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PREFACE

The AISC Load and Resistance Factor Design (LRFD) Specification for Structural Steel Buildings is the first of a new generation of specifications based on reliability theory. As have all AISC Specifications, this LRFD Specification has been based upon past successful usage, advances in the state of knowledge and changes in design practice. The LRFD Specification has been developed to provide a uniform practice in the design of steel-framed buildings. The intention is to provide design criteria for routine use and not to cover infrequently encountered problems which occur in the full range of structural design. Providing definitive provisions to cover all complex cases would make the LRFD Specification useless for routine designs.

The LRFD Specification is the result of the deliberations of a committee of structural engineers with wide experience and high professional standing, representing a wide geographical distribution throughout the U.S. The committee includes approximately equal numbers of engineers in private practice, engineers involved in research and teaching and engineers employed by steel fabricating companies.

In order to avoid reference to proprietary steels which may have limited availability, only those steels which can be identified by ASTM specifications are approved under this Specification. However, some steels covered by ASTM specifications, but subject to more costly manufacturing and inspection techniques than deemed essential for structures covered by this Specification, are not listed, even though they may provide all of the necessary characteristics of less expensive steels which are listed. Approval of such steels is left to the owner's representative.

The Appendices to this Specification are considered to be an integral part of the Specification. As used throughout the LRFD Specification, the term structural steel refers exclusively to those items enumerated in Sect. 2 of the AISC Code of Standard Practice for Steel Buildings and Bridges; nothing herein contained is intended as a specification for design of items not specifically enumerated in that Code, such as skylights, fire escapes, etc. For the design of cold-formed steel structural members whose profiles contain rounded corners and slender flat elements, the provisions of the American Iron and Steel Institute Specification for the Design of Cold-Formed Steel Structural Members are recommended.

A Commentary has been prepared to provide background for the Specification provisions and the user is encouraged to consult it.

The reader is cautioned that professional judgment must be exercised when data or recommendations in this Specification are applied. The publication of the material contained herein is not intended as a representation or warranty on the part of the American Institute of Steel Construction, Inc.-or any other person named herein- that this information is suitable for general or particular use, or freedom from infringement of any patent or patents. Anyone making use of this information assumes all liability arising from such use. The design of structures is within the scope of expertise of a competent licensed structural engineer, architect or other licensed professional for the application of principles to a particular structure.