{{unreferenced, date=March 2010
Allowable Strength Design (ASD) is a term used by the
American Institute of Steel Construction
The American Institute of Steel Construction (AISC) is a not-for-profit technical institute and trade association for the use of structural steel in the construction industry of the United States.
AISC publishes the Steel Construction Manual
...
(AISC) in the 14th Edition of the Manual of Steel Construction.
Allowable Stress Design philosophy was left unsupported by AISC after the 9th edition of the manual which remained an acceptable
reference design
Reference design refers to a technical blueprint
A blueprint is a reproduction of a technical drawing or engineering drawing using a contact print process on light-sensitive sheets. Introduced by Sir John Herschel in 1842, the process allowed ...
standard in evolving
building code
A building code (also building control or building regulations) is a set of rules that specify the standards for constructed objects such as buildings and non-building structures. Buildings must conform to the code to obtain planning permiss ...
s (e.g.
International Building Code
The International Building Code (IBC) is a model building code developed by the International Code Council (ICC). It has been adopted for use as a base code standard by most jurisdictions in the United States. The IBC addresses both health and sa ...
by the
International Code Council
The International Building Code (IBC) is a model building code developed by the International Code Council (ICC). It has been adopted for use as a base code standard by most jurisdictions in the United States. The IBC addresses both health and sa ...
). This presented problems since new research, engineering concepts and design philosophy were ignored in the minimum requirements and references in the aging 9th edition. As a result, structures that were code compliant based on design using the
Allowable Stress Design methods may not have been code compliant if reviewed with the
Load and Resistance Factor Design
Limit State Design (LSD), also known as Load And Resistance Factor Design (LRFD), refers to a design method used in structural engineering. A limit state is a condition of a structure beyond which it no longer fulfills the relevant design criteria ...
(LRFD) requirements - particularly where the LRFD procedures explicitly defined additional analysis which was not explicitly defined in the Allowable Stress Design procedures.
AISC's Allowable Strength Design applies a quasi-
safety factor
In engineering, a factor of safety (FoS), also known as (and used interchangeably with) safety factor (SF), expresses how much stronger a system is than it needs to be for an intended load. Safety factors are often calculated using detailed analy ...
approach to evaluating allowable strength. Ultimate strength of an element or member is determined in the same manner regardless of the load combination method considered (e.g. ASD or LRFD).
Design load combination effects are determined in a manner appropriate to the intended form of the analysis results. ASD load combinations are compared to the ultimate strength reduced by a factor (omega) which provides a mathematical form similar to Allowable Stress Design resolved with a safety factor.
This AISC Allowable Strength Design does not attempt to relate capacity to elastic stress levels. Therefore, it is inappropriate to refer to the procedure or philosophy as either Allowable Stress or Permissible Stress Design.
Construction
Engineering concepts
Structural steel