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Up Topic Welding Industry / Inspection & Qualification / Minimum Edge Distance on Base Plates
- - By QCCWI (***) Date 12-13-2005 14:33
OK I have my opinion on this but I would like the opinion of others. The drawings I have call for 1-13/16" holes in a 1-1/2" thick baseplate and the center of the hole is only 1-1/2" from the egde of the plate. The edge of the hole is only 5/8" from the edge of the plate. I say it the distance from the edge of the plate should be more than an 1-1/2" for a hole that size, but then agian who am I.

I think the edge distance to the center of the hole should be over 2" but my high school education might have failed me.
Parent - By swnorris (****) Date 12-13-2005 17:29
There are no tables that indicate minimum edge distances for holes in column base plates. When the holes are not subjected to a lateral force, even an edge distance that provides a clear dimension as small as 1/2" will normally suffice. Edge distances may be increased during the design stage in anticipation of field issues with anchor rod placements. This allows for some slotting or additional oversizing in the field if needed. Now, I can't possibly imagine why this is thought to be necessary, because we all know that anchor rods are always set exactly where they're supposed be.
Seriously, edge distance criteria is really dependent on what type of force the anchor rods are designed to transfer. Have you looked at the design drawings? They may show a specific edge distance. Detailers sometimes fail to correctly transfer design criteria to the shop drawings. If not, and you feel the edge distance on your shop drawing is insufficient, ask the EOR.
With a 1 13/16" hole diameter, your anchor rods should be 1" diameter. As you probably know, the requirements for anchor rods are much different, both in terms of loading and in terms of detailing, than those for structural bolts used in steel to steel connections. The AISC requirements for structural bolts, hole sizes, edge distances, spacing, etc. are stated in Section J of either the current AISC LRFD or ASD specifications, but these requirements do not apply to holes in base plates. Suggested hole sizes for anchor rods are listed in the AISC ASD Manual of Steel Construction, 9th edition, on pages 4-130 and 4-131. Also, the LRFD Manual of Steel Construction, 3rd edition, lists the hole size in Table 14-2 on page 14-27. Note that the later issued (LRFD) manual has larger sizes than the much earlier (ASD) manual. These hole sizes have been increased from the earlier ASD editions to provide a greater possibility for alignment with the actual performance of other trades in setting anchor rods. In many cases after erection, anchor rods are not relied on to transmit any force. Should the rods be required to resist tensile or shear forces in the design, the EOR must evaluate the resulting forces and stresses in both the steel and concrete elements of the foundation. This is where edge distances need close evaluation.
Parent - - By G.S.Crisi (****) Date 12-13-2005 20:09
The Good Engineering Practice says that the minimum distance between the edge of the hole and the edge of the baseplate should be sufficient to accomodate the anchor bolt washer.
In other words, the tip of the washer should coincide, as a minimum, with the edge of the baseplate and not protrude over it.
What's the Good Engineering Practice? I've answered that question on the post "Weld discontinuity", by FSMalley, on the Certification section of this Forum, dated September 26, 2005.
Giovanni S. Crisi
Sao Paulo - Brazil
Parent - - By vonash (**) Date 12-19-2005 20:46
Check LRFD 1999 section 16.1-243, para. 4 & 5. It is 1-1/2 times the bolt diameter.
Best regards,
Vonash
Parent - - By swnorris (****) Date 12-19-2005 21:34
vonash,

I have a silver 1998 copyright LRFD, Vol. 1, 2nd Edition, and I can't find "section 16.1-243, para. 4 & 5". Am I looking in the correct manual? Is it in the 3rd edition? I assume section 16.1, page 243? I also can't find it in ASD/LRFD Vol. II. I am aware of some minimum edge distances of 1 1/2 (d) for specific instances with regard to sheared edges, but edge distances for anchor rods does not apply. Keep in mind that bolts and anchor rods serve two different purposes, and they each fall under entirely different design criteria, as I mentioned in my initial post. Are you positive that what you posted applies to anchor rods, or strictly bolts? I'd really like to find it and take a look at it.
Parent - - By G.S.Crisi (****) Date 12-22-2005 14:04
Scott, Vonash,
1st. I confess my ignorance: what's the LRFD?
2nd. Back in my days of erector engineer, for several times I found baseplates that were too short.
What to do? Have the supplier to furnish new ones and delay the job until they were delivered? No way, erection jobs can not be held back just because of a base plate.
Make new ones at field? Sometimes this is possible and sometimes not.
In this latter case, if the base plate could accomodate the washer, as I said before, all of us, contractor and client, agreed that the baseplate was OK.
Giovanni S. Crisi
Parent - - By QCCWI (***) Date 12-22-2005 14:24
LRFD is stands for Load and Resistance Factor Design. It is one of the Manuals of Steel Construction. The ASD (Allowable Stress Design) and the LRFD have pretty much the exact same thing in them. As a matter of fact AISC combined the 2 books into one when they made the latest revision.
Parent - - By swnorris (****) Date 12-22-2005 16:47
Actually, the new Manual replaces both the 9th Edition ASD Manual and the 3rd Edition LRFD Manual, and much of the HSS Connections Manual has also been incorporated and updated in the new manual. Also included in the new manual are the 2005 AISC Specification for Structural Steel Buildings, the 2004 RCSC Specification for Structural Joints Using ASTM A325 or A490 Bolts, and the 2005 AISC Code of Standard Practice for Steel Buildings and Bridges, and much more. Did anybody go to any of the AISC seminars that introduced the new manual? We went to the one in Charlotte on 12/9. It was very informative. I got a reproduction of the very first AISC specification published in 1923.
Parent - By vonash (**) Date 12-24-2005 03:50
Dear SW Norris,
I stand corrected.
Best regards,
Vonash
Up Topic Welding Industry / Inspection & Qualification / Minimum Edge Distance on Base Plates

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