How to calculate the tensile capacity of rebars? 2

[bojoka4052]

I am looking at previous calculations, and they say that four 8mm in diameter rebars have a tensile capacity of 87.4 kN. How do they get to these numbers? I would assume then that if we have six 8 mm rebars they would be 1.5*87.4 kN = 131.1 kN?

 

[Ingenuity]

A = 4 x 8²Π/4 = 201 mm²; Assume f_sy = 400 MPa

T_sy = 201 mm² x 400 MPa = 80.4 kN ==> So your 87.4 kN would mean a F_sy of 435 MPa.

So yes, 6 @ 8mm dia bars would be 131.1 kN

 

[1503-44]

Hold on a second. A lot of assuming is going on here.
Where does bojoka4052 tell you that the bars have an Fy of 435MPa?

Assuming that it is not an ancient design and the bar's Fy is 60ksi, 435MPa, then yes it would be 131kN, however if the design used older bars with a typical 40ksi yield, 87 is the correct answer.

 

[centondollar]

You should direct your question to whoever made the calculation or, alternatively, familiarize yourself with the rebar strength and material partial factor assumed in the calculations.

 

[dik]

400 MPa has been common for decades, at least here... and I suspect other countries are similar (maybe not 3rd world ones). Until about 20 years back 300 MPa was only used for stirrups. I remember one project in the winter of 1969, I was out on site and accidentall dropped a 60 grade stirrup on a concrete sidewalk, and it broke.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[WARose]

As far as I know, the tensile capacity of a member is (by ACI): P_u=Φ(A_st)(F_y)

IIRC Φ is taken as 0.9

 

[kingnero]

@ dik, might want to specify "here"... Canada iirc?
Here (= Europe) the standard is B500, thus fy = 500 MPa, fu = 550 MPa.

 

[dik]

Thanks King... I did note, "at least here". Nice to know that they are using higher strength rebar... every little bit helps in reducing 'waste'.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik