the rigidity of shear wall

[Stormin74]

In our TGI Friday one story building, three sides are wood shear wall panel, one side is block masonry wall, #5@24"O.C. How do I get the relative rigidity for each side of wall to distribute the lateral force cause by wind or seismic since these 4 side are different material? Is any simply way other than calculation the section property? Or any software will do the job for me?

 

[JAE]

If your diaphragm is wood, then perhaps you have a flexible diaphragm and can simply distribute the loads by tributary width exposure?

 

[NKT]

The masonry shearwall will be much more rigid than the wood shearwall, so it may be reasonable to neglect the contribution of the wood shearwall for lateral forces parallel to the masonry wall. Then check the perpendicular walls and roof diaphragm for capacity to resist the torsion caused by the offset between the lateral force resultant and center of rigidity. This assumption would move the center of rigidity to the masonry wall line.

 

[haynewp]

If it really turns out to be a rigid diaphragm meeting code definition, develop the rigidity of the wood versus the cmu. There are formulas for cmu shear rigidities in Amrhein's masonry book because I have used them, here is something on wood shear walls but it is also in a wood text like Breyer. It is just relative rigidities. I don't know of any software that allows you to model cmu walls with wood shear walls. I don't think I would say to completely ignore the wood shear walls under direct shear without knowing more about the building, number of openings in the cmu etc.

http://www.curee.org/projects/woodframe/element5/modules/shearwall/deflection.htm

 

[hokie66]

I would take another approach. Since your structure is essentially wood framed, I would just pretend the masonry wall is a wood shear wall like the other side. The additional stiffness of the masonry wall would just be an added benefit.

 

[haynewp]

If you did that, the cmu would suck up more force than it is was designed for.

 

[hokie66]

Yes, but it should be well capable of doing so. This is only a single storey building, and the block wall is reinforced at 24" centres.

I really am just taking half on each wall, just as JAE suggested above.

 

[haynewp]

yes, probably fine in this case. As long as the foundations would be adequate either way.