Fiber-optic in smart bridge structures Author: CET Archis.........

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Although the concept of reinforcing brittle materials with fibers is quite old, the recent interest in reinforcing cement based materials with randomly distributed fibers is based on research starting in the 1960's. Since then, there has been substantial research and development activities throughout the world. It has been established that the addition of randomly distributed glass fibers to brittle cement based materials can increase their fracture toughness, ductility, impact resistance ... Since fibers can be premixed in a conventional manner, the concept of optic fiber concrete has added an extra dimension to concrete construction. 

To evaluate the mechanical behavior of optic fiber concrete, it is important to have a good understanding of the pull-out behavior of an individual glass fiber embedded in a cementitious matrix. Since fiber pull-out is the major mechanism contributing to the toughness of the material, pull-out tests were performed in order to investigate the parameters which influence the energy absorption for fibers bridging a crack without fiber rupture. Based on these findings, the behavior of high strength optic fiber concrete submitted to uniaxial compression and the influence of the steel quality of the fibres on this behavior were investigated

Even if properly designed, constructed and maintained, the service life of a concrete structure is often shorter than planned for. This is due to durability problems or changes in use and function, originally not foreseen. Hence, there is a considerable interest in the use of non-metallic reinforcement for building more durable concrete members , which can be used as a means for repair and strengthening. With this respect, advanced composites or "fibre reinforced polymers (FRPs)" gain more and more interest in construction practice worldwide. Today, FRP reinforcement can be regarded as a viable alternative to classical reinforcement, offering many potentials (among which high strength, low weight and corrosion resistance).

FRP materials consist of a high number of small, continuous, directionalized, non-metallic fibres with advanced characteristics, bundled in a resin matrix. Carbon fibre reinforced polymer (fibre diameter about 7 µm) are used as structural reinforcement for concrete, FRP is mostly based on aramid (AFRP), carbon (CFRP) or glass (GFRP) fibres in combination with a thermoset resin such as epoxy, vinylester or polyester. As structural reinforcement for concrete members, FRP elements are made available in the form of bars, tendons, ropes, grids, sheets or profiles. For new structures, they are used to reinforce and prestress concrete elements. In the repair sector, they are used to strengthen existing structures e.g. by means of external post-tensioning, external sheet bonding or in combination with shotcrete. Also, they are used as e.g. stay cables, ground anchors, structural shapes, etc. 

Use of fiber optic sensors in Smart bridges

The new technology in the Headingley Bridge, renamed the Taylor Bridge, is the ground floor of a new construction methodology called Œsmart structures¹ that will change the way highways, bridges and roads are designed and operated. ŒIntelligence¹ and Œcommunication¹ are two unique capabilities of the new bridge, located on Manitoba Provincial Road 334 over the Assiniboine River, west of Winnipeg in the Rural Municipality of Headingley, Manitoba. 

A Turning Point for Civil Engineering

The performance of these ACM girders is monitored by 64 single and two multiplexed fibre optic sensors, called Bragg gratings, embedded in the new girders, that can measure strain, loading and temperature. The ElectroPhotonics FOS system can communicate this information to MTH engineers, using a Fibre Optic Grating Strain Indicator (FOGSI() system from ElectroPhotonics Corp.
"This is a first for Manitoba," said Eden, "and it¹s a turning point for civil engineering in terms of new materials and instant information."
The two newest experimental multiplexed sensors were prepared by the UTIAS FOS Lab. The 66 sensors were installed on the ACM girders by an ISIS Canada team led by Robert Maaskant, vice president of ElectroPhotonics Corp., with the assistance of Paul Mulvihill, research engineer with the UTIAS FOS Lab, and researchers from the University of Manitoba. 
Fibre optic sensing was a natural outgrowth of aerospace research, because of its use in monitoring aeronautical and space structures composed of advanced materials. The use of fibre optic sensors results from immunity to electromagnetic interference and light weight, together with evidence of long term stability in advanced materials. The cross-over of this advanced scientific research from aerospace to civil engineering is exemplified by both the UTIAS FOS Lab, and by ElectroPhotonics Corp, a highly-successful, four-year old spin-off company from the FOS Lab. 
This new technology can give both civil engineer and architects to think smart and go fro smart buildings which will give a new dimension the construction world

CET Archis…….

Referances :
http://www.isiscanada.com
http://allserv.rug.ac.be/~ltaerwe/MagnelLab/Research/Research.html
http://www.surrey.ac.uk/CivEng/index.htm