PSI - Issue 37

Dmitrijs Serdjuks et al. / Procedia Structural Integrity 37 (2022) 555–562 Dmitrijs Serdjuks et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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4.2. Results of dynamic loading Dynamic test of the steel beam stand was carried out to determine the structural joint stiffness as a function of the vibration parameters of the structure. The joints stiffness was varied by the force of the nuts warping. The steel beam joints stiffness was numerically valued by the maximum bending moment, which it could take up. The stiffness of the joint corresponded to the values of torque moment varying during the experiment within a range from 0 to 150 Nm. The value of the maximum torque moment equal to 0 Nm corresponded to the pinned joint. The additional beam was vibrated by an electrodynamic actuator fixed on the edge of the additional beam (Fig.2 (b)). Vibration responses from two parts of the joint were recorded in 3 spatial directions by two 3D accelerometers, accelerometer 1 on the girder and accelerometer 2 on the additional beam as shown in Fig. 4 (a), and transferred to the computer. The differences in the vibration signals were measured in three directions: 0-1; 2-3 and 4-5. Normalized correlation factor was calculated according to the procedure described in 3.1. Т he maximum correlation factors in three coaxial directions 0-1; 2-3 and 4-5 were indicators of the structural joints stiffnesses. The obtained dependencies of the normalized correlation coefficient on the bending moment are shown in Fig. 5. The obtained dependence is non linear and the largest increase of the correlation factor was stated for torque moment within a range from 0 and 50 Nm.

Fig. 4. (a) layout diagram of accelerometers at the investigated joint ; (b) accelerometer placement at the joint .

Fig. 5. Torque moment as a function of the maximum coaxial correlation factors in direction 0-1; 2-3; 4-5.

5. Conclusions Non-model vibration analysis method for health monitoring of structural joints was proposed and experimentally tested using a steel beam stand. The experimental results obtained on the rigid and pinned joints adequately describe the results of analytical calculations. Structural joint stiffness was determined as a function of the correlation factor determined based on measured natural frequencies. The stiffness of the joint corresponded to the values of torque moment, varying during the experiment within a range from 0 to 150 Nm. The direct relationship was found between the correlation factor and the stiffness of the joint. The higher correlation factor corresponded to the larger stiffness of the joint. The obtained dependence is non-linear, and the largest increase of the correlation factor was stated for torque moment within a range from 0 and 50 Nm.