Re-Fer

Description
The conduits of the ‘Passerelle du pays d’enhaut’ in St.-Légier-Fenil are part of the water supply of the city of Lausanne. As part of the complete renewal of the structure, the two main girders with a span of approximately 18 m are also being reinforced against shear. This had become necessary due to the ageing of the existing structure, the smooth inner stirrups as well as an uncertainty about the actual amount of the same installed at that time. The system with memory^®-steel stirrups makes it possible to reduce the stress level in the existing stirrups as well as to actively close or stop any diagonal cracks that may exist.

The stirrups were delivered on site ready for installation. The side surfaces as well as the underside of the girders were roughened, followed by an initial filling with sprayed mortar over the height of the bars on the outside. Then the memory^®-steel stirrups were anchored into the slab at the top with Sika AnchorFix^®-3030 and at the underside with SikaGrout^®-314 N. The area between the two beams is also partially filled with grout to avoid secondary forces due to the eccentricities of the re-bar 10. After curing, the re-bar 10 stirrups are activated with a gas burner and thus pretensioned. Finally, the free lengths on both sides and on the underside are covered with Sika MonoTop^®-4012 sprayed mortar.

Advantages
The method allowed the simple application of vertical prestressing without hydraulic cylinders and complicated anchorages. The different steps (rough surface, sprayed mortar instead of damaged concrete, …) are very classic interventions in such renovations, the memory-steel solution can be easily integrated into the general concept. As the reinforcement has a pre-stressing, the stress state of the existing structure is positively influenced and its service life is considerably extended. It also remains to mention that memory-steel is 100% recyclable and can be fully recycled into the stainless steel production cycle in case of future demolition.

Product
A total of 54 memory-steel re-bar 10 stirrups with a length of L=4.6 m were anchored, activated and sealed with Sika AnchorFix^®-3030, with SikaGrout®-314 N and covered with Sika MonoTop^®-4012 sprayed mortar.