In 1996, the American Iron and Steel Institute, the Office of Naval Research, and the Federal Highway Administration introduced new high-performance steel (HPS) grades with superior strength, weldability, and toughness. Since then, HPS-70W has been used successfully on bridges across the country and is increasingly gaining popularity with bridge design professionals. As HPS-70W steel becomes a more viable alternative, designers are faced with two basic questions: When is HPS-70W steel economical? What are the advantages of its use? To determine the economy of HPS-70W steel, a study was conducted to compare the relative cost of steel designs using HPS-70W and conventional-grade 50W. Investigated were the conditions in which HPS-70W steel would offer economic advantages over grade 50W steel as well as its other advantages. The study considered three two-span continuous bridge arrangements with 45.75-m (150-ft), 61-m (200-ft), and 76.25-m (250-ft) span lengths. Variable bridge cross sections were considered with 2.75-m (9-ft) and 3.66-m (12-ft) girder spacing. Forty-two girder designs were developed and compared for weight and cost and submitted to fabricators across the country to obtain relative costs. From these data, cost comparisons of designs using HPS-70W steel and conventional-grade 50W steel were derived. Guidelines were also developed to aid bridge designers in evaluating the economical use of HPS-70W steel and various hybrid combinations and gain the advantages of HPS-70W steel through its efficient use in design.
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