shotcrete concrete pull out strength? 1

[yjung]

Hi,

I have a steel rod, 5 inch embeded into the f'c = 2000 psi shotcrete concrete about 7 in thick.
How can i compute the max allowable pull-out tension force that the concrete can resist?


thanks

 

[ishvaaag]

If unaffected by the proximity of other anchors, you need to verify your anchor for 4 limits to strength

1. Slippage
2. Formation of a sheared cone
3. Limit tensile strength of the rod itself
4. Flexural failure induced in the shotcrete lining under the applied force.

1. Slippage you check against the available perimeter at the tensile strength of the concrete, fct

2. The sheared 45º cone strength you may take equal to 0.7 fct on its projected area.

3. The limit tensile strength as 0.9Fy on the section of the rod

4. The flexural limit from structural analysis.

Further reduction factors are required if close to edges or close to akin anchors (start to think about these things at about 10 diameters of the rod to the incident thing). For an approximate calculation you may use the same reduction factors used for anchors with heads, or studs embedded for plates in precast parts, or spits, or whatever in these ways.

 

[ishvaaag]

Point 1 slippage needs be corrected,

1. Use fct on the available slippage (cylinder) area if only compression in the shotcrete. If there are tensile stresses affecting the rod, use two thirds of fct.