# Tall towers (engineering)

Dear Straight Dope and members,
According to the AISC design capacity tables (design member capacities in axial compression - buckling about any axis) Hollow tubing 273.1 x 12.7 CHS x 81.6 kg/m at a height of 1 metre will “squash” (not buckle) at 3,270 kN (54,739.8 kg)… Which equates to the tubing being able to reach a full height of around 3.93 km before squashing from its own self weight (3,270kN = 54,739.8 kg/81.6 kg)… Provided that it can be fully restrained against buckling… So 3.9 km less restraining method.

Buckling cannot be controlled using a single layer of (K type or other) webbing… ok for say 200 metres, then it starts to sway more and more the higher you go.

Going by the table, the tubing would need to be supported at every 1 metre of height… Sway is controlled by the diagonal members, ideally at 45 deg. to the tubing, so there would need to be connections i.e. diagonal and struts every 1 metre apart… This distance cannot be increased (although as you get higher in can be as there is less weight to support, but please disregard for the point of this exercise).

I have been working on a two-layer system. (less congested second layer).

Concentrating on tubing size (273.1 x 12.7 CHS).
With a single uniform length of tubing, to stop it from swaying you would need to add a layer of webbing (minimum of three sets to control all lateral directions… preferably four sets)… Then as it gains height, and as the dimensions cannot be altered, what is the obvious next step?… Another layer of webbing?

I have been building scaled down and full sized models, with occasional computer analysis help, in an effort to find some kind of a “formula”, so that FULL control against buckling can be achieved.
With my most recent design I believe that I have “found the answer”. Although it “looks complicated” at first sighting, it is really very simple and makes perfect sense… but I guess you would have to start from the humble beginnings as I have to see it that way.

What is needed now for full enlightenment, is someone with the necessary computer program skills (FE or other) to model and do an analysis on my present design… which I believe will be very close to the final outcome.

The webbing at present weighs around 45% of weight per metre of the tubing… so full height of around 2.5 km… Using larger diameter tube will require less webbing. – I believe I will be able to get the webbing down to around 10%… Therefore total height before squashing approx.’ 3.5 km uniform section… 6 km tapered.

What will this find mean for the building industry?.. Earthquake proofing for high-rise (with no intrusion to window space… Inbuilt “spinal” system that will also act as a heavy materials lifting crane that can almost “build itself”)… Arch bridges to 4 km (6km self weight only)… tall yacht and ship masts… communications towers… wind power generators…lightweight roofing for stadiums… etc’ etc’ etc’

I would be very interested in hearing from someone here with the necessary skills that would like to work with me on the impending formula. What I don’t need now though is someone that will “look at it” and maybe do some work on it “when time permits”… I have plenty of those!

1. Your first reaction will be that it “will not work because…” You will be naturally critical of the design… extreme wind pressures… outer members too light etc’. You have never seen this design before (there are a couple around that touch on the same theme, but nowhere near as close) but will always naturally refer to present “known” methods.

2. I do not hold any engineering degrees, but that is my advantage (uh oh!)… I have not been taught what is already known and have had to think for myself in most cases (out of the box)… Therefore I am not restricted with my thinking. – It is a result of over twelve years of building and testing, but more importantly “understanding” of… “how it all works”. - Believe me there are plenty of “hurdles” that will distract you!

It would be very easy to dismiss me as a “crackpot” (which most seem to do anyway) but if ever for a minute I thought that… maybe I’m wrong, I’d have given up a long time ago!… So please only serious replies.

Thanks, Davo. davidratcliff6255@hotmail.com
(sorry for having to “emphasise” everything)