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Re: Masonry Lintels Size Limit?

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Depending on the wall above, you may be able to arch over it.  I have in the past on masonry and precast plank  buildings used arching action of the wall above and lateral bracing of the wall by the precast plank.  The large opening was on the ground floor.  I designed the lintel as a tension tie and the wall directly above I designed to "hang" the section that would fall out of the arch from the arched masonry.  Essentially this is a 45 degree triangle.   I used horizontal and vertical reinforcing in the wall on the floor above to hang the wall and floor loads.  Since the walls were 4 stories high there was plenty of depth to arch over.  The masonry puts up temporary shoring until all the floors above are built and sufficiently cured, then removes the opening.  It makes a very good lintel for wide openings.  I went back after construction and didn't see any cracking in the wall panels.
 
Rich
 
 
On Tue, 9 Nov 2004 09:25:44 -0800 (PST) Jim Wilson <wilsonengineers(--nospam--at)yahoo.com> writes:
Is there a practical limit to the size of a cast-in-place masonry lintel?  A builder has asked to use grouted-in-place masonry block and rebar in lieu of a precast concrete beam.  The opening is 17ft and the depth of the lintel would have to be 6 courses deep of 8" block.  NCMA Tek 17-1b lists capacities for up to 3 course masonry lintels.
 
Are deep masonry lintels made with bottom course lintel blocks and then fully grouted regular block placed in running bond above that?  I can't find any design info in either the NCMA Tek notes or ACI 530 that discusses block types or shear reinforcement for this condition.
 
Jim Wilson, PE
Stroudsburg, PA


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