Dursey Island Cable Car
The Dursey Island Cable Car connects the Beara Peninsula with Dursey Island in Co. Cork. It was originally constructed in 1969 and underwent intermittent maintenance; however, no formal inspection and maintenance programme had been established. ROD-IS, commissioned by Cork County Council to undertake a complete structural health check for the Dursey Island Cable Car, performed a Probabilistic Analysis to determine the actual safety of the structure at the critical limit states identified in the deterministic assessment. While the deterministic analysis concluded that the un-deteriorated structure could demonstrate adequate capacity for the critical ULS under the considered load combination, visual inspection had indicated that the structure was clearly not un-deteriorated.
The Probabilistic Analysis, provided a quantifiable measure of the safety of the line support structure with respect to the level of deterioration, and as such indicated the deterioration threshold at which safety could no longer be demonstrated and when some form of rehabilitation would be required. As a result the methodology facilitated derivation of optimum times for intervention of the structure to ensure that minimum safety levels were maintained, the risk minimised and performance optimised. The level of safety was reported in the terms of the reliability index (β-index) of the structure computed at the limit state considered and compared to the minimum value required by the Eurocode. The probabilistic modelling undertaken considered the load and resistance of the structure, using both stochastic and deterministic variables, deterioration modelling (corrosion as the main factor) and damage mechanisms, loading uncertainties (such as dynamic coefficient, friction coefficient, steel dead load, breaking loads etc.) and material uncertainties.