Proposed AISC LRFD Design Criteria

The basic concepts of the proposed Load and Resistance Factor Design (LRFD) method for design of steel structures in sound, logical and appropriate for design of such structures. The purpose of the research described in the eight papers that summarize the research basis of the proposed American Institute of Steel construction (AISC) LRFD design criteria is to provide for the first time a real statistical basis for the rational implementation for this logical design method. This is the sharp contrast to the American Concrete Institute (ACI) approach where strength reduction factors and load factors were selected without a statistical study of variations in actual fabrication and materials properties relative to design values or of variations in design loads. Unfortunately, however, it is very difficult to bridge the gap between the theory of statistics and probability and the real world behavior of actual structures. Because of this, the writer is very concerned as a structural designer that the statistical results which are considered in some of the symposium papers in illustrating the development of load factors do not take into account some very important aspects of uncertainly in dead load and snow load.