Embedded headed studs in masonry

[Berniedog]

Does anyone have any references for headed studs in masonry? ACI 530-02 (2.1.4.2.3) does not address headed studs loaded in a group. How do you handle this?

 

[sundale]

For multiple studs, you need to consider the overlap of Ap areas per 2.1.4.2.2.1. This is a real trigonometric pain, but p.296 of Amerhein's 5th Edition of Reinforced Masonry Engineering Handbook has these reductions tabulated. To the best of my knowledge, these reductions apply to both the '94 UBC (upon which this book is based) and ACI 530-02 (still the same).

It would be interesting to calculate a stud group in masonry and the same stud group with the same boundary condition in concrete with ACI 318-02, Appendix D voodoo equations. My guess is that that the masonry numbers would be higher!

 

[Berniedog]

Doesn't Section 2.1.4.2.2.1 apply to anchors in tension? My case concerns anchor in shear. Equations 2-5 & 2-6 do not use
2-3 & 2-4.

 

[sundale]

Brian,
For shear (Bv), there is no reduction for spacing of bolts per '03 IBC. You still need to consider edge distance. You used to have to take a reduction per '94 UBC for spacings less than 8db (UBC 2107.1.5.3). Why the gurus changed this, I do not know. This is not intuitive and I share your confusion.

There are, however, very few instances where an embedded connection with multiple studs is subjected to pure shear. I can usually draw a FBD that puts a stud row in tension.

 

[Berniedog]

Thank you