Three-Dimensional Implementation of Modified Rolling Sphere Method for Lightning Protection of Giant Medieval Chola Monument in South India

With the advent of global warming, research studies have indicated concerns due to its impact on thunderstorm and lightning which could have detrimental impact on structures. Though there has been substantial progress related to protection of structures against lightning, research carried out during the past decades have led the lightning community to develop improved procedures for evaluating lightning exposure to structures. The location of vulnerable points struck by lightning and hence the placement of air terminals is obtained based on Rolling Sphere Method (RSM) whereby the striking distance is obtained as a function of stroke current. However, the model ignores dynamics of propagation of downward and upward leaders, geometry of the structure etc. This aspect becomes vital for smaller rolling sphere radii for tall structures with respect to several striking points. This research proposes carrying out detailed analysis based on utilizing the Modified Rolling Sphere Method (MRSM) which is based on the concept of an upward directed leader and its interaction with the downward leader during lightning strike on a tall structure. This research involves detailed analysis of lightning protection effectiveness based on MRSM for one of the tallest World Heritage Chola temple architectures in south India. Analysis based on varying lightning stroke currents has been carried out to ascertain the vulnerable points due to varying lightning protection levels. Further, a detailed failure analysis is also carried in line with the requirements of international standards to ascertain additional lightning protection requirements that would enable effective LPS for the proposed heritage monument.