Masonry Wall Beams

[OzEng80]

Hi

I have used reinforced (horiz and vertically) masonry walls as ‘wall beams’ on several jobs. These have been typically limited to well supported, lightly loaded, simple span walls and a simple first tier, strut tie analysis determined they worked comfortably. I have also done the same process with a concrete wall with irregular spans and a large cantilever. The wall was designed using finite element software with the reinforcing being based on limiting stress requirements in accordance with (Australian) concrete code requirements.

My question is how hard can I make a masonry wall work? Can a similar (limiting stress) approach be adopted? What would be a suitable value? Do other engineers use masonry walls in this manner?

Thanks

 

[OzEng80]

Hi

Thought id bump this thread as the lack of comment/reply has me concerned that my reasoning and use of masonry in this manner might be flawed.

There is enough documentation on concrete wall beams for me to design this type of element as concrete, but the design of masonry wall in the same manner is unclear. Given that a core filled wall is approximately as stiff as a concrete wall and much much stiffer than most transfer slabs, masonry walls will almost always attract in plane bending (on a transfer slab).

Therefore do other engineers utilize the vertical stiffness of masonry walls to distribute vertical load (in-plane bending) or are these elements being treated as carrying only vertical load?

What is an appropriate design approach to limit cracking (in service conditions) for a masonry wall subject to tension?

Thanks

 

[prsconsultant]

Take a look at the online TEK manuals developed by National Concrete Masonry Association.

Chapter 14. Structural - General has all the info.
Here is one of the links to access TEK manual.

http://www.ncma.org/map_pages/state_listings.cfm?state=RI

 

[msquared48]

You might also check the codes and references for the term "Deep Beams" which is the one I know the situation you describe by.

Mike McCann
MMC Engineering

 

[OzEng80]

Thanks Prsconsultant. That’s the info I was chasing - 'limiting reinforcing stresses under service conditions for masonry in tension'. I was initially surprised to see that the allowable stresses are comparable to concrete (I thought they would be smaller). Given that any tensile forces are required to be taken by the steel alone for both concrete and masonry the steel design should be similar.
Does masonry behave the same as conventional concrete in tension? Will the reinforcing elongation present as hairline cracking at mortar beads only? Given that a masonry wall has mortar bed 'crack inducers' at 200crs would you consider that a masonry wall would perform better than a concrete wall (ignoring tensile strength of concrete) in direct tension (less chance of a 'large' crack opening - just lots of small ones)??

Thanks for your times and assistance.