Swiss researchers have developed a reinforcement system for the reconstruction of damaged bridges, combining ultra-efficient fiber-reinforced concrete and memory-effect steel. The latter, doped with manganese, silicon and chromium, among other elements, is compressed after heating, thereby creating a pre-stress in concrete structures.
Researchers from the Swiss Institute of Civil Engineering Empa have replaced conventional steel reinforcement with rods made of an iron—based shape memory alloy (Fe - SMA), a "smart" material that can retain its original shape. After installation, the rods are heated to about 200°C. When they try to shrink, but are held by concrete, internal stresses arise. These internal forces can close cracks, lift deformed elements and extend the service life of the bridge, explains Callanish.
Fe — SMA rods (an iron-based shape memory alloy) are manufactured like conventional ribbed reinforcing rods and delivered to the construction site in a pre-stretched state. They are then installed and fixed in the existing reinforced concrete structure, heated, and then coated with concrete.
The researchers note that the materials used by the Empa team are quite expensive. "Thus, the system is particularly suitable for severely deformed or already damaged bridges – in other words, where traditional reinforcement methods are reaching their limits."
Author: Christian Kel Germany
Kallanish.com
