LRFD: Still Waiting

by Aine Brazil, Assoc.; Thornton-Tomasetti, New York, NY,
Robert DeScenza, Assoc.; Thornton-Tomasetti, New York, NY,
Thomas Scarangello, Assoc.; Thornton-Tomasetti, New York, NY,


Serial Information: Civil Engineering—ASCE, 1991, Vol. 61, Issue 6, Pg. 46-48


Document Type: Feature article

Abstract: Introduced in 1986, load and resistance factor design (LRFD), has a way to go before it becomes standard practice for steel design. LRFD-based design typically results in savings on gravity columns and base plates in mid- and high-rise buildings. Most building codes recognize live-load reductions for columns supporting multiple stories, leading to higher dead load-to-live load ratios. As this ratio increases, load-factor design brings greater economies relative to the ASD design approach. Two buildings in New York City, 420 Fifth Ave. and 546 Fifth Ave., are examples of projects that have successfully used LRFD design, with a total steel savings of about 4% on each building. However, the AISC has not integrated load and resistance factor design into its manual, instead introducing LRFD in a separate manual. Also, although many software makers have LRFD-compatible design programs, design firms are reluctant to invest in design software for a design method that isn't already widely accepted. The designer must also make the effort to learn the new code requirements. Many detailing shops are also reluctant to implement LRFD when their software (and experience) is compatible with ASD-based design. Available LRFD software includes CIVILSOFT'S STAAD-III, Ram Analysis' RAMSTEEL, AISC's CONXPRT and WEBOPEN, American Computers and Engineering's SCADA/S1, and SODA, from Waterloo Engineering Software.

Subject Headings: Load factors | Resistance | Design | Steel structures | Economic factors | Computer software | Load and resistance factor design

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