Construction of an Important Bridge Structure along the A8 Motorway

Context

The Talbruecke bridge was built in 1937 on the A8 Motorway south-east of the town of Chiemsee. A comprehensive repair of the bridge would not have made sense either economically or technically, so a new bridge with two separate superstructures is being built 11.63m north of the old structure. The new bridge will include two lanes per direction at first, but is designed for a future widening to 6 lanes.

The new bridge has a longitudinal gradient of 4.4% practically along its entire length of 364m and reaches a height of 35m at its highest point. The bridge axis is in a straight line between the abutments and then merges into a curve with a clothoid parameter of A = 600m. The structure is supported by accessible hollow box abutments and massive H piers that are 2.2m thick each and widen to 7m at the pier table.

The piers, which are built using climbing formwork, evenly broaden at an inclination of 35:1 towards their foundations. The foundations rest on drilled piles in those areas where the load cannot be transferred directly into the soil.

The bridge features spans of 45+ 60+ 80+ 65+ 60 +54m and a width of 38.5m between the guard rails. The two separate bridge superstructures with their overall height of 4.5m rest on the two abutments and 5 piers each.

Solution

The superstructures consist of post-tensioned box girders that were launched in segments in lengths of 16.3 to 30.5m. Due to the longitudinal gradient of 4.4%, the superstructures had to be stabilized by what is known as a hydro incremental launching facility during launching at the eastern abutment. The launching facility was equipped with additional strand jacks. The superstructures were post-tensioned both internally and externally.

For stabilizing the superstructures during construction, centralized post-tensioning in the bonded areas was sufficient. The eccentrically placed tendons that will accommodate traffic loads were only installed after completion of the two superstructures.

For the longitudinal tensioning of the new bridge, DYWIDAG supplied approx. 500t of 19-0.62" Strand Tendons, St 1860,150 mm², with MA Anchorages (passive and active anchorages) and Type SUSPA Systems Couplers. Approx. 83t of Type SUSPA Systems 4-0.62" Monostrand Tendons, St 1860, 150 mm², with MER and MEF Plate Anchorages were needed for the transverse tensioning of the superstructures. In addition, DYWIDAG supplied approx. 117t of Type SUSPA Systems Tendons, Wire-EX 66 for external prestressing, St 1470/1670 with anchorages. All of the prefabricated tendons were produced in Lagenfeld and installed, tensioned and grouted by DYWIDAG on site.

Total cost for the construction of the new bridge and the demolition of the old structure amounted to approx. 37.6 mio. €. Construction at the new bridge began in May 2010 and is scheduled for completion in June 2014.