New Tüfi bridge made of regional beech wood

04.11.2020

Line

The pedestrian and bicycle bridge Tüfi bridge in Adliswil is aging. Analyses have shown that replacing the bridge is almost as expensive as an extensive renovation. Today the new bridge - with beech wood from the surrounding forests - was installed over the Sihl river.

New Tüfi bridge made of beech wood – a pioneering project 

The Tüfi bridge is the first bridge completely made of beech wood. Wood construction pioneer Ernst Gehri used hardwood for bridges decades ago. In the case of the road bridge in Eggiwil, for example, hanging posts and cross beams are made of beech glued laminated timber. In each case it was combined with the softwoods normally used in construction.  

Assembly of the new bridge 


The beech – Mother of the Forest 

In Switzerland every fifth tree is a beech. This makes it one of the most widely represented tree species in Switzerland. Today, beech wood is mainly used as energy wood despite its good static properties. There are still few applications in the building industry. The Confederation believes that this should change and is financing research projects to increase the use of beech through the promotion of forest and wood research. Timbatec supports the use of domestic beech in the building industry - also in outdoor applications. The balconies on Saumackerstrasse in Zurich or the "Buchholz" playground in Witikon are good examples of this. Beech has also proven to be the best solution for the Tüfi bridge.

Spielplatz Buchholz

Playground Buchholz - naturally made of beech wood


The construction

The new bridge is a truss construction made of beech wood. It crosses the river Sihl with a span of 45 meters. The inclined struts made of solid beech wood are only loaded under pressure. The vertical steel tie rods absorb the tensile forces. The steel parts in the junctions allow a very high degree of prefabrication of the bridge and a quick assembly on site. The wood for the bridge was cut down by foresters last winter in the surrounding forests. Holztechnik Burch AG in Sarnen used it to make the new Tüfi bridge according to the plans and calculations of Timbatec.

Detail und Plan
Plan

Above: Cut of the bridge, below: Detail of the node in the bridge


Pressure impregnation 

Beech can be used outdoors if it is pressure impregnated. It is important that the pressure impregnation penetrates deep into the wood. Only in this way can the wood be sustainably protected. Small cracks will inevitably form as a result of weathering. They must not reach deeper into the wood than the impregnation. The "Imrägnierwerk Willisau" ensures the durability of the Tüfi bridge with pressure impregnation. The wood was cut by Konrad Keller AG. KBOB calculations show that pressure impregnated wood components are very environmentally friendly.

Montage der neuen Brücke

Assembly of the new bridge  

 
 
 

Switzerland:

Headquarters

Timbatec Timber Construction Engineers Switzerland Ltd.

Niesenstrasse 1, 3600 Thun

Tel: +41 58 255 15 10

thun@timbatec.ch


Zürich Branch

Timbatec Timber Construction Engineers Switzerland Ltd.

Ausstellungsstrasse 36, 8005 Zürich

Tel: +41 58 255 15 20

zuerich@timbatec.ch


Bern Branch

Timbatec Timber Construction Engineers Switzerland Ltd.

Falkenplatz 1, 3012 Bern

Tel: +41 58 255 15 30

bern@timbatec.ch

Austria:

Headquarters Vienna (A) 

Timbatec Timber Construction Engineers GmbH
Im Werd 6/31a, 1020 Wien 
Tel: +43 720 2733 01

wien@timbatec.at


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