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Modeling Diaphragm Stiffness of Unreinforced Masonry

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        Sorry for the delay in answering your question but, even though I had downloaded some of the FEMA chapters when you asked me, I had'nt had the time to read them. 
        If I understand correct, you mentioned chapter 7.  There it reads:

"[( lateral stiffness of masonry walls subjected to lateral in-plane forces shall be determined considering both flexural and shear deformations.]

[( masonry assemblage of units, mortar, and grout shall be considered to be a homogeneous medium for stiffness computations with an expected elastic modulus in compression, E me , as specified in Section]

[( linear procedures, the stiffness of a URM wall or pier resisting lateral forces parallel to its plane shall be considered to be linear and proportional with the geometrical properties of the uncracked section.]"

        As I see it, for an elastic analysis, they ask you to consider the whole section (uncracked) and to take into account the shear stiffness of the infill.

    Later, it is described how to determine the width of the strut for an uncracked section.  Since your analysis is non-seismic, the infill should never crack.  Then, as you won't be applying any reduction factors to the elastic analysis, I think it would be valid to use that formula for the stiffness of the diagonal compression strut. 

        Hope this helps.


Rodrigo Lema.