Mechanical properties of structural steel

Abstract

This report provides five types of mechanical properties for steels from the World Trade Center (WTC): elastic, room-temperature tensile, room-temperature high strain rate, impact, and elevated-temperature tensile. Specimens of 29 different steels representing the 12 identified strength levels in the building as built were characterized. Elastic properties include modulus, E, and Poisson's ratio, v, for temperatures up to 900 °C. The expression for E{T) for T < 723 °C is based on measurements of WTC perimeter column steels. Behavior for T > 723 °C is estimated from literature data. Room temperature tensile properties include yield and tensile strength and total elongation for samples of all grades of steel used in the towers.The report provides model stress-strain curves for each type of steel, estimated from the measured stressstrain curves, surv iving mill test reports, and historically expected values. With a few exceptions, the recovered steels, bolts, and welds met the specifications they were supplied to. In a few cases, the measured yield strengths of recovered steels were slightly lower than specified, probably because of a combination of mechanical damage, natural variability, and differences in testing methodology. Highstrain-rate properties for selected perimeter and core column steels include yield and tensile strength, total elongation and strain rate sensitivity for rates up to 400 s"'. Measured properties were consistent with literamre reports on other structural steels. Impact properties were evaluated with Charpy testing.Properties for perimeter and core column steels were consistent with other structural steels of the era. The impact toughness at room temperature of nearly all WTC steels tested exceeded 15 ft lbf at room temperamre. Elevated-temperature stress-strain curves were collected for selected perimeter and core column and truss steels. The report presents a methodology for estimating high-temperature stress-strain curves for the steels not characterized based on room-temperature behavior and behavior of other structural steels from the literature. The measured elevated-temperature stress-strain behavior of WTC steels is consistent with other structural steels from that era. For the truss steels, the report presents a complete constitutive law for creep deformation based on experimental measurements. For the steels not characterized, the report presents a methodology for estimating the creep deformation law.

Influence of elevated strain rate on the mechanical properties of hollow structural sections

“…A challenge with this installation was the large space required for a slack adaptor (Figure 8b). The slack adaptor test setup was similar to that used by Yu and Jones (1991) and Luecke et al (2005). A slack adaptor was required for the high-speed tests to allow the actuator to reach a specified speed prior to loading the tensile coupon.…”

“…These grips tended to remain elastic during a tensile coupon test due to their larger cross-sectional area, therefore allowing grip strain to be linearly related to grip stress. A similar procedure was used by Luecke et al (2005) and Yu and Jones (1991) to determine load at high displacement rates. Standard TML FLA series strain gauges were used for the grip locations.…”

“…Previous research on strain rate behavior of steel subject to blast loading has identified strain rates on the order of 100 to 1000 s −1 (Ngo et al, 2007). Accordingly, the majority of the recent research into the strain rate behavior of structural steel has been conducted in this range (Cadoni and Forni, 2015; Forni et al, 2016; Luecke et al, 2005; Marais et al, 2004; Sun and Packer, 2014). However, strain rates of that magnitude are not present in all blast events.…”

Thermally tunable band gaps in architected metamaterial structures

“…2where the upper and lower bounds shown correspond to the 95% confidence interval. Young's modulus decreases over 54% with an increase in temperature from −140 • C to 140 • C, while the moduli of steel is comparatively constant over this temperature range (less than 6% change in moduli[24]).…”

Design and Optimization of Dynamic System for a One-kW Free Piston Linear Engine Alternator-GENSETS Program

“…The second reason was the fact that sometimes the mechanical properties of the metal sheets are different in lateral and longitudinal directions. This is because of the metal forming processes and commonly the sheets in longitudinal direction have a higher mechanical strength [157]. To do tests, six standard specimens were cut using the same waterjet machine used for flexure manufacturing.…”