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Re: Seismic - Isolating CMU infill wall

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To Rodrigo Lema:

Answer the following questions:
	1.  	If you provide a gap which is a little bit more than the 
anticipated deflection of the frame do you think the frame will still lean on 
the wall?
	2. 	Assuming that the frame will lean on the wall but the wall 
was not designed to resist the shear or lateral load, what will happen to the 
wall?
		My guess is, it will fail ( or crack).
	3. 	If the wall will fail, will the frame be able to resist the 
lateral load that has designed for in the first place?
	4.	Since you can't rely on the strength of the infilled wall how 
can you use it for design?

	Manufacturers of CMUs have controlled environment to make sure that 
their products are manufactured as per the specified strength.  They do test 
their products using standard practice of testing.  This way they are sure 
that the strength of CMU in each specified design mix is attainable.  CHBs 
are not.  They are mixed at the site with some kind of proportion and without 
the benefit of testing.  For all I know, CHB's strength is only about 200 psi 
(I'm not sure on this).  If your clay brick is the same as CHB in reliability 
then it is hard to use the infilled walls to resist lateral loads without the 
support of standard testing.  I know where you were coming from when thought 
how these infilled walls can resist the lateral loads. But until somebody can 
come up with a more established and controlled environment in producing the 
CHBs or brick walls for that matter then using them for resisting the lateral 
loads is not advisable.  Use CMUs or Jack-Built instead. (Jack Built is a 
brand name of CMU).



Alfonso S. Quilala Jr., P.E.