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RE: Concrete Masonry Arch

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This is not specifically what you asked for, but I would think perhaps some of the info could be applicable to CMU arches.  In the past when I have designed and detailed brick arches, I used the technical guides on the Brick Institute of America’s website – http://www.gobrick.com/html/frmset_thnt.htm

Here are some technical guides that have some nice rules of thumb for brick arches (especially with regard to arch rise to span ratios), that I think might be applicable to CMU arches as well.

Brick Masonry Arches 31A [Oct. 1967] (Reissued July 1986)

Structural Design of Brick Masonry Arches - 31B Rev [Nov./Dec. 1981] (Reissued May 1987)

Structural Design of Semicircular Brick Masonry Arches 36 Rev [July/Aug. 1981] (Reissued Jan. 1988)

If the arch rise to span is appropriate, then it would seem that the masonry should principally be in compression, and no reinf. steel required; unless there are perhaps other considerations like minimum reinforcing requirements for seismic design category.

 

Hope that helps.

 

Randall Moore PE SE

Wilmington NC

 


From: Rich Lewis [mailto:seaint04(--nospam--at)lewisengineering.com]
Sent: Thursday, June 19, 2008 8:58 PM
To: seaint(--nospam--at)seaint.org
Subject: Concrete Masonry Arch

 

I’m looking for detailing tips and insight in concrete masonry arch construction.  I have a project where the architect has shown several masonry arches.  The wall construction is 8” CMU and a brick veneer.  I have seen many brick arches built but I have never seen a concrete masonry wall arch built.  I have some opening in the 15 feet span range.

 

I have NCMA TEK 14-14 which states the arch should be made of solid CMU or the CMU should be grouted solid.  I see the steps to construct the arch as being:

1.       Install arch form

2.       Create the first row of the arch using brick, either clay or concrete.  The architect will determine that.

3.       Build the brick veneer arch as a typical brick arch.

4.       Build the CMU backup arch using cut block.  I would assume hollow block.

5.       Grout the arch solid up to the crown height

6.       Put in a bond beam course directly above the crown.

7.       Build the wall above the arch as a typical wall.

 

I’m wondering if I should put some steel bars in that follow the arch curve, directly above the first row of bricks.  I know this area is in compression so I don’t see much use of the steel.  I’m also wondering if I should have some vertical steel in the arched section of wall, between the bond beam and the first row, above the spring line.

 

I open to suggestions for detailing CMU arches. 

 

Thanks.

 

Rich