Working out the length and weight of a helical

[Karl2015]

I am trying to work out the lenght and weight of a helical in tonne on a steel rebar cage,
The diameter of the cage is 100mm,
The length is 5meter
And the pitch if the spirals is 100mm

I know this isn't much info but any help on the formula for this would be much appreciated

Thanks Karl

 

[robyengIT]

You can sligtly modify this excel file (if you need)

 

[Karl2015]

thanks robyengIT,

if possible could you explain the file,

what is the DN? also do you know the formula used?

Am i right in thinking it would be Diameter x Pi 3.14 to get the circumference.
Then length of cage divided by the pitch of the helical to work out number of turns.

Then circumference x No of turns to work out Total length x reinf weight (km/m) divided by 1000 to work out weight in tonne.

 

[hokie66]

That's correct. You would have 50 turns, each 314 in circumference.

 

[robyengIT]

The program has been developped for reinforced concrete pipes. So DN means nominal diameter of pipe. Thickness is for concrete wall of pipe where, for me, the position of cage (that is diameter of cage) was :
1 - for single cage the mid thickness
2 - double cage : inner cage 50 mm from inside wall of concrete
outer cage 50 mm from outside wall of concrete

What above to use or to modify the program.

For the rest : you are correct. If you look in detail I used the same formulas

 

[prex]

Well, that way of calculating the length is not entirely correct (at least in mathematical, not engineering, terms).
For a single turn, the length is √((πD)²+p²). With the original data this produces an increase of 5%.

prex
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[Karl2015]

can anybody tell me if this is correct then,

for the question, What is the weight of the helical on a 5 meter cage, the gage being 100mm o/d (diameter), 5 meters in length and the turns at 100mm pitch is this correct-

100mm (Diameter) x 3.14 = 314 mm
length 5000mm / 100mm (pitch) = 50 turns

314 x 50 = 15.700mm / 1000 = 0.0157 meters

0.0157 x (kg weight per meter) 0.222 = 0.0034854 kg/meter

0.0034854 / 1000 = total weight in tonne 0.00000349

the part i can't understand is the helical covers the full length of 5 meters, so how can the total length be anything under 5meter.

 

[robyengIT]

PREX is mathematically correct : attached excel program
In your explanation there are mistake in transforming units : 15.7 are meters and not mm !!!!!!!

 

[Karl2015]

brilliant. thank You!