Clarification of cross-sectional vibration characteristics for damage identification of belt conveyor support structure

Belt conveyors, widely used in various industries worldwide, are often exposed to corrosive environment. Decades after construction, many of the support structure of belt conveyors have severe degradation, which may cause structural failure and functional stop of associated industries. Damage identification of the support structure is therefore important to ensure the safety and reliability. However, application of existing global vibration based techniques to these structures is difficult due to unavailability of baseline condition, the possible presence of multiple corroded members in a single structure, and the effect of non-structural components. In this paper, cross-sectional vibration characteristics are clarified on a numerical model of support structure. Numerical analysis reveals that there exist some eigenmodes, named as cross-sectional mode (CSM), in which the main member vibrates strongly in cross-sectional direction. When a part of the continuous main member is damaged, the cross-sectional mode becomes localized only to the damaged panel. In addition, the local vibration frequency decreases significantly from CSM. This mode is named as localized cross-sectional mode (LCSM). The sensitivity analysis of CSM and LCSM reveals that the presence of damage on a panel affects CSM frequencies and LCSM frequencies of other panels marginally. For multiple damages, multiple LCSMs corresponding to the damage severities and locations exist; multiple damages can be independently analyzed. The damage identification is therefore feasible by comparing the frequencies of CSM and LCSM, which is available from current state of the structure without the need for before-after comparison. The existence and observability of CSM are experimentally confirmed.