Technical Note: Determination of Allowable Strength Design Safety Factors in the 2005 AISC Specification

The 2005 AISC Specification for Structural Steel Buildings includes both allowable stress design (ASD) and load and resistance factor design (LRFD) methods. The determination of safety factors for use in ASD are directly proportional to the resistance factors used for LRFD. The relationship between the resistance and phi factors is derived based on a live load-to-dead load ratio of 3 and the development of an equivalent load factor for LRFD. Both the resistance and phi factors are tabulated in this paper for the various limit states and structural elements that appear throughout the 2005 AISC Specification.