by Didier Brazilliers, Thierry Kretz & Jacques Resplendino
On a french website.
Key directions for innovation:
Four major orientations emerge, that can be combined into the design of the structure.
1 – Lightening and economising of structures by using high-performance materials;
2 – Use of renewable materials and with lower environmental impact;
3 – Design of structures with no maintenance or whose maintenance can be programmed by the integration of “intelligence” into the structure;
4 – Design of evolving structures that can be adapted as needed.
The first direction is to move towards building lighter structures by using of higher performance materials: self-compacting concrete with very high performance, high-performance fibre-reinforced concretes, steels with very high yield strengths can yield gains in materials savings of from 30 to 60% compared to conventional solutions, while further improving the sustainability of the structures.
The second direction is the use of renewable materials and those with lower environmental impact: it can be concretes formulated with a lower proportion of cementacious materials – higher performance being obtained by the optimization of the granular skeleton and the reduction of water content – or recycled aggregates; it can also be developed the use of organic materials such as wood and structural fiber reinforced polymers.
The third direction is to design works which need zero maintenance or where maintenance can be programmed by the integration of “intelligence” into the construction. In the field of bridges, there is the example of innovative solutions of integrated bridges that is to say built without the need for road joints, with no bearings required; these are items causing high maintenance costs and direct or indirect discomfort to the user.
There is also the possibility of avoiding the need for painting of metal structures by the use of “autopatinable” (self-weathering) steel or stainless steel, or to design innovative hybrid structures where the steel parts are fully embedded or protected by concrete. Predeflected beams with embedded spacers on the supports or at the concrete abutments are research topics in the National Project “MIKTI” and presented in this same issue of “Travaux”, are also good candidates because the concrete cover is maintained in a state of compression or under little tension in normal service conditions.
Integration of “intelligence” into works is done by equipping the construction with sensors and devices facilitating inspection and maintenance, like in motor vehicles (Eg: corrosion sensors or detection of the penetration of chlorides, combined with the use of contact protection cathodes).
The fourth direction is to allow the adaptation of structures to changing needs, for example increasing capacity, changing purposes, the extension of life, seismic strengthening, etc..
The design of new structures must include the possibility of flexibility of use and increased performance. On existing structures, new techniques are appearing to allow adjustments and needed reinforcements.