Challenge To Build The Tallest Tower

dratcliff

Hi, I just popped in to see if there are any budding young engineers here (hope I got the right forum) interested in helping with a problem that I have been nutting out over the years... Hope your forum can help.

It is all about controlling sway and buckling of members and gaining the full compressive strength of materials... steel in particular.

My theory is that... If, provided that you could artificially control against buckling and swaying, steel has the ability to withstand almost 4,000 metres in height (uniform section) before it crushes from its own self weight/gravity... So, if we can control against sway and buckling with a type of webbing, and depending on the weight of the webbing (maybe down to 10% of the core weight), a uniform steel tower should reach a height of around 3,500 metres (tapered 7,000 metres).

I have started a thread on a catapult forum posing the question/challenge, so if anyone is interested in joining in and solving the problem, I would welcome your input.

Link

With thanks,
David

(If you have any questions I will reply here if you like)

J77

You'd have to build it in a stable environment - with respect to Earth movements.

I recall someone proposing a massive tower in the middle of Australia for these reasons.

Here you go: http://news.bbc.co.uk/1/hi/world/asi...ic/2628361.stm

dratcliff

You'd have to build it in a stable environment - with respect to Earth movements.

I am assuming that as the tower would be fully rigid it would also be fully earthquake and cyclone proof... and as it would be tapered, the upper section would have some give and be allowed to sway slightly... absorbing the energy from an earthquake.

I recall someone proposing a massive tower in the middle of Australia for these reasons.

Yes, it's not that far from where I live actually... The thermal tower (situated at Mildura), 1,000 metres high, was proposed to be made from reinforced concrete. From memory the size of a football field at the base, 1.2 metres thick and tapers up to 40 or so metres diamater at the top with 400mm wall thickness... I did contact the original designer in Germany as well as the people who were handling the job, but was met with absolute ignorance and arrogance from both... I even made up a design of my own using steel that would have been a fraction of the cost and a lot easier to build. link

Pyrrhus

I even made up a design of my own using steel that would have been a fraction of the cost and a lot easier to build.

I am interested in this. Why do you say your design is "more economic"?, usually reinforced concrete is cheaper than steel. I will like to see the tower design.

dratcliff

Cyclovenom,

Well for a start you would not need any scaffolding as the steel design link has external posts and webbing, so can be used instead.

They were planning on using a slip form for the concrete and would have had to pour continuously until they reached the top as well as fit the reinforcing prior to pouring... Big and risky job.

The steel idea would be very simple and quick and safe to construct. Check the links in my earlier post for more info.

Another thing too. "normally" when using steel you would expect there to be a lot of it for such a height as it needs to be bulky in order to fight against swaying and buckling... With my design, you have the inner webbing to stop the buckling and the outer web to control the sway... so the main columns are a lot stronger and can remain thinner and more economic... Lighter, stronger and more rigid.

dratcliff

I should mention that the design for the thermal tower was an earlier one, before I put this all together as it is now... It would actually be much lighter. The main ingredient is the two sets of diagonal bracing... There is no need for the outer chord to be a compression member, where it only needs to take tension... and the same goes for the middle chord.

That probably wouldn't make a lot of sense to anyone that has had any training in the area as you would argue that there needs to be at least two chords in compression to basically 'fight back'... I should redo it I guess...

The designer of the proposed tower also had a bicycle wheel type fixture inside the funnel every so many metres to stop the thing from screwing on its axis...

dratcliff

Link to new amended thermal tower section

Dark-half

Is there any specific design you're hoping to exhibit? Strictly vertical 'tower/skyscraper' or would any shape work?

Because if you're trying to make the highest tower -- er well, lets take sand for an instance, stuff it in a toiletpaper tube with tissue on the bottom held in place by a rubber-band now ram a wooden dowel hard into the tube, the weight/force gets displaced outward, correct? What if you impliment a design that would take the weight off and spread it outward instead of strictly downward like most skyscrapers. Granted it may not be the most economical or space saving, but if it's height you're going for. I believe this is the way to go...

http://img182.imageshack.us/img182/5821/ideaqi4.jpg

Tell me what'cha think. I want to know if I'm an idiot or genius in the making.

(Excuse me if I didn't really read all the posts and missed something.

)

dratcliff

Well the tower could be tapered, but going by the axial compression tables should'nt need to be as steel will reach a height of just under 4,000 metres... provided you could supply full artificial lateral restraint. So then if you could achieve even 2,000 metres, tapering would give you 4,000 metres.

(From the catapult site http://www.thehurl.org/tiki-view_for...ind=&forumId=2)

Grade 350 steel will reach a height of just under 4 kilometres... provided that you can supply full lateral restraint... before it will squash at the bottom. You can work that out from the tables where it shows the sizes of tube and loads at failure point (in kN)... then just divide by the mass per metre.

Also in the tables you can see that at certain lengths it takes the same weight as zero... which is where that size tube needs to be laterally restrained. There were three different sizes in the tables that do not change at 250mm, 500mm or 1,000mm so I cut and pasted together... Those three different size tubes are 76, 127 and 273mm respectfully... See attachment 1

The model I am using is based on the 273mm x 12mm wall thickness (I chose the heavier wall to have better control against vertical screw)... Therefore it will be supported at every 1 metre on the inner webbing.

This is all based on a uniform section so should be simpler to model... then it's just a simple matter of doubling the height if it were tapered. I am estimating that the webbing will be around 35% extra weight, so is then deducted from the 4,000 metres and you end up with 2,600 metres... Tapered would then be 5,200 metres. Attachment 2

Using a larger diamater tube, say 1.5 or 2 metres, the webbing should only be around 10% extra weight. So higher again.

The whole system should be fully rigid, so any wind loads will transfer to the bottom of the mast where guy wires would be a main ingredient... I'm tipping will have to be 1 to 200 metres up from the base. When you look at it the way that I have explained, and according to the tables, 3 kilometres should be possible.

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