Fire-Resistant Steel Mechanical Properties

This section compares the mechanical properties of a few kinds of FR steel in fire reported by different researchers inside and outside Japan, including:

• Fujino et al. (1993) reported a FR steel of Grade SM490B developed by Kawasaki Steel (denoted as KSFR steel)
• Sakumoto et al. (1992) and Sakumoto & Saito (1995) reported a FR steel of Grade SM490A developed by Nippon Steel (denoted as NSFR steel).
• Kelly & Sha (1999) reported a test programme on two FR steel samples of Nippon Steel (denoted as FR1 & FR2). The details of FR1 and FR2 such as thickness were not provided.

Figure 1 compares the reduction factors of yield strength of various FR steels reported in the above references. The yield strength was measured at 0.2% strain offset from the temperature-stress-strain curves. Although there is a large discrepancy between the test results, all FR steels are in the range of 2/3 yield strength at ambient temperature at 600°C.

Figure 1 Strength Reduction Factors for Yield Strength of FR Steel at Elevated Temperatures

Figure 2 compares the reduction factors of tensile strength of the FR steels considered. The tensile strength corresponded to the ultimate strength measured at over 5% strain during the tensile tests. Obviously, the tests conducted in Japan, comprising KSFR and NSFR, generate very compatible results. However, this is not the case for the tests FR1 and FR2 which were conducted outside Japan. The possible reasons include different test set-up and limited number of testing.

Figure 2 Strength Reduction Factors for Tensile Strength of FR Steels at Elevated Temperatures