PSI - Issue 37

Dmitrijs Serdjuks et al. / Procedia Structural Integrity 37 (2022) 547–554 Dmitrijs Serdjuks/ Structural Integrity Procedia 00 (2019) 000 – 000

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vibration analysis (Boscato et al. (2019), Kamgar et al. (2012), Rahgozar (2020), Fang et al. (2020), Masciotta et al. (2017), Maksimenko (2003), EN 1993-1-8 (2005)). The present study aimed to propose a vibration analysis method for the quality assessment of structural joints based on the correlation of coaxial accelerations from sensors orientated coaxially in space. The method does not employ ready-made mathematical models for vibration analysis. A stand composed of timber beams with a moment joint of variable stiffness was developed and tested using the proposed method to verify the feasibility of the latter. 2. Materials and methods 2.1. Method of coaxial correlations for quality assessment of structural joints To improve the quality of diagnostics of structural joints and make it more specific, a method and measurement system implementing the principle of correlation of normalized coaxial accelerations measured in 3D space was proposed. The method is based on the mathematical analysis of vibrations of structural joints in 3 spatial directions using 3D accelerometers located at different parts of a joint and orientated coaxially. Analysis of vibration in 3D space enables one to check the stiffness of joints of planar structures, such as a joint of girder and additional beam, considered below for testing the proposed method. The developed measuring device consisted of an electrodynamic actuator, two 3D accelerometers, a signals amplifier, an Arduino board for signals conversion and transfer, and a computer. The developed measuring device and its major components are shown in Fig.1. The steps of data collection were as follows: 1. The vibration of the structure applying a sweeping signal in a wide frequency range from 10 to 500 Hz and a duration of 0.5 second 2. Processing the obtained vibration signals by the Fourier transform and determination of the maximum magnitude frequency in the spectrum corresponding to one of the natural frequencies of the structure 3. The vibration of the structure applying a narrow sweeping signal around the resonant frequency and recording 6 vibration signals from two 3D accelerometers 4. Repetition of measurements at each step of stiffness of the joint Steps of data processing included: 1. Calculation of correlation functions between three coaxial directions of two 3D accelerometers placed on the joined beams 2. Determination of peak values of correlation functions (PVCF) in each coaxial pair of 3D accelerometers 3. Data averaging on several repeated measurements at each step of stiffness of the joint 4. Calculation of normalized peak values of correlation functions (further NPVCF (%)) as the main relative vibration parameter for the analysis, where the maximum PVDF value obtained in any of the coaxial pairs was taken as 100%

Fig. 1. (a) developed measuring device; (b) electrodynamic actuator; (c) Arduino board.