Gusset Plates Location, will it Make a Difference?

A picture would be worth a thousand words.

There are valid places for gussets as flange stiffeners and the like, but many gussets merely relocate a moment stress only far enough away to give, say, a 3 to 5 % improvement in the strength of a weldment.

dear tornado,

am trying to post the PDF file showing the case mentioned but am not able , did you try to attach a pdf before

thanks

dear tornado , the picture is attached below , i hope it is clear now , design wise , will it make a difference if the gusset location has been changed ?

The bottom illustration seems best, but the orientation of the beam looks funny; why are its flanges on the sides rather than top/bottom?

hi tornado, this is the beam made , it is used by this orientation as a support as per the picture attached , a top plate welded to the beam will come on the top , on top of the plate the pipes and supports will come , i don't know how it looks funny , but if have any suggestions regarding the orientation or the shape below kindly tell me..
now in the previous reply you preferred the 2nd option , but any reasons ? in other words will it make so much difference in taking the load if this location has been changed , and if no differences between the 2 options why the fabricator always go for option 1 which the experiment proved that it some times need modification at site when it comes to installation ...

In that orientation, this is a column, not a beam. I have some doubt that the gussets are necessary at all.

Now think about this for a minute. Assuming no gussets, if there is a sideways force at the top of the column, this force will be resisted by the cross-section of the column where it is attached to the end flange. As an example, suppose that the column is 20 feet (~6 meters) tall. Then let us add some gussets, say 1 foot (~300mm) high. Now the same column cross-section that resists the sideways force at the top has simply been shifted to the top of the gussets. The moment arm is 95% of what it was before, and thus you have gained very little (about 5%). Long diagonal bracing would be much better.

dear tornado

one point of view stand still ( correct it if it is wrong ).... dont you think that the presence of gusset even if it is not needed load wise ,provides more fixation to the column via strenghthening it`s connection with the base plate ? i mean when the gusset is welded to the coloumn from one side and accrodingly welded to the base plate , it gives more fixation to the structure isnt it ??

Dear Ahmed Yusuf,

Gone through the attached drawing and alternative arrangement of Gusset plate is OK. There is just difference of the wall thickness of the I beam, nothing else. By changing location of gusset plate if you can tighten the bolt properly to the full torque, its OK you can go ahead. As such you are not changing the direction of gusset plate but the location that too hardly max 12 mm or so

dear arun ,

thanks for cooperation , i appreciate ...

alot of thanks to tornado as well for his quick response ....

Has anyone consulted with the Design Engineer (Engineer of Record) regarding these field modifications? That's the first thing you should do before changing the gusset plate location, and hence the design.

A couple of questions for the OP:

1. Is the column shop welded to it's baseplate first, OR are the 2 gusset plates transferring the axial load (and any bending moments) from the column to the baseplate and hence to the concrete pier?

2. How are the gusset plates to be attached to the column flanges, bolted or field welded?

IMO, if you're going to split both of the gusset plates and then move them to the interior face of the column flanges, then you may want to filed weld a steel clip angle to both of the outside faces of the column flanges. This will help beef-up the rigidity of the connection (and hence the fixity and degree of rotational stiffness) of the connection....just make sure that you allow for enough nut-tightening clearances.

===signed,

Captmoosie, PE/ PhD

Civil, Structural and Environmental Engineer

dear captmoosie,

thanks for participating in the this thread , regarding your first question you asked ,it is yes, this modification suggestion came from the site to the us in the design department as they tried to tighten the bolts but they found the distance between it and the gussets too small if they gonna add the washers as well ( M20 bolts , 30 mm nuts )

regarding your question no.1 i think the columns are shop welded to its base plate first then moved to the site ...and the gussets it self also was welded before moving the whole structure to site ... regarding your suggestion if you can simply sketch it it would be great , but tell me.... do you think basically the column in such a case need these gusset plates? basically in know that gusset plates used to connect the structure joint together ,,but when you can say that you don't need it ?....

thanks

Am I correct to assume that your design department designed this column in the first place, or is designed by someone else?

I cannot really answer your last question because I have no knowledge of the applied design loads (and bending moment(s), if any). Also, we have no information regarding the unsupported heights in both axis, as well as the column size and design yield strength. IMO, it's not a wise idea to mess around with a structural design. Therefore I'd leave the gusset plates in the design, unless the design engineer signs off on it.

hi captmoosie ,

yes you are right , it was designed in our design department first , but let me tell you two things ..

when it was designed , off course the distance between the bolts and the gusset plates surely has been taken in consideration , but what happened at site is a different story...the client`s civil engineer had some fears when he found some columns exceeding 4 meter , so he changed the base plate bolts from M20 to a bigger size ( M30 if am correct) , hence they found this problem in those specific columns ...

regarding your 2nd point , the column is nothing but a part of pipe rack carrying vertical pipes of medium sizes over it ( mainly PVC and SS316 pipes ),

Due diligence on the run?

Wasn't the length of the columns shown in the design documentation that was then approved (by the clients CE) as fit for construction?

We have no business second guessing the design engineer's criteria so we must believe she needed the gussets, therefore, moving the gussets to the inside of the flange is the least bad solution if the welds are practical, geometry makes them difficult sometimes.

The concern should really be the thickness of the base plate. If it is thick enough, no gussets are needed as long as it is loaded as a column.

If there is any horizontal load, gusset plates may be installed parallel to the direction of load, if loading requires it.

This question should have really been posted under "civil engineering".

Agree with Posts 6 and 13.

You do not need any Gusset at all for this Pipe Support Column

Gussets are placed by draftsmen who think their bosses will like to see complicated looking detailing.

H 'beam' axial column strength cannot be enhanced by any Gusset.

And if there are transverse bending moments - a flexible Base plate will do it better .

mm

Agree. Any horizontal load should be taken with cross bracing between columns.

Passingtongreen is right. Why is everyone debating the validity of the gusset plates?It's irrelevant and not the issue. The question was simple...does it make a difference if they are on the inside? My opinion is no it does not assuming the weld strength is considered equivalent to the parent material strength. I can only assume the designers put the gusset on the outside because it's easier to weld all around and you have 2 gussets this way instead of 4.

BTW, I'm new here.

I would not assume anything about what the designer was concerned about. I do not believe it logical to think that the designer was concerned with ease of welding and not concerned with ease of bolting.

If the designer made this simple error of designing something that cannot be assembled, I would look around for additional errors.

I would investigate and find out if the gussets were added as a standard detail or the result of a calculation. If there is a PE stamp on the drawing, I would start with the PE.

GA!

Welcome to the CR4 forum.

Pretty Pictures -- but the M20 bolts would have snapped long before that much bending

MUKULMAHANT, your comment implies you're not familiar with FEA software. This particular one is Catia V5. The images represent deflection magnified 200x simply so you can visualize what is happening. This magnification can be changed depending on how you want to visualize the situation. The beam sizes and loads I used were arbitrary. It was simple to illustrate the behavior of the system and not to duplicate the actual case in question.

If you simply omit the gussets, what happens to the areas of maximal stress (red/orange)?

OP should give us the actual planned stresses.:Axial,bending/torsion/Shear

Remember --M20 Bolt

And the H beam's area moment of Inertia

And the Bolt Centers

And the Base Plate

And the Foundation Concrete detailed dimensions

-----

For the sake of satisfying your curiosity!

-Base plate is 10in x 10in x 0.5in (Yes I live in Canada and use the imperial system eh!)

-Beam is W4x13 x 36in long

-Gussets are 10in x 9.4in x 0.25in thk (tappered to 4in at the top)

-Load is 1000 lb applied to the face at the end of the beam direction normal to beam web.

-Max stress with gusset:18917 psi (peak only near joint beteen gusset and beam flange)

-Max stress without gusset: 20631 psi (peak at contact between beam and plate).

You can see that there's more stress along the beam flange without the gusset.

Average in the red area runs from 12000 psi near the top to 20000 psi near the

bottom along the flange. The gusseted version shows 4000 psi near the top and

2000 psi near the bottom.

This is purely academic and I know I'm gonna get slammed with another "Off Topic" rating. Hope you're happy!

Cheers.

The stress improvement from 20631 to 18917 amounts to about 9%. Maybe necessary, maybe not.

Are you bored? This thread is 3 years old! LOL.

Assuming that the hold down bolts have not been set yet...

....surely it would be easier to move the holes away from the gussets.

IF the anchor bolts were previously set in the concrete foundation, there is sufficient thread projection above the baseplate, and there is enough of an enlarged hold around each anchor bolt (usually they are oversized bolt holes), then IMO the easiest solution to the OP's problem is to plug weld the anchor bolt holes. This measure will ensure proper anchorage strength of the anchorage in lieu of using structural hex nuts and washers. In all actuality, this solution will result in a stronger achorage connection that the bolted one.

Also, leave the gusset plates in the design, as originally intended, instead of monkeying around with someone else's headache/design....do you wish to inherit the liability of a failure?

KISS SOLUTION..........

[That's why they pay me the big buckeroos....... LOL]

Indeed the best KISS way out.

Welding the anchor studs??...those are typical alloy steel with specific mechanical properties (yield,tensile,shear strength, etc) which are certified and engineers establish their calcs using these values. If you start welding these things, those numbers go out the window because the uncontrolled heating and cooling changes the mechanical properties (basically annealing). This means all the analysis reports are not valid anymore and cannot be made valid since it's impossible to know the properties of the studs after welding. I can't see any engineer signing off on that idea. Just saying...

Typically in this part of the USA (upstate NY) the cast-in-place threaded J-anchor bolts are usually ASTM A36 steel. Ditto with the column baseplate, it's leveling plate, and the column itself. As long as a Certified Welder is conducting welding operations in accordance with AWS Standards I see nothing wrong with this procedure. These are M25 anchor size (slightly more than 1-inch diameter), and thus most probably gross overkill with several order's of magnitude in regard to Factor of Safety (FS) against tensile failure due to prying action IF any bending moments and horizontal shearing forces are applied.

I won't even entertain a discussion here regarding welding procedure, as it's OT, and is IMO, not here nor now applicable to the thread discussion. It's up to the Engineer of Record to sign off on any field change that the OP submits before committal, not us.

Additionally, we do not known the availability nor the certification standards of welders in the OP's part of the world, nor do I care. It's his headache to solve. I have suggested a viable alternative for him/her to explore and discuss with the EOR, that's all.

FYI, I have witnessed many many times, as a Resident Engineer years ago with the US Army Corp of Engineers, and later on as a PE in private practice (34 years in the Biz), the very same procedure done in the field as part of a required field change due to a screw-up during the Shop Drawing process (not my error/mistake/omission, but a design engineer's headache and CFU)......said changes were proof load tested by an independent and certified testing agency, passing with flying colors.

IMO, it's still a viable KISS and elegant solution for the OP to explore. Nothing was altered/changed in regard to the original positioning and use of the gusset plates...IMO, the EOR had them included within the design for a purpose, most likely for fixity, translational suppression, and rigidity reasons, and as I have stated previously, debating with others herein the intent of the EOR's inclusion of the gusset plates is second-guessing, OT and beyond the original thread discussion; we do not know the design forces utilized, including seismic loadings. Let's not go down that merry path......

===signed,

CaptMoosie, PhD, PE

Civil, Structural & Environmental Engineer

CaptMoosie sealed this Topic so well!

My apologies if my comment sounded harsh Cap'n. That wasn't the intent. I work in aerospace tooling, lifting, and ground support equipment. I'm not as familiar with civil engineering standards and methodology as you obviously are. We're not allowed to use A36 material for any fasteners at all in structural applications. We typically use grade 8 hardware (SAE J429) and CSA G40.21 50W / 44W steel plate and structural members (65,000 psi tensile). I obvioulsy assumed incorrectly that it was similar in your industry. I agree with you 100% if those rods are typical A36 and oversized by large orders of magnitude then there is no issue at all since welding them has no effect on their material properties.Good discussion.

Best regards.

Have a great weekend.

Thanks for the info Terraman, and no need to apologize as I wasn't offended in the least!

Hey, I don't squat about Aerospace Engineering from a design end of things, so we're even! LOL The extent of what I know about AE is that I can sit in airliners, WWII Warbirds and modern Mil jets, apart from the time I was a volunteer at the now defunct National Warplane Museum (Geneseo NY) where I worked on drilling-out old heavily corroded magnesium rivets and installing new aluminum rivets on airframe restoration of a Spitfire Mk8b and Bf-109G. Those were pretty heady projects to be working on back then!

Have a great weekend and please keep warm up there in the GWN!

Best Regards,

CM

per #12: "...they found the distance between it and the gussets too small if they gonna add the washers as well."

If it is only the washers that are clashing with the gusset then why not omit (or trim) the washers? Circular holes in the foot plate, right?

In most instances you cannot eliminate the structural grade washers because the anchor bolt holes in the column baseplate are typically oversized. For example, for a 3/4-inch diameter anchor bolt, the holes in the baseplate may be anywhere from 7/8-inch to 1-inch diameter so as to permit final setting alignments in both the x and y axis. Setting anchor bolts in concrete is no exacting and somewhat difficult....not matching structural steel tolerances by ant stretch of the imagination.

Yes, you could possibly trim a portion of each washer, but IMO if you trim too much material off of the washer you could introduce an unbalanced high stress regime into the washers and they could possibly fail if bending moments are introduced into the column above, resulting in a "prying action" scenario. You see, the column baseplate anchor nuts & washers are torqued down to a high degree (to specification) to promote tensile induced clamping action already, and introducing any more tensile stress due to prying could theoretically result in a tensile regime failure.

IHTH....

I'd like to think that the bolts were set true with a template. We don't know how much clearance there is in the holes when the bolts are in place. We don't know how thick the baseplate is.

The function of vertical anchor bolt washers is to prevent punch through failure, clamping friction is not an issue

This is a just a freaking pipe rack ferkrisake.....

Usually the anchor bolts are not "perfectly" aligned and concentric with the bolt holes in the baseplate.

Yeah, this is a freaking pipe rack that can get hit by a forklift "ferkrisake".....and all of the stored pipe (possibly tons of it, even if PVC pipe now per OP statement, but maybe steel pipe in the future?) comes tumbling down on the forklift operator's head as well as anybody standing close by...... LOL

My personal design philosophy is to design for the worse case scenario.

How about installing 4 gusset plates in line with the flanges using a butt weld instead of lapping the gussets.

Good idea ronseto, as long as there is:

(1). Enough room left between the column flange tips and the edge of the baseplate.

(2). The gusset plate thickness is at least the column flange thickness, to promote stress continuity between the column flanges and the "extensions".

(3). Butt welding to be done by a Certified Welder in accordance with AWS spec, or it's equivalent. No doubt in my mind that the welder is going to have to employ some degree of preheating...

Dear Mr.pilot joe,

The answer for your question is YES. It will make a difference. This can be understood by drawing by Graphic Statics.

DHAYANANDHAN.S