Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

Re: CMU California Practice in the 1950's

[Subject Prev][Subject Next][Thread Prev][Thread Next]
This is what I found out on the issue from Mr. John Crysler of Masonry Institute of America (Mr. Crysler has been a source of invaluable information regarding masonry for many years).
 
Before the 1990s, a 48" spacing of rebars in the CMU wall was quite common, and partially grouted walls were widely used [for example, refer to Seismic Zone 4 requirements 1988 UBC, 2408(h)4B].  
 
With the code becoming more restrictive, and, particularly, with the introduction of the near-source seismicity, the rebar spacing had tightened, and the contractors, essentially, came up with the idea of grouting walls solid without the cost increase (saving on labor).  Ever since then, the solid-grouted walls became a more common practice (by no means a code requirement) in California.
 
Solid grouted walls have their advantages (moisture and fire resistance, sound insulation, etc.), but, of course, the weight remains a major drawback.  There is nothing wrong whatsoever with the use of partially grouted walls; the choice of grouting is still mostly dictated by economics and other non-structural issues.
 
As always - many thanks to Harold for valuable information.
 
V. Steve Gordin, SE
Irvine CA
   
----- Original Message -----
Sent: Monday, April 27, 2009 10:22
Subject: RE: CMU California Practice in the 1950's

CMU construction practice and the CMU open end unit availabilty are a function of region and time period.  The US Army Corps of Engineers had a lot to do with pushing the open end units.   
 
The A blocks (one end open) are not very difficult to find anywhere in the US.  The masonry contractors like them in the field because if the rebar spacing of 16" or more, you can have one lap splice at the dowel and let the vertical bar extend up to the top of the wall.  The block is then placed around the bar as opposed to up and over, or with a lot of lap splices. 
 
Once the contractors are accustomed to using the A blocks, they prefer them.  There are a lot of good details that the Corps has in their Std. Det. No. 00-90-04.

Regards, Harold Sprague


 

Subject: RE: CMU California Practice in the 1950's
Date: Mon, 27 Apr 2009 07:30:55 -0700
From: rgarner(--nospam--at)moffattnichol.com
To: seaint(--nospam--at)seaint.org

Correct me if I'm wrong, but I first saw the open-ended units in the '70s.  They weren't popular at first since the units tended to be somewhat warped and lent a basket-weave appearance to the finished wall - we used to call it basket-weave bond instead of running bond.

 

We used to grout only the reinforced cells back then.  This was back when grout was expensive and labor was cheap.  Ahh, the good old days.

 

Bob Garner (At the time, working in Oakland, San Jose and Santa Cruz, CA)

 


From: Bill Allen [mailto:t.w.allen(--nospam--at)cox.net]
Sent: Sunday, April 26, 2009 12:48 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: CMU California Practice in the 1950's

 

Really?

 

I know the preference for open end blocks which means grouted cells are really grouted double cells, but I'm curious if this is true.

 

After all, grouting solid is a heavier wall producing more force at the tie at the top and increasing the load on the diaphragm. If bars are only required at 48" (#4 @ 24" or even #5 @ 32"), that means half the wall can be un-grouted providing quite a bit of reduction in mass transferred to the roof diaphragm.

 

I've designed quite a few block walls grouted at steel only, all of them since 1980. I'm wondering if I'm out of step with standard practice. Of course, it wouldn't be the first time.

 

T. William (Bill) Allen, S.E.

ALLEN DESIGNS

Consulting Structural Engineers
 
V (949) 248-8588 F(949) 209-2509


I know that it has been the general practice in California to grout CMU walls solid since at least the 1980's. 


Regards, Harold Sprague


Windows Live™ SkyDrive™: Get 25 GB of free online storage. Check it out.



Rediscover Hotmail®: Get e-mail storage that grows with you. Check it out.