Do not know if you have noticed the powder, why do we have a common pole is circular? Why not make it into other shapes? Let’s take a look at the reasons below. machine parts
What exactly does a pole need to do?
First of all, we have to understand that poles are dry. Someone might say that, poles, isn’t it supporting wires? Well, basically correct ~ The main role of the pole is to support the wire and the lightning conductor so that the conductor and the earth and other buildings maintain a sufficient safety distance. As a support, its design and application is a category of engineering mechanics.
Some small partners with basic grid knowledge should know that there are steel towers in addition to electric poles, which are collectively called “pillar towers”. The shape of the tower mainly depends on the voltage level, the number of wiring loops, the topography and the conditions of use, etc. The wind speed, ground roughness, terrain, height, load, wind speed, ice cover, and wire ground model are taken into account in the design criteria. In general, 10kV and below lines are commonly used poles, and commonly used 35kV and above towers. machine parts
Really all poles are round? Not necessarily. Round poles are indeed mainstream, but you can also see a few non-circular poles. So, how do you make a pole for a pole?
It should be noted that what we call a “circular” pole is not a solid cylinder of equal diameter, but a hollow “pull tip”, or “annular tapered rod”. Smaller and larger can better meet the needs of bending resistance, because the lower bending moment (that is, easier to break), but also can make the upper end of the angle iron locking hoop self-locking (that is, can not slide it ~ friends).
Are the poles round? machine parts
There are mainly the following reasons:
1. The circular pole has better performance than square
Think about our common reinforced concrete poles, standing there, to bear a lot of “life can not afford to bear”, for example, it needs to support the wire, insulators and other laborious, the pole itself has weight, storm snow and ice will also bring To external force, if you accidentally break the line, there is a broken tension – just like you suddenly brake by the bus, inertia may make you fall. In short, various forces are also collectively referred to as “loads.” These “loads” all require poles to withstand.
The ability of the pole to bear the load itself is not only related to the material, height, etc., but also has a great relationship with the cross-sectional shape of the pole. The circular section is symmetrical in all directions, isotropic, and has high bearing capacity. Taking the steel pipe rod as an example, the characteristics from circular to polygonal to square cross-section were analyzed. machine parts
2, round pole is relatively more economical material
In the table above doubtful intelligence, Ar denotes the area of the cross section. It can clearly be seen that from round to polygonal to square, the product coefficient becomes larger and larger and the area becomes larger and larger. (Speaking people!) is a circular pole that saves more material.
There are also babies who may say that if you do not consider saving material? The radius of the circular ring section is relatively larger, the stress performance is better, and it is more stable.
3, round pole is relatively more beautiful, convenient and safe
Most people think that round poles are more beautiful. Convenience refers to the manufacturing process. For concrete poles, the factory processes it by means of centrifugation, so the section is circular. In terms of safety, if it accidentally hits a pole, it would be even worse for the flesh. Of course, if a vehicle hits a pole, it may not be much different… machine parts
4, high voltage rating pole, electric tower
We usually use angle steel towers and iron towers that use round steel pipes for support. Circular steel pipes have high bearing capacity, and steel pipes/steel pipe towers are also more attractive in cities or where there are landscape requirements. Relatively square steel pipe and round steel pipe are more convenient to assemble, and the secondary processing of the project is relatively easy. In particular, the component welding does not need to consider the direction problem.
Are there any disadvantages to a steel pipe/steel pipe tower? Hmmm… Not at all. After all, it’s expensive, so reinforced concrete poles and angle towers are common. However, from the point of view of the entire life cycle, the long life cycle of steel pipes is not so uneconomical…
Why are the poles near the railway mostly square? machine parts
The type of contact net pillar selection is, of course, the steel column, but in order to save expenses, the use of reinforced concrete pillars. After the electrification of China’s railways, the first “trapezoidal cement column” is as follows:
The force is the left and right direction of the line, and the force is not satisfied in the direction of the line. Another advantage is that it is possible to climb up by hand, to overhaul the contact network early, and it is very convenient to climb up. In addition, the new high-speed railway line uses the “equal diameter round bar”, and the feature is the name “equal diameter”. Many existing lines have also been able to retrofit the use of such poles. The trapezoidal concrete pillars in the front have gradually been eliminated. Now repairing the catenary and using a railcar has eliminated the need for pole climbing.
In addition, there are H-shaped steel columns, which have higher costs and are widely used in stations, viaducts, and bridges. machine parts
There is also a hard stride across special pillars that are used at stations to and from the station.
Conclusion: The use of “square” pillars in railways is an illusion, and the “square” pillar is actually a “trapezoidal cement pillar.” It is used in large quantities in the early stages and is gradually being eliminated. At this stage, especially high-speed rail, along with the construction of high-speed rail, The speed increase of the existing railway line will increase the proportion of equal diameter round bars will gradually increase. machine parts