Lifetime design of long-span bridges

Recently, lifetime has become a major design factor for long-span bridges due to their socio-economic importance. Current practices show that design lifetimes of 100 to 150 years seem to be achievable and have already been implemented in recent major bridges through appropriate maintenance planning and in terms of material durability. However, it is clear that the lifespan of materials alone cannot guarantee that of the structure itself. Accordingly, more rational and systematic design approach needs to be developed especially for long-span bridges. This paper reviews current practices for lifetime design and addresses issues to be considered to realise long-span bridges with extended lifetime since the design stage. Since the lifetime of a bridge is essentially influenced by issues related to material, design live load, fatigue and extreme or unexpected events, review is done for each of these factors. Possible solutions are suggested and additional requirements that will help designers in achieving extended lifetime of 200 years or more for long-span bridges are derived.