Iron-based shape memory alloy strengthening of a 113-years steel bridge

Abstract

This paper presents an application of iron-based shape memory alloy (Fe-SMA) for the strengthening of metallic girder of a historical roadway bridge in Petrov nad Desnou, Czech Republic. This is, to the best of author´s knowledge, the first application of Fe-SMA for strengthening of bridge structure worldwide, as the previous applications were mainly on building structures. The shape memory effect (SME) of Fe-SMA was used for prestressing of the steel girder. The SME is material property of deformed Fe-SMA to return to its original shape upon heating and subsequent cooling. A mechanical anchorage system was developed to apply pre-strained Fe-SMA plates to the steel girders of the 113 years old bridge, which is daily subjected to passengers and heavy vehicles. The SME in the Fe-SMA was then activated by heating to approximately 260 ℃ using heating ceramic pads. The test results showed that achieved recovery stress of the Fe-SMA strips led to a maximum compressive stress of −33 MPa in the lower flange of the steel girder. This compressive stress could significantly increase the yield and fatigue strength of the strengthened girder. Before and after the strengthening, the bridge was loaded with a 45.34-ton crane. Prior to installation of the strengthening to the bridge a static test was performed in the laboratory to examine the efficiency of the proposed strengthening method.