Anchor Bolt Design
Anchor Bolt Design
(OP)
Can anyone help me find a good reference(s)/example(s) regarding the design of anchor bolts for a sign support? The base plate is circular, the column is circular and the anchor bolts are in a circular pattern. I have many references with square/rectangular base plates and bolt patterns. Also, a good reference for anchor bolt embedment would be appreciated. The references I currently use are as follows:
AISC: Column Base Plates
Blodgett: Design of Welded Structures
PCI: PCI Design Handbook
AISC: Column Base Plates
Blodgett: Design of Welded Structures
PCI: PCI Design Handbook
RE: Anchor Bolt Design
Good Luck
RE: Anchor Bolt Design
4 is just a special case of the rectangular
method. If there were 8 or 12 bolts, use
2 times and 3 times your 4 bolt result for
the 4 bolt rectangular or square result.
You would have to calculate the lengths
based on the base circle diameter to determing
your square or rectangle.
RE: Anchor Bolt Design
(I' = I + Ad^2).
I think ACI 318 Appendix D might be a good reference.
I seem to recall a bond strength for determining embedment depth in the pre 1971 ACI 318, but have not seen it for years and don't recall the formula. Not sure that it would even be a recognized method today.
RE: Anchor Bolt Design
RE: Anchor Bolt Design
RE: Anchor Bolt Design
I've found some calcs in ASHREA and the CBC (California Building Code) but its difficult to get a handle on where to start. There seems to be some conflicting information.
thanks
jay
RE: Anchor Bolt Design
RE: Anchor Bolt Design
RE: Anchor Bolt Design
http://www.engineering-software.com/me/
RE: Anchor Bolt Design
I assume you have a moment type conenction, so that the rods are not equally loaded. In this case, figure out your worst case rod, and design for that embedment depth for all rods. Now if you have overlapping failure cones, you will have to reduce the capacity based on the reduction in projected surface area. So you might have to iterate a few times to get the correct answer. If you need to prestress the rods or have a significant ductility requirement, make sure you have enough rod length unbonded to provide for the required ductility. This may mean either extra long embedment depth, or connecting the rods to the columns some distance above the base plate.
For analyzing the stress at each rod, assume a neutral axis thru the middle of your round column, preferrably thru two of the rods. Now, assume a linear strain distribution. Using this, you can calculate the strain at each rod in tension based on its distance to the neutral axis. Once you have the strain, you can figure out the stress, and rod area required. This would be similar to a deep concrete beam with multiple layers of reinforcing steel. I actually had to do this analysis during a concrete exam back in university for a round beam with bars spaced around the perimeter. Kinda took us all by surprise, but the same method holds as for rectangular beams.
RE: Anchor Bolt Design
http://www.mdot.state.mi.us/specbook/
Refer to Section 810.03N
In my opinion, supporting sign bases on nuts and anchor bolts is preferable to counting on grout under the base plate, which is often of questionable quality.
RE: Anchor Bolt Design
RE: Anchor Bolt Design
The guide not only covers base plate design but also anchor bolt design. The guide has examples problems in both ASD and LFRD.
If you have a copy of the guide, check the AISC website since there is an errata sheet.
RE: Anchor Bolt Design
RE: Anchor Bolt Design
The AISC Design Guide is available from aisc.org for $60, but it is about 15 years old and does not address the new OSHA requirements or round base plates or circular bolt patterns. ASCE has a design "standard" for steel transmission poles in committee that will have a good example in it, but I don't know if it is in the present design "guide". It will be some time before the standard goes to press.
RE: Anchor Bolt Design
I was using from ASD:
Ft=0.5Fu
Fv=0.3Fu
But this is for Allowable Shear rupture. Can anyone clarify this for me. I don't think I am to use LRFD J5-2 Design strength of Connecting elements in Tension since this is not that type of connection (e.g. plate, gusset)
RE: Anchor Bolt Design
Would "Lufti" post a copy from an article that was published in Plan Engineering Magazine and will post a URL if appropriate.
RE: Anchor Bolt Design
RE: Anchor Bolt Design
The danger of "rule of thumbs" is that everyones thumb is a different size. I have seen 20 and 25 x nominal diameter for minimum embedment. ASCE's steel pole committee is discussing wether it should be 25 or 30 times nominal bolt diameter. By comparison, the 17 seems to be unconservative. For low strength bolts on large spacings, it may work, but not for high strength bolts on small spacings. Lots of variables at play -- bolt strength, bolt spacing, bolt edge distance, concrete strength, and transverse reinforcement.
RE: Anchor Bolt Design
1. Industrial Buildings, Roofs and Column Anchorage by AISC 1993
2. Column Anchorage Design: Base Plates with Moments or Shear by John T. DeWolf, 1988
3. Design of Headed Anchor Bolts by John G. Shipp and Edward R. Haninger, Engineering Journal AISC 2nd quarter 1983.
So with these I am moving ahead with my design..
RE: Anchor Bolt Design
In fastenind anything to the earth, you must remember the earth is round and not square....
RE: Anchor Bolt Design
I am anticipating a 1 1/4x6x6 pull out plate with these anchor bolts.
Thanks
RE: Anchor Bolt Design
ht
RE: Anchor Bolt Design
Hg
p.s. ...and feel free to write to the DOT and complain about how bookmarks to their manuals go away, but don't tell them I sent you!
RE: Anchor Bolt Design