On the 6th of May the construction of the Guangzhou TV and sightseeing tower reached its highest point. The total construction took 4 years and is set to be completed in a few months. The tower was designed by Dutch architects Mark Hemel and Barbara Kuit from Information Based Architecture. Their collaboration with the engineers from Arup resulted in a joint entry which won the design competition in 2004.
The principle of the form is simple: One ellipse at ground level and a smaller ellipse, which forms the roof, are connected by columns. The ellipses are twisted in opposite directions and a lattice structure is added. The tightening caused by the rotation of the tower forms a characteristic waistline which gives the tower a feminine and elegant shape. Spatially, the tower appears as a series of mini-buildings hung within the superstructure. As a result, the 610m high tower has 37 functional floors. The mini-buildings contain a restaurant, a 4D cinema and several viewing platforms. The highest viewing point is at 459.2m.
SKYWALK The lower floors contain the functional workings of the tower. The infrastructural connections, ingraining the tower in the city’s structure, include a subway and bus station, footpaths and a parking area. The lower floors also house commercial spaces. The first mini-building is located at a height of 75m and contains two cinemas, play halls and a tea room. On the roof of this mini-building, at 117m above ground level, is a sky-garden. On the roof of the next mini-building, at 168m, the Skywalk starts: this open staircase allows visitors to climb the tower up to a height of 350m.
On the Skywalk, the visitor is surrounded by both the view and the spatial structure: a set of stairs, a concrete core and a surrounding grid of columns, rings and diagonals. The core and the ‘façade’ are connected and together they form the supporting frame of the tower. As for the buildings, they are connected by the floors. Horizontal concrete joints were added to the skywalk to increase stability. The surrounding grid consists of 24 columns, 46 rings and 24 diagonals. Inside the tower, the rings dominate the views. These rings, with an 800mm diameter, are attached to the columns by a joint. They come away from the columns and appear to float.
NODE Technically speaking, the point where columns, rings and diagonals connect - the node – is the most essential element of the tower. Also, this node made the construction financially viable. In the original design, the grid was entirely random with hundreds of different nodes as a result. In the final design, all 1,100 nodes are based on the same basic connection. As a result of the rotation, a number of parameters differ, such as the diameter and the thickness of the various bars and the angles which they create. During the design stage it appeared that the costs for the nodes, and thereby the costs for the entire tower, could be greatly reduced by keeping the angle between the bars at a minimum of 25 degrees.
PARAMETRIC DESIGN The detailed design for the tower was created with parametric associative software. Boundary conditions were set for three criteria: strength, rigidity and maximum vibration permissible. By varying geometric parameters, models can be calculated of their effects on the tower. The parameters for which the effects of distortion were modeled were: the rotation of the roof in comparison to the ground level, the number of rings and the openness of the structures.
The models were created in order to calculate the minimum amount of materials needed to meet the criteria set for the tower. The tower needed to be able to meet these criteria, even under extremely demanding circumstances such as typhoons and earthquakes. The more open the structure, the less the load generated by wind. As a result, the scattered placement of the mini-buildings had a positive influence on the load distribution. Dampers needed to be installed in two places in order to meet the requirements set for vibrations. These requirements were set to increase safety as well as the sense of security for the visitor. The calculations were confirmed by wind tunnel tests and earthquake simulators.
STRAIGHT AS A N ARROW Although the rings are characteristic for the interior, the 24 columns form the eye catcher on the outside. They appear elegant and curved, but in fact they are dead straight. The columns consist of 3.7m prefab slabs. On the lower floors, the columns are 2m in diameter. The manufacturer ‘rounded’ and welded the 5cm thick steel plates. Towards the top of the tower the wall is 3cm thick and the diameter decreases to 1.1m. Although the original design features a gradual benched decrease , the final design shows the columns gradually narrowing, thereby reinforcing the elegant appearance of the tower. The column sections were stacked and joined on site, as were the columns, rings, diagonals and nodes.
After the various bars were leveled precisely, the seams were welded open and the bolted joints removed. Next, concrete was poured into the smooth columns for extra stability and fire resistance The concrete core, which houses the lifts and staircases, was entirely poured in table formwork. The tower is adorned with a antenna, which levels with the highest building in country.