JEC COMPOSITES MAGAZINE - Issue #44 - October 2008 - Special Asia - 38

FEATURE “Reinforcement” Design and fabrication of a GFRP road plate: for intermittent use during road works As a direct result of a EU directive concerning potable water and the need to renovate urban water distribution networks by eliminating lead piping, a broad campaign of works is under way in the Paris area. For this project, SRBG developed lightweight GFRP plates to replace steel hole covers. so it is eminently suited to the harsh conditions of the work-site and, importantly, it is easy to recycle. However, it is a heavy material, and this is where composites can come in. In that context, it was clear that the candidate material would be some form of GFRP and that the field of application would have to be carefully circumscribed. Following discussions between SRBG, Magnytude and Eurovia’s technical and scientific departments, the following specification emerged for the proposed new plate: • The plate should be no larger than a 1,200 mm x 1,200 mm square, with fixing holes on each side and some kind of handling system on at least two opposite sides; • The hole to be covered would be a 800-mm square; • The weight should be as close to 30 kg as possible; • The service load should be 6.5 tonnes at most, i.e. half the maximum axle rating on French roads; • The deflection of the composite plate under maximum load should be as close as possible to that of an average steel plate. 1- HONORÉ GOACOLOU, ENGINEER IN TECHNICAL DIRECTION, EUROVIA 2- DONALD HEARN, EXPERT IN COMPOSITE MATERIALS, MAGNYTUDE 3- PHILIPPE PARISSE, DIRECTOR, SRBG n view of the constraints of this particular site and the need to minimise public inconvenience, SRBG, a subsidiary of Eurovia, looked at ways to reduce on-site times. One important obstacle is the time required to remove and replace hole covers at the beginning and end of each working day. Traditionally, holes are protected by thick steel plates (12, 15, 20 or even 25 mm, depending on the size of the hole) that require mechanical assistance to be moved. Steel plates can weigh up to 100 kg. With 30 or more holes in an average suburban street, one can easily imagine the time "lost" in such manoeuvres. The question was to know if it would be possible to replace steel plates with a standard lightweight plate that could be handled by two people (or occasionally one), yet still offer the same safety guarantees as a steel plate. A point in favour of the standard plate approach was the fact that the holes in the road for this type of work are also standard (800 x 800 mm). SRBG asked Magnytude to come up with a technically and economically viable answer. I Design philosophy Based on Magnytude’s experience in the field of industrial composites, the design process had to include the choice of a moulding technique from the outset. In fact, the application required high-performance GFRP material, and thus a reliable technique capable of producing a fairly high glass content. The construction sector is not keen to develop new processes, so we opted for the tried-and-tested vacuum bagging method, which could easily be extended to vacuum infusion if needed during the product development stage. In much the same way, sandwich construction was the only practical solution capable of combining stiffness and low weight. However, in view of the high imposed service loads in terms of plate bending and the associated compression, very thick skins would be required, so that the usual skin/core thickness ratios were not feasible. Moreover, the overall plate thickness had to be minimised to avoid jolts to passing vehicles and undue dynamic loads on the road fixings. Design work started on the basis of a fairly bulky mat combined Design approach The use of steel for hole covers hardly needs justifying as it offers many intrinsic advantages, and a new solution seemed difficult to find. The material is relatively cheap, exists in almost any size and can be cut subsequently on demand for particular applications. In case of damage, it can be cut up into smaller pieces that can still be useful. Steel is durable and hard-wearing, JEC Composites Magazine / No44 October 2008

JEC COMPOSITES MAGAZINE - Issue #44 - October 2008 - Special Asia

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