Engineering Design Consultants

Non-linear Analysis

Cables hanging in a catenary present a difficult case to analyse: they rely on their deflected shape to provide stiffness against additional loads, and so second order effects must be accounted for.

While carrying out a CAT III Check for the Skysafe system for Babcock, Eadon Consulting used the non-linear cable analysis capabilities of STAAD/Pro to model a power cable hanging under its own weight between two pylons, to which moving asymmetric loading was applied. The use of this tool allowed accurate estimates of the deflection along the cable to be calculated to ensure that the necessary clearances from the railway could not be breached. The additional conservative assumptions that would need to be made to use hand calculation methods would have made the analysis too onerous and could have precluded the Skysafe technique.

One of the chief difficulties in using this technique was ensuring that the model was stable. Excessive deformation due to the applied load would prevent the software from converging to a solution. To overcome this, the deflected shape of the cable due to its own weight alone was calculated using hand calculation methods, and the cable was modelled in this shape, along with the appropriate preload, at the start of the analysis. The additional wind and live loads were then applied and the analysis carried out, resulting in lower deflections from the initial conditions and a more stable model.

For more information regarding our Analysis services or to discuss your design requirements, please telephone 0114 399 0400 or email us.

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