Application of sensitivity analysis in the life cycle design for the durability of reinforced concrete structures in the case of XC4 exposure class

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 (fcem), water-to-cement ratio (W/C) and cement type (CEM). By using W/C of about 0.4, fcem 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.