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RE: Concrete Masonry Arch

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Load bearing wall?  If so, how far above the arch?
What type of arch?  Circular?  Gothic?  Parabolic?
If the arch is of the appropriate shape, then it should be in pure compression...but that "appropriate shape" somewhat depends on the type of loading on it.  If the loading does not "match" well with the shape, then the bar following the shape of the arch might be useful as the arch might also be in bending.
As noted in another post, BIA has some good tech notes on the subject of arches.  While they are aimed at brick arches, the basic principles should still apply.
Adrian, MI
-----Original Message-----
From: Rich Lewis [mailto:seaint04(--nospam--at)]
Sent: Thursday, June 19, 2008 8:58 PM
To: seaint(--nospam--at)
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.