Research On Annual Lightning Strike Frequency Of Tall Buildings Based On Three-dimensional Multi-upward Leader Mode

The lightning strike probability and annual lightning strike times of buildings are one of the most important parameters to determine the lightning protection category and risk assessment of buildings.In this paper,the multiple upward leaders three-dimensional model is used to simulate lightning strikes on buildings.By changing the lightning starting position,lightning intensity,building height and building shape to simulate,analyze the lightning strike characteristics of buildings in different situations,and calculate the lightning strike probability of buildings when lightning starts from different positions.The overall situation of hitting the building at the beginning of a certain range above the building,integrate the lightning strike probability in the 1.5km range above the building,calculate the annual lightning strike times of buildings with different heights,and finally obtain a The empirical formula for the annual number of lightning strikes on buildings for calculation of lightning intensity.Change the shape of the tip of the building,add needle-shaped and inclined building models,study the lightning strike characteristics of buildings with different needle-shaped heights and inclined surfaces,and compare the lightning strike probability and annual lightning strike of buildings with flat roofs,needle-shaped and inclined surfaces Trend of frequency change.The main conclusions are as follows:1.The three-dimensional simulation results of negative ground lightning strikes near buildings with different heights show that the lightning strike probability of buildings is positively correlated with the height of buildings.When the average lightning density is 1(unit: km-2)and the lightning intensity is-40 MV,the annual lightning strike times for buildings with a height of 100-600 m are 0.39,0.66,0.86,1.33,1.51,and 1.94 respectively,and this is given by An empirical formula for the annual number of lightning strikes about the height of buildings,among which the annual number of lightning strikes for buildings with a height of 100 and 600 m is closer to the observation results,compared with the formula in the national standard,more consideration is given to the annual number of lightning strikes by lightning itself on buildings Impact.2.By changing the lightning intensity and simulating buildings with different heights,it is found that the attenuation rate of the lightning strike probability curve of buildings with weakened lightning intensity will increase significantly.The annual lightning strike times of buildings under different lightning intensities are obtained by integrating the lightning strike probability.With the weakening of lightning intensity,the number of annual lightning strikes increases with the height of buildings,and its growth rate obviously decreases.Through the integration of the formulas of annual lightning strikes for buildings obtained under the three lightning intensities,an empirical formula for the annual lightning strikes of buildings with a height of 100m-600 m is finally obtained.3.The needle-shaped and inclined-surface buildings are introduced into the model.Through the comparison of the simulation results,it can be seen that the needle-shaped buildings and the tip of the inclined surface are more likely to trigger the upward leader,and the probability of triggering multiple leaders is significantly lower than that of the flat-topped building.By calculating the lightning strike probability and the annual number of lightning strikes of the two types of buildings,it is found that the lightning strike probability and the annual number of lightning strikes of the needle-shaped buildings are significantly greater than those of flat-roofed and inclined buildings,and the annual lightning strikes of inclined-surface buildings and flat-roofed buildings The values are similar,and the formula for the annual number of lightning strikes of needle-shaped buildings calculated by using the lightning intensity is finally given.