# Mechanical Properties of ASTM A572 Grades 50 and 60 Steels at High Temperatures
## 3 Results and Discussion
### Proposed Reduction Factors for the Strength and Elastic Modulus
#### 3.2.3 Tensile Strength
The proposed equation is higher than the reduction factor for the elastic modulus for EN1993-1-2 and AISC because the distribution of the literature data is generally higher than the code values  
Figure 14: A comparison of the reduction factors for the yield strength with the literature values and standards at a 0.2% strain level. (i.e., EN1993-1-2 and AISC). The proposed equation for the elastic modulus (Equations (7) and (8)) and the standards (Eurocode and AISC) were compared. The elastic modulus results of the compared standards and equation at 700 \({}^{\circ}\)C are summarized in Table 10 from Figure 15. At 700 \({}^{\circ}\)C, the difference in the elastic modulus reduction between MS (Equation (7)) and EN 1993-1-2 is 30% (Table 10, (a)(1)), and the difference between HSS (Equation (8)) and EN 1993-1-2 is 25% (Table 10, (a)(2)). At 700 \({}^{\circ}\)C, the difference in the elastic modulus reduction between MS (Equation (7)) and AISC 2016 is 26% (Table 10, (b)(1)), and the difference between HSS (Equation (8)) and AISC 2016 is 21% (Table 10, (b)(2)). On the other hand, at 700 \({}^{\circ}\)C, there was no difference in the elastic modulus reduction between MS (Equation (7)) and NIST (0%), and the difference between HSS (Equation (8)) and NIST is 5% (Table 10, (c)(1), (c)(2)). As with the yield strength results, the proposed elastic modulus equation (Equations (7) and (8)) was found to be closer to NIST compared to Eurocode or AISC. The difference between the proposed equation and Eurocode and AISC is noteworthy because the proposed equation of the elastic modulus reduction factor in this study includes the extensive experimental data of the previous study. Therefore, more research is required to derive the elastic modulus equation according to the steel grade. Figure 16 shows the regression equation for the proposed tensile strength reduction factor with a comparison to the literature (Table 2) and code values. The proposed equation graph is higher than EN1993-1-2 and tends to be similar to NIST. Above 300 \({}^{\circ}\)C, the proposed graph underestimates the tensile strength factor, as compared with AISC. The proposed equation for tensile strength (Equations (9)-(14)) and standards (Eurocode, AISC) were compared. The tensile strength result of the compared standards and equation at the main temperatures (400 \({}^{\circ}\)C, 700 \({}^{\circ}\)C) are summarized in Table 11, in which the values were converted by the reduction values from Figure 16. At 300 \({}^{\circ}\)C, there was no difference (0%) between the standards (Eurocode, AISC) and the proposed equation (Equations (9)-(14)) in the tensile strength reduction factor. However, at 400 \({}^{\circ}\)C, the difference in the tensile strength reduction factor between MS (Equations (9)-(11)) and EN1993-1-2 is 5% (Table 11, (a)(1)), and the difference between HSS (Equations (12)-(14)) and EN1993-1-2 is 6% (Table 11, (a)(2)). At 400 \({}^{\circ}\  
EN1993-1-2 is 10% (Table 11, (d)(1)), and the difference between HSS (Equations (12)-(14)) and EN1993-1-2 is 8% (Table 11, (d)(2)). At 700 \({}^{\circ}\)C, the difference in the tensile strength reduction factor between MS (Equations (9)-(11)) and AISC (2016) is 2% (Table 11, (e)(1)), and the difference between HSS (Equations (12)-(14)) and AISC (2016) is 0% (Table 11, (a)(2)). The difference between the proposed MS and HSS equations (Equations (9)-(14)) and the tensile strength reduction factor of NIST (2016) is 3% at 300 \({}^{\circ}\)C. At 400 \({}^{\circ}\)C, the difference in the tensile strength reduction factor between MS (Equations (9)-(11)) and NIST is 4% (Table 11, (c)(1)), and the difference between HSS (Equations (12)-(14)) and NIST is 3% (Table 11, (c)(2)). At 700 \({}^{\circ}\)C, the difference in the tensile strength reduction factor between MS (Equations (9)-(11)) and NIST is 8% (Table 11, (f)(1)), and the difference between HSS (Equations (12)-(14)) and NIST (2016) is 6% (Table 11, (f)(2)).