In the community of Mersch in Luxembourg, a new, 260 m long, four span stay cable was recently built. The bridge has span lengths of 2 x 43.3 m and 2 x 86.7 m and two 30 m high pylons. The Pont Haubané Mersch is the world's first stay cable bridge to feature stainless steel slim ducts built by DSI.
For the special stainless steel stay cable duct (stainless steel grades 1.4307 and 1.4404), suitable partners for the welding work, special components and surface processing had to be fund. Furthermore, an assembly concept had to be developed for the stainless steel ducts that are considerably more susceptible to damage and less elastic than common ducts.
New strand lifting concept was a European first
Finally, a new strand lifting concept was used that was a European first. The existing welding machine also had to be remodelled completely in order to meet the changed requirements. The Hintzen Edelstahlverarbeitung Company produced the technically and architecturally vital special components – vandalism protection pipes, transition ducts, sleeves and flange ducts – and carried out the welding work on the continuous ducts. Type DG-P37 and DG-P31 stay cables, 20 – 80 m long, were used for this project; the Type DG-P31 stay cables were filled with 27 strands. In total, 42 t of grade 1860 N/mm², 150 mm² strand for the stay cables were installed.
For the slim duct that had been chosen by the engineer (Slim-Duct, 156.0 x 3.0 mm), procedural concept studies for the supporting strands due to the limited space available had to be provided. Finally, the decision was made to push the strands in from the bridge deck towards the pylon using different compaction clamps. Thanks to the equipment that had been especially adapted the up to 80 m long stay cable strands could be pushed in completely. Afterwards, the stay cables were stressed in two steps.
Post-treatment robot applied final polishing to continuous stainless steel ducts
After completion of the stay cable assembly, the ATIS post-treatment robot was used. Its special rotation brushes applied the final polishing to the continuous stainless steel ducts shortly before the bridge was opened to traffic. This new development will be used for the regular main assessments of stay cable bridges with stainless steel ducts to permanently maintain the stainless steel appearance and surface structure.
After a construction time of approximately three months from site setup to technical approval, the complete work was handed over without any complaints. In particular the fact that there were no visible welding seams on the stainless steel components including the continuous ducts illustrates the high quality of the products and processes that were used.