The conducting structure of a re-enforced building represents one if not the most important level of protection inrelation to lightning strikes. A complete re-enforced structure, that is one where the roof, wall and floor reenforcingbars are all inter-connected, provides an effective if not ideal faraday cage. This is turn protectssensitive and hazardous items which may reside within such structures. Of course the effectiveness of thesestructures will depend on the state of these interconnections and as such experimental techniques need to beestablished to ensure that these interconnections are intact. The ‘as built’ information may not give sufficientassurance, because building records may no longer be fully available. In addition, the process of ageing, andsubsequent maintenance activity may have perturbed the original conditions. This paper describes the methodapplied for routine testing, aimed at establishing the integrity of the interconnections through electricalfield/impedance measurements. Theoretical models are allied to this experimental approach to confirm that theexperimentally derived impedance measurements are commensurate with a fully intact structure. The modelsare also used to characterise the detailed current distribution in the conducting structure and the field distributionwithin the structure when subject to a lightning strike. In addition these theoretical models will predict therelative loss of protective performance as a result of imperfections in the interconnections. The theoreticalmodel together with some typical results is presented.
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