Experimental direct lightning current distribution in a reinforced concrete building

When a building is hit by a direct lightning strike, the communication equipment may be damaged due to the current flowing on the columns, girders, and walls. Therefore, it is necessary to determine the current distribution and establish preventive procedures. Previously, the linear model in which the columns and girders are expressed in terms of lumped elements has been used for estimation of the current distributions in the buildings. However, few buildings have been studied. It is very important to understand correspondence between the models and the actual structures, such as the treatment of the buildings' walls and floors. The researchers in the past have experimentally investigated the equivalent impedance of the columns and girders with complex shapes and measured the currents on the actual columns and girders by designing a large-diameter Rogowski coil. Based on these results, a Lightning current application experiment was carried out using a steel-reinforced concrete building and a model scale without walls and floors. The effects of the ground, walls, and floors were studied and a comparison was carried out with the conventional computational method using the Linear model. The current distribution characteristics of the columns and girders were revealed. It was shown that, in the calculation of the current distributions, the ground resistivity needs to be considered in addition to the equivalent impedance of the columns and girders. Also, in the case where the exterior of the building is concrete walls, the current flowing through the steel reinforcement of the exterior walls is about 30% of the current flowing into the building. (C) 1999 Scripta Technica, Electron Comm Jpn Pt 1, 83(4): 53-62, 2000.