Coordination question RE: CMU wall & CMU shear wall construction

[RHTPE]

Not having had a wealth of exposure to CMU construction, I'm looking for some insight regarding efficient construction of CMU walls on top of reinforced concrete foundations.

Obviously, proper coordination between the CMU dowels + the CMU core locations + CMU control joint locations + actually dowel installation prior to the foundation placement is essential to avoid future conflicts.

What has everyone's experience been with ensuring that this has been successfully accomplished?
- Who should establish the dowel locations (other than the EoR stating the spacing)?
- Who should determine the layout of the control joints (which require a dowel either side of the joint)? I realize that the A/E determine the CJ spacing, but someone has to assign an actual dimension to their locations.
- How does this information get conveyed to the concrete sub who has to install the dowels?
- To what degree would mis-located dowels be acceptable?

I am on the periphery of a dispute between the CM (a paper pusher), the concrete sub, a very superficial rebar detailer (no locations, just spacing & projection height), and the mason.

I would love to have better insight as to how this gets successfully accomplished and who provides the driving force to get it right. Anyone care to chime in with their experience?


Ralph
Structures Consulting
Northeast USA

 

[Ingenuity]

I can provide my personal and recent experience with this issue, but it was NOT in the USA, and whilst I also work in the USA, I too have limited experience with CMU in the US - so take this with that in mind.

On this project the GC recognised that there was a disconnect between concrete foundations & slabs and CMU when it came to dowel placement, joints etc, so the GC took charge of marking out control joints, dowel locations etc. He walked each area with the mason foreman subcontractor marking approx joint locations then based upon block dims worked out the actual joint location, and from there core spaces for dowels. The concrete sub just came by and placed dowels as per the color-coded markings that the GC provided. Worked very well.

This GC tended to self-perform more tasks than most generals, so the above may not be representative of US general contractors.



“…structural engineering isn’t rocket science. Evidently, it is considerably more difficult.”
Norbert J. Delatte, Jr., PhD, PE. 2009. Re Harbour Cay Condominium Collapse, March 27, 1981.

 

[manstrom]

We usually detail the dowels to be drilled and epoxied. Not the cheapest way, but it avoids this type of conflict.

At the very least, the concrete sub could locate the vertical rebar. Control joints could be drill and epoxy.

I don't see a lot of this as being the responsibility of the SER. This is means and methods.

If it's a heavily reinforced shear wall, this is all the more reason to use concrete over CMU.

When I am working on a problem, I never think about beauty but when I have finished, if the solution is not beautiful, I know it is wrong.

-R. Buckminster Fuller

 

[Ingenuity]

We usually detail the dowels to be drilled and epoxied. Not the cheapest way, but it avoids this type of conflict.

Curious, what do you do/specify with long CMU retaining walls (on concrete foundation), with both vertical dowels and control joints?

“…structural engineering isn’t rocket science. Evidently, it is considerably more difficult.”
Norbert J. Delatte, Jr., PhD, PE. 2009. Re Harbour Cay Condominium Collapse, March 27, 1981.

 

[RHTPE]

Ingenuity

I suspect your situation is more the exception than the rule. A very wise move though to recognize that the coordination was necessary.

Unfortunately my client is dealing with a CM who does little more than pass paper and schedule meetings. I think his only site personnel consists of a superintendent & site "engineer" who watches everyone else work.


Ralph
Structures Consulting
Northeast USA

 

[Ingenuity]

Ralph,

Oh, the 'paper' contractor - does not own or use power tools, or even a tape measure. Just collects margin off each of the subs, who don't get paid until he gets paid, so he does not even bank-roll the project.

It is shame what construction contracting has become.

Best of luck in resolution - but definitely a 'means-and-methods' item for one of the sub/contracting entities.

“…structural engineering isn’t rocket science. Evidently, it is considerably more difficult.”
Norbert J. Delatte, Jr., PhD, PE. 2009. Re Harbour Cay Condominium Collapse, March 27, 1981.

 

[RHTPE]

What disturbs me the most is the lack of what I call "aggressive coordination" or "aggressive cooperation". There used to be a consistent effort to coordinate between design disciplines, as well as between trades on the project. BEFORE construction was underway.

Now it seems more common that each sub is forced to work in a vacuum with regard to coordination.

Just doesn't seem to me that it's in the best interest of all involved to execute a project in this manner.


Ralph
Structures Consulting
Northeast USA

 

[wannabeSE]

I like an elevation for each shear walls. The elevations have all of the openings, reinforcing, control joints, etcetera.

 

[Guastavino]

Who should establish the dowel locations (other than the EoR stating the spacing)?

I typically detail special areas with a typical detail. Special areas are wall corners, cells adjacent to openings, control joint locations and wall ends. Then I tell them the spacing in-between. For complex jobs with lots of openings I go the extra mile and detail a wall elevation. It takes time, but so does field corrective measures.​

Who should determine the layout of the control joints (which require a dowel either side of the joint)? I realize that the A/E determine the CJ spacing, but someone has to assign an actual dimension to their locations.

If you are like me, you have seen control joints installed in the middle of openings. I kid you not. This is what happens when you leave it up to the mason. My thoughts are if you want to be able to tell the contractor a joint needs to be moved for any reason, you better show them where it is. My interpretation of the MSJC section 1.2-(h) (using 2008 msjc) regarding construction documents is that you should show the locations. But, that is my interpretation. I just don't trust a contractor to figure it out.

How does this information get conveyed to the concrete sub who has to install the dowels?

If I detail it on my drawings, then I convey that information to them. If they change it, it's on them. Every time the contractor goes against my drawings my liability decreases (to a degree). I don't welcome this, but if they don't follow my drawings I can't control that. If I don't detail where they are and something goes wrong, I feel like it's on the designer for failing to communicate that. Control joist locations are critical to the performance of masonry.​

To what degree would mis-located dowels be acceptable

Depends on where. Code requires the special zones to be have reinforcing within a certain distance. If it's not provided it's not up to code.​

With all of that said, I don't think it is standard practice in my locale to provide joint locations. But I don't care, I go above and beyond. I see other engineers drawings sometimes and I wouldn't know how to build the structure, and I'm an engineer looking at the drawings. Put that into a contractor's hand and they will do what they want.​