ACCURATE AGEING PREDICTION FOR STRUCTURES
Whether one is interested in management of existing structures or in designing new structures, one of the main issues is controlling their lifetime whilst ensuring an optimal response for the performance requirements (serviceability, structural security). The civil engineering durability studies represent an essential point of structures’ preventive management, and have many applications, such as the examples hereafter of standard OXAND studies.
Modelling of ageing kinetics of nuclear power plants’ pressurised water networks.
Forecast of industrial chimneys and cooling towers’ cracking and deformation.
Prognosis of the failure probability and risk analysis of a sheet pile quay subjected to several corrosion mechanisms.
How does it work?
The predictive ageing models are incorporated most of the time in the risk management process of civil engineering infrastructures. One of the aims is to quantify the frequency and the impact of ageing related failure modes.
Risk management process for civil engineering infrastructures (patent n°03-02970)
They are based on the knowledge of the different ageing mechanisms of reinforced concrete (chloride corrosion (Download the technical sheet), carbonation (Download the technical sheet), alkali-aggregate reactions (Download the technical sheet), …), and of their mathematical models acknowledged by the international scientific community.
These predictive models are performed thanks to dedicated softwares.
Oxand has partnerships with the LERM for material characterisation and with SITES for the measuring and inspection devices.http://www.lerm.fr and http://www.sites.fr
PREREQUISITE FOR RELIABLE PREDICTIONS
MODELS ABLE TO SIMULATE AGEING OF INFRASTRUCTURES, CAPITALISING EXPERIENCE FEEDBACK OF MANY YEARS
In order to increase the reliability of the predictive evaluations of constructions’ performance (validity range, limits of the models…), OXAND takes into account the maximum possible feedback on existing structures. OXAND has, for example, assessed and compared the performance of its own simulators to those of other concrete specialists during the benchmark test of the “Rance beams” (french project from 2003 -2005).
- Benchmark des poutres de la Rance, Revue européenne de Génie Civil, vol 11 1-2, 2007- O. Poupard, V. L’Hostis, S. Catinaud, I Petre-Lazar, “Corrosion damage diagnosis of a reinforced concrete beam after 40 years natural exposure in marine environment”, Cement and Concrete Research, Volume 36, Issue 3, March 2006, Pages 504-520
- V. L'Hostis, C. Brunet, O. Poupard and I. Petre-Lazar, “Validation of mechanical models for reinforced concrete structures: Presentation of the French project "Benchmark des Poutres de la Rance"” Journal de Physique IV (Proceedings NUCPERF 2006), Vol. 136 (November 2006), p. 273
PROBABILISTIC CHARACTERISATION OF THE PERFORMANCE OF CONSTRUCTIONS
A concrete structure is subject to spatial variability due to the nature of the material and its various components (thickness, steel, production conditions…). Moreover some of the parameters which are input data for the models may present uncertainties related to lack of experimental data for example. That is why OXAND applies probabilistic approaches for the predictive evaluations of a structure’s performance.
Added value of this kind of approach: characterisation of the predictions’ reliance.
- L. Augé, B. Capra, M. Lasne, R. Comby, P. Bénéfice, “ Ageing of reinforced concrete pipes subjected to seawater in nuclear plants: optimization of maintenance operations”, Risk, Reliability an Social Safety (ESREL 2007), Volume 1: Specialisation Topics, p. 2189
- B. Capra, J. Le Drogo, “ Reinforced concrete corrosion: application of Bayesian networks to the risk management of cooling towers in nuclear plants”, Risk, Reliability an Social Safety (ESREL 2007), Volume 1: Specialisation Topics, p. 2195
International research projects or networks on this subject in which OXAND is involved:
- APPLET : Probabilistic Predictive Approaches of Performance (ANR project),
- NANOCEM (European network).
Other major projects on the subject :
- BRIME - BRIdge Management in Europe
- DURACRETE - Probabilistic Performance Based Durability Design of Concrete Structure
- REHABCON - For decision making in the management and repair of concrete structures
- EPIQR – Energy Performance and Indoor Environmental Quality Retrofit
- Project MEDACHS- INTERREG
This project aims to provide administrations with a decision-making support tool for maintenance of historical buildings or transport structures. There are 3 major studies. The first studies the damage causes of the different materials in a marine environment, the second the damage of structures and the third develops the decision-making tool and implements it on the Atlantic coast monuments. The project plans to test various materials: stones, steel, concrete, woods, etc. http://www.medachs.u-bordeaux1.fr
LARGE APPLICATION FIELDS WITH HUGE ADDED VALUE
Taking into account durability when designing or inspecting high stakes structures is a key point for durable management of infrastructures.
Examples of recent buildings for which performance criteria related to durability properties appeared in the specifications: Vasco de Gama Bridge (Lisbon), Channel Tunnel, Condamine Port (Monaco), Millau Viaduct.
Thanks to its know-how and experience, OXAND helps its clients to assess and control the risks and costs related to the ageing of their infrastructures.
Safety demonstration, Life extension file creation for high stakes structures, etc.