huangyhg

anchor bolt pullout strength in concrete
for steel anchor bolts, embedded in concrete during the concrete pour (i.e. no epoxy), can anyone direct me to a table or simplified calc method. interest is in 3/4" to 1" ab, various embedment between 12" and 96".
concrete can be assumed to be 3000psi.
my web search has yielded no useful results. my structural books seem to focus on steel to steel connections only.
thank you
pacificsteve
in ubc chapter 19, there is a table at the end (i don't have my ubc with me, so i can't tell you the exact number) that has allowable loads for various diameters and embedments. edge distance and spacing also enter into allowable loads. for your deeper embedments, i would just use the maximum allowable given as the steel cross section starts to control.
this is as simple as you're going to see. anything else is analytical and a royal pain.
if you want to get somewhat analytical (but not much, really), take a look at division iii - design standard for anchorage to concrete in the 1997 ubc (assuming this applies in your area). it details a method to calculate service load design values for both tension, shear and combined tension and shear, including a check on the adequacy of the anchor bolt material (in tension only!).
hope this helps.
tom
for tension only, one can use the projected-cone calculation. the area of pyramids (apex at anchor head) projected to the surface of concrete define potential failure planes in tension (use 1:1 projections).
i believe aci has a similar approch, but in canada, a23.3 defines pr = 0.3 ag (fc')^0.5 where ag is the total projected area from anchor head(s).
fc' = 20.7 mpa
for single bolt, 12" embedment case:
ag = (12"+12")^2, or 0.37 m^2
and pr = 0.3 x 0.37 x 20.7^0.5 = 505 kn (113 kip)
for single bolt, 96" embedment case:
ag = (96"+96")^2, or 23.78 m^2
and pr = 0.3 x 23.78 x 20.7^0.5 = 32 462 kn (7,298 kip)
these values are lsd resistance values intended to be used with the basic dead & live load factors 1.25 and 1.5 respectively.
aci ab-81 "guide to design of anchor bolts and other steel embedment" is a good start - i bought mine from the aci web site. thence it's the various structural engineering handbooks out there and check out the hilti and simpson strong-tie catalogs - both available on the web.
appendix b (steel embedments) of aci 349-97 is a method for determining anchor bolt pullout strength. i think this appendix is now part of the latest aci 318 design guide. it is based on a simple formula for the shear strength of the concrete times the surface projected area of a stress cone radiating toward the attachment from the bearing edge of the anchor. the calculation is simple unless you have multiple bolts resulting in overlapping projecting areas in which case it becomes a tricky geometrical problem especially in a trial and error solution. i found a website that has a projected area calculator:
use at your own discretion. i checked its results against my own calculations and found slight differences, but as i recall they were fairly close.
see simpson catalog
inspector jeff in florida
thanks for all the good information, i have a handle on this now.
pacificsteve

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