On Tendon cables per ANSI/ASTM A 416 - 74 2

[Iasonasx]

I wonder, with a grade 250 steel why ANSI/ASTM A 416 - 74 on page 384 we get breaking point well before the yield point. I never worked on this subject before but I just wonder if there is some important safety factor that is already incorporated. For example, the 1/4" cable is suggested to break at 9,000 lbf. If we simply apply the cross-sectional area of that and multiply it by 250 kips we get 12,271 lbf for yield, let alone breaking. Not only we disregard all the plastic region but a serious portion of the elastic region of the material. Could someone please give me some insights on this? Thanks!

 

[hokie66]

The "Grade" of prestressing cables does not mean "yield point". It is the minimum breaking stress.

 

[Ingenuity]

As hokie66 stated, and FYI high strength prestressing steels do not have a defined yield point so the "yield" is often taken as a % strain offset, parallel to the E modulus. Also, the elongation of high-carbon content prestressing steels is considerably less than mild steel. ASTM A416 requires min of 3.5% elongation, but strand typically test close to 8%.

 

[Iasonasx]

Thank you hokie66 and Ingenuity.