Analysis of the insulation resistances of a high-speed rail transit system viaduct for the assessment of stray current interference. Part 2: Modelling

• The insulation resistances of a concrete high-speed railway viaduct are studied during the viaduct construction.
• An equivalent circuit of the viaduct shows that the insulation resistances depend mainly on the earth wire to rebar resistance.
• Measured insulation resistances are used to estimate the earth wire to rebar resistance values.
• The earth wire to rebar resistance depends on the type, extension and anchorages of the viaduct metallic fixed installations.
• A good agreement is found between the insulation resistances calculated by means of the equivalent circuit and those measured.

In this paper the insulation resistances of the concrete structures of a high-speed rail transit system viaduct are analysed by means of an equivalent circuit. It is shown that the insulation resistances between a span and its respective piers and between adjacent spans depend on the earth wire to rebar resistance of the spans. The insulation resistances measured during the construction stages of the Ticino viaduct of the Italian ac high-speed line are used to estimate the earth wire to rebar resistance in three sections of the viaduct with different characteristics. The variation of the earth wire to rebar resistance along the viaduct can be related to the type, extension and progressive installation of metallic fixed structures in the spans. A good agreement between the viaduct insulation resistances calculated with the equivalent circuit and the measurements is found. An assessment of the stray current interference on a viaduct span is made with reference to the standard EN 50122-2:2010.