Public Safety—Is It Compromised by New LRFD Design Standards?

Abstract

Factors of safety for flexural members designed using the ASCE 7‐88 and American Institute of Steel Construction (AISC) LRFD 1986 standards are investigated and found to represent a significant reduction in reliability compared to previous AISC allowable stress methods for typical flexural members. This contradicts statements in the commentary of AISC LRFD 1986, which states that the reliability index for typical members has not been reduced. Also, experience from structural failure investigations and peer reviews shows that actual dead‐load variations are not consistent with the 1.2 dead‐load factor used in these standards. Further development of consistent load and resistance factors by a joint committee of practicing structural engineers under auspices of ASCE, AISC, American Concrete Institute (ACI), and American Institute of Timber Construction (AITC) is recommended. Suggestions are also made for interim load and resistance factors that maintain the reliability level inherent in current working stress design in steel.