Interrogation of Relation between Design Load Level and Lifetime of Individual Building and Its Element

摘要

The common wisdom is to design cladding and components using a lower level wind load than the main structural frames, i.e. a shorter recurrence period wind load is used for cladding design than for frame design. This paper first discusses the design wind load levels for structural frames and for cladding and components. Next, the design wind loads of scaffolds for building construction, those of buildings in the construction stage, and those of so-called "temporary" structures such as site offices are discussed. In Japan, the design wind load for scaffolds is defined as 1-year-recurrence wind load, because its average setting period at one construction site is around 6 months, but this paper clearly proves the inappropri-ateness of this design wind load estimation concept. Then, it is shown that there is no relation between the design wind load level and its lifetime at an individual site. Finally, even for the design wind load for main structural frames, it is clearly demonstrated that the design load level may not be able to be determined based on the lifetime of an individual building. Therefore, although the LCC concept is applied in design load estimation, it is strongly recommended that the optimal design load level should be decided considering total LCC for the city or nation as a whole, and treat design as involving a group of buildings, rather than attempting to optimize the LCC of individual buildings. Clearly, the cost associated with social or national security must be included.