Answers by Ir. Dr. Lim Char Ching:
1. "Design working life" (or service life) is a new design concept for structure and was introduced, first ever, in Eurocode. It differs very much from the "design life" concept in all previous BS.
2. "Service life" of a structure may be regarded as "repair-free period" of a structure. Service life model comprises the "initiation period" and "propagation period".
3. Cover requirements in EN 1992-2 are intended to meet the service life of 50 years or 100 years. For maritime structures, where chloride-induced corrosion is the main deterioration mechanism, the covers given EN 1992-2 correspond to the "initiation period" i.e. 50 or 100 years for chloride ions to penetrate the full cover thkness provided.
4. Analytical models are available to predict the initiation period & propagation period. They are very complex. Current Eurocode does not require such computation to be done. Designer may conveniently select covers from Eurocode to meet the required service life of 50 or 100 yrs.
5. Concrete structures (bridges or buildings) design to EN 1992-2 are intended to be "repair-free" for either 50 or 100 years, depending on the selected cover.