Recently, I have been thinking deeply about the difference between the lightning protection down lead and the lightning protection down lead for buildings. Although my understanding may not be entirely accurate, I would like to share some of my personal reflections with you.
According to the provisions of Article 4 3 3 of the Code for Lightning Protection Design of Buildings GB 50057-2010, there should be no less than 2 special down conductors, and they should be evenly and symmetrically arranged along the perimeter of the building and the inner courtyard. Its spacing should not be greater than 18m along the perimeter. When the span of the building is large and it is not possible to set down the lead in the middle of the span, the down lead should be set at the end of the span and the spacing of other down leads should be reduced, and the average spacing of the special down lead should not be greater than 18m.
Article 5 3 8 stipulates that when the second class of lightning protection buildings or the third class of lightning protection buildings are steel structures or reinforced concrete buildings, the connection between the steel members or steel bars meets the requirements of this code and uses them as down conductors, when the vertical pillars play the role of down conductors, it is not required to meet the spacing between special down conductors.
Judging from the provisions of these two normative provisions, "special down-lead" and "down-lead" are not the same thing. Many people think that "special down leads" is lightning protection down wires, which is actually incorrect. Because from the 5 3 8 standard, when the building is a steel structure or a reinforced concrete building, there is no requirement for the spacing of the down conductors.
Many designers follow the old practice, that is, no matter what structural form of the building, the lightning protection down line spacing is set according to the code. However, when the building is a steel structure or reinforced concrete building, each downlink steel bar or steel column in all structural columns should be used as a lightning protection down lead, instead of our design is artificially designating a certain steel column or a certain two steel bars in the column as a down lead.
And Specification 43.I think the "special down lead" mentioned in Article 3 should refer to the situation that the building does not have structural steel bars or steel columns as down leads, such as wooden pavilions, pavilions, corridors, etc.
The above are some of my personal views and thoughts on the difference between the lightning protection line and the lightning protection line of the building, and I hope to share it with you.
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