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Clamp Design for Suspending Tube Steel

10/05/2012 1:52 AM

Hi Everyone,

It's great to be back online and on the forum!

Here's my new challenge -

I have to suspend 4"x4"x3/8" HSS below W16x24 I beams.

Here's an illustration of the SE's recommended tube clamp

I don't have a rendered drawing, sorry. The shackle pin goes in the hole, of course.

The spec calls for Grade 8 threaded rod and hardware.

Here is an illustration of the clamp we would like to use instead -

These use 6" x 3/8" A36 bar stock, formed in our press brake.

Which one is your preference? Why?

Which one is the stronger connection to the 4x4 tube?

Looking forward to lots of comments on both methods.

Thanks!

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#1

Re: Clamp Design for Suspending Tube Steel

10/05/2012 4:12 AM

I couldn't read the bolt diameter, but surely the x-sectional area of two of them is much less than that of a 6 x 3/8 flat bar. Therefore, I think your design is better; indeed, quite a bit better.

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#9
In reply to #1

Re: Clamp Design for Suspending Tube Steel

10/05/2012 12:45 PM

Thanks Tornado!

While we are trying to get our work done on this project, it seemed like a good idea to step back and look at what the end-game should be.

I had not thought of the x-section comparison - which makes perfect sense and will go straight into my "look at it this way" toolkit.

I looked at it like this:

In my clamp design (TC2), even if all the bolts fell off, the shackle would keep the clamp from falling off. We liked this idea because we could put the clamps on the tubes while sitting in a bosun's chair, and slide them into final position... then add the bolts.

I am concerned about Moosie's comment on the stress imparted from the bending. While the engineers calculate, we are hoping the 1000 pound load will be within limits on the TC2 design.

BTW - we did a similar project a few years ago where we got into the big drawn-out discussion about proper bolt torques vs. lock washers vs. no lock washers.

We were told to torque all the 1/2" bolts to 85 ft/lbs and to use only one heavy lock washer per connection. Then we got a note to go back and rework every bolted connection. Disassemble, replace with new lock washer, and reapply with Blue Loctite. THEN, someone said "you have to put nylocks on those bolts..." (due to their concern over vibration).

But - the bolts were 2 inches longer than needed, so they instructed us to only run the nylocks onto the bolts until 2 turns were exposed past the nylon. So, we had lock washers, properly torqued bolts, loctite, and then these goofy-looking nylocks hanging out at the ends of the bolts.

THEN - we got the word that the nylocks were not to secure the bolts. They were there to stop the nut and lock washer from vibrating off and falling and hitting someone or damaging something.

Bottom line - once these things are in place, is the best thing to just damage the threads right at the nut?

Or, open another can of worms and suggest jam-nuts?

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#2

Re: Clamp Design for Suspending Tube Steel

10/05/2012 6:56 AM

If they are truly I-beams, both designs look like overkill to me. Just a thought.

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#3

Re: Clamp Design for Suspending Tube Steel

10/05/2012 8:02 AM

your design does a better job of reinforcing the load points on the hss. the SE's design would be less costly?. i like your design, but it might over kill.

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#4

Re: Clamp Design for Suspending Tube Steel

10/05/2012 8:51 AM

For the tube, your design is better as long as you are not pinching the corners of the tube, is the inside radius of the clamp equal to, or less than, the outside radius of the tube corner.

I am more interested in the connection to the bottom of the beam. The SE's design would work for the beam although I would look at tees running across the beam.

This all said without knowledge of the magnitude and type of loads and whether it is permanent or temporary or inside or out, and that makes me feel queasy about what I said above.

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#5

Re: Clamp Design for Suspending Tube Steel

10/05/2012 9:38 AM

If for no other reason, your design is better, because you are not drilling holes in the I beams. It's best to avoid doing that, if possible.

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#6

Re: Clamp Design for Suspending Tube Steel

10/05/2012 9:39 AM

Hey Tex,

I apologize for not getting back to you on this earlier this week, but I am swamped all of a sudden with a new client's structural "emergency" that had to be dealt with in a timely fashion.

I like your design in some regards, but I do have some concerns about you being able to bend that 3/8-inch steel plate to the required radius so that it fits tightly to the outside corner radius of the TS4x4x3/8. Additionally, bending the steel to a 90-degree angle lie you've shown will undoubtedly induce some undesired high stresses in the steel. Not a very safe option, and a bit of over-kill too with the bolts.

I have a suggestion for you that would involve less fabrication, be less costly, involve less labor, and be a much better structural connection:

Weld two short pieces of an appropriate length of WTXxX to the underside of the TS, one each for each suspender. A WT is a piece of Wide Flange beam cut in half at it's neutral axis (half way up the height of the WF beam). These are normally used for all sorts of structural hangers in the construction industry. You can provide a drilled or punched(preferred) hole in the vertical stem (web) for your shackle pin attachment.

For instance, a WT5x11 is actually a W10x22 cut in half. Look in the "TEE SECTION" of your AISC STEEL MANUAL. Also, ASTM A36 W10x22 wide flange beams are readily available as most steel fabricators usually have then in their stored stock. You could probably ave gotten away with a W8x10, but the flange width (bf) is the same dimensional width as the TS4x4x3/8. You need something with a widen flange to accommodate the welds. A WT5x11 has a bf=5.75", and a stem (web, tw) thickness of 0.24", which is much thicker than the WT4x5 tw=0.170".

All you need to do is make sure that the web thickness is structurally sufficient enough to resist the applied loads.

Another issue: I looked at the SE's framing plan that you sent me, and I only see a pair of parallel-oriented W12x14 roof beams where you are handing your cabinets, and in two locations a W16x26 and W14x22 roof beams where the cabinets are hung. Is the SE's framing plan correct, or has it been revised?

Problem as I see it is attaching the ends of the proposed TS4x4x3/8 cross members to the existing roof beams. I don't think that the information for Copper Industries connectors that you emailed will be sufficient here, as you have to make up the 2-inch difference in the beam depths. Also, they don't appear to me that they have a sufficient Allowable Working Load rating based on the load info you supplied to me. Another condition I don't like is that the roof is sloped and so would be the new cross pieces between the existing roof beams. If the clamping bolts for the Copper Industries devices ever become loose for whatever reason, the TS4x4 cross beams will slide out of the cradles. This is a potential problem I can see happening, especially when there are induced sound vibrations from your speaker cabinets over a period of time. What is needed is a much better structural connection....a more positive one that will be resistant to sound-inducted frequencies. Additionally, I'm not fond of hanging important structural framing from the bottom of beams, but it can be done, IF carefully designed and detailed. I cannot stress this important enough.....you would only be relying on bolts and clamping plates to achieve a proper connection.....you must use structural grade bolts in this case that must be properly torqued....say ASTM A325 bolts. These are readily available too.

We can get more into the TS4x4 end connections later....

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#7
In reply to #6

Re: Clamp Design for Suspending Tube Steel

10/05/2012 11:11 AM

Thanks Everyone, for all the great insight... I should apologize for not including more information!!!

The clamps I showed earlier are just for the 4x4 HSS tube steel. The I-beam clamps are a different discussion... here ya go...

PLAN 1 (SE plan)

As Moosie points out, there is a difference in beam size at two points. The SE wanted a shim under the end of the tube steel, and a bolt through the tube. Our issues with this are:

1) we don't like drilling all the holes in the TS prior to install because we have a very difficult technical climb to access these points and to make the climb just to measure/check the ironworker's accuracy on the steel, then drill the TS, then re-climb and hoist the TS up 60 feet (and find a way to magically penetrate the plaster ceiling between floor and roof beams) is a double-climb, at least.

2) The TS sits on top of the flange, which at first seemed good for ultimate security, but does require the shim at one end, and the load applied wants to rotate the WF beam and we know that's bad.

3) Even after making two trips to suspend the TS, we would have to make another trip to add the TS clamp to each tube that is the clamp for the load connection, which is well approximated, but not exact, until the cabinets are hung. So climbing trip #3 adds the suspension clamp, we shoot a laser dot down to the ceiling, rappel down, cut a hole in the ceiling, drop the suspension cable through the ceiling hole, and hope it hits the speaker frame dead-on. If not, either the speakers move (not good especially if there's a rotation in the Z axis) or the ceiling gets a "slot" for adjusting the cable... and a 4th climb to move the clamp above into the final position.

Here's the SE illustration of the TS - to - WF connection at the roof beams

We would add either Tube Clamp One (TC1 -The top and bottom plate with bolts holding the load) or Tube Clamp Two (TC2 - the press-braked wrap-around clamp) to this tube, and approximate the location between the beams.

3/8" 7x19 GAC on 5/8" shackles makes the drop down from the beam to the speaker points.

Changing the location of the drop means climbing back up to the beam, sliding the clamp on the tube and whoops!!! that changes the drop height which tilts the cabinets, which means make another cable, or add a turnbuckle to compensate for the X-Y change. We did not like this plan (plan 1) , so I suggested plan 2...

PLAN 2

I beam clamp mounts the the I beams:

Orange - 1/2" steel

Green - 1/16" and 1/8" steel shims stacked to flange thickness minus 1/16th inch to allow clamp to squeeze flange.

Red - 5/8" bolt pin anchor shackle WLL 3.5 tons

Load on Shackle - Maximum 1200 pounds

We install these clamps on the beams and add 3/8" drops down to the 4x4 tube.

Now we are done accessing the roof.

The tube hangs using our (Tube Clamp 2) like this:

The distance from beam to tube is now variable so all tubes hang at same Z above floor regardless of sloping roof height.

Tubes hang level, so change in X does not change Y.

Load is applied through the center of the beam, reducing torque on the beam.

Little to no tendency for the clamps to slide on the tube. We deform the end of the tube so that once the clamps are applied, they cannot slide off. The clamps fit tightly, and do not slide under any conditions we have ever been able to create.

Suspended load weighs 1200 pounds. Max load per beam clamp 1200 pounds in the instance that the speaker load is directly under the WF beam and there is no load sharing to the other beam.

6 foot span on 4x4 tube steel.

Center point load places 600 pounds on each beam.

Now what do you all think? Any more suggestions on how to improve either the beam clamp or the tube clamp?

Thanks!!!

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#8
In reply to #7

Re: Clamp Design for Suspending Tube Steel

10/05/2012 12:17 PM

I don't have a clear picture of your problem. Is this a frame composed of 4x4 tubes welded up to form a grid and suspended by WR that extends through a ceiling? If so, what prevents motion in the X/Y plane? WR alone will not prevent X/Y motion. You need something to restrict motion. This sounds like a large speaker array suspended from a grid (for easy relocation). Its hard to give a good answer based on assumptions.

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#10

Re: Clamp Design for Suspending Tube Steel

10/05/2012 8:26 PM

I second Moosie's concern about the clamp plates and bolts hanging for the bottom of the beam. I would also highly advise against the shims between the "T" and the clamp plates. I can't emphasize this enough. I understand you want to "squeeze" the flange but that's bad for the bolts but also...

#1. Lots of "prying action" going on there.

#2 You would not be able to properly torque your bolts because you'll always have a gap between the clamp plate surface and the shim. If you do manage to torque the bolts enough to close the gap then your clamp plate is bent and not fully contacting the beam flange face. Surfaces no longer in full contact means you have no sliding resistance (line contact only).

#3 A gap means limited friction capability and increased potential for the "T" to slide relative to the clamp plate because of the slot in the "T"

#4 If that bolt ever loosen's (even a little!), you loose the little amount of clamping force you have and the "T" slides relative to the clamp plate. Game over!

A more robust clamp method is required for the beam.

You were also afraid to inducing twist in the beams but you can't get away from that regardless of what you do. The beams are on an angle and your load is suspended and applied downward. You would need to cross brace them but to be honest your 600 lb additional load is negligble for beams that size.

I have an idea for you...in my next post.

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#13
In reply to #10

Re: Clamp Design for Suspending Tube Steel

10/05/2012 11:19 PM

TM -

Agreed about the slot issue. It's not really a slot, but a series of holes to locate the bolts as close to the flange edge as possible.

I flipped the plate so the slot is on the downhill flange.

The reason for the slot/holes is we have to make one clamp that fits on 4 different Wide Flange beams - W14 and W16 and two different weights.

It takes 3 to 4 hours to climb to the roof steel to each point, and there is zero access from the beams to the floor. Everything that gets installed has to be carried in our backpacks. We want to use one clamp for all the locations. Which, yes, screams using the scissor clamps for the adjustable jaw width. But, the SE is absolutely against them. I believe his reason is (possibly) justified. More on that in a bit.

Here is the revised Clamp orientation, and a view of how the slots are really holes.

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#11

Re: Clamp Design for Suspending Tube Steel

10/05/2012 9:04 PM

Txmedic, why not just purchase standard beam clamps? There are many types available. This type looks like it would suit your application. McMaster Carr p/n 8941T25. It fits beam flange sizes 3" to 7 1/2", max fl. thk 7/8.

Seems like less headache than trying to design your own.

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#14
In reply to #11

Re: Clamp Design for Suspending Tube Steel

10/05/2012 11:46 PM

Regarding beam twist -

According to three PE SE engineers on previous projects:
The reason the scissor clamps are not good when the beams are tilted (and we see this a lot where the beams are 10-45 degrees off plumb) is that the distance (Xc) from the shackle pin to the beam's center is increased as the flange width narrows, the scissor gets longer, and it is always a lot farther off center than the plate clamps. When the beams are plumb, we use the scissor clamps all the time. They do cost a lot more ($150-200 for USA product vs. $45 for the plate clamps) but are easier to use.

Here's how I have been taught to address the torque by moving the shackle to the center of the web (vertical center).

Is this correct? Please explain if we are doing something wrong...

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#16
In reply to #14

Re: Clamp Design for Suspending Tube Steel

10/06/2012 11:26 AM

The one on the right is definitely better; I think putting the load at the center of the lower flange (or one hole to the left) would be better still.

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#17
In reply to #16

Re: Clamp Design for Suspending Tube Steel

10/06/2012 12:50 PM

Actually, by placing the load as far right as you can will counteract the rotational instability (which in this case is currently in the counterclockwise direction in respect to the NA) of the existing roof beam, therefore this far right placement would help stabilize the situation and minimize the influence of bi-axial bending and torsional (twisting) effects.

By placing the load to the far left, you are in fact increasing the bi-axial bending stresses (fbx and fby). Torsional stresses will undoubtedly increase.

As I have stated before, I sure hope that the SE on this project checked the existing beams ability to accept new loads as well as the bi-axial bending and torsional issues.

This is not a good situation! I'm glad it's not my P.E. License on the line......

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#12

Re: Clamp Design for Suspending Tube Steel

10/05/2012 9:19 PM

I wish I had more time to devote to this blog thread. It has been a crazy and stress- filled week for me trying to complete an Engineering Report for a desperate new client.

I'll have to give this more thought over the weekend, and hopefully I can to come up with some workable solutions for you Tex.

Terraman is right about the prying action + slipping action.

Also, ideally, the proposed cross beams should frame into the webs of the existing W16x and W14x roof beams, rather than the under-slung connection, which is always a recipe for disaster. But that would entail either field welding connection angles to the existing beam webs or drilling bolt holes for connection clip angles.

With the presence of a ceiling below (suspended?) I wouldn't want the liability of that ceiling catching on fire due to welding activities. I recommend against field welding, unless you can protect the ceiling, as well as the paint and primer areas on the beams adjacent to your welding locations.

One thing I don't like about this situation, and it is not your fault Tex, is that the beams are tilted with the roof slope, thus causing the existing roof beams to bend in both principal axis (ie, Bi-axial bending). It appears that whoever the SE was that designed the original structural steel didn't know what the heck they were doing, unless they specifically checked the bi-axial bending condition pursuant to AISC to assure that it was a safe design. I just don't like hanging more stuff on these existing beams, because to do so will induce more eccentricity and hence more rotational instability. Not a good situation. I sure hope that the SE currently involved in this project has performed an analysis on these existing rook beams and taken into account the bi-axial bending conditions in his calculations with the additional new loadings. If he/she didn't, that would scare the Bejesus outta me.

Honestly, this is not an ideal situation where you hang heavy vibrating speakers from this type of framing arrangement. If anything, I would install some sort of vibration dampers to isolate/minimize the transference of the vibration frequencies produced from the equipment to the structural framing. Also, any bolted connection here should feature VIBRATION-RESISTANT STRUCTURAL BOLTS, WASHERS AND NUTS. You can find a listing of a handful of companies that make these in the Thomas Register. Do not use the "pinch" type bolts, as that leaves zero (or nearly so) threaded bolt projection beyond the face of the clamping nut/device. There are ones specifically designed for structural steel applications that support HVAC and other rotating equipment where it needs to be vibration resistant.

Cya on the rebound......

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#15

Re: Clamp Design for Suspending Tube Steel

10/06/2012 2:18 AM

I don't know how to use the drawing software you used here. I am still using a drafting tool and drawing board. Maybe I can explain it in words. I would use a long hinge and bend it so that it fit around the tubing. Then the shackle could be put through a hole in the hinge. This would then not need bolts, nuts and washers. If you use a spring pin shackle, then there would be no risk of the product coming loose due to vibration. Then to suspend it from the I beam Two separate pieces that wrap around the base of the beam with an extended piece downward from the beam and bolted together. A large enough hole could be drilled in the wrap around pieces to allow the shackle to fit through them. This would create and easy to disassemble product which will serve your purpose.

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#18
In reply to #15

Re: Clamp Design for Suspending Tube Steel

10/06/2012 4:29 PM

I drew a picture of what I was trying to explain in words. Hopefully, this will make it more clear.

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#19

Re: Clamp Design for Suspending Tube Steel

10/06/2012 6:16 PM

It doesn't matter where the vertical drop is located. You will always have a turning moment at the top flange. To prevent this, you need a gusset plate between flanges.

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#20
In reply to #19

Re: Clamp Design for Suspending Tube Steel

10/06/2012 6:22 PM

X-bracing between the two parallel roof beams would be ideal.......

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#21

Re: Clamp Design for Suspending Tube Steel

10/06/2012 9:00 PM

Txmedic, have a gander at these. Full size available here. It's self explanatory so I won't go into detail but this will solve your clamping issues and the beam twist thing if that really is a concern.

Cheers.

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#22

Re: Clamp Design for Suspending Tube Steel

10/06/2012 10:22 PM

Txmedic, I have some not so good news. I hope your shop guys didn't bet any cars or their wives on your bracket design being the better of the two. I was rooting for you but...yours will start to bend at about 10000 lbs give or take. The PEs concept is far stronger and will take double that before yielding. The problem with your design is the bending in the corners and what that does to the bolts holding the 2 halves together. Have a look.

You can see in the cross sections (images with pinkish background) that there's more stress on your bolts and shackles through the holes. To be fair, the PE is using a 1" hole and yours is slightly smaller. However the advantage in his design is that the hole is passing through one solid piece of steel. There's no bending going on so stress is distributed more evenly. His bolts have a tendency to bend somewhat as the angle deflects but is minor. There's a way to alleviate that and is explained later.

I set the color threshold to start showing red at 18000 psi and magnified the deflection 200x so you can visualize the bending action. In fact you couldn't see it because total deflection is only .005 with 10000 lb load. PE's design is about the same deflection but it's not due to the angles bending. It's due to bolt stretch which is to be expected because in his design the bolts are in tension. Bolt stretch is better than plate bending. Bolts are designed to stretch and that's what they do when torqued. Mind you in PE's design, I'm not sure how they plan to properly torque the bolts. The more you torque the more the angle will bend. If you torque one side to much the angle won't sit flat on the square tube. So his design isn't great as is. To make his design optimal, you need to install sleeves on the bolts with a length just shy of the tube height. This will stop the angle bending once the angle faces make contact with the sleeves and you can continue torquing the bolts to spec. This would also complete eliminate the bolt tendency to bend. If I were doing this...I would go with Mr. PE design.

Full res images here

Image above shows 37000 psi along that entire bend radius (you can just make out the number). That's the beginning of yield.

Image above shows how the bolts bend. You can see a high stress zone at the top of the diameter.

Image above shows high stress extending almost to center of bolt shank. It's due to the bending you saw in the images above. This image is a 1X deflection magnification.

Image above shows stress in the shackle pin due to the bending. It extends almost to the center of the shckle bolt shank.

PE's design above shows better stress distribution. Red areas are in the 17000-19000psi range for the same 10000 lb load

In case your wondering why there seems to be a high stress zone on the edges of the upper an lower angle...there isn't any. That's only because I needed to restrain those angles from slinding along the tube. To do that, I had to add a virtual clamp to those edges and that's the stress you see. It's false stress we don't consider.

Notice his shackle bolt does not suffer from bending stress because it pass through a solid section of steel.

Sorry big guy!

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#23
In reply to #22

Re: Clamp Design for Suspending Tube Steel

10/06/2012 10:37 PM

His load was given as 1200 lb max.

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#24
In reply to #23

Re: Clamp Design for Suspending Tube Steel

10/06/2012 10:47 PM

Yes I know. It has nothing to do with his bracket not being strong enough for his 1200 lb application. He PMed me and aksed if I could help him with his "competition" against the PE. He wanted to know who's bracket was stronger and what the limit was. Apparently there are bets going on with beer, cars, and who knows what else!

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#25
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Re: Clamp Design for Suspending Tube Steel

10/06/2012 11:03 PM

In that case, time for some destructive testing! Can we get invited? I nominate CaptMoosie as emcee!

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#26
In reply to #25

Re: Clamp Design for Suspending Tube Steel

10/07/2012 12:51 AM

I'd be honored to be "emcee"......I'll bring my best Bullwinkle voice with me! Also, as final condition, I'll only come as long as I get to bring a few pounds of C4 Plastique for the destructive testing! LOL

What can I say? I like to blow up things! hehehehe

If Tex uses a 3" long section of TS5x5x3/8, say 3 inches long, he could slide them over the TS4x4x3/8 cross beam, and make final adjustments that way. You would need to hold the TS5x5 into place with 1/2" A325-F set bolts, one on each vertical face at tapped holes. In lieu of thses bolts it is probably wise to use "Vibration-Resistant Structural Bolts" as the set screws.

All that is needed is to weld a PL 3"x3"x 3/8" at the bottom that features the appropriate hole diameter for the hanger pin. Use full 3" length 1/4" E70XX Fillet Welds each side of the plate for proper stress design of the welds,

I think this would be the simplest way to do this.....there would be approximately 1/8" play on both sides, but the set bolt will do the trick holding the TS5x5 in place.....or once the tube clamp assembly (as I call it) in it's final location, Tex could drill through the side holes of the TS5x5 to produce a dimple into the sides of the inside-located TS4x4.

I hope this makes some sense, because it's nearly 1 AM and I'm beat.

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#27
In reply to #24

Re: Clamp Design for Suspending Tube Steel

10/07/2012 1:04 AM

In true Mythbusters fashion, having lost the bet, I must now blow something up...

We will make both clamps, get some tubing and break out the video camera.

We will do some destructive testing, and it will be interesting, if not spectacular.

Have not loaded something to failure in a while (except my spine and my bank account).

We will get both clamps made and we will probably bend some 4x4 tube along the way.

Meanwhile, I have another idea to eliminate the clamps on the tube altogether, and maybe eliminate the tube in the process...

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#29
In reply to #24

Re: Clamp Design for Suspending Tube Steel

10/07/2012 3:31 AM

Okay Ya'll -

How about one of these three versions ----

This is the spanning beam that hangs below the I-beams.

No tube clamp needed at all, no bending.

Top Version 1- 1/2" Plate, 8" tall, with 3" plate welded down one side as stiffener. Okay, nevermind that, it's really just a T-beam on its side, right? Or an I-beam cut down the middle of the web. That means no welding, just punching. Fabrication just got a lot easier.

Middle Version 2 - 1/2" plate, 8" tall, with 2" stiffeners on both sides. I don't see the point of doing this when version 1 does same thing.

Bottom Version 3- This is 4x2 tube. We could fabricate a stockpile of the 2" punched top/bottom strips and weld to the top and bottom of the tube in the locations needed. Or we could just make a lot of stock with the strips full length. We would use at least a foot of pre-punch so we would have some field adjustability.

Which of these would strike you as the best approach???

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#30
In reply to #29

Re: Clamp Design for Suspending Tube Steel

10/07/2012 3:10 PM

My preference is #1. We always try to avoid welds in direct tension if at all possible. It also seems the simplest to fabricate.

Having said that, there's also nothing wrong with your original clamp design...for the amount of load it will see. Both your clamp and the PE's has a minimum 10:1 safety factor on yield. Don't get confused by what you see in the images. That deformation is amplified to provide you with visual that otherwise you could not see...and it's loaded to 10000 lb!!. The purpose was to show you the mechanical behavior of the assembly under load. It doesn't mean it won't work.

Keep things in perspective.

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#32
In reply to #29

Re: Clamp Design for Suspending Tube Steel

10/10/2012 7:45 PM

#1 bothers me, I would never use tee in that position unless it was the last resort. #2 is probably best as the least work method. #3 is okay if you have good welders, they are in tension and a bad weld end could be the start of a zipper, but I guess not under those loads.

My ideal would be similar to #3 but would use a full depth plate with the tube split into channels and welded on the side, The channels would not be racked but would still be effective as beams. But this may be more expense than can be justified.

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#33
In reply to #32

Re: Clamp Design for Suspending Tube Steel

10/10/2012 11:02 PM

Thanks Passington for the punched-Tee ideas.

Here's what the client says about the "punched, no-clamp beam" -

"no, and hell no"...

They did not mention the requirement to slide the tubing clamp in 1/4" increments along the tube.

"Oh", I said. This changes the game a bit.

So... back to the 4" tube and the sliding clamp, which might evolve to this V3, more so if the consensus is this one is best:

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#34
In reply to #33

Re: Clamp Design for Suspending Tube Steel

10/10/2012 11:34 PM

V3 is definitely not the best. Think about what is happening to the bolts on the top! Your original clamp idea is far better. You don't want large spaces between bolts. Ever!

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#35
In reply to #34

Re: Clamp Design for Suspending Tube Steel

10/11/2012 3:36 AM

Very Interesting, TerraMan! This is great education and experience, and the discussions in the shop have lead to scale models and cardboard and tape, and the guys are staying through lunch trying to win the prize - which is now ramped up to three day's vacation during Thanksgiving week.

So...

Version One, with the bolts in the vertical orientation, holding the load, which at first seemed to be not as strong because 4 bolts have far less cross section than the 6" wide 3/8" plate (see Tornado #1), and requires welding to make the tees the right size, appears to be the strongest design when FEA modeled, but has large spaces between the bolts, which we don't want, ever (TerraMan #34).

Confusing Point Number 1 - The bolts, in tension, are stronger than the same bolts, in shear?

Version Two, weaker in load capacity before failure than Version One, keeps the bolts short, no welding required, and is far stronger than needed for the load applied.

Version Three, reduces the stress in the bends, but the bolts in shear (and large spaces we don't ever want) makes this the least desirable of the the three.

Version Two Wins??? I get to keep my Hilti PD40 and the shop owes me dinner???

I bet I know what happens next, the guys will figure out that if we use the "top" of Version Two, and the "bottom" of Version Three, one of them will take the prize. I can't wait to see if one of them gets it before lunch.

I love this... the controversy and conversations will surely continue in the morning! CR4 members - any more thoughts???

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#36
In reply to #35

Re: Clamp Design for Suspending Tube Steel

10/11/2012 6:54 AM

In V3, the long bolts will bend upward slightly leaving a narrow, short thread to bear on a smooth, straight, surfaces at the shoulders. It is likely to bite in order to deliver the load. These bolts will be subject to bending, shear and tension.

I like the hybrid of the last paragraph.

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#37
In reply to #36

Re: Clamp Design for Suspending Tube Steel

10/11/2012 10:06 AM

I still like my idea of using an appropriate length section of TS 5 x 5 x 3/8 with two 1/2 Vibration-Resistant bolts through the sides (drilled and tapped accordingly)......the entire assembly can be slipped over the end of the TS 4 x4 cross beam and field- positioned in the correct location, then the side bolts are torqued to spec, thus fixing the assembly into place and taking up any slop (approx. 1/8-inch each side) between the TX 5 x5 and the cross beam. All you have to do is fillet weld a section of WT with a wide enough flange plus drill and tap the outstanding stem to accept the hanger connector.

This scheme will eliminate a number of sins.....shear, bending, and prying action to name a few. Side horizontally-oriented bolts vs. vertically-oriented bolts will eliminate "Falling-out" issues, especially if they feature a lock-down. You could always apply Loctite "BLUE" superglue to the bolt threads, just like what gun smiths do every day when fixing muzzle flash suppressors or muzzle brakes on the end of a rifle barrel.

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#38
In reply to #35

Re: Clamp Design for Suspending Tube Steel

10/11/2012 6:45 PM

"Confusing Point Number 1 - The bolts, in tension, are stronger than the same bolts, in shear?"

Yes. Always. Bolt shear strength is on average 60% of tensile strength.

Also, be careful what you identify as "shear". You need to consider shear, tension, and bending when looking at bolted applications and determine which is the governing factor. In V3, bending is the most critical therefore it is the governing factor. V3 can work but you need to use larger bolts on top.

All ideas are workable they just need tweaking. V1 needs spacers. V2 is fine for given load. V3 works with larger bolts that can handle the bending.

Hybrid of V2 top and V3 bottom as you pointed out is a good one.

But...if you want to do away with bolts altogether, cut the component weight in half, achieve positive locking, eliminate welds in tension, eliminate associated bending issues, simplify fabrication...just make the water jet your friend !!

...and the crowd goes wild with applause!!

...thank you, thank you...no...please, oh...you're too kind...

I'll be here all week. (...walks off stage)

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#39
In reply to #38

Re: Clamp Design for Suspending Tube Steel

10/12/2012 8:10 AM

GA, excellent but I have the impression that the client wants continuous adjustment because he vigorously turned down a functionally, in its use, similar proposal.

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#40
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Re: Clamp Design for Suspending Tube Steel

10/12/2012 8:39 AM

Yeah, clients always want things that sometimes are irrelevant to functionality. They don't always see what designers see. The 2 end supports will be aligned under the plate clamps attached to the WF beams. Adjustment can be ballpark and a slight angle in the suspension cables are better to prevent swing. The center support will in between the outers so... Clients always take the fun out of the work. :-(

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#28
In reply to #22

Re: Clamp Design for Suspending Tube Steel

10/07/2012 1:06 AM

TerraMan,

How do you get your images to load at the larger and clearer size?

jpeg, tiff, png???

DPI?

image size prior to upload?

It seems that no matter what adjustments I make, all I get is the little fuzzy images on the forum after upload...

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#31
In reply to #28

Re: Clamp Design for Suspending Tube Steel

10/07/2012 3:22 PM

I have the same problem and they don't always turn out. Don't use a pic size larger than 800 x 600. Use .png format and the trick is to fill the entire 800 x 600 frame with what you want to show. That's why the analysis pics look clear. I zoomed in before snagging the view. The other issue is text. If you add text to your pics, you need to oversize it like 24pt or 36pt. I use Snagit. It's really easy to grab anything on the screen and add text.

BTW,the pics you posted look clear to me.

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#41

Re: Clamp Design for Suspending Tube Steel

12/20/2012 6:35 AM

Thanks for sharing this post with us It's really useful for me.

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