Origins of R=3

Current model building codes, such as the International Building Code (ICC, 2006) and NFPA 5000: Building Construction and Safety Code (NFPA, 2006), require that the risks associated with seismic activity must be addressed in design and construction of buildings in all regions of the United States. The provisions in these model codes attempt to achieve a consistent minimum probability of life safety across a wide variety of applications and options in design and construction. This probability is influenced by many different factors, including the ground motion intensity, soil characteristics, occupancy characteristics, building type, structural system used, and the amount of seismic damage the system is capable of absorbing. To address these factors, both model building codes utilize the same set of reference standards to specify the requirements for design and construction of buildings in all regions of the United States. In all cases, multiple standards must be used together to determine the full set of requirements for design and construction. For structural steel systems, there are three primary standards that must be used: ASCE/SEI 7, AISC 360, and AISC 341.