Loads of Tower Structural Support Chimney

Chimneys are very common in industrial buildings. In the past, tall chimneys were generally made of concrete chimneys. However, the construction of ultra-high concrete is difficult, the quality is not guaranteed, and the construction period is long. With the improvement of steel production capacity and high-altitude hoisting capacity, steel chimneys Applications are becoming more and more widespread. Today, I will talk with you about the design of tower-type steel chimneys, and hope to be helpful for the engineering application of steel chimneys.

Steel Chimneys include three types of self-supporting, cable-stayed and tower-type. Self-supporting steel chimneys are mainly subjected to bending and cannot give full play to the performance of structural materials, and are mainly used for low chimneys. The cable-type steel chimney is subjected to the combined force of the bending of the steel cylinder and the tension of the zipper, which can better exert the performance of the material and can be used for thin and tall steel chimneys. However, the arrangement of the zipper in engineering applications is often limited by many , the application is not very extensive. The tower-type steel chimney generally relies on the steel cylinder to bear the vertical force of its own weight, and the tower bears the horizontal load, while the tower-type steel chimney as a whole is a vertical truss, and the material properties are fully exerted, which is economical and applicable, and should be widely used.

Loads of Tower Structural Support Chimney

1. Structure and equipment weight. The self-weight of the structure and equipment shall be calculated according to the relevant provisions of the load code. When calculating the self-weight of the tower, the weight of the gusset plate, flange and weld should be considered. Generally, the self-weight of the tower member can be multiplied by a factor of 1.15 to 1.20.

2. Live load. The loads on the maintenance platform, rest platform and aviation obstruction light maintenance platform on the tower are all live loads. The live load of the maintenance platform can be determined according to the actual situation, but it shall not be less than 3KN/m2. The top platform shall consider the ash accumulation load, the concentrated load of a single member of the rest platform shall not be less than 1KN, and the uniform load can be taken as 2 KN/m2.

3. Wind loads. Wind loads play a decisive role in the tower structure. The structural internal force caused by wind load accounts for about 80% to 90% of the total internal force. Therefore, in the design of tower-type steel chimneys, it is a very important consideration to minimize wind resistance. The system coefficient of various section steels is μs=1.3. For circular cross-section rods, the shape coefficient depends on the Reynolds number. When the diameter of one-shaped cross-section rods is small, μs=1.2, and the diameter is large and H/d≥ At 25, μs=0.6. Therefore, circular section rods have the least resistance to wind. In order to simplify the calculation, in the calculation of wind load, the windshield area of all connecting plates is not calculated separately, and only the total area of the members is appropriately increased. For round steel structure and steel pipe structure, the increase factor can be 1.1, and for round steel composite structure and section steel structure, 1.15~1.2 can be used. For tall structures, in addition to the load calculation in the downwind direction, the vibration check calculation in the crosswind direction should also be carried out.

4. Ice load. In areas with high air humidity, when the temperature drops sharply, the surface of the structure will freeze, which is called ice wrapping. Freezing mainly depends on the meteorological conditions in the area where the building is located, that is, the size of the air humidity and the temperature. Colder regions are not necessarily the places with the thickest ice, and warmer places are not necessarily the places with thinner ice. The higher the ground in the same area, the thicker the ice pack. Generally, ice wrapping occurs when there is no or weak wind. However, in the calculation, it should be considered together with the wind of moderate intensity, and the combination coefficient is taken as ψcw=0.6. The temperature when wrapping ice is calculated as -5°C.

5. Temperature load. The connection between the tower platform and the chimney is generally connected by a slideway, which can be freely deformed in the longitudinal direction. The slideway should have sufficient lateral expansion clearance to ensure free lateral deformation. The temperature stress and temperature deformation of the tower structure can generally be ignored.

6. earthquake load. In the seismic fortified area, the seismic load should be considered.