Research on Reliability of Structural Members Subjected to Snow or Wind Load for Design Working Life of 100 Years in China

Various national and international standards for building structures and other common structures specify a design working life of 50 years. Therefore, the statistical parameters of loads and the design expressions in current design codes are also based on a design reference period of 50 years. When the design working life is not 50 years, the variable load adjustment factor for the design working life needs to be considered. The corresponding load adjustment factors of office building live load, residential live load, snow load, and wind load are given in (GB50153-2008), (GB50009-2012), and (GB50068-2018) with different design working life (5, 10, 20, 30, 75 and 100 years), respectively. However, the recommended values presented in these documents are inconsistent and no provisions are found in those specifications for the selection of load design parameters in the design expression, which will result in designers having doubts in choosing design parameters, especially for building structures designed for a working life of 100 years. Using different design parameters in the design expression, the implied reliability level of the members with a design working life of 100 years was clarified in the paper. Furthermore, guidance for the specification in actual design is provided. For structural members designed for working life of 100 years, 14 representative structural members were selected to calculate their partial factors of resistance. Considering two simple combinations (dead load and wind load, dead load and snow load) and common load effect ratios, the reliability analysis of each member are carried out according to the load partial factors in China’s old and new codes. The study indicated that the structural importance coefficient of 1.1 needs to be taken in the design expression to increase all the load effects on the structural members designed for 100 years. The basic wind pressure and snow pressure should be taken with a return period of 100 years and the variable load adjustment factor for the design working life should not be considered.