دانلود رایگان مقاله انگلیسی کاربرد تحلیل حساسیت در طراحی طول عمر برای دوام سازه های بتن مسلح در کلاس XC4 - الزویر 2018

Abstract

The aim of this study is to develop a new design procedure for the durability of the Reinforced Concrete (RC) structures in aggressive environments. The study approach developed here includes: (i) a qualitative analysis phase to characterize the design parameters and environmental exposure conditions of RC structures; (ii) a quantitative analysis phase, to establish the relationship between service life and design parameters and environmental exposure conditions using the service life prediction model firstly, and then to determine the most influential design parameters on service life using sensitivity analyses; and (iii) a final design phase, to design RC structures using some favorable values of the most influential design parameters firstly, and then to compare the service life thus obtained with that of RC structures designed using a standardized approach. An application is also proposed on simulated RC structure exposed to carbonation in Madrid (Spain). This RC structure follows the recommendations of the European standard EN 206-1 for XC4 exposure class. The sensitivity analysis results are discussed in detail including influence trends, importance ranking, non-monotonic effects and parameter interaction influences. The most influential design parameters obtained are cement strength class (
), water-to-cement ratio (/) and cement type ( ). By using / of about 0.4,
 of about 52.5 MPa and CEM I cement type instead of their limiting value as recommended by EN 206-1, the service life of the RC structure is significantly improved.

4. Summary and conclusion

The present study was conducted to develop a new design procedure for the durability of RC structures through resistance to carbonation induced corrosion. This innovative approach consists in combining the techniques of the prescriptive and performance-based approaches and in integrating the sensitivity analysis of service life in the design stage. The durability design phase has focused on the most influential parameters with a view to setting them at their most favorable value. With suitable calculation tools, this proposed procedure will be easy to use by designers. Through the case study presented here, we found that cement strength class (
), water-to-cement ratio (/) and cement type ( ) are action levers. Design engineers may take these action levers carefully into account during the durability design step of concrete exposed to carbonation. When setting the action levers at their most favorable values instead of their limiting values as recommended by EN 206-1, the service life is significantly improved. The requirement for minimum cement content () in EN 206-1 for XC4 exposure class should be re-examined in order to reduce concrete costs and environmental impacts. The most influential parameters, including /,
,  , ambient temperature (Y) and relative external humidity (WX), should therefore be carefully considered in future research works conducted to address the problem of carbonation-induced corrosion damage modeling in RC structures.