Hollow Core on CMU Bond Beam

[nuche1973]

Greetings,
I was given a detail that shows hollow core plank forming a joint on top of a 12" CMU Bond Beam. Each plank has 4" of bearing and there is a 4" gap between the ends. The cells are not grouted, but there is a 3" topping slab that will cover the joint and fill the 4" gap (I know PCI notes a 2" TS, but the arch wanted 3"). There are bent dowels that extend into the bond beam and alternate between the opposing plank with in the 4" gap (I assume to pin the ends). The wall calcs out for the load, in general, but I want to check the bond beam wall/edge for bearing. How do I do this? Any advice would be greatly appreciated. Thanks.

 

[JAE]

Max. bearing stress for CMU with f'm = 1500 psi is 375 psi I believe (from ACI 530).

 

[nuche1973]

JAE,
Is there a method to check bearing on one side of a bond beam block?

 

[concretemasonry]

An f'm of 1500 would certainly be very conservative.

The bond beam units are not tested for f'm in prisms and the unit strengths of bond beams are not tested according to the ASTM C140 procedures (sawing and truncating is required) because the masonry panel is a structural element made of similar units.

The detail you are referring to is a standard proven detail with 3" bearing, because that is the norm for application with 8" walls. Depending on which/witch assumptions you make on the detail, you can make it work or not work.

Dick