A Structural Dynamic Approach to Evaluate Modulus of Elasticity of Cantilever Beam

Abstract

The modulus of elasticity is an important property of any structural member or machine component. It has a vital role in designing the structural components or machine components for their specific use. This paper discusses evaluation of modulus of elasticity of cantilever beams made out of Self-Compacting Concrete (SCC) using a structural dynamic approach – the free vibration test. The concept of free flexural vibration essentially involves setting up a specimen (beam) into ‘free vibration’ by imparting an initial condition, such that the specimen vibrates in its fundamental natural frequency. The digital data were stored using an efficient data acquisition system (Daisy lab version 5 software) and processed using Fast Fourier Transformation (FFT) (Acceleration v/s Time). The fundamental natural frequencies thus obtained were used to evaluate dynamic modulus of elasticity of SCC specimens using well established basic equations of structural dynamics. The study revealed that the dynamic modulus of elasticity for the cantilever beams were equal to the initial tangent modulus obtained by conventional compresso-meter method as per ASTM C 469-02. Moreover, the free vibration tests exhibited high consistency and repeatability. This technique can be of potential use as Non-Destructive Testing (NDT) for monitoring the health of in situ structures or machine components.