The Wiesental Bridge in the town of Lörrach is the third longest road bridge in Baden-Württemberg at 1201 meters and is also one of the longest in Germany. It is part of the A 98 between Luckepass and Homburg Forest and crosses the river Wiese, the federal highway 317, the Grütt Landscape Park and the Wiesental railroad from north to south. The four-lane highway route is curved in plan and rises to the south towards the slope. As Lörrach is located in the highest German earthquake zone, the structure was designed to be earthquake-proof.Wiesentalbrücke Lörrach, p. 3. Since it was opened to traffic in 1983, the Wiesental Bridge has continued the A 98 in an easterly direction. An automatic counting station at the east portal measures the traffic volume on the bridge. In 2020, around 23,000 vehicles used the structure every day, with heavy goods vehicles accounting for a good 10%. Most of the piers of the Wiesental Bridge were officially approved for legal graffiti by the city of Lörrach in summer 2010. Since then, the pillar images have become known nationwide as the Bridge Gallery.
History Based on an expert opinion for the 1965 traffic plan, the demand arose to build a highway along the High Rhine on the German side, the section of which was begun from Märkt with the Weil am Rhein highway intersection to Rheinfelden in the 1970s. In December 1966, the planning approval process began for the area around Binzen with the help of the B 317, construction of which began in late summer 1968. The section of road through Lörrach to cross the Wiesental valley was originally planned as an underground route, i.e. the A 98 would have run under the Wiesental railroad. In October 1970, the Federal Ministry of Transport decided on the general alignment of the High Rhine highway, and in the same month the planning approval decision was issued for the construction section between Lucke and Waidhof.
It was not until the revised plans in 1976 that a viaduct was planned to cross the Wiesental at an elevated position. For cost reasons, it was initially envisaged that the bridge would only have one laneSchmidt: A 98 – Umgehung Lörrach. p. 61. The structural core of the "Lörrach Bypass" section was the Wiesental Bridge, which carries the freeway over the Wiesental valley near Lörrach and thus simultaneously fulfils the function of a bypass to get traffic out of the town. In the subsequent planning process, it was determined that the cost savings from the earthworks in the cuttings in Rötteln and Homburg Forest were not significant. A one-way expansion would have significantly impaired the ongoing traffic, so that the decision was made to fully expand the Wiesental Bridge, contrary to the original plans.Schmidt: A 98 – Umgehung Lörrach. p. 62.
Construction
Once the planning approval had been granted in July 1976, preliminary earthworks between Wiesental and Waidhof began in early 1977. Before work began, burial mounds were found in the Homburg Forest, which first had to be excavated. In addition, extensive sinkholes had to be filled in. The excavation in the Homburg section amounted to 1.3 million cubic meters.Schmidt: A 98 – Umgehung Lörrach. p. 63. Construction work on the freeway section in Lörrach itself began in spring 1978. During the foundation work near the Haagen commercial canal, two stone cannonballs were found in 1978, which were attributed to a presumed enemy defence of the rulers of Rötteln Castle. The objects found are now in the Dreiländermuseum.Schmidt: A 98 – Umgehung Lörrach. p. 65.
After the Wiesental Bridge consortium, led by the construction company Bilfinger and Berger, was awarded the contract for the construction work in November 1979, construction of the Wiesental Bridge began from the south in December 1979. During the construction phase, increased safety requirements had to be met, as the bridge crosses a 300-hectare water protection areaWSG 019 Lörrach: TB 1 - 4 Grütt, WSG-Nr-Amt 336019 available at udo.lubw.baden-wuerttemberg.de and the city of Lörrach has extensive infrastructure for the municipal groundwater supply in Grüttpark.
For this purpose, the bridge was designed in such a way that the surface water is drained away without damage using longitudinal pipes in the box girder of the superstructure. During the construction work, the construction site was connected to the municipal water supply system, parking and workshop areas were sealed and an oil weir was set up. The embankments, including the drainage troughs, were sealed with strong plastic sheeting in the entire roadway area. The manholes and pipelines had to meet special requirements in terms of impermeability. The area of the Wiesental bridge was additionally secured with a 1.5 meter thick sealing layer to prevent any disruption to the water supply in the event of a serious accident.
As is usual for highway bridges in Germany, the bridge was built by the Federal Republic of Germany. The contracting authority was the road construction office in Bad Säckingen, which transferred the construction management to the town of Lörrach. The bridge and civil engineering department of the Freiburg Regional Council was responsible for the technical supervision and the tender design. In addition to Bilfinger and Berger, the Wiesentalbrücke consortium included Gustav Strumpf from Rheinfelden and Locher & Cie from Switzerland. The structural engineering work was carried out by the engineering firm Schmidt + Partner from Basel. Leonhardt, Andrä und Partner from Stuttgart was entrusted with checking the structural analysis and design.Wiesentalbrücke Lörrach, p. 11.
After laying the bridge piers, the consortium concreted the first span of the box girder in October 1980 and was able to complete the superstructure by July 1982.Wiesentalbrücke Lörrach, p. 10. The formwork was built on a feed scaffold. The scaffolding girders required for the construction were moved using a hydraulic bearing.Walter Jung, Gerhard Moehring (Hrsg.): Unser Lörrach 1981. Eine Grenzstadt im Spiegel der Zeit. 1981, p. 63, 65.
The highway bridge was officially inaugurated for public traffic on April 11 and opened on April 12, 1983, after months of delays. In addition to the mayor at the time, Egon Hugenschmidt, the opening was also attended by District President Norbert Nothhelfer, the Federal Minister of Transport at the time, Werner Dollinger, and the State Minister of Economics, Rudolf Eberle. A schoolgirl from Lörrach cut the ribbon with the federal colors to mark the opening of the section, and then a convoy of cars several kilometers long with political celebrities moved across the opened section of freeway from the freeway junction Mitte in the direction of Waidhof. At the time of the opening, the Wiesental Bridge in Lörrach was the longest road bridge in Baden-Württemberg.City of Lörrach (ed.): Unser Lörrach 1983, eine Grenzstadt im Spiegel der Zeit. (Volume 14), Kropf und Herz, Lörrach 1983, p. 214.
Since opening
Since 2005, the Federal Highway Research Institute has been systematically recording traffic volumes at the southwest portal of the Wiesental Bridge using an automatic counting station.
In 2008, the Wiesental Bridge was renovated at a cost of one million euros.Road construction report 2008, p. 19. In 2010, the city of Lörrach officially released the surface of the bridge piers for legal graffiti, known as the Bridge Gallery.Kai Hendrik Schlusche, Stefan Dieterle: Graffiti am richtigen Platz. Die Bridge-Gallery in Lörrach in southern Baden. (PDF; 1.2 MB) In: Stadt und Gemeinde Interaktiv. Journal of the German Association of Towns and Municipalities Berlin/Bonn/Brussels No. 6.2011, p. 268 ff.Kai Hendrik Schlusche: Kunst aus der Dose & Nie zu spät für Spraygeschichten. (PDF; 2.8 MB) In: Regio Magazin. August 2011, p. 7 ff; Badische Zeitschriften GmbH Freiburg.Willi Adam: Graffiti an Brückenpfeilern: Bridge Gallery wird zur Attraktion. In: Badische Zeitung. August 15, 2011.
In the summer months of 2012, the top of the bridge was extensively renovated at a cost of around two million euros. One lane was completely closed at a time and traffic was diverted to the other. Among other things, the damaged drainage spouts in the roadway slab on the top of the bridge were replaced so that the de-icing salt water on the underside could drain away easily and not damage the prestressed concrete. In addition, the old sealing layer of the road surface, which was now 30 years old, was renewed. This involved demolishing 12,000 square meters of the old bridge deck.Sanierung der Wiesentalbrücke der A 98 bringt Staus. In: Badische Zeitung. April 12, 2023.
The bridge underwent further maintenance work in 2020.Maintenance measures 2020 in the administrative district of Freiburg
Description
Location The 1201 meter long Wiesental Bridge spans the Wiesental valley near Lörrach and leads the A 98 freeway in a wide arc from the Luckepass downhill to Lörrach, before gaining height again, taking the route over the Homburg Forest, which belongs to the Dinkelberg, and on to the Waidhof Pass. Along the valley, seen from Lörrach, the bridge describes a concave curve and lies between 6 and 24 meters above the Wiesental. In the northwest, the north and south bridges begin in the valley basin at an altitude of 299 m NHN and run south to 339 m NHN (south bridge) and the north bridge at 335 m NHN.
Around 900 meters of the bridge structure run in the narrow water protection area of the city of Lörrach. To ensure that traffic can easily negotiate these ascending and descending curves, the transverse inclination of the bridge varies between 4 and 6%. The access and exit ramps to the B 317 federal highway are located in the north-western part of the bridge, which passes underneath between piers 3 and 4. Junction 5 is called Lörrach-Mitte and is directly connected to the bridge structure via a curved ramp construction. The intersection of the junction's entrance and exit with the B 317 is known as the Hasenloch junction and is considered a supra-regional traffic junction in the district. The Wiese river between pillars 1 and 2, the Wiesentalbahn railroad line between piers 12 and 13 and Brombacher Straße between pillars 22 and 23, which used to be part of the B 317, are also underpassed.
Foundation and abutment
With the exception of pillar pair 26, the entire Wiesental bridge has a shallow foundation. This shallow foundation is possible because the gravel soil in the Wiesental valley rises to the surface and the permissible soil pressure of 3.5 kg/cm2 is not exceeded. Due to slope debris and irregular subsoil conditions, pillar pair 26 was constructed as a pile foundation. Each pillar stands on four large bored piles, each measuring 120 centimeters in diameter. The piles, which project into the rock at a depth of between 13 and 18 meters, stand on a limestone cliff. Pillars 27 to 29 are located on the rising slope of the Dinkelberg. As the mountain has layers in the rock parallel to the slope at this point, larger and more complicated excavation work was required. Both abutments of the Wiesental Bridge are designed as box abutments. The abutment in the north-west is directed against the embankment fills and slopes. There are further bridge structures in this area, which form the approaches and departures of the Wiesental Bridge. In the area of the south-eastern abutment, which is located on the slope, the support of the superstructures is offset by one bay due to the inclination of the terrain. In addition to a 45-metre-long wing wall, there is a connecting wall between the roadway axis and the two abutment halves. The abutments with the retaining walls also have shallow foundations.Wiesentalbrücke Lörrach, p. 4
Pillar system