Mechanical Impulse Technique Used to determine the Elastique Characteristics of Welded Steel Bars of Concrete Reinforcements Compared with those Obtained by Analytical, Numerical and Experimental Methods

Obtaining hard and rigid structures, so necessary in the field of constructions, can he obtained by pouring concrete over reinforcements formed of steel or polymer bars and which by drying acquire the desired characteristics. The joints of the bars are made by splicing them with steel wires. The replacement of this time-consuming technique by a welding of steel bars brings not only an increase in productivity, but also an increased quality and safety of these joints. This paper aims to develop and validate a technique based on the analysis of vibracoustic signals obtained by applying a mechanical impulse to welded bars, in order to determine their elastic characteristics. The tests were performed on six dimensions of the welded steel bars, and the acquisition of the signals is as done by means of an acoustic sensor consisting of a dynamic microphone of high fidelity in the frequency range of 20 Hz-20 kHz. Spectral analysis of vibration signals was done using the Fast Fourier Transform (FFT) and the Prony Series Method (PSM). The first frequencies in the spectrum were compared with those obtained theoretically by approximating the cylinder bars, respectively with those obtained numerically using the Modal Analysis (MA) based on the Finite Element Method (FEM). For the comparison of the longitudinal modulus of elasticity (Young modulus), resulting on the basis of the acoustic method, the classic tensile test method was used.