An interior footing for Hardy panels - suitable for Fort Knox?

[dkdesign]

We are doing a remodel on a 1-story home, wood framed with exposed 16' long ceiling beams 6' o.c., with perimeter wall providing a 24" crawlspace.
A 5'6" interior wall, located in the middle of the span under one such ceiling beam, needs be sheared up (there is no other shear wall in same direction within 52' of it!).

The structural engineer calculated that a double 2' wide Hardy panel would do the job. So far so good. But we need a footing or foundation for this baby, and now trouble starts ;-(

The SE specifies a 40" wide, 30" deep footing, running perpendicular, all the way from one existing footing to the other, i.e., 15'. His footing would have 5 longitudinal bars (#6) at the top and at the bottom, and also #3 ties between top and bottom at each 12". Furthermore his footing is epoxied into each existing footing w. four dowels #5, 6" into the exist footing and 24" (!) into the new footing.

I would really appreciate your judgment. I get the sense that this is way over-engineered; more suitable for Fort Knox than a small residential remodel. Any thoughts? Any suggestions?

I realize my description may be hard to follow, so you may want to check out snippets from the specs and my attempt to visualize the specs. See

http://picasaweb.google.com/crawlspacequestion/FoundationWall?feat=directlink

Thanks

 

[concretemasonry]

First, you did not post your location, which can require specific designs.

Second, The description provided did not give an accurate picture of the situation and the suggested design. The details show some serious reinforcement.

Without knowing what that information, is could be a little over the top, but without seeing the site home plans, it is hard to give an intelligent answer. - Are you in a severe seismic zone?

If there is no shear wall within 52', you must have a very large home and it couple be possible for a new wall to pick up a lot of shear. What additional parts of the structure are there to resist the shear loads?

You mentioned "shear walls". What do you think is a "shear wall" and how much lateral load can it absorb especially if it is a relatively flexible wall?

I think you be looking at the amount of concrete and not what load the wall can transfer into the footing/foundation unless you have some strange building configurations and soil/moisture/seismic conditions.

Dick

 

[dkdesign]

Sorry for not providing enough info. Let me make amends...
We are in Northern California, and yes, there is some rattling here. The home is from 1959 and has stood up to past quakes. The structure must comply to California Building Code (CBC); there are no special conditions at play.
The house is kind of weird: flat roof and a foundation footprint of 84'x16'; current project adds another 16' to the length (yes!).
I am posting the full foundation drawing FYI]
Thnx

 

[dkdesign]

And sorry to be so fragmented: here is the SE design basis on seismic load

Seismic importance factor, I = 1.0
Mapped spectral response accellerations, Ss=2.37 and S1=1.23
Spectral response coefficients, Sds = 1.58 and Sd1=1.23
Seismic design category, SDC=E
Response modification factor, R=6.5
Seismic response (base shear) coefficients for strength design, Cs=0.244

 

[rowingengineer]

what about the soil conditions? any idea's onj the foundation material?
What is the existing building on, Piles?


When in doubt, just take the next small step.

 

[msquared48]

Sounds like you have one H(*& of a lot of lateral force with not much shear wall to resist it, resulting in a large overturning force and resulting grade/transfer beam.

Sounds believeable to me. There are other options though, but with a one story home, I'm not sure there would be much savings, if any.

Mike McCann
MMC Engineering

 

[dkdesign]

@rowingengineer

Soil conditions: nothing special, hilly area but the building pad is pretty flat; visible rock outcroppings around the flat area; no soil report required or provided.

{now quoting from the blueprint notes:}

Existing perimeter footing, with 2x6 mudsill and 4x6 rim joist on top. Three 4x6 joists, 4’ o.c., running on the long side of the house, supported by posts on piers, 6’ o.c.

Existing crawlspace is 27 ¼” from pad (dirt) to bottom of subfloor; 21 ¾” below bottom of joists.

 

[hokie66]

I can believe the 40" wide x 30" deep footing for resisting the overturning on this wall. As it is in the middle of the building, it will try to collect more than half the load on the entire structure. I am not familiar with these steel "Hardy panels", so can't comment about the capacity. How is the shear wall connected to the roof, and how does the roof load get to the wall (diaphragm action?)?