145m Long Strand Anchors Stabilize a Railroad Bridge
The rail connection between Innsbruck and Bregenz, also known as Arlbergbahn, runs across the approx. 111 year old Muehltobel Bridge. During routine inspections, the Austrian railway company Österreichische Bundesbahn AG (ÖBB) discovered that the high gypsum percentage of the Maehrenalpe Mountain had caused displacements that endangered the bridge. Consequently, the railway bridge had to be further stabilized.
The engineering company Geotek suggested installing additional strand anchors for stabilization that were to be anchored in a newly erected anchor beam located at the bridge abutment. According to the geotechnical report, the stable layer in the slope was situated at a depth of approx. 130m, which posed a unique challenge during the project. A special construction company drilled the necessary boreholes at both abutments through the 6m strong reinforced concrete up to a depth of 145m.
DYWIDAG was the only company that was technically able to produce a total of six 8-0.62" double corrosion protected (DCP) DYWIDAG Strand Anchors in lengths of 151m, to place them on a special drum and transport them to the construction site. Once DYWIDAG had been awarded the contract, the six DYWIDAG Strand Anchors were produced at DYWIDAG’s production plant in Koenigsbrunn near Augsburg.
The installation of the anchors posed an additional challenge. As the anchors had to be installed at an incline of only 10%, there was a risk of the strand anchors getting stuck during insertion. The professional partners on site flushed the boreholes thoroughly so that the permanent strand anchors could be pushed in up to a length of 145m without any problems. Afterwards, the bond lengths were grouted for a length of 25m.
After a curing time of one week, the first Permanent DYWIDAG Strand Anchor was tensioned in the presence of employees of Cottbus Technical University. Initially, the anchors were tensioned to more than 1,200kN, and afterwards, anchoring was carried out at a working load of 700kN.
DYWIDAG produced and supplied the exceptionally long DYWIDAG Strand Anchors on drums to the site just in time. Furthermore, DYWIDAG experts also supported the construction site during the installation of the anchors and during grouting and provided the necessary equipment and expert personnel for tensioning.
Thanks to the seamless co-operation of all partners, the project was completed on time and to the full satisfaction of the client.