Steel Structures Design ASD/LRFD

Abstract

The purpose of this book is to introduce engineers to the design of steel structures using the International Code Council’s 2012 International Building Code (IBC). The International Building Code is a national building code which has consolidated and replaced the three model codes previously published by Building Officials and Code Administrators International (BOCA), International Conference of Building Officials (ICBO), and Southern Building Code Congress International (SBCCI). The first Code was published in 2000 and it has now been adopted by most jurisdictions in the United States. In the 2012 IBC, two specifications of the American Institute of Steel Construction are adopted by reference. These are Specification for Structural Steel Buildings (AISC 360-10) and Seismic Provisions for Structural Steel Buildings (AISC 341-10). This book is based on the final draft of AISC 360-10. Where appropriate, the text uses the 13th edition of the AISC Steel Construction Manual, which includes AISC 360-05, as the 14th edition of the Manual was not available at the time of this publication. The design aids in the Manual are independent of the edition of the Specification. Traditionally, structural steel design has been based on allowable stress design (ASD), also called working stress design. In ASD, allowable stress of a material is compared to calculated working stress resulting from service loads. In 1986, AISC introduced a specification based entirely on load and resistance factor design (LRFD) for design of structures. In 2005, AISC introduced a unified specification in which both methods were incorporated, both based on the nominal strength of a member, and this principle is continued in the 2010 Specification. In accordance with AISC 360 Sec. B3, structural steel design may be done by either load and resistance factor design or by allowable strength design. Allowable strength design is similar to allowable stress design in that both utilize the ASD load combinations. However, for strength design, the specifications are formatted in terms of force in a member rather than stress. The stress design format is readily derived from the strength design format by dividing allowable strength by the appropriate section property, such as cross-sectional area or section modulus, to give allowable stress. In the LRFD method, the design strength is given as the nominal strength multiplied by a resistance factor and this must equal or exceed the required strength given by the governing LRFD load combination. In the ASD method, the allowable strength is given as the nominal strength divided by a safety factor and this must equal or exceed the required strength given by the governing ASD load combination. This book covers both ASD and LRFD methods and presents design