Abstract
This study focuses on the large-scale application of a Fe-Mn-Si shape memory alloy (Fe-SMA) for strengthening a historic roadway bridge in Petrov nad Desnou (113-years), Czech Republic. To the best of the authors’ knowledge, this is the first application of an iron-based SMA (Fe-SMA) for prestressed strengthening of a bridge. In this study, the shape memory effect (SME) of the Fe-SMA was used for the prestressed strengthening of bridge girders. A mechanical anchorage system was developed to apply multiple Fe-SMA strips to the steel girders of the bridge subjected to daily passengers and heavy trucks. The SME of the Fe-SMA was activated by heating to approximately 260 °C using ceramic heating pads. The test results showed that the recovery stress of the Fe-SMA strips resulted in a compressive stress of approximately –33 MPa in the lower flange of the bridge girder. This compressive stress significantly increased the yield and fatigue capacity of the strengthened girder. Before and after the strengthening, the bridge was loaded with a 45-ton crane to assess the efficiency and performance of the system. Laboratory experiments were performed to optimize the mechanical anchors and examine the feasibility of the proposed strengthening method prior to application to the bridge. Finally, long-term monitoring of the prestressed Fe-SMA plates after installation on the bridge was conducted. The results showed that the main loss of the prestressing force caused by relaxation occurred within the first 30 days after activation and was approximately 20% of the original prestress.
Highlights
The aging of historic steel bridges is a global problem
The results showed that the designed Fe-Mn-Si shape memory alloy (Fe-SMA) strengthening using six 120 mm × 1.5 mm plates was sufficient to resist the dead load with a compressive stress of approximately 35 MPa in the lower flange
The results indicated that the main loss of the prestressing force induced by relaxation occurred within the first 30 days after activation and was approximately 20% of the original prestress achieved after activation
Summary
The aging of historic steel bridges is a global problem. 70% of steel bridges in Europe are older than 50 years, with 30% being in service for more than 100 years [1]. There are many bridges in the Czech Republic that have reached the end of their design life or have already exceeded 100 years of service [2]. Bridge authorities often seek repair solutions to combat this problem. Repairing existing bridges is often cheaper than replacing the entire structure and helps achieve sustainability by extending the service life [3]. CFRP materials are effective for repairing existing bridges and buildings [4], and prestressed CFRP can significantly improve the effi ciency of CFRP repairs [5,6]. The placement of hydraulic actuators is complicated because of the limited space near anchorage devices [7]
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