Lorzentobel Bridge
Lorzentobelbrücke is the name of three bridges standing close together on the border between the communities of Baar and Menzingen in the canton of Zug ( Switzerland ). They lead over a deeply cut gorge of the Lorze , the Lorzentobel, and connect the higher-lying villages and communities of the canton of Zug with the plains.
The second Tobel Bridge, the arched viaduct , is popularly referred to as the old Tobel Bridge and the new concrete bridge as the new Tobel Bridge - although the small wooden bridge is actually the oldest of the bridges. In the inventory of the protected monuments of Baar and Menzigen one can find the entries Old Lorzentobel Bridge: wooden bridge and Lorzentobel bridge: stone bridge / arched viaduct .
situation
A special feature is that the previous bridges have been preserved to this day. The three bridges next to each other clearly show the various construction techniques that have been used over the centuries.
The first Tobel Bridge
The first bridge on the valley floor dates from the Middle Ages and was controlled at that time by the Lords of Hünenberg from nearby Wildenburg . A covered bridge from 1531 was torn away from the Lorze during storms in 1643 and 1662 and had to be rebuilt. Today's wooden bridge dates from 1759. As with the newer bridges, long discussions preceded the construction. In the end, it was paid half by Menzingen and the city of Zug .
The wooden bridge is formed as a blasting carried out / truss structure and covered with a tile roof. The structure has a span of around 14.5 meters. The clear width is 2.36 meters and the clear height is 2.48 meters.
The location of the bridge down in the ravine was unsatisfactory in the long run. The difference in height had to be overcome twice, which was particularly difficult for horse-drawn vehicles . The industry in the Ägerital and a planned tram also made new demands on this transition.
The second Tobel Bridge
The second bridge, the arched viaduct, has a long history. Eight projects were worked out from 1860 to 1893, but it was not until 1905 that the canton engineer presented the project that was carried out later. A year later, in 1906, the people approved the project with 65% yes-votes. The building permit was issued on February 23, 1907. The bridge was completed in 1910 at a construction cost of around 430,000 Swiss francs. The arched viaduct is 187 meters long and has five openings of 30 meters each and an opening at the edge with a clear width of 15 meters. The usable width is around 6.5 meters, the maximum pillar height 58 meters. The foundations are made of concrete , the pillars and the superstructure were made of Aegeri sandstone . The meeting took place on December 21, 1910 and the bridge was immediately opened to traffic.
The bridge was not only used for road traffic, but was also used by the electric tram in the canton of Zug . The tram service over the bridge ended on May 23, 1955 and was replaced by buses with trailers.
The third Tobel Bridge
In 1960, exactly 50 years after the arched viaduct was completed, various cracks were found in the masonry. Since renovation costs of around 3 million francs were determined, the road construction administration considered a new building. The people rejected such a new building project in 1976. Then 12 further variants were examined and in 1980 the Cantonal Council finally approved a redimensioned project called Wildenburg 2 . Construction work began in 1982 and in the summer of 1985 the new bridge with a total span of 568 meters was opened to traffic at a construction cost of 13.9 million Swiss francs .
The structure has five fields with spans of 77 meters for the two peripheral fields and 138 meters for the three inner fields. The bridge superstructure is a prestressed concrete structure and has a box-girder cross-section in the transverse direction with a deck slab width of 11.33 meters and a floor slab width of 4.63 meters. The construction height of the superstructure is 7.5 meters above the approximately 60 meter high double piers and decreases to 2.9 meters towards the center of the field. The road bridge was built using a cantilever .
See also
literature
- Ernst Moos: Former bridges in the Lorzentobel . In: Swiss engineer and architect , 1986, pp. 250–251.
- Ueli Eicher: The new Lorzentobel Bridge . In: Swiss engineer and architect , 1986, pp. 255–264.
Web links
- Documentation by the Society for Civil Engineering
- Photo of the description board at the Tobel Bridge
Individual evidence
- ↑ Inventory and directory of the monuments of the canton of Zug (accessed on May 29, 2020)
Coordinates: 47 ° 10 '44 " N , 8 ° 33' 22" E ; CH1903: six hundred and eighty-four thousand six hundred and ninety-six / 225925