 0.01w for the lateral seismic response.

It is not a dual system. You would use one R for one way and another R for the other direction...but again, with SDC A this doesn't matter since you would fall under the 0.01w criteria.

A dual system is when you have a shearwall and a moment frame in the same line, sharing load together.