CMU walls- NO hook into bond beam

[ChiefInspectorJ]

While doing threshold inspections I have noticed the absence of vertical to horizontal 8" rebar hooks into the bond beam. The vertical rebar is 6" vertical into the bond beam? I assume the rebar functions as a anchor bolt but it is not spliced to the horizontal bond beam rebar. The CMU walls were 22" high and in 140 mph wind zone.
What is the difference in uplift capacity between the 2 methods?

 

[txeng91]

Do you know how far they are embedded into the bond beam? It’s not ideal but if the bars extend to the top of the bond beam you would think they would develop enough strength to exceed the capacity of whatever is connecting to it applying the uplift loads, unless your uplift is really high. How deep is the bond beam and what’s framing to it?

 

[dik]

Is the bond beam at the top of the wall? and, is the vertical reinforcing really required? if not, then no need for development.

Dik

 

[ChiefInspectorJ]

It is an 8" CMU bond beam.Trusses or bar joist span 60'. Rebar is 48" oc. Truss anchorage does not always line up with the rebar. So I assume the bond beam and lintels are held down by the 6" embedment into the bond beam.I have seen these CMU bond meams ripped off the top of house walls by 100 mph winds.

 

[ChiefInspectorJ]

Also this type of wall has quite a few voids in it.

 

[dik]

Then you need better anchorage... a roof membrane had blown of a water treatment building in Lindsay, Ontario twice before they secured it to the top of the masonry wall... next time it blew off, it took of the top course of block...

Dik

 

[ChiefInspectorJ]

A large SE firm designed the wall.

 

[JAE]

Ask the SE if there are net wind uplifts along the wall....per code wind there may not be any.

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[JLNJ]

A single high bond beam might not be deep enough to develop a hook or, said another way, a hook might not provide any additional capacity over the 6" straight embedment.

 

[dik]

JLNJ: it should... don't know how much, but, it is an improvement.

As JAE pointed out... is there any uplift on the roof connection... if not, then anchorage is not an issue. It is, however, nice to have...

Dik

 

[txeng91]

Unless you have concrete on the roof there’s going to be a good amount of uplift. If so, the whole system seems a little suspect if you ask me. 60’ joists anchoring into an 8” bond beam and a 22’ wall with rebar at 48” doesn’t sound like it’s engineered for 140 mph. If you wanted to tie the bond beam down a little better you could use some Simpson light gauge straps with 1/4” concrete screws that extend from the bond beam down a few courses to help develop the rebar.