The Rethe Bridge: DYWIDAG Geotechnical Systems for Europe’s largest Bascule Bridge
The Rethe Lift Bridge was built in 1934 at the southern rim of Hamburg’s inner harbor area in Germany. It is currently being replaced by a new structure which rests on a single substructure and features separate superstructures for road traffic and the harbor train. The old grade level crossings are being replaced so that road traffic will no longer be held up by passing trains. Shipping will also benefit from the considerably widened waterway, which will have a width of 64m instead of 44m.
Both the road and the railroad bridge are designed as double-winged steel bascule bridges with a counterbalance at the bottom. The bridges’ main span measures approx. 104.2m between the pivot bearings. The road bridge has a total width of approx. 14m, the railroad bridge has a total width of 10.2m. The main girders are designed as welded hollow box girders.
The single span foreshore bridges south of the bascule bridges are designed as separate superstructures with a distance of 40m between supports that rest on the abutment of the lifting bridge.
The railway bridge is built using the steel construction method, and the foreshore bridge of the road bridge is designed as a composite structure consisting of steel and concrete.
As they are located in the Rethe River, the construction of the two leaf pillars required a watertight excavation employing a tied-back underwater concrete slab. The existing foundation soil required a deep foundation with grouted piles. The two excavations had dimensions of 28 x 34m and 29 x 34m.
The excavations were reinforced with interior walers and sets of struts. The grouted piles were used as uplift control for the underwater concrete slab during construction and then used as deep foundation elements after completion of the structure. Consequently, the grouted piles had to be anchored in the underwater slab and in the foundation slab of the leaf pillars. The grouted piles were arranged in a grid of 1.8 x 1.8m and in lengths of 25 to 30m beneath the bottom edge of the underwater slab. In order to prevent any possible movement of the leaf pillars, the pillars were additionally tied back using grouted piles.
DSI produced and supplied DYWIDAG Micropiles made of GEWI®Plus steel that were installed as grouted piles into the foundations and used as tie-back anchors in the leaf pillars. In total, approx. 18.000m of double corrosion protected, Ø 63.5mm and Ø 75mm DYWIDAG Micropiles made of GEWI®Plus steel were installed at the jobsite. Additionally, DSI also supplied the complete range of accessories needed for the micropile systems including anchor heads and couplers. DSI also rented the equipment necessary for the pile and anchor tests as well as for tensioning the micropiles.
Thanks to the excellent co-operation between all parties involved, the DYWIDAG Micropiles were supplied just in time to the jobsite. The project is scheduled for completion at the end of 2013.