Prescriptive/proportional requirements for ring beams in unreinforced masonry? 2

[Lomarandil]

I'm fairly new on the masonry side, let alone unreinforced masonry.

Does anyone know of prescriptive or rule of thumb requirements for when an unreinforced masonry (infill) wall needs to have a ring beam at the top? Or when a tall infill wall should be interrupted by a reinforced concrete element?

I can calculate the infill panel capacity for out of plane loads per MSJC Appendix B depending on panel proportions, but I want to be sure I'm not missing other guidance. Not familiar enough to know where to look.

Thanks!

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just call me Lo.

 

[Lomarandil]

Bringing this back up for one more pass. Thanks!

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just call me Lo.

 

[r13]

What is the use of wall - free standing property wall, building wall supporting slab/roof/beam/joist? Need more information to have meaningful discussion.

 

[dhengr]

Lomarandil:
No particular code citations, I haven’t bought that last few eds. of any of the codes or stds., so I’m a little in the dark on the latest complexifications. Just some food for thought and some engineering common sense. I think that what you are talking about in the way of a “ring beam at the top,” is what we always called a bond beam. It’s a std. conc. blk. shape, usually ‘U’ shaped, and has a couple #5 rebars in it and is conc./grout filled. In this case, it ties the top of the wall together with a fairly meaningful structural element. It prevents cracking/splitting of head joints and most movement in the bed joints. They provide a good bearing surface for roof framing, bar jsts. for example, and the distribution of the reaction loads. They can act as chord members for tying the roof diaphragm and wall together. I’m not sure I know what you mean by “infill wall,” what it does, how it is loaded and supported, etc. Even on interior walls, we apply a min. of 5lbs./sq.ft. lateral loading, or any other lateral or eccentric loads from storage shelving and the like.

Lower in the wall, where there is some nominal compression loading (at least DL) the wall is inherently more stable in terms of bond and shear strength in the horiz. joints, rendering the wall system more stable against various loadings and differential movements. Even in unreinforced or ungrouted walls we usually used horiz. jnt. reinforcing in every other joint, to tie the wall together and limit/distribute cracking.

 

[r13]

dhengr,

Excellent response. I guess the "infill wall" is a sandwiched wall with mortar/concrete filling.