limitation of fy used in ACI shear friction calculation 3

[jiing]

Hi,

Can anyone tell me why ACI 318-05 section 11.7.6 limits the value of reinforacement "fy" to 60 ksi for the shear friiction calculation? I am hoping to use high strength dowels with fy=120 ksi to increase the shear friction capacity. Thanks!

 

[JAE]

Maybe because the shear friction is limited by the interlock possible between the concrete surfaces. Shear friction works, not based on shearing through the rebar, but on shear interlock across the joint. The rebar simply are there to keep the two surfaces in contact.

Much of the shear friction research was probably limited to 60 ksi bars and the resulting formula based on that research. Since 60 ksi steel and 120 ksi steel have the same modulus of elasticity, E, the behavior using higher strength bars doesn't do you any good....that's my guess anyway.

 

[hokie66]

I am sure JAE is correct. The strength of the bar makes no difference. The clamping force would cause the same elongation in any strength bar.

 

[NS4U]

I would say because shear friction is empirical and testing is limited to bars with Fy=60ksi