Behaviour of a Preloaded Asymmetric Multi-Bolted Connection Under Cyclic Loads by Experimental Research

This paper reports on experimental investigations of a preloaded asymmetrical multi-bolted connection under operating conditions. At the beginning of the tests, the bolts were preloaded in a predetermined optimal order, in three passes, monitoring the bolt force values by means of a calibrated measuring system with strain gauges. The main tests were carried out on an Instron 8850 testing machine. The connection was subjected to sinusoidal loads with amplitudes of 10 kN and 20 kN at various frequencies. The data obtained was collected and recorded using prepared measurement pathway components, and then processed in MATLAB/Simulink R2018b. The observed measurement results are depicted in graphs displaying the distribution of forces in bolts as a function of cyclically varying operating loads. We have demonstrated that the forces in bolts also vary cyclically relative to their initial preload values. Due to the asymmetry of the connection, this variation was different for individual bolts. The results show bolt force deviations within ±2% and confirm the stability of the connection under cyclic operating loads. The presented results complement the database of experimental results, on the basis of which we will validate the systemic approach to modelling multi-bolted connections.