Modeling of Lightning Exposure of Buildings and Massive Structures

Abstract

A dynamic model for exposure of grounded objects to direct lightning strokes has been generalized to apply to buildings and massive structures. The model also applies to the mixed situation where a slender air terminal is installed on the top of a building to provide lightning protection. The basic elements of the model comprise a general criterion for continuous upward leader inception the validity of which is independent of the building or structure topology. This is followed by initiation of an upward leader trajectory which would either lead to a successful encounter with the negative downward leader through a final jump or to an aborted positive leader. Based on recent work published by the author, the model does not require any assumption regarding the ratio between the negative and positive leader speeds as has often been done previously. The modeling procedure has been facilitated through the use of dimensionless variables relating to the proximity effect of the building on space potential distribution, leader inception space potential, critical mean ambient ground field, and, finally, the attractive radius. A slender rod of the same height as the building is used as basis for comparison.