New construction of Altberg observation tower, Dänikon

The project
During the competition phase, it was agreed that the tower should be built in as delicate a construction as possible, similar to the Eiffel Tower. But how is the shape of the Eiffel Tower compatible with the footprint? How to create the staircase and a respectable platform that provides enough space for visitors to see all around? So the idea was born to turn the Eiffel Tower upside down and take it as an abstracted negative from a cubic envelope. The spiral staircase spirals outward in the freed-up space until it reaches the platform at a height of 30.15 meters. The viewing platform is located about 5 m above the treetops and provides a good panoramic view.

The construction
For the wooden structure, we chose larch laminated timber because of its better weather resistance. Primary structural components are made of wood, connections and stiffeners were made with steel components. The main structure consists of four rows of 9 columns each. The load transmission of the main supporting columns into the foundation cross is carried out by glued-in threaded rods (Ferwood system). The outer stringers support the stair treads and at the same time form the distance between the load-bearing columns.

The challenge
The inner posts, stringers and railings are supported by steel brackets, which allowed for a rather filigree construction. Bracing against external forces such as wind is provided by a tension rod system. The viewing platform is covered by a hipped roof made of hollow box elements.