10DBMC International Conference On Durability of Building Materials and Components LYON [France] 17-20 April 2005 Sustainable tools and methods for estimating building materials and components service life. J. Hans, JL. Chevalier CSTB, 24 Joseph Fourier Street, F-38400 Saint Martin d'Hères, France [email protected] TT4-90 ABSTRACT The need of building materials and components service life assessment is strongly increasing in the actual building construction sector. This phenomenon is due to new techniques developments and new environmental requirement and sustainable development principles. The behaviour of material performance within time in several environments has been largely studied, and good models contribute to a reliable evaluation of service life of materials when environmental and external solicitations are well defined. On the other hand, evaluation of components service life is not so well known. It can be explained by the complexity of the components and the lack of knowledge on the failure scenarios of these components. Furthermore, the feedback management is not efficient, and the knowledge is not enough collected and accessible. Our main interest is the development of tools and methods for service life assessment which remain perfectly suitable to the possible evolution of research and standardisation on the numerical characterisation of the different factors impacting the components service life. Our research and development activity is focused on three complementary tools to answer this task: (Failure Mode Effect and Criticality Analysis method; Product service life data base (including material service life data base) and associated tools compatible with ISO 15686; Data fusion). The purpose of this paper is the presentation of the efficiency and the complementarities of these tools and methods. Indeed, by the use of these tools, we are performing a multi scale analysis of building product and component (at the scale of the product itself (data base, data fusion and F.M.E.A.), at the scale of the component (data base, data fusion and F.M.E.A.) and of the material (data base, data fusion). Further more, data base and data fusion are much more efficient at the material scale, especially if the material is subjected to one identified load. The F.M.E.A. allows us to evaluate the service life of the product from the service life values of the different materials loaded by one unique identified solicitation. We can thus use this result of service life at the scale of the product to feed the product service life data base. This study highlight the need of performing F.M.E.A. analysis to obtain reference service life without performing long, complicated and onerous tests at the scale of the product, and to collect these data into a data base which take into account all the information accompanying the service life value. A project of F.M.E.A. software is on his way in order to facilitate the analysis. KEYWORDS Service life assessment, F.M.E.A., ISO 15686, data fusion 10DBMC International Conférence on Durability of Building Materials and Components LYON [France] 17-20 April 2005 1 INTRODUCTION The aim of this article is to propose a methodology to estimate the service life of products and components by the use of several specific tools developed by the CSTB and suitable with ISO 15686 standards application. Indeed, the development of the ISO 15686 standard is generating new approach for estimating the service life of product and component. We will first shortly introduce this method. This approach is highlighting the lack of building products and components service life data. The second paragraph will describe the interest of using F.M.E.A. to collect reference service life data (RSL). Finally, we will present the tools developed in CSTB, and a general methodology which is using these tools to estimate service life data of building products in a specific case study. This methodology intends to be an operational tool for construction stakeholders, (Designers, managers, manufacturers…) compatible with recommendation of ISO 15686. Furthermore, according to the fact that knowledge in term of characterisation and quantification of factors impacting the service life is limited, this methodology try to propose a sustainable solution, which take into account the evolution of knowledge in this domain. 2 "FACTOR METHOD": ISO 15 686 2.1 Presentation of the method The factor method is a simple system to estimate service life when there is limited knowledge of long- term performance of components. (ISO 15686-1, ISO 15686-2 and ISO DIS 15686-8) This method is using the following equation to estimate service life of building product and component: ESLC = RSLC × FactorA× FactorB × FactorC × FactorD × FactorE × FactorF × FactorG (1) Where: RSLC is the reference service life of component ESLC is the estimated service life of component The estimated service life of a component (ESLC) is a function of the reference service life (RSLC) and a number of factors: A: Material/Component factor B: Design factor C: Workmanship factor D: Internal environment factor E: External environment factor F: In-use factor G: Maintenance factor This formula acts as a reminder of what should be taken into account when estimating service life. TT4-90, Sustainable tools and methods for estimating building materials and components service life., J.Hans, JL Chevalier 10DBMC International Conference on Durability of Building Materials and Components LYON [France] 17-20 April 2005 2.2 Reference Service life Our capability to Collect RSL is the key issue for the performance of the factor method. A step further in the factor method is the calibration of the influence of the factors on the ESL. At this stage the factor are supposed to be representative of the difference between the reference in use condition set and the condition of the case study. According to the fact that we can use several RSL for the same product, it is not possible to propose a unique quantified scale for each factor according to associated conditions. This highlight one of the interest of the notion of intrinsic reference service life (IRSL) describe in paragraph 4.2. 3 INTEREST OF MULTISCALE ANALYSIS TO COLLECT RSL The behaviour of material performance within time under one identified sollicitation has been largely studied, and good models contribute to a reliable evaluation of service life of materials when environmental and external solicitations are well defined. This evaluation became more complex with the coupling of the external and environmental solicitations. Therefore there is still a strong need of experimentation in order to improve the models for complex and coupled cases study. If the elaboration of models seems to be possible at the scale of materials, it is not as simple at the product scale. The evaluation of products and components service life is a difficult task, due to the complexity of the components and the lack of knowledge on the failure scenarios of these components. Concerning experimentation: Taking into account that products have several functions, constitutive materials, and are submitted to complex environment, we do believe that realisation of accelerated ageing difficult is tricky. The size of the sample is also an obstacle for laboratory testing. The number of constitutive materials of the product create problem to accelerate ageing without changing any ageing mechanism Concerning modelling: Numerical modelling of product ageing assumes to be able at least to perform thermo- hydro-mechanical modelling of heterogeneous components. It also imply to model interaction between materials. Furthermore, the feedback management is not efficient, and the knowledge is not enough collected and accessible. According to this context, we have developed a tool which allows us to get service life information at the scale of the building product by using the one at the scale of the material. This tool is based on F.M.E.A. (Failure Mode and Effect Analysis) (Talon [2004], Lair [2002]). Using first structural and functional analysis and then a Failure mode and effect analysis, this analysis provides us all the potential failure scenarios of the product in use in its environment. Failure event graph is then drawn for a better exploitation of the result. (Figure 1). By the use of this graph we can define for each scenario, several stage of degradation implying a material under a single solicitation. TT4-90, Sustainable tools and methods for estimating building materials and components service life., J.Hans, JL Chevalier 10DBMC International Conference on Durability of Building Materials and Components LYON [France] 17-20 April 2005 Initial Step 1 Step 2 Step 3 Step 4 Failure of Failure of State componant product - Deviation of temperature - Thermal shock - Shocks - Pressure - Wind Cracking Breaking Failure Glazing of absorber of absorber of absorber Liquids Pollutants Failure Vertebrates Corrosion Holing Failure of the Hail of coating of coating of coating product Coating (Absorber) Breaking of coating Figure 1: Failure event graph used to present result of F.M.E.A. Illustration with two components (Glazing and Coating) of a solar panel. The determination of the kinetic of each of these degradations allows us to calculate the service life of each scenario. (Figure 2 and equation 2). ni SL[][Scénario(i) = ∑ SLmat (mat( j), perf ( j)) ] (2) j=1 Where: • i is the number of the studied scenario • ni: successively degraded materials in scenario number i (stages of the scenario) Considering the service life of each scenario, it is possible to obtain a service life of the product. Indeed, the characterisation of the criticality of each scenario allows us to select representative scenarios from the initial exhaustive list. Then, the determination of duration of these scenarios gather a service life data for the performance associated to the scenario (equation3): SL[ product, perf ( j)] = min(SL[Scenarioselected (i( perf ( j)))]) (3) If we consider the need for characterisation of durability and\or service life of the product.