In concrete reinforced buildings, the steel framework is required to be bonded and is oftenudused as a cost effective method of lightning protection. In defining lightning protectionudzones, it is essential to understand where the lightning current due to a direct strike willudflow. A number of models exist to evaluate the current distribution, but are often appliedudto relatively simple structures.udUsing Maxwell’s equations, an approximate skin effect model is proposed and used to eval-uduate the lightning current distribution in a complex structure. A reduced scale model ofuda structure, consisting of conductors arranged in rings, is developed to verify the model.udParticular attention is given to the return path of the current, ensuring an even distrib-udution of the current in the structure.udThe equivalent circuit showed an even distribution of current across each conductor atuddc and low frequencies and a distribution that concentrated in the outer conductors forudhigher frequencies. The measurements from the structure confirmed that the current con-udcentrates in the outer conductors at high frequencies. Applying a reduced scale lightningudimpulse, it is shown that the majority of the current flows on the outermost conductors.udAny current on the inner conductors is not only greatly decreased in magnitude, butudsignificantly slower in time than the applied impulse.
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