Ramboll has been the main contractor for the supply and erection of a 125m tall tower in Karlskrona, Sweden. The contract included the design and delivery of a special rock foundation.
The client Teracom is the main TV and Radio Broadcast provider in Sweden and Denmark and operates more than 700 guyed masts and self-supporting towers.
In order to install a new HDTV-antenna in the tower, the old tower from 1960 had to be replaced. Thence, Ramboll designed a custom-made tower in order to fulfill Teracom's specific requirements. The tower was designed using circular tubes for both the legs and bracing members to reduce the wind load on the tower.
A narrow piece of work
The 125m tall tower (incl. topantenna) is very narrow with a width in the bottom of only 7m and 1m in the top. This was essential in order to obtain the same overall geometry as the old tower. The top part of the lattice tower with the height of 24,5m also has a width of only 1m in order to fulfill the requirements from the antennas.
In the top of the tower a GRP-cylinder with a Tuned Mass Damper (TMD) has been installed to reduce the amplitudes of vibrations caused by vortex shedding.
3D-modelling and advanced erection
Since the tower is very narrow and more than 100m tall, a stochastic analysis of the tower was carried out using the Ramboll in-house developed program Mainmast. A full 3D-model of the tower including ladders, platforms etc. were made in Tekla. The model was used for the workshop drawings as well.
The foundations consist of 4 x 8 pretension Dywidag rods with a length of 11m. Three different methods were used to erect the tower: A Mobile crane for the bottom; further up a self-climbing crane fixed to all 4 legs, and in the very top, a Dereck crane.
More in this project:
The tower was manufactured by Metalogalva, Irmaos Silvas SA in Portugal.
The foundation was prepared by Svensk Entreprenad AB in Sweden
The erection of the tower and the disassembling of the old tower was done by Perfekt Werner in Poland