ABSTRACT
The prescriptive methodology is convenient to use for designers, however, still has some defects: firstly, the prescribed values for concrete cover, water-cement ratio and other parameters in prescriptive codes are usually derived from empirical judgments of experts and researchers, which cannot explicitly reflect the deterioration mechanism of concrete structures; secondly, the majority of parameters, which govern concrete structures durability performances tend to be random variables, while the prescriptive methodology cannot deal with the effects of parameter uncertainties on durability performances. Moreover, the specified values of parameters in prescriptive codes do not correspond to a target performance level that includes service life, reliability and deterioration level. Therefore, the prescriptive methodology cannot ensure an explicit design that may result in an excessively conservative design or dangerous one. An excessively conservative design will considerably increase the construction costs, but a dangerous one will increase the failure risk of structures.
