An Introduction to Load and Resistance Factor Design for Steel Buildings

Load and Resistance Factor Design (LRFD) is a major advance toward a simple, rational design of steel-framed buildings. It combines limit states of strength and serviceability with a modern probability-based approach to structural reliability. The essence of LRFD is the assignment of resistance and load factors on the basis of consistent reliability. Developed by T. V. Galambos and his associates at Washington University, St. Louis, LRFD is based on a project sponsored by the American Iron and Steel Institute Committees of Structural Steel Producers and Steel Plate Producers. This paper introduces LRFD, illustrating the treatment of loads and resistance and describing how the numerical values of load and resistance factors were established. Two companion papers also appear in this issue of the Engineering Journal: one describes the proposed LRFD Criteria and Commentary for steel buildings, which are the end product of the research project; the other summarizes design office studies conducted by two consultants during the projects evaluation phase.