On The Lightning Striking Characteristics Of Tall Buildings

Probability of lightning striking of tall buildings is a critical parameter when a lightning protection system is designed. According to the national standard (GB-50057-1994) of lightning protection design, we can calculate the number of lightning striking of tall buildings by considering the length and width of buildings with the lightning ground flash density around them, however, this technique exists much defects. In order to improve the predicting accuracy of the lightning striking of tall buildings, based on random breakdown method of lightning, this paper considers the influence of tall buildings on the atmospheric electric field and simulates the distribution characteristics of 100 lightning striking points. The results are shown as following:1. Analysis of lightning striking characteristics of single tall building(1) The probability of lightning striking increases with the height of the building. For a building with a size of 30m length and 30m width, the struck probability and side striking of the building with a height of 60m are 1.3 times and 3 times as much as that with a height of 10m, respectively.(2) The corner of the building has higher probability of lightning striking because of a bigger curvature; the increase of affiliated structure can reduce the probability of lightning striking the main building.(3) The building has higher probability stroke by lightning if the lightning occurs right above.(4) The building near a mountain has lower probability of lightning striking than that on a flat ground level.2. Analysis of lightning striking characteristics of architectural complex(1) The probability of lightning striking decreases with the increase of surrounding buildings. For a building with a size of 20m length and 20m width, the struck probability decreases 33% when the height of surrounding buildings change from 10m to 60m.(2) The probability of lightning striking increases with the increase of the distances between surround buildings. For a building with a size of 20m length and 20m width, the struck probability increases 43.75% when the distance of surrounding buildings change from 10m to 60m.3. Analysis of the interception efficiency of lightning rod(1) A lightning rod reduces the probability of lightning striking to be in the range 44-70%. (2) The interception efficiency of two lightning rods is higher than that of a single lightning rod, and the interception efficiencies of two lightning rods located on the top of a building and on the ground level are 32% and 70% more than that of single lightning rod, respectively.(3) In the lightning protection zone defined by national standard (GB-50057-1994),tall buildings has a probability of lightning striking ranging from 16% to 38% by using the method adopted in our paper.