Killesberg Tower
The Killesberg Tower in Stuttgart in the Killesberg Park is a 40.4 m high observation tower that was built in 2001. It is located north of the city center as part of the “ Green U ”, an amalgamation of green and recreational areas, which also includes the palace gardens and Rosenstein Park .
predecessor
A lookout tower was planned for the 1939 Reichsgartenschau . However, it was only built in 1950. The tower was designed by the garden show chief planner Hermann Mattern and was built by the Esslingen machine factory , the Stuttgart glass factory Galetzki and the Zaiser elevator on the same hilltop on which the viewing pavilion from 1939 stood. It was named Zaiser Tower after the company that founded it. On its top it carried a transmitter. In 1974 the Zaiser tower was demolished because it needed an urgent renovation and there was no investor willing to pay the costs.
Guiding principle and objective
In 1985 the city of Stuttgart was awarded the contract to hold the International Horticultural Exhibition in 1993 . In order to give visitors an overview of a large part of the site, an artificial elevation was necessary. The place on the Killesberg, on which the Zaiser Tower had previously stood, was the ideal location .
Planning a suitable shape for the tower turned out to be much more difficult than finding the location. The tower should be filigree and fit into the landscape without disturbing its surroundings and the “green U” in its appearance. The ambitious goal was to show that modern construction technology can be compatible with its environment , even if a tower is to be high and equipped with several, in some cases very large, viewing platforms.
Ultimately, Jörg Schlaich made the proposal for a rope net tower , which was also implemented. The model for this was the static principle of the cable network cooling towers of power plants .
Project history
The first plans for the tower, which were already available in 1986, were further developed in terms of shape and execution from 1987 to 1991 and detailed plans were made.
However, the local council stopped the project in 1993. The organizer of the IGA had miscalculated in its cost calculation and exceeded its budget . Since funds now had to be redistributed, the Killesberg tower fell out of planning. But just an hour after the decision of the municipal council, the Schönerungsverein Stuttgart e. V. asked for help. With its activities and efforts, this association had already achieved a great deal for the appearance of Stuttgart and also had experience in collecting donations. The idea was for the association to collect donations for the construction of the tower and the city of Stuttgart to raise the outstanding amount. The beautification association offered its help, but not the city of Stuttgart. Here those responsible were of the opinion that the association alone should bear the costs.
Then the IGA in 1993 took place without a tower. Between 1994 and 1997, the Beautification Association became the client . The attempt to collect donations, however, had little success. After real estate sales, some money came into the association's coffers, but nowhere near enough to finance a building project of this magnitude. The missing sum was 400,000 marks .
In 1998 the idea of “tower sponsorship” emerged: every person or company could secure one of the steps with a sponsorship and have their name or a dedication affixed to a donor sign . Thanks to this idea, the financial gap was finally narrowed to such an extent that the association could dare to build the tower. It was to be assumed that the outstanding sum of 100,000 marks would be received during the construction period. The groundbreaking ceremony took place on October 25, 2000, and the tower was opened almost nine months later on July 17, 2001.
construction
The main structural elements of the tower are the central, around 40 m high mast, the foot of which is articulated on the central foundation, and the network of triangular steel cable meshes. The net is tensioned between a ring-shaped heavy-weight concrete foundation and a pressure ring ("Advent wreath") at a height of 33.5 m, which in turn is connected to the mast head via suspension ropes.
The four viewing platforms at heights of 8, 16, 24 and 31 m are articulated on the inside of the mast and attached to the network on their outer circumference at the crossing points of the network cables with press fittings . These fastenings are omitted at the two recesses in the platforms for the stairs, so that you can see how the cable network "dented" a little. The diameters of the platforms are chosen so that the tower has a slight waist.
The two spiral-shaped spiral staircases - one each for ascent and descent - are only supported by the cable network, in that their tubes are clamped to them at the points where they cross the stay cables. At free crossing points, the ropes of the net are connected with simple clamps so that they do not rub against each other.
The connection clamps of the railings and the cable clamps for fastening the platforms and stairs to the cable network are partly made of cast steel, partly milled.
Open spiral ropes with a diameter of 18 mm or 24 mm made of 37 or 61 wires with a diameter of 2.6 mm are used for the suspension and net ropes. The tensile strength is 1.57 kN / mm². Thanks to these relatively strong wires, the ropes are insensitive to the transverse pressure on the clamps. A particularly long lay length was chosen here because - unlike on bridge masts - the ropes of the tower were installed almost straight.
All ropes and their fittings are galvanized. Thus, corrosion protection is guaranteed for years without a coat of paint. In addition to being galvanized, all steel components were given a double coat of paint. The hollow profiles, which include the mast and the stair tubes, are galvanized both inside and out. The corrugated sheets of the platforms and stairs are galvanized.
Manufacturing and assembly
Prefabrication in the workshop
Steel and rope structures such as the Killesberg Tower are generally prefabricated in the workshops in the largest possible individual pieces (which can just barely be transported). They are then assembled, welded or screwed together on the construction site . Exceptions are the foundations , which are manufactured on site.
The need for precise prefabrication increases with the complexity of the construction . To ensure accuracy, particularly critical segments of the stairs and platforms of the Killesberg tower were assembled in the workshop for testing purposes and then dismantled again for transport.
A great deal of effort was also required for the steps: the 174 steps were manufactured individually for each of the two staircases, as the tower is not only helical, but also conical upwards. The preparation time for the production of the individual steel parts was up to three weeks.
The construction site assembly
During construction site assembly, high demands were placed on the exact cutting to length of the ropes so that the net later assumes its specified geometry and all ropes are evenly tensioned.
Instead of erecting the mast first and then stretching the net in order to finally attach the stairs and the platforms, the tower was erected in several sections from bottom to top. The former option would have had the disadvantage that the platforms would have had to be broken down into small parts so that they could fit through the mesh of the net. Since a lot of welding work would have to be done on the construction site, the construction company decided against this option.
With the scaffolding system, the individual platforms, which in the meantime served as work platforms and auxiliary supports during the assembly of the actual platforms and stairs, were presented until the mast was erected in its entire height. The scaffolding was laid out with steel decking on the individual levels. Access to all work stations was made possible by integrating decks with integrated ladders into the construction over the entire height of 40 meters. The platforms were placed from bottom to top on the scaffolding system that grew with the child, articulated on the mast and welded.
A steel ring was then clamped around the mast in a similar way to a pipe clamp. The welded platform was then temporarily attached to this ring with steel cables. Now it was possible to build up the scaffolding to the next platform and to assemble the next level in the same way. The distance between the auxiliary levels of the scaffolding and the tower platforms was 1 meter.
Before the upper pressure ring was finally to be installed, the stairs and platforms were attached around the mast as auxiliary supports. Only now were the net ropes installed loosely between the upper net ring and the foundation ring and the platforms still lying on the scaffolding could be attached to their outer circumference.
In order to give the net its load-bearing capacity, the net ropes were then individually pre-tensioned to the foundation anchorage in order to ultimately also bear the weight of the stairs, which were now attached to the net. The platforms were lowered by 6 to 8 cm and were thus exposed. The difficulty here was not to let the platforms collide with the scaffolding when bracing. Last but not least, the auxiliary supports could be removed, leaving the tower free.
The standing time of the scaffolding for the Killesberg tower was 18 weeks. A total of 4000 m 3 of scaffolding was used. In addition to the almost 2,000 m of steel cable, 75 t of steel construction were used.
Weather vane
The weather vane of the Killesberg tower was designed as a tower cock by the graphic artist Bernd Schuler based on the Green U logo designed by the landscape architect Hans Luz .
The logo was created from a plan figure that shows the interconnected parks of the Green U from the New Palace to the Bärenschlössle in the Deer Park . After turning around 180 degrees, the signet merges into the figure of the tower cock.
- “The“ Green U ”signet designed by Professor Hans Luz, which is also visible from afar and adorns the top of the Killesberg tower, clearly shows the concept of several interconnected parks and forest areas that form the shape of a U: starting from the palace garden via Rosensteinpark, Leibfriedscher Garden, Wartberg area, Killesbergpark and Kräherwald to the black and red deer park. The new castle is symbolized as the starting point by the four-pronged crown, the Bärenschlössle as the destination by the three-pronged crown. "
Security of the tower
The city of Stuttgart is responsible for ensuring the security of the tower and its visitors. The security of the Killesberg tower came into public discussion in autumn 2001 on the occasion of the suicide of a mentally ill woman who fell to her death from the Killesberg tower.
The operational safety of the tower was subsequently called into question. Representatives of the Beautification Association, the Garden and Cemetery Office, the police and the designer Professor Jörg Schlaich met in October 2001 for deliberations. The participants agreed that there is no way of preventing people who are determined to throw themselves from this tower. Precautions to prevent this would have required a complete renovation.
Illumination of the tower
At night the tower is illuminated by the floodlights installed under its platforms. There are six spotlights under each of the four platforms. However, a problem arises from its geometry. If you looked at the Killesberg Tower at night and under lighting, you couldn't see its actual shape, namely that of a cone, from a distance. Since only the underside of the platforms were illuminated, the tower looked more like a truncated cone at night. The end of the tower above the last platform was not illuminated. In the meantime, additional lighting has been installed above the last platform.
use
The Killesbergturm is free to visit for an admission fee. The opening times are from 7:00 a.m. until dark. It is also possible to rent the Killesberg tower for private parties and celebrations. The marketing is currently carried out by the Schönerungsverein Stuttgart e. V. Since the Killesberg tower has neither an elevator nor a wheelchair ramp, it is not barrier-free .
Follow-up costs
The Beautification Association Stuttgart is the owner of the Killesberg tower. He bears the insurance costs and the small construction maintenance as well as the expenses for public relations. The city of Stuttgart bears the costs for the operational safety of the plant.
Project, planning and execution participants
- Client: Beautification Association of the City of Stuttgart
- Planning and construction supervision: Schlaich, Bergermann und Partner , Stuttgart
- Surveying work: Walter Köpf, Stuttgart
- Foundations: Wayss & Freytag Ingenieurbau AG, Stuttgart
- Steel construction, production and assembly: E. Roleff GmbH, Esslingen
- Rope construction: Pfeifer Seil- und Hebetechnik GmbH, Memmingen
- Nets and railings: Carl Stahl, officium design engineering, Stuttgart
- Execution of the outdoor facilities: Garden and Cemetery Office of the City of Stuttgart
The Killesberg Tower in numbers
- Construction costs: approx. € 1.18 million
- Height: 40.4 m (without weather vane)
- Width at the base: 21 m
- Dead weight: 80 t
- Load capacity: 185 t
- Viewing levels: 4
- Number of spiral ropes: 48
- Number of steps: 348
- mast
- Pressure force under preload (VS) alone: 3500 kN
- Diameter: 508 mm
- Wall thickness: 25 mm
- Rope net
- Tensile force in each of the 48 ropes under VS: 88.5 kN
- Upper pressure ring
- Max. Compressive force in the ring: 410 kN
- Max. Tensile force in the 24 suspension ropes: 186 kN
- Upper platform
- Max. Horizontal deformation under one-sided load and full wind: 110 mm
- Max. Vertical deformation of the outer edge under full load and wind: 22 mm
- Coordinates of the Killesberg Tower: 48 ° 48 ′ 18.9 ″ N , 9 ° 10 ′ 16.7 ″ E
panorama
literature
- Lookout tower in Stuttgart. In: Detail. Zeitschrift für Architektur + Baudetail 41.2001, pages 1524–1526.
- Cornelie Kraus-Mattmann: You should be free from giddiness. Lookout tower on Stuttgart's Killesberg . In: Deutsche Bauzeitschrift 2001, issue 12, page 72 [1] .
- Hans Luz : Speech by Prof. Hans Luz on the inauguration of the Killesberg tower on July 17, 2001 . Online (accessed in 2013): [2] .
- Hans Luz : All about the Green U , manuscript, Stuttgart 2012, pages 96-101.
Web links
- Our observation tower in Killesbergpark , Schönerungsverein Stuttgart eV
- Killesbergturm.de
- Killesberg observation tower , Schlaich Bergermann und Partner engineering office
- Killesberg Tower. In: Structurae
Individual evidence
- ↑ a b Photo of the information board with construction drawing on the tower, on commons.wikimedia.org
- ↑ Petra Kiedaisch (editor): Towers are dreams. The Killesberg Tower by Jörg Schlaich. With an essay by Christoph Hackelsberger. av-Ed., Ludwigsburg 2001. ISBN 3-929638-51-7
- ↑ #Luz, Hans 2001 , #Luz, Hans 2012 , page 101.
- ↑ #Luz, Hans 2012 , page 96.
- ↑ The »Green U« on killesbergturm.de
- ^ Rüdiger Bäßler: suicide at the Killesberg tower. In: wn.com. August 28, 2001, accessed on September 22, 2017 (reference to an article in the Stuttgarter Zeitung).
