Reinforced concrete support: construction and installation features
Reinforced concrete pylons for power lines have appeared since electricity was invented. At first, such pillars were made of wood, but today they use more technological materials for them. This fact cannot be called surprising, because ferro-concrete structures, when compared with wooden structures, are more durable, able to undergo high loads, and also possess stability and reliability.
Power lines can be air or cable, the latter are sunk into the soil. As for the first, for their use are used reinforced concrete supports. Their installation is carried out in those regions where the air temperature does not fall below -55 ° C. This limitation is due to the characteristics of the material For the reason that concrete has micropores, it has a tendency to collapse during temperature fluctuations.
The basis of such structures is a vibrated or centrifuged stand, which is made using dense cement mortars reinforced with metal structures. Reinforced concrete support will have a special durability and strength, if you make it using a centrifuged rack. Such structures are suitable for the installation of power lines from 35 to 110 kV.
Additional design information
The supports may consist of the following elements:
- support-anchor plates;
- lower concrete cover;
- anchors for fastening braces;
- wide range of steel structures.
Among the latter, we can distinguish traverses, cable-resisting, caps, extensions, delays, clamps, attachment points and internal connections.
The advantages of concrete pillars
Reinforced concrete pillars are manufactured using high-quality concrete. It is reinforced with reinforcing bars or reinforced wire. Among the main advantages of these structures should be highlighted:
- affordable cost;
- corrosion resistance;
- resistance to moisture;
- resistance to chemical reagents;
- ability to undergo temperature fluctuations within reasonable limits.
If you compare the cost with the price of all-metal counterparts, the reinforced concrete supports benefit. They are more durable and resistant to excessive moisture.
Preparation for installation: manufacturing technology
Reinforced concrete power transmission poles are reinforced with metal to ensure higher strength. At the first stage, Portland cement is prepared. It is combined with chemical additives and water in appropriate proportions. Mixing is carried out in a concrete mixer. The composition is brought to a homogeneous consistency and immersed in a concrete paver. Next, proceed to the preparation of the metal structure, which will serve as a reinforcement cage.
The rods are cut into individual blanks of the desired size, then anchor caps are prepared. The next step is to mount the contour spirals and the formation of loops. The algorithm of the work involves the preparation of a ground loop rod. Reinforced concrete pillars are poured into a form, the inner surface of which is cleaned and lubricated by means that prevent the build-up of concrete.
Spirals are distributed, the rods are heated. In the heated form they are distributed on the lined stops. The spiral should be drawn between the rods and strengthened at three points. At the ends of the mold, the liners are distributed as evenly as possible, after which tubes and loops are fixed with fixation to the inner surfaces of the formwork. At the next stage, the mixture is filled and the product is formed.
General installation information
Depth of the supports into the soil is carried out by installing the structure in a drilled pit. It must have a circle in cross section. After installation, the cavity is filled with sand and gravel. In order to ensure the strength of the installation on weak soils, the underground part is reinforced with a deadbolt, which is grasped by semi-clamps. Through-bolts or clamps are used to install the hinged metal structures.
For the construction of overhead lines, the voltage of which does not exceed 750 kV, reinforced concrete supports are used. The overhead line in this list is approximately 80% of the total length of the lines under construction. Support have durability and high mechanical durability, at operation they do not demand big expenses.Their assembly takes less effort than when installing metal or wooden analogues.
However, reinforced concrete supports have some drawbacks, which are expressed in an impressive mass and increase in transportation costs. In addition, during installation and assembly there is a need to use heavy-duty technology. Assembly of supports is carried out on a flat platform, which is pre-cleared of foreign objects and debris. Racks of supports laid out on wooden pads, this team is engaged in scaffold workers. In this case we are talking about the poles of 35 kV and above. As for 10 kV reinforced concrete poles, they are engaged in the assembly team.
When laying racks, it is important to ensure that they do not interfere with the crane and the earthmoving machine. In the process of assembling of single-column structures, the beam, cross-bars and cable-resisting are fixed on the rack, while the grounding slope is laid, if it is provided for by the project.
Method of work
The single rack concrete support is assembled according to a specific algorithm. In the first stage, he envisages the lifting of racks.The top of the support is lifted by a lifting mechanism, the support is lowered to the ground. If we are talking about centrifuged racks, then their tip is lifted by the device or rotates around the longitudinal axis.
The second method involves the deployment of the rack on the lining so that the through holes are horizontal. They are inserted into the bolts for fixing the apical pins, braces and traverse. Then the rack rotates so that the heads of the bolts are at the bottom. On them traverses are put on, and after that nuts are tightened. Polyethylene caps are stuffed onto the pins, and insulators are screwed onto them. Nuts of bolts need to be pinched and put on the rack a serial number of support.
Additional installation guidelines
When the support is assembled in a populated area, a double pin head is used to double-mount the wires instead of the apical pin. While the four-traverse will replace the two-pin. Additionally, if necessary, beams and base plates are installed.
A single rack 110 kV concrete column is assembled starting from the layout of parts.Using a crane to the rack fix the lower, middle and upper traverse. Then proceed to the installation of cable-resistant. After the support is assembled, it is pushed to the foundation pit using a crane or wooden rollers.
Reinforced concrete supports have many advantages, but they have one important drawback, which is expressed in low strength. Among other things, the dimensions and impressive weight of such products turn into wastes during transportation and installation. However, such designs are presented in a wide range. They can be intermediate and are used for straight sections of the route. Among others, anchor type supports, as well as end and corner supports should also be highlighted.