Designing lightning protection for a residential apartment house!

April 28, 2017

The number of high-rise residential houses has increased recently. This interest towards high-rise buildings is understandable. Buildings higher than 100 meters allow accommodating many people at a small territory. Moreover, this is an excellent opportunity to allow the residents to view the city from height. This is however not as easy. The requirements for builders and developers are pretty tough.

There are external dangers which may cause problems for a multi-apartment residential house, such as lightnings. The higher the facility, the more attractive it is for this natural event. For this reason, the requirements for lightning protection and electromagnetic compatibility to high-rise facilities should be elaborated with a high quality.

The ZANDZ Technical Center often receives requests to consider or offer various options for solving such tasks. One of them will be considered herein.

Calculation example

Facility: four-section, multi-apartment residential house.

Terms of reference for the design:

To provide lightning protection using a lightning grid;
To protect the facilities installed over the roof (vent shafts) using lightning masts;
All metal elements located on the roof should be connected to the lightning grid;
To use reinforcement bars installed in the reinforced concrete structure walls as current collectors;
To use pile reinforcement as a vertical ground terminal;
To use a reinforcement cage of the foundation grille as a horizontal ground terminal;

Figures 1 and 2 show plans of roofs by sections, without the lightning protection.

Figure 1. Roof plan, sections 1 and 2 (17 floors)

Figure 2. Roof plan, sections 3 and 4 (18 and 9 floors)

The lightning protection is made as per SO 153-34.21.122-2003 Guidelines for Arrangement of Lightning Protection of Buildings, Structures, and Industrial Utilities and RD 34.21.122-87 Guidelines for the Lightning Protection of Buildings and Structures.

The facility is classified as Category 3 lightning protection. The system reliability shall be at least 0.9..

Solution

The facility lightning protection is made as a lightning grid using a steel copper-plated wire with the diameter of 8 mm and coating thickness 70 mcm (GL-11149). The objects being above the roof (vent shafts) are protected using lightning masts GL-21105G secured using holders GL-21201 GL-21201 (foot spacing is 0.7 m). The current collector is connected using clamp GL-20023;
The current collectors are installed using clamp GL-11711 on the flat roof, and GL-11703А on vertical surfaces. The clamp spacing is 0.8 to 1.0 m;
Multi-purpose clamp GL-11551A is used for securing rolled metal products along their distance, as well as in the grid nodes;
All metal elements located on the roof must be connected to the lightning grid using clamps GL-11545AStairs and handrails are connected using clamp GL-11514;
Reinforced bar with the diameter of at least 8 mm laid in the reinforced concrete structure walls is used as current collectors;
Pile reinforced bar is used as a vertical ground terminal. The reinforcement cage of the foundation grille is used as a horizontal ground terminal;
Connection to the facility reinforcement is made every 20 m using clamps GL-11563А.

The results of calculations performed using the software developed by the OJSC Krzhizhanovsky Energy Institute (OJSC ENIN):
lightning discharge to the ground is 6 strikes per sq. km per year;
total lightning strikes to the system is 0.76 (once in 2 years);
total breakthroughs (strikes directly to the facility bypassing lightning rods) is 0.083 (once in 12 years);
the system reliability is 0.9.

Figures 3 and 4 show the arrangement of equipment by sections.

Условные обозначения - Legend

Figure 3. Equipment layout, sections 1 and 2 (17 floors)

Figure 4. Equipment layout, sections 3 and 4 (18 and 9 floors)

Securing assemblies are shown in Figure 5.

Установка молниеприемника на вертикальную поверхность - Installation of lightning arrester onto a vertical surface
Соединение проволоки в узле пересечения молниеприемной сетки - Wire connection in the crossing node of the lightning grid
Крепление проволоки к металлоконструкциям - Wire securing to metal structures
Организация крепления проволоки при изменении уровня размещения - Wire securing arrangement when changing the placement level
Крепление проволоки к ограждениям на кровле - Wire securing to roof fencing

Figure 5. Securing assemblies

The list of equipment is provided in Table 1.

Table 1. List of equipment

№	Fig.	Part number	Name	Q-ty, pcs
1.		GL-21105G	GALMAR Vertical interception rod (lightning mast) (5.7 meters)	48
2.		GL-21201	GALMAR Lightning mast holder	48
3.		GL-20023	GALMAR Lightning mast clamp GL-21104G/GL-21105G for current collectors (stainless steel)	48
4.		GL-11149-50	GALMAR Copper-plated wire (D 8 mm/S 50 mm²; 50-meter bundle)	38
5.		GL-11545A	GALMAR Conductor rain gutter clamp for current collectors (painted galvanized steel)	110
6.		GL-11551A	GALMAR Current collectors connection clamp (painted galvanized steel)	270
7.		GL-11711	GALMAR Flat roof clamp for current collector (plastic, concrete)	500
8.		GL-11703A	GALMAR Current collector facade clamp for current collector providing 15 mm elevation over the clamp (painted galvanized steel)	1400
9.		GL-11514	GALMAR Ring clamp on rainwater pipe for current collector (tinned copper)	65
10.		GL-11563A	GALMAR Control clamp for connecting currnet collector wire + wire (painted galvanized steel)	35

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