Headed stud anchors in CMU

[braves25]

This maybe a simple question, but want to make sure I set this up correctly. In the ACI 530-11 code section 2.1.4.3.1.1 and 2.1.4.3.2 for the allowable tension and shear loads for anchors in CMU. For the steel portion of the checks, there is the specified yield strength of steel for reinforcement and anchors (fy) as part of the equation. My case is where I have a steel bar joist bearing on top of a CMU wall. Embed plate as a bearing plate with headed stud anchors to resist shear and tension. For tension the equation is Bas = 0.6Abfy and for shear Bvs = 0.36Abfy. For the A307 steel (headed studs) do I use 36 ksi for the fy or something else.

Side question: the ACI 530-11 provides a nice equation for the Apt for multiple anchors. Anyone have an equation for multiple anchors in shear to calculate Apv?

Thanks and have a great day.

 

[braves25]

One more additional question to add...in looking back at the ACI530-05 code, for the tension and shear bolt equations 2-1, 2-2 and the shear equations, I see a rather large increase in the constant. I realized that the 1/3 increase is no longer valid, but from the 05 code to the 11 code the Bab equation went from 0.5Apt(fy) to 1.25Apt(fy). And steel tension Bas = 0.2Ab(fy( to Bas = 0.6Ab(fy).

Why the large increase? FYI, I'm looking at allowable stress.

Thanks.

 

[spats]

According to my information, for HCAs/Nelson studs, yield is 51 ksi, and ultimate is 65 ksi. These properties are listed in Table 7.1 of AWS D1.1 (I have 2010).

 

[wannabeSE]

AWS D1.1 lists 49 ksi for type A studs and 51 ksi for Type B studs.

I have not looked in a while. But CMACN may have some equations for Apv in a past Masonry Chronicle. See

http://cmacn.org/masonry-chronicles.htm#past

In 08 or 11, ACI 530 changed anchor bolt equations so there was better agreement between ASD and Strength design. In 05, there were significant differences in the ASD and strength capacity.

 

[hokie66]

I know you said this is about "the steel portion of the checks", but does the strength of the steel ever affect the capacity of headed studs in masonry?

 

[wannabeSE]

Hokie,
Typically it will not govern but it can.

consider 1/2" headed stud in tension w/ 8" embed in 12"CMU

A_pt = π8² = 201 in²
B_ab = 1.25A_pt sqrt(f'm) = 1.25(201)sqrt(1500) = 9730 lbs
B_as = 0.6A_bf_y = 0.6(0.20)(51000) = 6120 lbs