First situation:
Imagine a 3rd story wood shear wall: the east end supported by an east-west beam and the west end supported by the east endpost of the wall below.
Technically, this is vertical irregularity 4, and columns and beams supporting this wall should be designed including overstrength per ASCE 7-10 12.3.3.3. I think it is obvious that the beam should be designed for amplified seismic load, and whatever column supports the east end of the beam. But what about the east end post of the second story shear wall, which is below the west end post of the 3rd story shear wall?
1) Perhaps, since this end post is part of a shear wall, is need not be designed for any overstrength.
2) Perhaps, since this post supports the discontinuous beam, it should be designed for 3rd story overstrength loads, but 2nd story loads need not be increased
3) Perhaps all earthquake loads, even 2nd story loads, should be amplified, since I found nothing in the code explicitly considering 3rd story and 2nd story loads separate.
Second situation
Now imagine a 3rd story shear wall with a large opening below it, but both end posts are continuous to the foundation. The west end post is supported by the east end post of a 2nd story shear wall. The east end post is supported only by a continuous post; there is no shear wall below this end. Should either 2nd story post be designed for omega?
1) Perhaps both are considered continuous parts of the shear wall and neither is designed for overstrength. This seems to contradict ASCE 7-10 12.3.3.3, but it might be interpreted that in wood framing these columns are not discontinuous and only need be designed for redundancy.
2) Perhaps the east column is designed for amplified seismic load, as it is a "column... supporting [a] discontinuous wall... having... vertical irregularity type 4", but the west post, being part of a wall, need not be designed for overstrength.
3) Perhaps the west post is also considered a column supporting a discontinuous wall, rather than just part of another wall, and should also be deigned for overstrength.
Imagine a 3rd story wood shear wall: the east end supported by an east-west beam and the west end supported by the east endpost of the wall below.
Technically, this is vertical irregularity 4, and columns and beams supporting this wall should be designed including overstrength per ASCE 7-10 12.3.3.3. I think it is obvious that the beam should be designed for amplified seismic load, and whatever column supports the east end of the beam. But what about the east end post of the second story shear wall, which is below the west end post of the 3rd story shear wall?
1) Perhaps, since this end post is part of a shear wall, is need not be designed for any overstrength.
2) Perhaps, since this post supports the discontinuous beam, it should be designed for 3rd story overstrength loads, but 2nd story loads need not be increased
3) Perhaps all earthquake loads, even 2nd story loads, should be amplified, since I found nothing in the code explicitly considering 3rd story and 2nd story loads separate.
Second situation
Now imagine a 3rd story shear wall with a large opening below it, but both end posts are continuous to the foundation. The west end post is supported by the east end post of a 2nd story shear wall. The east end post is supported only by a continuous post; there is no shear wall below this end. Should either 2nd story post be designed for omega?
1) Perhaps both are considered continuous parts of the shear wall and neither is designed for overstrength. This seems to contradict ASCE 7-10 12.3.3.3, but it might be interpreted that in wood framing these columns are not discontinuous and only need be designed for redundancy.
2) Perhaps the east column is designed for amplified seismic load, as it is a "column... supporting [a] discontinuous wall... having... vertical irregularity type 4", but the west post, being part of a wall, need not be designed for overstrength.
3) Perhaps the west post is also considered a column supporting a discontinuous wall, rather than just part of another wall, and should also be deigned for overstrength.
