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Probabilistic service life design

Photo: COWI
Nowadays, civil engineering structures such as bridges, tunnels, marine structures and other infrastructure projects, are designed for a service life of 100, 150 or even 300 years. This substantially exceeds the assumed design service life of most regulatory codes and standards

COWI spearheaded the development of rational service life design through the DuraCrete approach, which has developed into fib Bulletin 34 and the new fib Model Code.

This approach will be transferred into an ISO standard in the near future. COWI’s involvement in these developments allows us to provide a modern fully probabilistic design methodology for durable concrete constructions.

Our probabilistic service life design conforms to EN 206 Annex J “Performance-related design methods with respect to durability” as well as many international reinforced or prestressed concrete design codes.


The operational approach to design for durability is to define durability as a service life requirement.

In this way, the non-factual and rather subjective concept of ‘durability’ is transformed into a rational requirement of a ‘number of years’ during which the structure performs satisfactorily without unforeseen high costs for maintenance.

In this way, time is introduced as a design parameter. Service life design based on these functional requirements is carried out in a similar way to the load and resistance factor design concept used for structural design.

The probabilistic service life design approach effectively combats chloride and carbonation induced reinforcement corrosion. All uncertainties regarding exposure conditions, material properties and deterioration mechanisms are taken into account.


Probabilistic service life design is an integral tool in COWI’s comprehensive service life management system used during the design of most types of reinforced concrete civil engineering structures and is implemented in most new designs.

LAST UPDATED: 03.02.2017