The 2005 American steel structures design code

The American Institute of Steel Construction was founded in 1921 and issued the first US structural steel design code in 1923.1 It was 10 pages long and based on the principles of allowable stress design (ASD). The ASD code was subsequently published in various editions, through the ninth in 1989. No substantive changes have been made to this document since the eighth edition (1978). Limit state design, or Load and Resistance Factor Design (LRFD) as it is called in the United States, was officially introduced by the first (1986) edition of the LRFD Specification. It was based on extensive research and development carried out over 15 years. This code has since been revised twice; the current version is the third edition (1999).The presence of two design codes has created difficulties for US designers and industry. The AISC Committee on Specifications therefore undertook to develop a single, unified structural steel design code, which has just been approved (April 13, 2005). The paper describes the key concepts of the new code, including the use of nominal strength criteria in combination with appropriate measures of reliability. Among many other developments, significant additions have been made in the requirements for stability and bracing design for framing systems, including novel methods using inelastic criteria.