IMPACT OF LOAD AND RESISTANCE FACTOR DESIGN SPECIFICATIONS ON SHORT- TO MEDIUM-SPAN STEEL BRIDGES

In 1993, AASHTO adopted the "Load and Resistance Factor Design Bridge Design Specifications" (LRFD specifications) as an alternative to the "Standard Specifications for Highway Bridges" (standard specifications). Its adoption raises many questions regarding the specification's impact on the resultant bridge members' proportions and the design process itself. The implication of the provisions of the LRFD specifications on the design of steel highway bridges relative to those of the load factor design (LFD) provisions of the standard specifications is investigated through a dissection of the specifications into the load and resistance sides of the LRFD equation. A simple design example illustrates the impact of the LRFD specifications. Finally, the design process and effort required to apply each set of provisions, LRFD and LFD, are discussed on the basis of the example. Through the dissection of the LRFD specifications into the load and resistance sides of the LRFD equation and the discussion of the design process, the general impact of the specifications on the economy of short- to medium-span steel bridges and on the design community in general is assessed.