design for shear 4

[leitao110]

I want to know what is the difference of these two formulas.On the design of concrete structures book, in the calculation provided concrete shear formula, Vc = 0.17λ√fcbwd. But in the ACI Code 11.2.1, Vc = 2λ√fcbwd. Why do they always will be a difference of nearly 10 times factor.I am a Chinese student of civil engineering in the concrete structure design principle of our books, involved in concrete on shear and tensile strength of concrete is concerned, Vc = 0.7ftbh. Is √fc equivalent tensile strength of concrete.

 

[allgoodnamestaken]

I don't have my ACI book with my at the moment, but offhand I'd guess units.

 

[cl220]

My concrete books have shear as Vc = 2λ√fcbwd.

 

[Lomarandil]

Agreed, the difference you notice is probably due to units of the f'c value. The ACI equation starting with 2 expects f'c to be in units of psi. I am not familiar with your equation starting with 0.17, but I suspect it expects f'c in different units (metric, perhaps?). Because the equation relies on the square root of the compressive strength, the units don't work out correctly unless combined with a hidden unit typically buried in that leading coefficient.

Typically, the tensile strength of concrete (we call it the modulus of rupture) is considered proportional to √fc

 

[wannabeSE]

The difference is units: SI vs US customary units. Look at appendix F of ACI 318 for equivalent SI formulas.

 

[leitao110]

Thank you