work on Zurich side at the institute.

Bring your strings, foil, rope, bottles etc. Lets produce prototypes.

 

We had external consultation from both: prof. Hebel from Singapour and Ing. Schlesier from Hamburg. This is

their comment:

just as a short summery of our discussion this afternoon, this is what I would recommend:

Calculate how much load there is to be expected on the lowest elements.

Load tests on the ‘bricks’ with different bindings methods (foil, stipes, wires, etc …) should be done by using simple materials such as concrete bricks, sand bags, water buckets, whatever is available, but you should know the weight of course. A test should be done on the ultimate strength of the element observing the mode of failure (i would assume that the bottles that are already a bit deformed yould buckle first). Bottles filled with water or sand are an option for the lower members. The tests should be documented with pictures as well.

Then a test on the expected load of the self weight and a test of – lets say – twice that weight should be done as long-term tests for at least a week – maximum exposure to sunlight. Be aware that wind load will increase the compression for the elements considerably in the structure later!

Talk to the respective people in charge of the event and athority and make them part of the process. If it is ‘their baby’ they will also support it. Maybe some guys from ETH have some shortcut to those people?!

Introducing the design I would also introduce a safety concept that shows that you have a plan about it. My proposal: a ‘no-go’ area would be set up by a simple fence with a radius of minimum the height of the tower along with a watchman if strong wind is expected with the option to do a controlled demolision in case of a strom approaching.

I am very sure you cannot do without the wind bracings if it is a stand-alone structure. The connections of the cable ends to the tower will be details that need some rigidity – e.g. a wooden ring beam (hidden in the structure).

To give you some rough numbers concerning the support of the structure: According to the standards with every meter of height of the tower, assuming a diameter of ten meters, a horizontal load of 10 kN (1.0 to) can be expected, making it 15 tons of horizontal load for a tower of 15 meters of height. This would mean that as a ballast weight for the cables you would need more than 20.0 to of weight for each foundation which would be equivalent to 20 m³ of water or 10 m³ of sand or concrete. The additional compression caused by the wind within the tower for sure then can not be handled by the PET bottles …

However, this would be a rough estimation up to standards – meaning, up to standards it wouldn’t be feasible. But who the hell needs standards? So you really need to clearify it as soon as possible with the people in charge how you can deal in such a short-term situation (e.g. the worst case storm scenario described above).

Its nice challenge, so keep smiling! I am really looking foreward to the test results and your design ideas!

And email conversation afterwards:

Am 01.05.2012 12:50, schrieb Dirk Hebel DRKH:

Dear Katarina and Karsten,

I am so happy to hear, that Karsten is on board and his inputs are fantastic. After a sleepless night through jet lag, I had an idea I want to share with you: The easiest and most safe way for me to construct the tower would be to build it on ground, laying on the side like a big sushi roll. than, we will put a steel cable always through the middle of the tower (while building it), tie one end to a foundation (water pillows, or concrete panels) and the other one to a car crain. I just looked it up, there are car crains which can go up to 57 meters and hold 60 tons. In fact the tower could have an diameter of just 1meter !!!!

The advantages would be clear: erecting the tower would just take minutes. It can be done only if the weather is OK. NO PERSON would work above ground. If bad weather arrives, the crain will just let the tower down. Also, it would allow for a flexible structure, because while pulling the tower up, it would bend quite a bit. I would propose for an evening erecting time, when winds usually calm down. Also, with some strong lighting, it could be a beautiful night sculpture!

what do u think?

Hey there,

I thought about the crane option myself, to support the tower but then thought that during a strong wind the crane could not remain connected …

but dirk is right, it could basically be a cable that just hangs and the bottles are connected to it. it is just set up if there is hardly any wind. it would be an option to have some sushi rolls on the ground of a limited length and then as the crance lifts them up piece by piece, the next roll is hooked on. by that the crane could remain in its position.

later you just erase the crane by phtotoshop 😉

cheers,
karsten

Last but not least:

dr. Kotnik from ETH consulted our brick and thinks its nonsense and wouldn’t carry almost any load. He gives this system 5 meters height. He proposes to create some more stable component by flattening the bottles and

creating bricks from bottles without air. If the bricks are reliable afterwards, more interesting structures could be built of it, not only dependent on load. It could be a nice Outcome of the Thesis elective: do focus on the basic element again and try to come up with innovative PET brick. The final presentation is on 14th at 2:00! All former critiques are invited.