forces in motion

Hamburg: Steel plates bridge 2.5-meter gap on the elevated highway K20. Hamburg. In September, there was applause and relief on Germany’s longest road bridge, the elevated highway K20 in Hamburg: within 55 hours, 30 Mega-MMBS were installed, each weighing up to 8t. These foldable steel plates from MAURER can move in longitudinal direction and will bridge a 2.5-meter gap, which will emerge across the highway and the entrance ramps, for the next five years. The applause was directed at the entire assembly team that mastered this unparalleled major construction task in three-shift operation. The six-lane A7 highway from the 70s is chronically congested and is to be renovated and extended to four lanes in each direction. Building owner is DEGES. A special highway section is the K20 (elevated highway Elbmarsch), a stilted section of the A7 highway in the Hamburg port area south of the Elbe Tunnel. This longest road bridge in Germany is a multi-segment construction with roadway expansion joints in 52 axes. In total, the bridge features 110 pier axes with about 500 piers. In three axes, so-called mega supports are installed. These mega supports bear the structure in longitudinal direction. They are the fixpoints where the longitudinal forces of the bridge are transferred. The normal bridge piers feature a diameter of approx. 60cm, the mega supports are over 5m in diameter. Despite these huge dimensions, the concrete mega supports with a length of 8 to 10m as well as the crossbeam are damaged by chloride due to the use of thawing salt. Therefore, they have to be completely dismantled and newly built – while traffic is running. That is supposed to last about five years. In the process, the bridge is supported by a steel construction. The challenge is a 2.5m wide gap across the roadway right above the crossbeam that results from the dismantling work and has to be bridged – with so-called Mega-MMBS.