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

There are several problems in the current codes and standards that need to be rectified to produce wind-resistant buildings and structures. One is the recurrence period of the design wind load for structural frames and cladding/components, namely the design wind load levels for structural frames and cladding/components. The tendency is to design cladding/components using a lower wind speed than the main structural frames (i.e., a shorter recurrence wind load is used for cladding design than for frame design in some countries). For example, according to the Building Standard Law of Japan (BSLJ), allowable-stress design criteria are combined with 50-year-recurrence wind loads for structural frame design, and the same recurrence wind loads are used for cladding/components design. However, 500-year-recurrence wind loads are applied for the ultimate state structural frame design, whereas cladding/component design is not obligated to reach this design level. Therefore, although the LCC concept is applied in design load estimation, it is strongly recommended that the optimal design load level 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.