ICFHybrid,

You make some good points.  Have you ever used Agilia self-consolidating concrete by LAFARGE?  Designs that require congested rebar can benefit by using Agilia.

No, most of my prior experience with concrete was on factory and warehouse builds and I don't think any of them were difficult enough to require special products like the Agilia.

The engineer on my ICF residential project was remarkably well informed and I learned a lot from him about concrete composites. Not sure why people are in such a hurry to avoid engineers or engineering costs. I can't think of a time I used an engineer that didn't save money, time and hassles. I've consistently found them to be the best value on the job site.

Budden

To give a brief example

If you have the correct amount of rebar you should have no issues.

If you have too little rebar you can have a failure, the failure should be visible before it happens, I.e. cracking in the concrete.

Too much rebar and you won't see the failure starting to happen, the concrete will sudden collapse, no warning, no cracking, no nothing, just sudden failure that no one could have seen.

A typical layman can see stress cracks in concrete and know something is not right, but over rebared and no one can see it until its too late and that could be catastrophic.

I know that there can always too much of a good thing, but it's hard to imagine one could stuff too much steel in an ICF residential project. Just use google images and search california rebar earthquake and you'll likely see some serious rebar filled structures. On the other hand, when you do this search you'll also see images of some nasty concrete failures.

Here's an article talking about challenges with rebar placement in high rise structures built in california:
http://www.concreteconstruction.net/concrete-construction/concrete-california-style.aspx

Their main issue is getting consolidation between the elaborate and congested rebar columns, so they use the 3/8 aggregate and some use SCC . . . sound familiar?

It's obvious that most everyone has a handle on this. It's just concrete, and concrete can be designed to withstand it. Concrete, being brittle has to overcome it in strength, and wood, being flexible, has to overcome it with ductility. Dollar for dollar, a wood one can withstand an earthquake more cheaply.
But there is a big point that often gets overlooked in the Great ICF/ Earthquake debate. You can get all of the strength of the concrete wall and a reduction in the mass using a waffle wall. Back in my Polysteel days, I did a lot of research and calculating on it. It's simply less mass, and for that reason, a waffle wall will get you in and out much more efficiently.

Waffle shmaffle, Jerry. Let's face it, do you really want a wall you can shove a rake handle through?

Ray, I think you're confusing waffle with screen, which has areas without concrete and solid EPS between. At the thinnest part, the waffle is 2" of concrete. And when considering the mass for seismic effects and solid (though not uniform) concrete, it is well worth looking in to.
And for the screen wall (does anyone still make it?), you can't shove a rake through 8" of solid, high-density EPS.

I might have a tough time shoving that rake handle through (or maybe not), but my sister the twister can sure do it.

I am wondering if anyone here ever used fibermesh within their concrete pour? Supposedly fibermesh really helps in the concretes ability to withstand cracks and it supposedly helps when pouring it that it envelops the re-bar. Of course it doesn't substitute the need for re-bar and a 3,000psi + pour but it an additional plus.

From what it looks, right now, the ideal pour for a seismic zoned ICF would be:

6" ICF with a 3,000-4,000 psi pour
#5 re-bar @ 16" OC
Fibermesh in pour
Lightweight metal roof with wood truss
Post-tension slab

I don't think Fibermesh is a solution to any seismic structural issues with ICF.

Helical steel inclusion, however, is promising.

Your vertical steel schedule is only a small part of the story if you are interested in additional seismic resistance. What is more important is how the footing and floors are constructed and attached.

Posted By ICFHybrid on 25 Nov 2011 02:19 PM
I don't think Fibermesh is a solution to any seismic structural issues with ICF.

Helical steel inclusion, however, is promising.

Your vertical steel schedule is only a small part of the story if you are interested in additional seismic resistance. What is more important is how the footing and floors are constructed and attached.

Initially the 2nd floor would be attached with "j-bolts" every 16" OC from the ICF wall. These J-Bolts would attach to wood I-beams. The home has a portion where the 1st floor is completely open to the 2nd floor (mainly the living room and kitchen portion).

Seismic zones around the country differ in what kind of forces they might be subject to. Up here in Puget Sound, for example, we aren't very "shaky" on a regular basis like California, but when the quakes come, they are big and powerful. The actual hardware or reinforcement you use and where you place it is dependent on the forces expected which is, of course, also related to the building size and configuration. Some codes might specify standard residential construction, but as the building gets farther from standard construction, only an engineer will be able to determine what the reinforcing should be.

J-bolts are more of a hold down than seismic reinforcement. They have a little end, probably less than 2" long, to resist pullout. Seismic reinforcing in concrete consists of lengths of #5 and #6 bar projecting 2' and 3' around corners. Shear wall connectors can be 1" formed and hardened bar with 2' of concrete embedment and pre-deflected metal plates with 30 or 40 fasteners each, to specify just a few examples.

There is an article in a recent issue of "Fine Homebuilding" issue #222, Sept 2011 that deals with seismic reinforcement and retrofitting.