I don't have a beam or column to develop the bars into -- only a round or square footing (flagpole type) x the depth required. Appendix D only allows headed anchor bolts to be embedded a maximum of 25" (D.5.2.2 ) and we usually use min 1 1/4" dia anchor rods -- tough to get a hook on that size. Lapping with a deformed bar is questionalbe at best. So I am left with increasing edge distance, increasing concrete strength, increasing number of bolts. Any of these adds up to lots of extra costs. Most of my footings now are about 6 ft + square for a 20" square base plate. If the diameter gets over 6 ft. I don't even design it for that -- just go for the square one.
Jim Persing
On 9/13/07, refugio rochin <fugeeo@gmail.com> wrote:
I think the solution to the problem lies in the development length. If you develop the anchor bolt as reinforcement ie 22 db with hook or 44 db (example) long steel, then one can develop the anchor into a column or deep beam... No? I tend to add the minimal ldh that the ACI includes for the anchor development after running through the App D to the development length.
2007/9/13, Jim Persing <omega.two.0@gmail.com>:(Rant on) It's going to be interesting to see all of my past structures fall down (primarily gas station canopies) now that the anchor bolt connections suddenly do not work anymore. ACI 318 Appendix D is certainly an exercise in ......, well something. I'm not sure what. I now have to justify to my clients why they have to have larger footings than before with larger and longer anchor bolts (but not over 25" embedment!), higher strength bolts, higher strength concrete and special inspections that they never had to have before. My spreadsheet for anchor bolts is 4 pages long - and that's only for my special purpose anchor bolts. Between anchor bolts -- whoops, rods, and wind loads I'm glad that I'm getting close to retirement :) (Rant off)
Jim Persing, SE
On 9/12/07, Tom.Hunt@fluor.com < Tom.Hunt@fluor.com> wrote:
Christopher,
(turn on rant) Welcome to ACI 318 Appendix D. Once again a major code writing entity has slain a mighty paper dragon. It now takes half a grown tree just to design a few anchor bolts; sheeez! (turn off rant).
ACI 318 Appendix D "does" allow you to take advantage of supplemental reinforcing steel (refer to Section D.4.2.1 and it's commentary). The problem is that ACI came up with a rocket science thesis on how to design anchor bolts but provides no guidance on how to take advantage of supplementary reinforcing steel. To me this is a total let down of ACI and I have brought it up several times with Dr. Ghosh during his seminars and from his response I believe he totally agrees. There may be other or better documents but you might try finding a copy of ACI 349 Appendix B from the early to mid 1980s. Hard to believe we have to go back 25 year to find a document to help us design to a 21 Century code.
Thomas Hunt, S.E.
Fluor
"Christopher Banbury" <cbanbury@arkengineering.net >
09/11/2007 05:26 PM
Please respond to seaint
<seaint@seaint.org> embed plate design
I am looking for guidance on the design of steel embedment plates primarily subject to shear loads. In particular I am looking at a weld plate with anchor rods cast in a concrete column that supports a steel beam. I am unable to get the connection to work using Appendix D methodology. ACI 318 Appendix D seems to be overly conservative for calculating the capacity of the embedded anchors as it does not give significant credit for the reinforcement intersecting the failure plane.
I have had similar problems with concrete piers subject to shear and uplift loads.
Thanks in advance.
Christopher Banbury, PE
President
Ark Engineering, Inc.
PO Box 10129, Brooksville, FL 34603
22 North Broad ST, Brooksville, FL 34601
Phone: (352) 754-2424
Fax: (352) 754-2412
www.arkengineering.net
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