Strengthening of road composite bridge using Fe-SMA

Exceeding creep actions on newly built composite bridge in Karlovy Vary led to rapid repair works of the excessively deflected structure. Activation of retrofit prestressing system in confined places is usually a difficult task. Instead of space-demanding hydraulic actuators, prestressing system of thermally activated shape memory alloys was used under low filler beam bridge to act against the creep inflicted deflection. Method of thermal activation of Fe-SMA with use of heating ceramic pads with resistance wire was performed on all of 17 filler beams. This method was proven as most suitable for field activation in previous application. Strengthening was done in February 2021 without any intervention into the traffic on the bridge. It is the first permanent Fe-SMA application of its kind in the world. Wireless monitoring of the bridge started before the prestress activation and continued for several months. Static load test with use of 32-ton trucks was conducted. Based on the long-term monitoring, the relaxation of Fe-SMA is evaluated and compared with the results from the experimental analysis conducted in laboratory conditions on the same retrofit system.