Shims vs Filler Plates

Date 06-13-2004 16:19

I can't tell enough from your note to understand how the "shims" are used. Are they used to fill gaps between members to be joined? Are they shims for base plates to achieve proper elevation? Do they serve as backing for partial penetration groove welds with root openings? Are they used as fillers for fillet welds with gaps? Shims are not necessarily required to be removed after welding is complete. But there are some cases where "shims" should not be used. Filler metal is an electrode or wire that is consumed as part of the welding process (not to be confused with slugging). Please provide more info.

By jwright650 (*****)

Date 06-14-2004 11:32

Mark,
This becomes something the EOR ends up settling. Give a little more detail about the situation and someone can advise you a little better. This AISC's code of standard prctice give some direction on the use of shims or fillers. I suggest getting your hands on a copy, I think paragraph 6.4 (dimensional tolerances) gives permission to use shims and filler for certain situations.
Hope this helps,
John

By swnorris (****)

Date 06-14-2004 14:47

Hi Mark31,

As previously indicated, more information from you is needed, but another factor to consider in addition to the sizes of filler plates is whether or not they are being used to transfer loads, which needs to be determined by the EOR, as John mentions. If the field guys are just tacking two sides, this may not be acceptable. If they are used to transfer loads, the plates will at the very least need to meet the criteria set forth in D1.1 at 2.10.
To me, fillers and shims are basically the same thing. They do the same thing, which is to fill a gap. When I think of a shim, I tend to think of a thinner piece, such as 1/8". To me, either one could be permanent. When I think of fillers, I tend to think that fillers are more permanent.
The AISC Code of Standard Practice has references to both fillers and shims. In Section 6, Shop Fabrication and Delivery, 6.4.6 states in essence that variations of beams and girders resulting in abrupt changes in depth at the splices shall be taken up with filler plates. In Section 7 Erection, 7.8.3 states in essence that the fabricator shall furnish shims that are shown necessary for make up of permanent structural steel to structural steel connections.
What are these shims/fillers doing in your application? Are they in bearing, shear, compression, tension?

By jwright650 (*****)

Date 06-14-2004 15:30

Thanks Scott, I didn't have my copy when I replied and was relying on memory. They have changed that section to "Fabrication Tolerances" from the older version.
John Wright

By swnorris (****)

Date 06-14-2004 16:13

Hi Mark31,

Incidently, you mentioned tack welded shims. There is an excellent article about tack welds in Welding Innovation, Vol. XX, No. 1, 2003, entitled "Pay Attention to Tack and Temporary Welds", that may be of interest to you. Here's the link:

http://www.jflf.org/pdfs/papers/design_file103.pdf

By jwright650 (*****)

Date 06-14-2004 16:51

Hi Scott,
Thanks for sharing that article. I copied some of our people here on that article. Trying to get people to share my concern over these seemly trivial details is hard without having it right there in black and white for them to read for themselves. It doesn't take any longer to do it correctly the first time, but we always seem have time to do it over again.
John Wright

By swnorris (****)

Date 06-14-2004 18:30

I hear you John. You hit the nail right on the head when you said "it doesn't take any longer to do it correctly the first time." My sentiments exactly. In fact, in most cases it actually takes less time to do it right the first time. A point that I find myself repeating way too often.

By CHGuilford (****)

Date 06-15-2004 17:01

Just to add my 2 cents... Shims to me are small squares of steel, of varying thicknesses, that are used under column base plates or machinery supports or similar applications. Usually they stay in place and grout is put in place afterwards. Sometimes they are tack welded for convenience but their function is to take up space and transmit compressive forces. We make them by the barrelful to be used at our various jobsites.

Filler plates, to me, mean plates that take up the space between structural members, suc as when beams of different section depths must connect together. Sometimes they are welded and sometimes drilled through for bolting. Another application is in the end gap of bolted column splices where the gap is larger than allowed. In those cases, the filler plates take up space to prevent putting the bolts in shear. Or filler plates make can make up for erection/fabrication errors where parts don't meet properly.

Regardless of what the drawing calls them, if the filler plates are to be welded and must transmit a tensile loading, I would expect to see some reasonably sized welds somewhere. And in the case of the precast panels, there should be enough weld to do the job, even though it doesn't sound like a big deal. The welding should have at least the strength of what the original connection required.

Is there an engineer that you can refer the matter to? I think that would be the easiest and best solution in your case.

Chet Guilford

By swnorris (****)

Date 06-15-2004 18:59

Hi Chet,

I agree with what you're saying. The structural fabricator I used to work for in the late 70's, Owen Steel, kept barrels of 2" x 2" plates in thicknesses of 1/16", 1/8", 1/4", 3/8', and 1/2". We called them shim packs, that are as you said, used underneath column base plates. We haven't had to furnish any of these in a few years, but we used to all the time. I think shim packs were more necessary then because most of the columns were anchored with two bolts and because of this were harder to level up. OSHA got involved somewhere down the line, I think it was in 2001 and started requiring a minimum of four anchors per column, which in turn makes levelling a little easier with the use of levelling nuts underneath the base plate and lessening the need for shim packs.
We have occasionally supplied finger shims, which as you probably know are plates that have slotted holes all the way through the edge of the plate, that can be slid between members and up against bolts to fill a gap. Our applications of these are primarily used in beam to beam, or beam to column connections, where the overall beam length came up short.

By CHGuilford (****)

Date 06-15-2004 21:38

sw,
I had forgotten about those good ole finger shims. What a pain they were to make in quantity, at least on the old flywheel punches I started out on. I remember that the superintendent didn't want us using new punches on them. We had to use the rounded off, worn out ones that bound up and yanked the shim up through the stripper. After hammering them back to nearly flat, we would saw out the slot on an old Grob saw. I don't miss that task. I think the promoting of using slotted holes in clip angles helped those go away.

I think you are right that the 4 hole base plates have reduced the need for shims. We still make them but nowhere near the quantity we used to.
Chet

By swnorris (****)

Date 06-15-2004 22:38

Hi Chet,

Yes they are such a pain to make. I don't know how you make them now, but here's a good way to make finger shims if all you have is an ironworker machine. We have a 175 ton Kingsland and this works well for us:

When shearing the plates, double up on the width and slot length. For example, if a 2 1/2" wide x 6" long finger shim is needed, with two 13/16" x 2" slots, shear the plate 5" wide x 6" long, and punch two 13/16" x 4" slots. Then shear the plate in half, back to 2 1/2" wide. You then have two finger shims, with no stripper problems, bending, or hammering. If the longest slotted punch you have is say, 1 1/4", it would take around six punches to make a 4" slot, and if a side bar is clamped to the punch table, the side of the shim plate can slide along side of it as it's being punched, which helps keep the slots straight.

I agree that slotted holes in clip angles have lessened the need for finger shims. I don't know about what you're seeing with the use of slotted holes, but my problem is that sometimes the detailers use long slotted holes (usually 13/16" x 1 7/8") on the angle leg that bolts to the beam web, and every single time, they fail to detail out plate washers. The AISC is very specific about the use of plate washers or a continuous bar over long slotted holes, when the slots are in an outer ply. These clip angles are usually "wired to ship", so when I see this condition on the shop drawings, I have to make sure that we make plate washers for each clip angle, and to tell the guy who orders field bolts that the bolts for these connections are going to be too short. I keep telling these detailers over and over about this, but I may as well be trying to nail jello to a tree.
The AISC designates a short slot for a 3/4" diameter bolt as 13/16" x 1", and a long slot as 13/16" x 1 7/8". We have these two punches, but we also have 13/16" x 1 1/4" punches, and 13/16" x 1 1/2" punches, which I guess sort of fall into a gray area as far as requiring plate washers. I am able to get with the EOR and sometimes they allow me to use the 1 1/2" slots, which saves us from having to make plate washers and order longer bolts. I have yet to find anything indicating the requirement of plate washers for 3/4" diameter bolts over 1 1/2" slots, so as far as I know, I'm ok.

By jwright650 (*****)

Date 06-16-2004 10:49

Chet, Scott
Have either of you found with the long slotted clips any squaring and plumbing or elevation problems in the field? We have just recently started using short slots in our standard angle connections, and some long clips are an exception, one fair hole and the rest are short slots. So far it seems to be working out. It does eliminate the use of different clips for several web thicknesses, primarily at the smaller beam sizes where the webs are not all that different.
I have noticed that we don't make up those finger shims by the hundreds anymore, also. I really hadn't stop to ponder why. When I was detailing, I do remember going to the 4 anchor system and I think it still allowed 2 anchors but it was for very light columns, if memory serves correctly. I think that was done before 2001, but I can't be for sure. I was in the detailing department from 1991 - 1998 and I thought it changed sometime around there.
John Wright

By swnorris (****)

Date 06-16-2004 12:14

Hi John,

I'm not sure I understand you about one fair hole and the rest short slots. Are you referring to the shop bolted leg? Ever since I've been in the fabrication business we've used AISC short slots horizontally in the outstanding leg of our standard framing angles, with 4" c/c, and the other leg welded to the beam web. We keep standard framing angles 3 x 3 x 5/16 by the barrels. Our 2 and 3 row clips have a 1 7/8" gage, our 3, 4, 5, and 6 row clips have a 1 13/16" gage, and our 7 and 8 row clips have 1 3/4" gage, which covers most web thicknesses. Although 4" c/c is intended, sometimes these angles get detailed for thicker beam webs. We allow the 4" c/c to vary +/- 1/4", and although this rarely happens, we find that the connection will still bolt up in the field.
If framing angles have long horizontal slots in the shop bolted or wired to ship leg, and the outstanding leg is either bolted or field welded, the long slots are sometimes necessary because exact field conditions are not known, and the long slots should make up the difference, as I'm sure you're aware. If they don't make up the difference, then of course finger shims or filler plates are needed, or sometimes the angles are reworked. We recently had a job using wired to ship framing angles with long slots in the wired on legs, and the outstanding legs were plain and field welded to vertical embed plates in the walls. As you probably know, the walls are usually either not exactly where they should be, or not exactly plumb, and the slots are detailed long enough so that the angles can slide out or in far enough to flush up with the embed. To answer one of your questions, I'm not aware of any problems in the field with squaring or plumbing due to the use of long slots.
Incidently, I always get a set of job specifications and erection drawings with my shop drawings. Before I do anything else, I look through the specs. for anything unusual, then I thumb through the shop drawings and get familiar with what's on them. Next I look over the erection drawings to see how the building goes together. This usually takes 20 minutes or so on the average. I've been doing this so long I can pretty much tell how everything ties together in the field without looking at the erection drawings.
If I know what the spec's will allow, and I know what the AISC allows, as far as hole sizes and minimum edge distances, and I know how everything ties in, then I know where slots or oversized holes are needed to help with erection. I make some notes and get with the EOR to see if I can add slotted or oversize holes, and I'm almost always allowed do do what I'm asking. By using oversize holes or slots in certain scenarios, it may mean the difference of whether our erectors use drift pins or not, and we end up getting a good report from them that everything fits.

By CHGuilford (****)

Date 06-16-2004 13:48

Scott,
I may have mis-understood your post on plate washers, if so bear with me. I want to point out that the AISC Steel Construction Manual, LRFD Edition 3, RSCS section, Table 6.1 (and Section 6 overall), tells you where to use plate washers, both hardened and un-hardened.

John,
Another company I worked for years ago used to use standardized clips with slotted holes, similar to what Scott described. We too, made hundreds at a time for stock. Several types covered most applications. That company had their own detailing department so the drafters made sure to use those clips wherever they could.
We don't do detailing where I am now, it's all farmed out (and usually very challenging/entertaining).
For some reason, I'm not sure why, it is hard to get the detailers to use standards clips. Maybe they don't know what to do or maybe our engineers have not told them but that's a separate issue I can't do much about at the moment.
At any rate I think standard clips are starting to disappear because of machines called "Angle Masters". Many fabricatiors are able to load a stock length of angle into the machine, punch a few buttons, and voila!, you get your clips as you need them. It would still be a good idea to use standard angles and slotted holes but because of the versatility with new machines, detailers know they don't have to.

I think the biggest reason slots aren't used as much as they should is because of "reluctance". (I am being diplomatic because many people read this forum). Standard round holes are always acceptable. Oversized holes and slots require permission if not allowed in the contract documents.

As far as finger shims, I have seen those used mostly as Scott described, where actual conditions are uncertain. When the shims were not pre-planned and there is an errection problem, the erectors usually just weld the clips instead of bolting them. I know that is not always a good idea, but it happens a lot, sanctioned or not. When they get caught, that's when we get the call telling us about our shortcomings.

A bit longer than I originally planned,
Chet

By jwright650 (*****)

Date 06-16-2004 13:59

Chet,
Speaking of "Angle Masters", I have Peddinghaus in the shop as I'm typing, working on ours. Can't complain though it's about 10 years old and no major problems. This visit is gonna cost us as we have several worn out parts to replace. Ours is old enough that it uses a Windows 95 operating system at the console.

We used to stock "all" round hole clips of various gages and number of rows of holes out of L3x3x5/16 as Scott described. Here as of late we started using the 13/16x1 SSH and cut down on the number of different gaged clips required for the various web thicknesses. And as Scott stated we also use long slots and washers for members bearing on masonary or framing to an embed that is set in the face of a wall. Connecting to any existing structure usually requires us to supply long slots as well.
John Wright

By swnorris (****)

Date 06-16-2004 16:11

Hi Chet,

All of our detailing is farmed out too, and dealing with some of these outside detailers can be frustrating. Some of these detailers have no clue as to what goes on in a fabrication shop, let alone what we have to go through sometimes to do what they put on the drawings. In addition to that, I have problems with the drawings conforming to AWS and AISC requirements, or they can't seem to remember to put AESS notations on applicable members, etc., etc. I tell them about these things, but they turn right around and do the same things on the next job. I may be going out on a limb here, but does any of this sound familiar?
All shops have somewhat different practices, and like to see things detailed certain ways, and a lot of shops have a detailing standards manual. I wrote our detailing standards, which encompasses practices most economical and efficient for our shop. A copy is sent out to all the detailers we use and they are "required" to apply as much of it to the job as they possibly can. Our manual also includes things such as common welds on items like column base plates (outside of one flange, inside of the other, both sides of the web for a length of half the column depth). It also includes sketches of our standard detail material, such as standard bottom chord stablizer plates for joists and marked j1, (with that OSHA hole), 4" c/c framing angles, marked a1, a2, a3, a4 and so on, (for framing angles) and our standard AISC shear bars marked p2, p3, p4 and so on (for beam to beam, beam to column flange, and beam to pipe and tube column connections). The number in the piece mark indicates the number of holes in the piece. All the angles and plates have short horizontal slots. It's extremely beneficial to have standardized connection material, for several reasons. One reason is that barrels of these can be made in advance, or when the shop guys get caught up, this can be used as fill in work, rather than make them on a job to job basis. The more secondary material can be standardized, the more beneficial it is to the shop. We also have standard base plates made in advance, in thicknesses of either 3/4" or 1", and ranging in squares of 12" x 12", up to 16" x 16", with standard hole patterns with either 1 1/16" or 1 5/16" holes, and standard marks like bp1, bp2, bp3, and so on. The problem is getting the detailers to use the standards and the correct marks. One problem is that if they're doing autocad drawings, and they finish doing drawings for someone else, they sometimes don't take the time to change their program to suit your standards.
Also Chet, are you familiar with or have you checked out the green AISC Manual of Steel Construction's Allowable Stress Design? On page 5-71 under Size and Use of Holes, at 2e, in part it states that "Where long slotted holes are used in an outer ply, plate washers or a continuous bar with standard holes, having a sufficient a size sufficient to completely cover the slot after installation shall be provided", and goes on to state that "the materials shall be of a structural grade, but need not be hardened." "If hardened washers are required, they shall be placed over the outer surface of the plate washer or bar." I am familiar with some of the LRFD requirements, but I don't have a copy. I read your comments about this Table 6.1, and my question is can you tell me if plate washers are required over 1 1/2" slotted holes? Table J3.1 in the green manual defines short and long slots, but shows nothing for slot lengths in between, which without any knowledge of Table 6.1, lead me to call this "in between" area a gray area, and I saw it as a (for lack of a better word), loophole not to use plate washers.

By jwright650 (*****)

Date 06-16-2004 17:56

Scott,
I see what you are getting at in regards to "what to call a slot that is 13/16 x 1 1 /16" thru 13 x 1 13/16".(the in-betweens)
Chet, this is the grey area he is speaking about. Table 6.1 only specifies Short Slot and Long Slot, Table J3.3 defines a Short Slot as 13/16 x 1" and a Long Slot as 13/16 x 1 7/8". We treat *anything over* 13/16 x 1" as a long slot and add the plate washers as required. I'm not 100% sure that is the correct interpetation of Table J3.3, but that is what we do. It does look like the AISC would have defined better parameters rather than listing "Nominal" sizes.
Are we any more confused than we were already?
John Wright

By jwright650 (*****)

Date 06-16-2004 18:01

Scott,
The newer "Dark Blue" LRFD third edition book contains the "Green" ASD ninth edition also.
John Wright

By swnorris (****)

Date 06-16-2004 18:38

Hi John,

No confusion here. Maybe I should take your approach of treating any slot length over 1" long for a 3/4" bolt as a long slot, and add the plate washers, but with hardened washers being 1 1/2" in diameter, which should be sufficient to cover at least the 1" slots after installation, I can't justify using plate washers. I just hate spending that extra time and money for something that may not be required. I guess I could treat it as a worst case scenario, which means to use the plate washers and purchase longer bolts, then I'm covered. I have a call in to the AISC, and I'll post their interpretation. We actually have the LRFD third edition, or should I say had a copy, because someone in the front office loaned it to an erector before I ever had a chance to look at it.

By jwright650 (*****)

Date 06-16-2004 18:56

I checked with our engineers here and they all concurred with my interpetation of treating the long slots as such. It still doesn't mean we're right, just that at our plant we all agree on how "we" treat a slot longer than 1" for a 3/4 bolt (as a long slot).
John Wright

Chet, Any thoughts?

By swnorris (****)

Date 06-16-2004 19:25

Hi John,

According to the AISC, your interpretations are correct. They promptly returned my call and said that the short slots shown in Table J3.1 are the maximum length for a short slot, and that the long slots shown are the maximum length for a long slot. Anything over 13/16" x 1" is considered a long slot. I politely mentioned to him that it does not say "maximum" in the table, and I asked him if there is some reference to that somewhere, and he said no. I explained to him about the gray area, and he said he could understand where it could cause some confusion, and that it has to do with the o.d. of the F436 washers not being sufficient to cover anything beyond a 1" slot for a 3/4" bolt after installation. He also said that they need to add notes in the next edition that should make it clearer. I guess I'll have to make our estimators aware of this now so that they adjust their costs and man hours, and also have to tell my boss that I was wr wr wrr wrr wrroonnnggg. There. I said it. That didn't hurt a bit. Seriously, thanks to all of you for all the responses that led to the phone call, or else I probably would have never known.

By jwright650 (*****)

Date 06-16-2004 19:49

Scott,
I didn't know the reasoning, but it was just a standard that I had been following. Thanks for posting your findings.
John Wright

By CHGuilford (****)

Date 06-16-2004 20:10

Wow! in printing this out so I could keep track of the questions I ended up with 10 pages.

Scott, yes we run into the same problems that you described with detailers. It seems universal. We too issue our drawing standards to the detailers but what happens is that every job seems to be fast track so nobody has time to do it "our way". (And project managers are afraid doing it right will lead to increased money and schedule on the next job.)Other than piece marking, I'm pretty sure our standards are the same as everyone else as far as welding symbols, sectional views, etc. It's all industry standard, just that it seems that today's upcoming Autocad techs want to invent their own wheel.

The "blue" version of the AISC manual is pretty much the same as the "green" one, on this topic. I now see what you are talking about in the gray area. However, I interpret those dimensions as the MAXIMUM sizes for nominal hole types. In other words, if a slot is longer than 1-7/8" for a 13/16" wide slot, it is no longer a "standard" long slot and the engineer must evaluate the connection because it is outside specification provisions.
The same as using a 1" round hole for a 3/4" bolt. The engineer must evaluate it because it is larger than the standard oversized hole dimensions provided.

So in the case of a long slotted hole greater than the chart shows, the engineer could determine that only F436 standard washers are needed if conditions permit. But the fabricator should ask for clarification when no info is given and the situation is beyond what the AISC manual allows.

The reason I arrive at this interpretation is found in the RSCS section, Table 3.1, note "a", that gives the upper tolerance of the hole and slot dimensions as 1/32". (There is no minimum because the bolt must fit into the bolt hole.) To me, that means the dimensions given are maximums.

Helpful hint (possibly)- if slots longer than nominal long slots are required on contract documents but plate washers are not shown, then requiring them after the fact should be a change order, because long slot requirements do not automatically apply.

Does that answer your question? I interpret all this as, you need plate washers, but again, just my opinion.
Chet

By swnorris (****)

Date 06-16-2004 22:06

Hi Chet,

Yes that answers my question. Our estimators should pick this up during pricing and we'll try issuing change orders to address this as the need arises. Thanks.