No abstract

For applications related to the structural health monitoring of steel bridges, novel weldable strain and temperature sensors based on fibre Bragg gratings were developed. These sensors, which can be directly welded to metallic structures, reveal linear responses over typical required measurement ranges and stability over thousands of load and temperature cycles. Proper installation procedures and in-field mechanical protection were also developed and implemented. The significance of the developed sensors was demonstrated through the installation of a complete sensing network on a new circular pedestrian bridge in Aveiro, Portugal, where it was used for loading tests, and also for in-service monitoring of its structural health.

Abstract:To monitor a new circular pedestrian bridge, new strain and temperature sensors based on fiber Bragg gratings were developed to be directly welded to the steel structure, as well as proper protection and installation procedures.

The present paper describes the study and the repair of a steel water pipe concerning the dimensional stability by finite elements methods, selection of materials and the repair procedure. The water steel pipe transports water from a dam to an electrical power. The structure presented some areas with corrosion and other parts with lack of material "pitting". There were some solutions for the repair, but due to atmospheric conditions, local access and the advanced corrosion conditions, it was decided that the right solution would be with composite materials. Composite materials turn out to be the most attractive solution to the repair because it can easily be done, possibility to transport the raw materials near repair local and good mechanical properties of the composite laminates. The finite element method predicted the number of carbon fibre layers necessary to recover the initial mechanical resistance of the water steel pipe. Dry fibres and a thermosetting matrix were selected according to the atmospheric conditions, its mechanical properties and the joining of dissimilar materials. A repair procedure manual was done according to the results obtained.

The implementation of a large sensing network based on fiber optic sensors for the structural health monitoring of a new five arch stone bridge with a total span of 60 m over Vizela River (Felgueiras, Portugal) is presented. In addition to the implemented instrumentation with conventional sensors, four different types of fiber Bragg grating based sensors were specially developed for measuring temperature, strain and displacement in several critical points of the structure. In total, 85 Bragg sensors were installed and more than 800 m of fiber cables were deployed along the bridge. The fiber optic sensing network installed on the bridge was entirely monitored by using a single measurement unit designed for collecting and archiving the signals from all the fiber Bragg grating sensors, and also to allow remote access to the important data through a standard GPRS connection.