Innovation: memory®-steel prestressing techniques

Conventional strengthening

Currently, externally bonded reinforcements made of steel or CFRP lamellas are often used as strengthening systems for building components in flexure. However, the force transfer from adhesive reinforcements into the concrete substrate is often insufficient. The main reason is that loads are introduced via an adhesive layer into the structural substrate only through the concrete cover, which often exhibits cracks. Additionally, concrete in outdoor applications can be heavily influenced by frost, de-icing salt, carbonation, etc. before the repair. CFRP lamellas with a low ultimate strain of 1.5-2.0% are very brittle and fail prematurely. Redistribution of forces in the event of settlement or in the event of an earthquake is not possible with these reinforcements. CFRP lamellas are approved by the building authorities for components subjected to static loads, and only in exceptional cases for elements subjected to dynamic loads.

Innovation: Robust strengthening with memory®-steel

In strengthening with memory®-steel «re-plate», the prestressing force is introduced into the core concrete through a mechanical end anchorage. This strengthening measure is very simple to install and can be applied without great preparation to the load-bearing concrete substrate and prestressed in a few minutes.

In strengthening with the «re-bar» ribbed steels, the force is introduced into the concrete core through a new mortar layer which replaces the damaged concrete layer. Existing cracks in the bearing substrate are significantly reduced by prestressing with the memory®-steel. Owing to the high ductility and ultimate strain of >20%, concrete compressive failure in the compression zone constitutes the prevalent failure mode under flexure. While enabling force redistribution, memory®-steel is also eligible for seismic retrofitting.

The dynamic, continuous load and relaxation of the internal reinforcement occurs on a lower stress level after the strengthening.

Sika repair mortars protect re-bar, as well as the internal reinforcement against corrosion in the long term.

Manufacturing of memory®-steel

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