Industrial formwork

[TalGed]

I am trying to construct formwork for concrete wall, I used plywood coated with steel, I am using UPVC conduit as spacer, and rebar 8mm as a connector, I am trying to design the lock at the end of rebar, so it will use principal of "clin" knok it to lock and knok again to un-lock. Do you have better idea, this system is "idiot proof" in my opinion, I tried to use bolts 80-90% were lost after first casting?

 

[Ingy]

TalGed,
Sounds like you are trying to re-invent the snap tie. The snap tie is about 1/4" diameter steel with headed ends and a crimp. To fasten to the form you use a steel wedge which is hammered under the headed end. It is held in place with a 16d nail. To remove, knock the wedge out and then break the tie off at the crimp.

For heavier loads we use taper ties which have a coarse "coil rod" threading at the end. The ends are fastened with big "wing nuts" called catheads. Since the rod is tapered, to removed you release the catheads, then hit the narrow end with a sledgehammer.

Also, why coat the plywood with steel? Typically I see steel frames sheathed with plywood or the entire system is steel.

John

 

[TalGed]

Thank Ingy!

The reason I am trying to re-invent the weal is that i am working in Nigeria, mostly you can not buy here ready made assesories. I am not using ply wood coated with steel becoze the size of the work does not justify to built steel shatering, the ply wood in this country is compresed saw dust, so to have some reasonable number of cycles we have to re-invent.

 

[Ingy]

TalGed,
I understand.

How about using or #4 (12 mm)rebar for ties. Field bend the ends 90 degrees and wedge in place. Not sure what the capacity would be but you could build a mockup and see what it takes. You'd have to torch one end to remove...

To use your idea, which I think is a good one, you need some kind of head at the end of the rebar. How about tack welding a steel head at the end. Then you could wedge under it. If you are able to thread one end of the rebar, you could put a plate washer and nut on that end and wedge the other, that way you can remove the "tie." You could use 8 mm rebar for this. But, since your improvising, I'd recommend a mock-up (test) to determine what the capacity really is, then use 50% of that for the field.

 

[DTGT2002]

If you have a sustantial number of pvc spacers, you might be able to run all thread through the spacer and reuse the threaded rod each time, though I don't know the quality of the rod in your area and wheter or not your spacers can keep enough grout out to be reuseable.

Also cleaning concrete off threads can be time consuming but labor is probably fairly reasonable in your area.

While I don't know of any products made to function for wall ties here in the US that function with a cam lcking type or wedge system to rebar, there are forming methods involving pencil rod - smooth or deformed wire, nominally 1/4" - and clamps installed with a set screw that function to wedge a tie in place. I would think either a cam wedge system or set screw could be used successfully. That said, it would take a lot of front end work.

Are there no coverage requirements for the "tie"?

How many linear feet of wall or will the system be used repeatedly in the future?

Good luck!

Daniel

 

[TalGed]

Thanks John!

I am stil trying to experiment. Bent 12mm will not give me acurate thickness of the wall, but it is very good idea, I building now kind of lock that combines two thick iron triangles (90d 60d 30d)one is fixed (bottom) other is removable (upper), both are locked in 1mm steel frame with hole in the midle, the upper one will humered to the rebar, probably by monday I'll be able to try it.

Tal

 

[TalGed]

Tanks Daniel,

I am actualy already using the system proposed by you, I am using binding wire to "stich" the panels together. And you are right, the manpower here is very chip ~5$ per day.

The walls that I am building are various in their thickness, and I have approximatly 500 sq.m of it. I am actually building box culver (3m x 3m x 13m) and one short span bridge (2x15m).

I am planing to use the same formwork for abutment walls and precated beams, so as you see the work does not justify construction of steel formwork.

Tal