 |
| Author | Post |
|---|
greg q
Registered Member
| Joined: | Mon May 24th, 2010 |
| Location: | |
| Posts: | 1 |
| Status: |
Offline
|
|
Posted: Wed May 26th, 2010 09:04 pm |
|
Howard,
I have been looking into doing most of the seismic retrofit work myself and have the some questions.
First some information. We live in Pacifica (second to the worst shaking intensity on the ABAG charts) on clay soil. It is a down slope home with braced walls with a relatively large slope built in the 70s. The maximum height of the braced wall is approximately eleven feet. It is L-shaped. The living room, dining room and kitchen (20'x32'=620 ft2) is on the short leg of the L with the brace walls (11’H). The brace walls are 2"x6"@16" centers. There are ½” dia. Anchors @ 48” centers. There is a substantial grade beam on the uphill side. The long leg of the L is two levels.
Using the basic shear equation, I think I would need to size the shear walls for approximately 7,000 pounds shear. Using Structural 1, 15/32” w/10d nails @ 4” centers, I would need approximately 14’, say 16’ length of shear wall. I intend to place 11’Hx 8’W shear walls at the corners of the down sloping cripple wall. I would install hold downs at the ends of each 8’W shear wall and the appropriate number of A35 strong ties.
With regards to the sloping cripple walls, I was thinking of using a couple of the HDU8-SDS2.5 at an offset and anchored to the upslope grade beam and attached to the rim joist (doubled for thickness).
My questions are:
- Does this look reasonable? Am I missing something?
- Does a 11' high shear wall act the same as an 8' high shear wall, do I need to derate the shear wall due to its height?
Thanks,
Greg
|
Howard
Administrator
|
Posted: Wed May 26th, 2010 10:41 pm |
|
Howard,
I have been looking into doing most of the seismic retrofit work myself and have the some questions.
First some information. We live in Pacifica (second to the worst shaking intensity on the ABAG charts) on clay soil. It is a down slope home with braced walls with a relatively large slope built in the 70s. The maximum height of the braced wall is approximately eleven feet. It is L-shaped. The living room, dining room and kitchen (20'x32'=620 ft2) is on the short leg of the L with the brace walls (11’H). The brace walls are 2"x6"@16" centers. There are ½” dia. Anchors @ 48” centers. There is a substantial grade beam on the uphill side. The long leg of the L is two levels.
Using the basic shear equation, I think I would need to size the shear walls for approximately 7,000 pounds shear. Using Structural 1, 15/32” w/10d nails @ 4” centers, I would need approximately 14’, say 16’ length of shear wall. I intend to place 11’Hx 8’W shear walls at the corners of the down sloping cripple wall. I would install hold downs at the ends of each 8’W shear wall and the appropriate number of A35 strong ties. Use L-90s, they are much better.
With regards to the sloping cripple walls, I was thinking of using a couple of the HDU8-SDS2.5 at an offset and anchored to the upslope grade beam and attached to the rim joist (doubled for thickness). Not sure what you are describing here but I can tell you we don't do it this way and we have been doing this everyday for 15 years. Go the the hillside home section of the website and see if you live in a hillside home. If so, don't bother with plywood. You can email me a drawing to bayareareterofit@aol.com
My questions are:
- Does this look reasonable? Am I missing something?
- Does a 11' high shear wall act the same as an 8' high shear wall, do I need to derate the shear wall due to its height? An 11 foot high shear wall will have very strong overturning forces. If you have 500plf shear walls and they are maxed out you will have 5500 pounds of overturning force. There is a good chance your foundation will not be able to handle it.
|
Current time is 12:15 pm | |
|
|
|
|
