The specific method is to use the foundation horizontal ring beam as the natural horizontal grounding body, weld and connect the main reinforcement in the ring beam with the main reinforcement of the foundation pile and bearing platform, connect the two foundation reinforcement at the outermost of the building into a closed loop, connect with several selected horizontal and longitudinal axes to form a grid shape, reliably connect with the downlead, and connect the reinforcement of each section of the ground beam with the loop, In this way, each foundation can be connected into a grounding body, and the reinforcement of the ground beam forms a good horizontal grounding ring to form a complete grounding system.
When the lightning arrester has a good electrical connection with the earth, the charge stored in the earth can be quickly neutralized with the charge of thunder clouds, which greatly shortens the overvoltage time caused by lightning and greatly reduces the harm of lightning.
The internal lightning protection device is composed of lightning protection equipotential connection and spacing distance with the external lightning protection device.
The bridged flat steel shall be concealed as far as possible and welded reliably.
It is a part of the external lightning protection device.
The lightning protection device of the building is composed of external lightning protection device and internal lightning protection device.
Round steel with diameter of 12 shall be used for lap welding, with double-sided welding and welding length of 12cm.
The hot-dip galvanized flat steel shall be bridged.
The grounding body is divided into artificial grounding body and natural grounding body.
The spray water source and transmission power are provided by the water tank and multi-stage pump respectively.
For the sake of insurance, a part of the connection points shall be selected during construction × 4.
3.3 grounding device the grounding device is a metal conductor buried in the underground soil, which is composed of grounding wire and grounding body.
(3) The down lead made of the main reinforcement in the concrete column shall be reserved with flat steel at the roof, which shall be reliably welded and connected with the nearby steel structure frame or structural beam according to the specified spacing, and serve as a natural down lead to connect the metal roof with the grounding body.
The lightning protection grade of buildings in the project is class II.
The top of the building is flower shaped by steel structure and special-shaped metal roof.
The external lightning protection device is composed of lightning arrester, down lead and grounding device.
According to the provisions on down lead in gb50057-2010 code for design of lightning protection of buildings: steel beams, steel columns, fire ladders and other metal components of buildings and metal columns of curtain walls should be used as down lead, but their components should be connected into electrical connection, which can be connected by copper zinc alloy welding, fusion welding, crimping, welding, screws or bolts; Each metal member can be coated with insulating material.
The downlead reinforcement shall be marked and bridged in time during the main construction.
The connections between steel structure frame and section steel column and section steel beam, and between section steel beam and section steel column are welded and connected with high-strength anchor bolts, which are reliable and can directly conduct lightning current to the grounding body.
Jincheng culture and Art Center project is a key project of Jincheng city.
3.2 the flow pipeline of the downlead enclosure spray system is mainly composed of straight through, tee and PPR water pipe.
Its function is to evacuate the lightning current to the earth to limit the high voltage of the lightning protection device to the ground.
compared with ordinary buildings, metal roof and glass curtain wall have higher requirements for lightning protection.
The building foundation of the project is reinforced concrete foundation, so its foundation pile and bearing platform should be used as natural vertical grounding body [2].
The north and south facades of the building are equipped with high-level floor wind resistant steel quilts, and a large-area glass curtain wall is installed outside.
The lightning arrester must be connected with the grounding body through the grounding down lead to safely conduct the incoming lightning into the ground.
This paper introduces the lightning protection system of metal roof as lightning arrester and the lightning protection technology of glass curtain wall.
All metal pipes in and out of the building shall be connected with the grounding body nearby..
The probability of lightning stroke near it, especially for objects lower than it, will be greatly reduced.
(2) On the other hand, eight concrete frame columns directly leading to the roof shall be evenly selected at the circumferential spacing of the building, and two diagonal main reinforcements in each column shall be selected as lightning protection downlead.
Making the grounding body into a grid has two advantages: one is to make the potential of the whole grounding body equal, play the role of voltage equalization and reduce the indoor step voltage; Second, it is convenient to lead out the grounding terminal and facilitate the grounding of various equipment (such as elevator) and metal objects.
The down lead is a conductor used to conduct lightning current from the lightning arrester to the grounding device, and its function is to connect the lightning arrester with the grounding device.
3.
The traditional lightning receiving mode of buildings adopts the conventional lightning receiving belt (Network) or the combination of lightning receiving rod and lightning receiving belt, but the metal roof is more vulnerable to lightning and difficult to install, so it is more difficult than the general building lightning protection design.
The natural grounding body is also used as various metal components in direct contact with the earth, such as steel structure of buildings, buried metal pipelines (except combustible liquid and combustible gas pipelines), etc.
The thickness of aluminum veneer is 4.0mm and the metal grid is 150 mm × three hundred × 4.
At the same time, the reinforcement in the roof concrete slab is connected into an electrical loop at the outer ring and reliably connected with the downlead in each column.
Metal roof should be used as lightning arrester.
If local operation space is insufficient during construction, single-sided welding can also be used with welding length of 12cm.
There are no inflammables under the aluminum grid and metal plate, which meets the specification requirements.
The cross-border method is to use round steel with diameter of 12 at the straight thread sleeve connection of the main reinforcement, The welding length between the round steel on both sides of the straight thread sleeve and the main reinforcement is 12cm.
Key technology 3.1 lightning arrester lightning arrester is a metal object specially used to intercept lightning flash.
Pay attention to the use of multi-stage pump: fill the pump with water before use.
Therefore, the grounding resistance of the grounding body should be small.
Artificial grounding body refers to all kinds of processed section steel or steel pipe directly driven underground for grounding.
2.
Project overview in recent years, with the rapid development of science and technology, a variety of buildings appear in front of people, breaking people’s cognition of traditional buildings, such as special-shaped structure, glass curtain wall, metal packaging, metal roof, etc.
The connection method can not directly weld two reinforcements.
The lightning arrester must be a good conductor.
Lightning protection principle when thunder clouds appear at high altitude, the earth will inevitably induce charges opposite to the thunder clouds due to electrostatic induction.
The metal roof materials are mainly single-layer round hole aluminum veneer and metal grid.
In addition, it must be able to withstand various effects of lightning current and have certain size and mechanical strength.
Because the lightning arresters are located at the highest part of the buildings on the ground, it is easier to attract the lightning downlink leader and concentrate the main discharge on it.
In addition, all raised metal structures and pipes on the roof shall be reliably connected with the main reinforcement in the structural column or roof steel column.
The specific methods of the down lead in the project are as follows: (1) the metal plate of the metal roof is directly fixed on the steel structure frame with metal screws and self tapping screws, which have formed a perfect electrical connection.
After welding, the welding slag shall be removed and the anti-corrosion paint of the same color as the steel structure frame shall be painted.
The building structure of the project is a mixed frame structure of steel and reinforced concrete.
1.
However, according to gb50057-2010 code for design of lightning protection of buildings: except for class I lightning protection buildings, buildings with metal roofs should use their roofs as lightning arresters, and should meet the following requirements: ① the connection between plates should be permanent electrical connection, and copper zinc alloy welding, fusion welding, crimping, seam connection, screw or bolt connection can be adopted; ② When there are no inflammables under the metal plate, the thickness of lead plate shall not be less than 2mm, the thickness of stainless steel, hot-dip galvanized steel, titanium and copper plate shall not be less than 0.5mm, the thickness of aluminum plate shall not be less than 0.65mm, and the thickness of zinc plate shall not be less than 0.7mm; ③ When there are inflammables under the metal plate, the thickness of stainless steel, hot-dip galvanized steel and titanium plate shall not be less than 4mm, the thickness of copper plate shall not be less than 5mm, and the thickness of aluminum plate shall not be less than 7mm; ④ The metal plate has no insulating coating.
