143Mechanical Properties

HPS50W steel is produced by conventional hot-rolling or controlled rolling. Plates up to 4 in. (10.2 cm) thick, similar to those of conventional Grade 50W steel, are available. The minimum yield and tensile strengths of HPS50W (HPS345W) grade steel are 50 ksi (345 MPa) and 70 ksi (485 MPa), respectively.

HPS70W steel is produced by either quenching and tempering (Q&T) or thermal-mechanical controlled processing (TMCP). Plates produced using Q&T are available up to 4 in. (10.2 cm) thick and 50 ft (15.25 m) long. Those produced using TMCP are available up to 2 in. (5.1 cm) thick and 125 ft (38 m) long. The minimum yield and tensile strengths of HPS70W (HPS485W) grade steel are 70 ksi (485 MPa) and 85 ksi (585 MPa), respectively.

In addition to strength, another important property of steel is fracture toughness. To avoid brittle failure above an anticipated service temperature, steel use in bridge construction must satisfy an AASHTO Charpy V-Notched (CVN) toughness requirements for a given temperature zone. There are three temperature zones as shown in Table 14.2, with Zone 3 being the most severe.

It has been shown experimentally (Fisher and Wright 2000; Wright et al. 2001) that the two HPS possess toughness not only higher than that of conventional bridge steel but exceeds the AASHTO CVN Zone 3 requirements. Table 14.3 shows a comparison of the minimum CVN values between HPS70W and the conventional Grade 70W steels. The enhanced fracture toughness of HPS is apparent.

TABLE 14.1 Comparison of Chemical Compositions (in Weight%) Between HPS and Conventional High-Strength Steels
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