Determining elastic and shear moduli of cold-formed steel at elevated temperatures using a new sonic resonance method

Abstract

An understanding of the mechanical properties of cold-formed steel (CFS) at elevated temperatures is critical for the design of CFS structures and analysis of these structures under fire; however, not much literature exists on mechanical properties at elevated temperatures. We report the measurements of elastic and shear moduli for CFS (ASTM-A1003) at elevated temperatures up to 350°C using a novel sonic resonance method. A Bode 100 network analyser was used to excite the CFS samples hanging inside a high-temperature furnace via a simple tweeter-type speaker, and for each the response signal was then detected by a Polytec OFV-5000 Laser Vibrometer Controller (Polytec Inc. Irvine, CA 92618). The resonance frequencies in both flexural and torsional modes are measured by the network analyser as a function of temperature, which allowed us to determine the elastic and the shear moduli. Both the elastic and the shear moduli decrease as the temperature increases. The results reported can be used in the CFS structure design and modelling at elevated temperatures. The new experimental methodology has been validated by a classical coupon test.

Keywords::

• cold-formed steels
• elevated temperature
• mechanical properties
• elastic modulus
• shear modulus
• sonic resonance method