Galvanized Light Gauge Steel Connections

Hello Vince,

You may want to check in with the Steel Joist Institute (SJI) for examples to see how their manufacturer members connect the truss webs to the top and bottom chords, since it appears that your product is somewhat similar to open web steel joists. Never have I ever encountered a bolted-up SJI truss; most of their connections utilize shop welds, but please keep in mind that their open web steel joists have chords that will be much thicker than yours, hence they can use much larger welds than you are able to use. The 18 Ga. Galv. steel you're using is pretty thin stuff and will severely limit the effective weld throat and hence its load transfer capacity.

So, what sort of truss spans are you contemplating with your design? Loads? Floors, and roofs too?

www.steeljoist.org Their technical services office is located in Myrtle Beach SC.

A couple of quick questions for you Vince: Are you a trained Structural Engineer with a BS or higher degree in Civil engineering, or, are you an Inventor with no engineering degree? Both?

You mentioned in your OP that these trusses of yours have been tested? If yes, by whom? Was an independent testing agency involved, and did it adhere to AISI guidelines and procedures? What were the results of these tests? Published?

Since I'm somewhat intrigued by your design and want to see more innovative structural products make it into field, then may I suggest the following excellent handbooks and textbooks to you that'll help you out in the design of your truss members and structural connections:

1). "Light Gage Cold-Former Steel Design Manual", American Iron and Steel Institute, latest Edition.

2). "Cold-Formed Steel Design", Wei-Wen Yu, John Wiley & Sons, Inc., New York, 1985.

3). "Design of Welded Structures", Omer W. Blodgett, The James F. Lincoln Arc Welding Foundation, 16th Edition - 2002.

You may also want to browse through the US Patent office while you're at it.....to avoid stepping on someone else's toes, so-to-speak.

Please keep in mind also that several of the larger US manufacturer's of light gage steel members have already developed (some are still in development and Beta software testing) design procedures and criteria so that Structural Engineers can design their own light gage steel trusses....

Good luck with your product design & development!!! Please have a great sunny day!!

Hi CaptMoosie,

I wish you a Happy New Year and thank you for your prompt and comprehensive reply.

Some additional info:

I am a professional engineer (University of Toronto, Civil Engineering Class of 1972) and presently involved in R&D and product development..

My expertise of red iron OWSJ has led to a design & development of new light gauge open web steel joists and trusses.

Floor Joist Prototype fabrication and testing was done in confidentiality with the assistance of Dofasco, (now a division of Arcelor Mittal) in Dofasco's R&D Laboratory in Hamilton Ontario, with successful correlation of computer analysis and tests results.

Limit State Design contemplated was primarily for the housing market floor and roof construction.

Steel properties: Fy=345MPa, Fu 448 MPa.

Mass of the Joists and Roof Truss: 2.3 lb/ft

Floor Joist

Live Load: 1.9 kPa (40 psf); Live load @ 16" o/c X 1.33 = 53.32 plf

Dead Load: 1.25 KPa Deflection Limit L/480

Total factored Load: 72.5 psf

Depth: 300 mm Span 6100 mm

Depth: 600 mm Span 9700 mm

Roof Pitched Warren Truss (Structural Analysis only)

Live Snow Load: 5.76 kPa (120 plf)

Dead Load:0.5 kPa (20 plf)

H=1900mm; Span 9144mm: Deflection Limit: L/240

As engineers we use the tools we learned to solve problems, in so doing sometimes we come up with new design and products. So we are tagged as both inventors and engineers.

I feel that inventors, especially without the knowledge of all the familiar theories, procedures and standards that engineers are familiar with, have more freedom to let their imagination and creativity fly and sometimes to great heights. That's serendipity at work.

However, sooner or later one must consider the formulas, and, as Leonardo rightly implied, R&D also depends on knowing what has been done in the past.

I have personally done an exhaustive search of the subject on US Patent Office and the European Patent Office. To date I have not applied for a Patent and will do so internationally only together with a successful industrial partner with deep pockets to defend from possible future infringements.

In any case, to date I have kept all the subject matter confidential.

The above is photo of the 10" X 18'-0" floor joist of the prototype tested.

Thanks again

Vince

I come from a control and electrical engineering background so this may be totally ridiculous, but have you thought about using adhesives to do the bonding. There are some really strong adhesives out there and they have been extensively used in the aviation industry for decades now so it might be worth talking to them.

A sensible suggestion indeed!

Hi Masu,

your suggestion is not ridiculous at all. Adhesives are used in exterior building panels and other connections such as in a GFRP bridge in Germany.

However for steel joists, I'd be concerned about fabrication time, and, above all, its fire resistance, not to mention testing and code approvals for the housing market.

As you know, the building industry is extremely conservative and still using Babylonian material technology.

Prior art and code constraints comprise mostly mechanical (i.e. screws, bolts, rivets, nails, crimping) and welded assemblage.

Thanks for your input.

Enjoy your summer, we're freezing up here.

Vince

"As you know, the building industry is extremely conservative and still using Babylonian material technology."

That's a very good point and getting something approved is an important factor that needs to be considered during the design stage.

I don't know if you are aware of how they build gliders but basically they start off much like the average plastic model kit that you can buy at toy and hobby stores. The fuselage usually starts off with a right and left half that are glued together after the internal structure has been installed. The wings are built in a similar way except with an upper and lower section with the main spar being installed in the lower prior to the upper being glued in place.

Anyway it might be worth getting in contact with companies like Grob Aerospace or Schempp-Hirth who have lots of experience manufacturing gliders and other aircraft that rely heavily on the use of fibre reinforced polymers and phenomenally strong adhesives. I don't know of any glider manufacturers in Canada but it might also be worth contacting the Canadian Soaring Association as there has to be at least somebody repairing gliders in Canada that may be able to help. Canada have also manufactured some pretty good aircraft over the past so I might also be worth getting in touch with them as well.

I would really like to know how things ultimately turn out so it would be greatly appreciated if you could post your findings and final solution.

"Enjoy your summer, we're freezing up here."

So I hear. You may be interested to know that last night (Monday/Tuesday) Melbourne recorded it's hottest night ever with the temperature never going below 30°C. We're in Sydney and it hasn't been that bad here but nevertheless the temperature here hasn't gone below 20°C for at least a week and probably note even this year.

Hello Vince,

Thanks for the information! Looks like you've come a long way all on your own regarding your invention. Congrats are in order!!!! And yes, I'd also be very leery of patenting it until I had found some deep pockets in the manufacturing world that employed Barracuda Lawyers to help fight off patent rip-offs....

I see that someone suggested a space age adhesive. That's definitely thinking outside the box and could work, but I'd be worrying about passing fire code testing and Factory Mutual testing and acceptance. Like you said, Babylonian mind sets et all! But fire if fire no matter where you go....and all you have to do is look at the World Trade Center attacks of 9-11 to see what happened there when the fire-proofing got blown away. Since then it seems that the construction industry in regards to technical innovation has become even more entrenched. It's a fine line....or double-edge sword we walk upon?

Any how, I was thinking overnight about the plight of your web-to-chord connections versus available options that were also economical and straight forward to employ in a factory setting. What came to mind was the use of U-shaped mechanical connections with the bent portion of the "U" also shaped to conform to the inside radius of your web rods (I presume they're a rod) where they're bent.....it'd be a sort of "saddle" arrangement. You could employ resistive spot welding to connect all the pieces together where-ever a web rod comes in contact with a chord. To me, using that weld is far safer than Arc Welding and would avoid "burn-through".... it would be fast and simple.....a KISS approach!

Just a few more Cents added....

Boy, it's freaking cold outside here too Vince....I'm south of Albany about 60 miles, give or take. Are you near Hamilton, by chance?

Hi Capt Moosie,

thanks for the kudos.

Masu is better off than both of us! Here in Toronto is -10 °C this am.

I see the grey cells are working overnight solving problems. It's a good healthy thing and keeps us young.

Concerning the web elements yours is a good idea, however although rods could be used, the preferred embodiment in my design for both chords and webs is 18 ga cold formed steel.

BTW Try the nectar of the Gods, hot wine with honey, to keep warm.

Cheers.

Vince

Hi Vince,

Many thanks for the advice. I do think that I shall partake in few glasses of that "Nectar of the Gods" to get me through this Winter chill today and to help ward off my nasty head/chest cold.

Do you have a suggestions on regards to preferred wine, errrr poison?
LOL

Me fears I shallnt get shit done today after imbibing a tall warm one before lunch.....eh? Ahhhhh well, it's only Monday afterall...........I knew I should have looked up a good Mead recipe last week before this bloody cold set in... LMAO

Beers & Cheers My Good Fellows!

Da CaptainMoosie ****THE MOOSE IS LOOSE!!!!****

Hello again CaptMoosie,

I would never call wine poison, it would be sacrilegious, considering it was Christ's very first miracle.

I too make my own with California's Cabernet Sauvignon grapes.

I would also recommend Muscat for the ladies more gentle palate.

Alla Salute.

Vince

Hello Again Vince,

I forgot to mention in my previous posting that you may want to ask CR4 Forum

admin to either "fuzzy-up" or remove your photograph, or else someone may see exactly how your "non-patented" invention is actually constructed/configured. Makes no sense to give away the farm.....

Just some advice.....

Hi CaptMoosie,

thanks for the concern and advice.

The photo shown is of a prototype that cannot be patented since the configuration is prior art and the actual cross sections are secret and not disclosed anywhere.

Cheers

Vince

"Joints of chord and web elements."

I take it then that we have three webs...two on each side, and another across the top, like a toblerone box with a flat side up?

A mechanical rolled edge such as one would find sealing a tin-can would join all the long edges, and the bottom rolled edge could be joined with an enclosed tension wire in the roll. Such a method would (could) be very fast to produce. Rolled edges used to join metal have a long history, and engineering tables for different types of rolls are extant.

http://www.engineersedge.com/Design_Data.shtml

(If designed right, could even have a centre hinge down the length of it in the top chord which would allow the whole truss to fold flat for less expensive shipping. But I digress....)

...o-------o------o <----rolled corners.

......\ ............../

........\ ........../ <----fancy punched sides made from 12 inch 18 ga. strip

..........\ ..... /

..............O <----rolled corner with enclosed wire or rod re-enforcement.

A couple of minutes on google found a few companies which will manufacture roll rings suitable for this job.

For instance...

http://www.shmusa.com/rollrings.html

Or have I got ahold of the wrong idea here totally?

Hi Yousef1,

You have an interesting solution, but not what I was looking for.

My joist design requires joining two plane surfaces for example by arc spot welds. The top & bottom chords and web are all coplanar.

All the the technology already exists, I am trying to optimize production, perhaps some experts in automotive robotic welding might have a proven solution for "Galvalume" light gauge steel.

It seems you have found a way of producing economical space frames!

Thanks for your interest.

Keep warm.

Vince

Hello Vince,

You need a fast, simple and strong method specifically developed for joining lightweight steel. I suggest you go to btmcorp.com and look at their Tog-L-Loc equipment. It has been widely used in both automotive and the appliance industry with excellent results. I have worked with them on several projects and found them extremely competent and honest.

Good luck on finding some deep pockets!

Hi Hire Me!

Clinching is certainly a possibility to be considered.

In my research I did consider clinch fastening, and in 1982 BMT Corporation produced a tool for EasySteel Homes in Australia, with a comparative cost analysis vs self drilling screw on light gauge truss fabrication.

One of the disadvantages is that the tool design is not generally compatible with traditional on-site building techniques especially if one has to do some repair on site. Another is production application.

I also investigated self piercing rivets by Henrob with comparable advantages and disadvantages.

Thanks again

Vince

A great solution is the TOX sheet metal joining system. With solid punch and die geometry, it allows you to fit a high strength joint in a small area close to other elements and geometries. There is good information on the website www.tox-us.com for your review.

The TOX joint can be used in conjunction with adhesives too, if needed.

Dear Guest,

thank you for your input. I shall investigate TOX with interest.

Best regards

Vince

Dear Guest,

I spoke to Ziggy at TOX. He is very knowledgeable and helpful.

Unfortunately, clinching does not meet my load requirements for single shear on 18ga.

It seems that spot welding is the way to go.

Thanks for the referral.

Vince

I hope that you can spot weld onto galvanized steel. I know in MY shop, we refuse to weld galvanized steel because the fumes are so dangerous and hard to contain, and the zinc tended to spoil the weld. I suspect that this is an old problem which has been solved years ago though because I have seen a lot of spot welded galvanized boxes.

(just thinking out loud here....)

Hi Yosef1,

You are right. Your concern is the reason why I asked help on CR4. although the problem with fumes seems to have been resolved by the automotive industry.

A viable alternative would be rivets.

I am in the process of investigating Self Piercing Rivets, however it seems that the systems available perforate only the top layer(s) and create a button on the lowermost (i.e. Henrob).

I would prefer to have a punch through rivet, but it appears that unless I develop a new tool, the known process (drilling, riveting, hammering) is time consuming and not practical.

Thanks for your input

Vince

• "I would prefer to have a punch through rivet, but it appears that unless I develop a new tool, the known process (drilling, riveting, hammering) is time consuming and not practical."

This goes back to the deHavilland comet which was the first jet powered airliner. Initially the aircraft performed well and placed deHavilland in a position to dominate the airliner building business. However, several aircraft were lost in quick succession when for no apparent reason the aircraft suffered a catastrophic in flight failure with the aircraft disintegrating shortly before reaching their cruising altitudes.

Ultimately the problem was tracked back to metal fatigue which was compounded by the use of windows that had corners with too small a radius curve. The metal around the windows than suffered from metal fatigue every time the aircraft went through a pressurization/depressurizing cycle. Ultimately this caused cracks that slowly, but inevitably grew till they reached a critical point and caused a catastrophic failure.

The image below show the window section that triggered the catastrophic failure and you can clearly see how the corners were the weak link.

(Clicking on the image will take you to a high resolution copy)

Ok, most of you probably knew all that, but there was something else the investigation found.

It turns out that the rivets where the cracking started were Self Piercing Rivets SPR which when installed created micro‑fractures in the surrounding metal. These then gave the fatigue process a starting point and ultimately accelerated the process.

Now, if you go to the high resolution image and look closely (particularly in the lower right hand corner of the window) you will see that the rivets go through more than a single layer.

So, that would tend to indicate that at least back in the late 1950 to early 1960s there was a way of utilizing Self Piercing Rivets that created holes in multiple layers of the metal rather than the single layer the Henrob system does.

PS: Something I just though about on the certification level is the use of aircraft fitting and fixture techniques and materials. The aviation industry uses probably the most stringent certification standards there are so there's a pretty good chance that any aviation based techniques, materials, etcetera you use probably already has the certification you need for the building and construction industry.

Hi Masu,

Many thanks for your excellent input.

At first glance of your photo, I would dare to say that there are too many rivets too close around the Comet's window and that crack propagation was indeed inevitable.

Good suggestion on the P.S., I have a cousin (Fernando Cicci) now a retired aeronautical engineer who got his PhD in the late 60's in Southampton Univ. - England, on metal fatigue while working with deHavilland here in Toronto. I shall ask for his input and keep you informed.

Cheers

Vince

There's something else that I just remembered, but unfortunately I can't remember where I saw it.

It was a technique for forming holes that used two conically shaped mandrels. Basically it worked by forcing the material where the hole was outwards so that the surrounding metal was slightly denser than the norm. The guys that developed this were somewhat surprised when they got to the testing stage because the result was not only stronger than samples that were drilled or punched but stronger than a sample that had no holes at all.

It's not what you're looking for as it involves separate hole forming process but I though I mention it just in case

Hi Masu,

I spoke to my cousin, he confirmed pretty well what you wrote adding that it was also the stronger aluminum alloy which contributed to the metal fatigue failure not attributable directly to the rivets. He is also pretty certain that the Comet did not employ SPR.

Thanks again.

Vince

Hello Vince,

Is the prospect of fastening prior to galvanization or other corrosion preventative measure prohibitive?

Hi Bwire,

Good thinking, however the strip steel used in the roll forming of the sections would be already galvanized or AL-Zn coated as in "Galvalume" steel.

Thanks for your thought.

Vince

Then forming the materials creating and interlock may assist fastening and retain structural integrity.

Indeed, that is part of my pre-jigging process.

Cheers

Vince

Vince:

Something else you may want to consider is, "Does a fastening system comply / meet the building code requirements?" Henrob Self-Piercing Rivets (SPR) comply with the 2006 International Building Code as outlined in ICC-ES Evaluation Report ESR-2023. A link to the report: http://www.icc-es.org/reports/pdf_files/ICC-ES/ESR-2023.pdf. My experience is that the Canadian building regulations will accept, or adopt, the IBC. Further, I would think you would also want to market your design/product in the USA.

A point of clarification to the discussion going on. Masu's comment that Henrob rivets/process only pierce the top layer of material is NOT accurate. Henrob SPRs pierce the top LAYERS and form in the bottom layer - as you accurately stated above. This can be seen on the various cross sections at this web link http://tinyurl.com/yekadsb.

Also with my 15 years as a technical staff member at Henrob and also consulting with other technical staff at Henrob, one with 20 years and a British Aerospace past, it is very, very highly unlikely that the Comet was assembled with "self-piercing rivets".

Dear Guest,

Thank you for your input.

Indeed, according to other sources, the Comet did not employ the SPR.

BTW Failure was due to metal fatigue not attributable to the rivets, although the cracks initiated at the connections.

Cheers

Vince

Vince,

Please do not hesitate to let me know if there is anything Henrob (Livonia, Michigan) can do to assist you with both in your investigation and the building of any assemblies.

Regards,

Mike LaPensee

Henrob Corporation

Livonia, Michigan

Ph: 800-4-HENROB

Hi Mike,

thanks for your interest. I'll be in touch

Vince

This comes from an wapedia article on the deHavilland Comet;

• "The problem was exacerbated by the punch rivet construction technique employed. The windows had been engineered to be glued and riveted, but had been punch riveted only. Unlike drill riveting, the imperfect nature of the hole created by punch riveting may cause the start of fatigue cracks around the rivet."

It may not be correct and I might also be misinterpreting the term "punch riveted" to mean "self piercing riveted", but this does seem to indicate that the rivets around the windows on the Comet did not use predrilled holes.

Anyway, that's not definitive so when I have some free time I will do some more searching to see if I can come up with a reliable answer.

I am curious as to the "new" technology of melting holes in metal with friction, and then tapping the hardened melted blob. This strikes me as a remarkably good and fast fastening method. The link shows how easy this is to do, it is a youtube video showing the process. I don't think it is used much and I don't really know why not. It has occured to me that I have seen this method used a lot to create tapped holes, but I wonder if it has ever been used to simply weld two plates together....

http://www.youtube.com/watch?v=NhkWINPRK3A

Hi Yusef,

good thinking! Something to investigate further. Thanks

Vince

G'day gals, guys & gurus,

The video of the friction forming process somehow reminded me of a forming that utilized explosives to supply the high pressures needed to form thick metals.

Anyway, I have never seen this done and I have no idea if it would work, but I wonder if you could utilize small shaped explosive charges to weld the two pieces of metal together. Provided you can keep the supersonic gasses contained you wouldn't need much of an explosion to melt and ultimately weld two layers of metal. Something similar to these charges (see image on right) that are used in Hilti Tools to fasten sheet metal to steel frames would more than likely have more than enough energy.

Regards, masu

Hi Masu,

Good thinking. There a is a study on the Engineering Journal /Fourth Quarter/2000 : "Experiments on the Effects of Power Actuated Fasteners on the Strength of Open Web Steel Joists" by Michel D. Engehardt et al., reporting results of a series of tests comparing Hilti PAF and puddle welds.

However, I would be concerned about high production costs and provision to automated/robotic assembly lines.

The more I look into this, it appears to me that spot welding might be the best alternative.

Thanks again for your interest.

Vince

"The more I look into this, it appears to me that spot welding might be the best alternative."

I must admit that I am in agreement with you on that, but it's always good look at other and often newer options.