[Various Architects] - Cheongna City Tower - competition entry

[Jimmern]

This is our first competition entry since starting up in January 2008. The tower is designed in collaboration with Ramboll Whitby-Bird.

This project didn't place, but now that the judging is over I wanted to share it with the rest of you. After two years of participating here at PPB as an employee at Snøhetta this is also an opportunity to introduce our new company - Various Architects AS in Oslo, Norway. My friend and colleague Ibrahim ElHayawan and I have started Various Architects together after 12 years at Snøhetta.

text extracts from the competition description:


Design Concept

The design of the tower is inspired by hyperbolic geometry, elegant mathematical forms, and the dynamic yet infinitely balanced taegeuk. The result is an iconic sculptural form that is reminiscent of natural phenomenon. The lattice tower design removes the central core which is archetypical of tall observation towers and replaces it with a lightweight and transparent structure. Within the vast vertical interior space two spheroid volumes that contain the observation platform and educational / entertainment program are suspended in the void creating a tower that is both introvert and extrovert.

We believe that our solution is unique to observation towers in that the tower functions are contained in volumes suspended on the inside of the structure, creating an opportunity for dramatic views both outside of, and inside the tower itself. In addition to high-speed inclined elevators on the tower interior we have also proposed a one-of-a-kind external panorama ride that would lift visitors to the top of the observation tower while slowly spiralling through 450 degrees of views.

[Jimmern]

Shabolovka Tower, Moscow

The mathematics of hyperbolic geometry and the application to building design was first established in the late nineteenth century with the work of Vladimir Grigorievich Shukhov. Shukhov’s exploration of doubly curved structural forms led to the steel lattice tower at the 1896, 16th All Russian trade and industry exposition and twenty years later the Shabolovka Tower in Moscow (1919), see below. The latter is particularly relevant to our Cheongna Tower submission as it used the principle of stacked hyperboloids. This meant that the ‘neck’ or ‘waist’ between the tension rings of each individual hyperboloid is not read within the context of a large tapering tower. The tower was originally designed as 350m tall in 1918 and would have been 50m taller than the Eiffel Tower. The tower was built with each stack assembled on the ground and successively lifted in position like extending a telescope. It is claimed that if the original scheme had been built it would have used a quarter of the material of the Eiffel Tower.

[Jimmern]

Site

The City Tower is the key element for activating Central Park, a large open area for recreation in the center of the city plan. The green space available is important with the dense urban structure which is proposed elsewhere. The tower and it’s supporting facilities will act as a cultural magnet for attracting visitors to the park. The wide base of the tower apparently rises up from the Central Lake with all of the lower tower functions at lower levels inside the sunken central garden provides a spectacular and suprising view up the inside of the tower. Outdoor garden functions and a circular dock also give access to water-taxis and tourist boats.

Access to the tower by car is from the motorway to the west. Underground parking is available to the north-west and south-west of the tower. The two parking lots are connected to the tower via an underground passageway. This passageway is creatively lit with lightwells that frame the tower from strategic views. This approach creates suspense as the first close-up view of the tower is from the interior courtyard.

Pedestrian access from town or from the Central Park is also connected to the same passage via openings on the walking path. This could be supplemented by bridges to make access for pedestrians easier. The proposed cable-car or gondola system travels through the park and the gondolas pass through the lattice of the tower to a station on the inside. From here visitors can enter the tower, or follow the passageway out to the road and other public transportation into the city.

[Jimmern]

Tower program


Observation sphere

At the top of the tower an ovular volume surrounds 4 floors of functions related to the observation tower. In addition to a floor dedicated to observation this volume contains a skybar, souvenir shops, and entrance/exit from the panorama ride. With a top floor height of +425 meters the observation floor provides stunning views of the city and landscape around the tower, as well as breathtaking views back down the tower structure. The bar at the bottom level would be placed in the middle of a large circular patch of glass floor, testing visitors resolve when the que up to order a drink. Hanging in the middle of all floors is a massive concrete “tuned mass damper” which helps prevent tower sway.

Education and entertainment sphere

Two-thirds of the way up the tower a large volume with 6 suspended floors houses the main educational and entertainment space within the tower itself. This is divided between a Technology Museum and a series of restaurant / bar spaces.

To celebrate the technological achievements of South Korea and the Cheongna area we propose the inclusion of a science and technology museum in the tower. This features three floors of hands on exhibits for both children and adults. A sphere containing a planetarium and/or Imax theatre is placed at the lowest level such that it’s exterior is a visible element of the tower.

The top two levels contain restaurants and cafe’s with an open terraced space on the upper floor. From here you can enjoy the view from +295 meters up or watch the light show from the inside of the tower at night. With the panorama ride, planetarium visit, lunch and the science museum the tower can easily become a whole-day destination for tourists or the local population.

[Jimmern]

Tower lighting

The open lattice structure of the tower with it’s suspended glowing volumes, internal vertical lifts, and the spiral track for the Panorama Ride create the opportunity for spectacular effect lighting of the tower. One of the most unique aspects of the tower is the transparency of the structure from a distance. At night this transparency can be even more striking as the objects inside are lit by a computer controlled lighting program. It will be possible to get the sense that the orbs are floating above the Cheongna skyline. The Panorama Ride track accentuates the spiral nature of the tower and shows off it’s changing section as it climbs skyward, the spherical orbs slowly tracking up and down the entire structure. The skin of the technology museum could be lit up like a giant planetarium, and lightshows would be a major evening attraction at the restaurants and bars of the tower and lower tower.

[Jimmern]

Vertical transportation and emergency escape

There are four forms of vertical transportation utilized in this tower design proposal.


Spiral Panorama Ride (shown in blue)

The external spiral panorama ride is a unique proposal that relates to the spiral design of the tower. This would be a tourist attraction in it’s own right, much the same as the London Eye. The spherical cars carry visitors to the top for a 30 minute ride through more than 360 degrees of rotation to ensure that they can enjoy the view in all directions. The ride includes a programmed guide and multimedia presentation inside each cabin with information about Cheongna and South Korea. Each cabin would hold from 20-30 people comfortably with seating provided in the middle, and unobstructed views at the edges. Visitors can begin or end their visit with the panorama experience. Half of them would purchase a ticket to take the ride up to the top, where they can disembark at the observation level before taking the inclined elevators down to the entertainment and educational offerings of the technology museum. The other half could work their way up the tower to the observation level, and then take a relaxing ride down before enjoying the facilities at the tower base.

The panorama ride would require more research and development to be feasible. It could likely be constructed as a spiral funicular lift, using ski-lift/gondola technologies, or with techniques from amusement park rides. While we consider this ride to be a unique and exciting feature of our tower proposal, it is not a necessity for the project’s function due to the inclusion of the other types of lifts for direct access.


Duo-lift inclined elevators (shown in green)

For rapid transport from the lower tower level to the technology museum or observation levels visitors would use the duo-lift inclined elevators. The hinged cabins of these lifts follow a vertical plane up the inside of the tower structure. Inclined lifts use exiting technology and can be found in The Luxor Pyramid in Las Vegas, The Pinnacle Tower in Portsmouth, and in the Eiffel Tower in Paris. Of these the Eiffel tower also uses the duo-lift principle where two cars are attached to the same pull-cable. The balance in weight between the lifts is an energy efficient way to power the lifts. Lift size and capacity can be adjusted to suit visitor numbers. There are 6 lifts in the current scheme - two pairs that stop at observation and technology museum levels, and one which only services the museum and it’s restaurants. Service elevators can be provided using dual level cars. This is also an alternative way to increase capacity without increasing the number of lifts. These lifts stop only once per volume, separate lifts are provided for internal communication.


Internal elevators

Additional internal lifts would be provided within each of the observation sphere and the technology sphere. These are traditional mechanical or hydraulic short run lifts that span 4 and 6 floors respectively. Mechanical rooms provided locally.


Escape Stairs (shown in red)

Two means of escape are provided from all levels of the tower. Next to the inclined elevators on each side of the tower there would be an enclosed fire stair which follows the interior curve of the tower. Larger enclosed waiting areas can be placed along the exit route if necessary. The panorama ride may require an alternative exit in case of failure, this could be incorporated to the inside of the structure or as part of the rail system for the cars. It is possible that this could be an alternative to the vertical escape stairs shown in the communication diagram. This design provides for multiple possible escapes, the physical separation of the two exit routes due to the width of the tower could offer a more robust escape strategy than a traditional concrete core tower. A more detailed study would be required in the next design phase.

[Jimmern]

Structural concept

Our solution for the Cheongna Tower competition uses established, but rarely used, ideas of geometry to create a dramatic but efficient structure and one which achieves a lightness of touch from simple repeatable elements. We believe that in this way it will be practicable to build without a high cost.

Circular and Elliptical hyperboloids of revolution of changing diameter are stacked one above each other and rotated about a central point. Advanced parametric modelling software has been used to tune the shape and quickly investigate different geometries.

The hyperboloid shapes are triangulated and formed from either structural steel or concrete filled structural steel members with upper floors for the public facilities comprising full height structural steel trusses spanning across the width of the tower.

The structural solution for the Cheongna City Tower uses established, but rarely used, ideas of geometry to create a dramatic but efficient structure and one which achieves a lightness of touch from simple repeatable elements. We believe that in this way it will be practicable to build without a high cost. Advanced parametric modelling software has been used to tune the shape and quickly investigate different geometries.

[Jimmern]

Structural Challenges

There are many challenges to overcome in the design of the tower structure.

• The tower itself must be stiff enough not to deflect more than proscribed limits in order to avoid damage to brittle finishes and to ensure the comfort of the users of the tower. Similarly the lateral and rotational accelerations under wind loads must be carefully considered to avoid feelings of discomfort.
  
• The tower elements must be slender, in order to retain the impression of lightness but have sufficient axial load and moment capacity to resist the stress imparted by the horizontal loads (wind, notional horizontal load and seismic factors) and by the floors within the tower.
  
• The tower will be located in a zone of low to medium seismic activity and hence will need to be designed to cater for the IBC and/or South Korean seismic design code requirements.
  
• Our tower design envisages floors at high level spanning between the outside skin. The spans are in excess of 60m and hence will require deep trusses to support the floors.
  
• A further challenge is that of the definition of the geometry. In order to model the tower and investigate the structural action via computer based finite element analysis software the location of the nodes (the common points of the triangulated geometry) must be accurately determined. It is also important that the nodes can be accurately set out during construction. The facilitate these we have modelled the tower used a logic based, 3D, parametric CAD software package, Microstation Generative components.
  
  
• The foundations of the tower must be appropriate to the site conditions. These have been kindly supplied by the competition organisers. See later description of the foundation parameters.
• Finally, the tower must be of a form that can be constructed using known technology and of a form which uses the least amount of material, hence reducing cost.

[Jimmern]

Structural Elements


Tower Skin

The sizes of the structural elements gradually vary over the height of the tower in order to preserve the sense of lightness and scale as the vertical members close together.

At the lowest level of the tower the vertical elements are composed of concrete filled, hollow, structural steel sections. All of the members within one storey are of the same cross section and length in order to create an economic structure.

The joints between the lower and upper vertical members and that of the horizontal members (acting in tension under vertical loads and restraining the lateral thrust of the curving form) will be moment connections.

The vertical sections change in cross section from 3.0m square at ground level to 1m square at the upper floor. The horizontal bands of the towers are composed of 1m square elements


Internal Floors

The internal floors of the tower, supporting the observation, education functions etc are to be composed of conventional structural steel beams and lightweight composite concrete floors. Because of the large unsupported spans of these floors they will be supported by deep structural steel trusses (two storeys deep) with the raking elements of the cross hidden within partition walls.


Structural action

Two 3 dimensional models were analysed for static and dynamic load; firstly an investigation was carried out of a ‘plain’ Shukhov tower of 450m in height in order to check the validity of the concept and secondly the final form of the tower was then analysed in order to confirm the structural performance (see later)

Wind loads were applied at node points and have been calculated according to a ratio of actual elevational area of the structure divided by the projected area. The structure is therefore acting as a porous body with interacting jets.

Vertical loads from the floors within the tower were calculated as reactions from floor trusses spanning across the tower and positioned at node points for ease of analysis.

Only the results of the final tower are discussed in detail below. The loadings used are set out later in this document.


Method of analysis

The tower has been analysed using CSC S-Frame and Sofistik finite element software We have looked at several different models, including evaluating a structure of basic circular, hyperbolic geometry (as per the Shukhov Tower) to gain a feel for the efficiency of the form. We have also carried out basic hand calculations to confirm the validity of our computer models and check the answers (see later)

[Jimmern]

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[Jimmern]

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[Kristen]

Nothing to do with your post really but congratulations on the start of your new company. I wish you well.
It's a shame you finished at Snöhetta I was going to ask you about the project in RAK. K-special showed a documentary here last month about Snöhetta's first contacts with the Sheik and the beginning of the project......and I saw you on tele I do not envy what I saw your ex-workmates go through down there but the succeeded in the end and I was impressed with the result. The proposed building looked amazing and according to the schedule, construction should have started very recently. I don't know if you can say anything about this in another thread.

[JesseJacob]

Very interesting project Jimmern.

You have very detailed (and interesting) information about the structural and functional aspects of the lookout tower.

Im interested to know more on what generated the form of the building?, not the structural system, but the outside line. "The result is an iconic sculptural form that is reminiscent of natural phenomenon".

(Sorry for butchering your render, they look bloody good mate, go maxwell!).

[Jimmern]

Jessejecob - The form is generated by rotating an elipse and changing the proportions of the elipse as it moves up the 450 meters of the tower. You get a pretty good idea of it in the view up in post #8. The base elipse is 160 x 140 meters! The scale of this thing was just insane...

I made the first sketches of the form in SketchUp and the engineers at Ramboll Whitby-Bird converted it into a parametric based model in Generative Components. After that we went through a series of iterations to tweak the form, member size, and number of members. I brought the model back in to sketch-up for rendering and additional detail.

The form is very dynamic and changes quite a lot as you move around it - it`s a shame we couldn`t submit an animation. We`re now working on dividing it up into pieces to print a model on the new 3D Printer.

Kristin - there is a thread about RAK here, not much more I can say about it these days now that I have moved on.

[gorgon]

Jimmern
Congratulations on getting your own office up and running.
Are you based in Norway still? I assume Ibrahim isn't Norwegian either? Will you stay there?

I think your tower project (if you half the scale) would make a great telecoms tower but I don't like it much as a piece of architecture. It seems like the structure is the interesting bit and then you then shoehorned the functions in rather than their being some kind of simbiotic relationship. Besides filling the frame takes away what is so dynamic about the form (that image in post 2 is amazing!).

The scale of this thing was just insane...

agreed

Sorry to be a bit harsh, I respect your thinking and architecture skills and you're an excellent particpant here. I hope to see more of your own work posted.

[Jimmern]

...Winning projects now posted online and in this post:

The first and second prize obviously did a lot of work on their projects and presentation and presented schemes which were well integrated with an extended ground level area (something I'm afraid we under-prioritized). I don't really get the third place project, which is strangely deconstructavist.
The honorable mention project from IaN+ is the best of them all in my opinion, they do really good work and this was no exception. The weakest of the 5 prized projects is the second honorable mention from SWiMcau. It contains about the same program elements and sizes as our project and the diagram for both projects is more or less the same, but their solution is still a traditional solid core tower with a skin wrapped around it.

Having now seen the other projects I would say we didn't take the site plan and associated areas seriously enough for the judges tastes. I suppose we could also have been more poetic in our metaphors and had a catchy tower name. No grudges, you win some you lose some... Thanks for your comments Gorgon, we've posted here for feedback, so don't hold back.

[vOid]

Nice work, Jimmern! I suppose it must be an unfamiliar and difficult scale to handle (it would be for me).
The structure seems to be very well thought out and results in an extremely powerful image (I was unaware of this structural concept, so this was also a very instructive thread to read ).
The spheroid volumes seem too unrelated with the dominant geometry of the structure, Gorgon already mentioned this and it was also my first thought. The structure looks very simple and clean with its triangulated grid, maybe a solution that grew from this would have worked better. I imagine the secondary structure to hold those spherical volumes in place would be quite complicated and noisy.
Also, I wonder if the lifts would work better climbing along a structural alignment instead of adding another element to the composition.
I agree that the surronding space seems to have been overlooked.
Overall it's a very positive proposal, congratulations!

[minwsuh]

As a participant of the same competition, I totally agreed with your opinion.
One thing the competition host group should have done was that they have to get rid of ‘idea’ from the main title: ‘International (Idea) Competition for Cheongna CITY TOWER’…

[Jimmern]

minwsuh - Well, it was an "idea" competition in the sense that the winner does not get a contract to continue on with the job. The Korean Land Company will take over the rights to the design and can build it as they see fit, which is why the prize money was so high (their words).

The program was intentionally vague and competitors were encouraged to come up with ideas for the tower and lower level program. The winning entries both proposed a tower that was closely integrated with the base program, which was obviously what they were after.

[Jimmern]

Well, we might not have won, but we got it "built" it anyway, albeit in a slightly smaller scale.


Images and 3D print of the tower by John Harding of Ramboll Whitby-Bird.