by When reinforcement in concrete is used as downlead, the design of downlead shall be in accordance with gb50057-2010 Article 4.3.1 of code for design of lightning protection of buildings Article 5.
In the traditional cast-in-situ concrete structure building, the lightning protection design of the building gives priority to the use of two main diagonal bars in the structural column as the lightning protection downlead.
Characteristics of prefabricated concrete structure buildings according to the requirements of GB / t51231-2016 technical standard for prefabricated concrete buildings, prefabricated concrete structure buildings are divided into three categories: prefabricated integral frame structure buildings, prefabricated integral shear wall structure buildings and prefabricated wall panel structure buildings.
It is easy to form the lightning electrical path in the form of reinforcement thread sleeve or lap welding.
These prefabricated components are produced by the prefabricated component factory, transported to the construction site, and assembled by hoisting equipment according to the hoisting drawing, as shown in Figure 1.
Taking the lightning protection downlead design of a fabricated building project as an example, this paper discusses the lightning protection design ideas of fabricated buildings at the present stage, and solves the lightning protection downlead construction problems of fabricated buildings.
Therefore, the reinforcement in the upper and lower precast columns does not form a continuous electrical path.
1 split diagram of prefabricated components of prefabricated concrete structure building because the prefabricated building is assembled by various modules, in the connection mode of prefabricated components, the connection between beams and plates is usually designed as prefabrication and cast-in-place layer, while the connection of longitudinal reinforcement between upper and lower prefabricated columns is connected by sleeve grouting technology.
4.4 Article 3 the location and quantity shall be set according to the lightning protection category of buildings.
Compared with the traditional building lightning protection design, the lightning protection design of the prefabricated building is not mature at this stage, and there are many problems in the construction process.
In the design of lightning protection downlead of prefabricated buildings, in order to realize the electrical connection between components and meet the lightning protection requirements, it is necessary to design additional special conductors in prefabricated components (mainly precast columns).
This paper “Discussion on design and construction key points of lightning protection downlead for prefabricated buildings” was published in Fujian building materials, issue 10, 2019, Author: he zengping (Fuzhou Construction Engineering Quality Supervision Station).
Prefabricated buildings refer to the buildings assembled on the construction site after factory prefabrication of beams, floors, columns, walls and stairs in traditional buildings.
The first type is mostly used in public buildings, the second type is mostly used in residential buildings, and the third type is suitable for multi-storey houses with seismic fortification category C.
At present, two downlead connection nodes in upper and lower precast columns are usually used in the design drawing ะค 10 round steel is connected with two main reinforcements in the prefabricated column, and sufficient length is reserved outside the column as an additional special conductor..
When the main reinforcement in the precast column is used as the lightning protection downlead, special measures need to be taken.
This paper introduces the process and construction characteristics of fabricated building structures, combined with gb50057-2010 code for design of lightning protection of buildings According to the relevant requirements of the current design of lightning protection downlead of prefabricated buildings, this paper discusses its construction points and measures, and discusses different design ideas and construction methods of lightning protection downlead according to the characteristics of prefabricated buildings, which is very worthy of reference and study.
The construction process is completed by the cooperation of the on-site electrical constructor and the structural constructor, with simple construction process, time-saving and material saving.
It can be seen from Figure 2 that the gap between the grouting sleeve of the upper precast column and the reinforcement of the lower precast column head has been filled with grouting material.
Their advantages are fast construction speed, less restricted by climatic conditions, labor saving and improving construction quality.
The prefabricated building cancels most of the cast-in-situ and masonry work on the construction site.
Figure 2 Schematic diagram of precast column grouting sleeve connection (Note: refer to the key process of illustrated prefabricated building construction – sleeve grouting for details about the characteristics of sleeve grouting process) lightning protection downlead design downlead is used to conduct lightning current from lightning arrester to grounding device.
A project adopts the prefabricated frame shear wall structure + prefabricated exterior wall panel structure system, which is composed of prefabricated columns, prefabricated composite beams, prefabricated composite floors, prefabricated exterior wall panels, prefabricated stairs and other prefabricated components.
Fig.
4.4 The appropriate diameter shall be selected according to the provisions of Clause 5, and it shall also be in accordance with Clause 4.3.2 of the specification Article 3.
At the same time, it puts forward different construction requirements for the electrical construction of the prefabricated building, especially the construction of lightning protection.
