PROBABILITY-BASED SERVICE LIFE DESIGN OF STRUCTURAL CONCRETE

摘要

Today there is an increasing demand for designing concrete structures with 80, 100 or 200 years service life and low maintenance costs. Predictions over such a long period are impossible without reliable models. In order to allow for uncertainties in de model parameters, probability-based models are needed. In this contribution a probability-based guideline for service life design is presented. The guideline only deals with initiation of corrosion due to chloride penetration for exposure classes defined as XD and XS. For determining the resistance of the concrete against chloride penetration the Rapid Chloride Migration test has been adopted. The basis for the guideline is the DuraCrete methodology, developed in the nineties in a European research project [1]. For a required service life the required maximum migration values depend on cover depth, type of binder and the exposure class. For practical design purposes design tables have been compiled. The original DuraCrete model and its parameters were used as the basis for these tables. Modifications were made based on new results and additional knowledge. Three options are provided to the designer: (1) maximum chloride migration coefficients for a range of concrete cover depths depending on the binder type (2) semi-probabilistic calculation based on a safety margin on the cover depth; (3) probabilistic calculations, for which a full set of parameters (including their mean values, standard deviation and distribution type) are specified.