How is the wind load on such large-diameter pipes calculated?

How do you calculate the force? Static calculations for wind loads are not difficult; the challenge lies in wind-induced vibration calculations. There is no clear basis for determining whether these can be calculated using the methods specified in building structure load codes.

First, I have to complain about this diagram of yours – it’s too avant-garde. At least use CAD to create it; it’s really hard to understand. Whether it is a tower or a steel chimney, the calculations applied to them have their own scope of application, specifically for cylindrical devices standing alone. The one on your right side doesn’t seem to be a support point; personally, I think it’s unlikely for the pipeline to rely on support only at the bottom. I think you should change your approach – instead of focusing on steel chimneys or towers, you can consider it as a steel component and apply the calculation methods used for steel structures. Today, there are also many methods and software for the analysis and design of steel structures, such as Midas, etc. Towers and steel chimneys represent special cases in the calculation of steel structures, with wind loads and seismic forces both being considered as part of these calculations. Discussing it with a qualified structural engineer might yield some good ideas; if you want to discuss this here, it’s recommended to refine the diagrams – at least avoid such abstraction.

Let me add that: the diagram below shows a typical flue duct used in waste heat power generation. On the left side, it is connected to the equipment or pipes using non-metallic compensators. Due to the very low stiffness of these non-metallic compensators, their restraining effect on the pipes is generally not taken into account in calculations; in other words, the end connected to the non-metallic compensator is considered free； I’m not discussing only this one model format; there are many more complex versions as well. Although, from a structural perspective, the distance of the left cantilever is somewhat too large and may not be reasonable, many renovation projects are subject to various constraints – it’s not always possible to install supports in any desired location. Therefore, it’s inevitable that the support positions may not be ideal in many cases. Whether it’s a cantilever support or multiple supports working together, the wind load on the model should not change depending on the number and location of these supports. My main goal for now is to calculate the magnitude of the wind load; of course, sometimes it’s also necessary to determine the magnitude of the seismic load, before further considering the load carried by each support location ； Of course, this goal may be achievable based on conventional approaches that rely on mathematical formulas; if it is used with finite element or steel structure software for calculations, the positions of the constraints must be taken into account, otherwise the software will not be able to produce any results. It’s definitely not appropriate to use the standards applicable to steel chimneys and towers for such calculations. Currently, there are no relevant standards available in China in this area, which makes things quite difficult. Failing to conduct calculations poses risks, but knowing how to proceed with the calculations is also a challenge... The difficulty with such models lies in their irregular shape and large height differences; some parts are quite high, extending from the sides of the building, with heights ranging from 60 to 90 meters above the ground

I think you’re overcomplicating things. In my opinion, engineering calculations should be kept as simple as possible. For your model, it would be advisable to calculate it as separate, upright towers or steel chimneys, treating the pipelines on the sides as attachments or eccentric loads to simplify the analysis. For wind loads, it is possible to increase the wind load proportionally to the area, and then the pipelines adjacent to it can be simplified as eccentric loads acting on the vertical pipeline. Given the eccentric loading effect due to earthquakes, seismic forces can be taken into consideration. I think the pipelines on this side actually impose some restriction on the displacement of the vertical pipelines; it seems that the stress distribution is better in this case compared to when calculating solely for the vertical pipelines. The above are just personal opinions; if analysis and design are considered, it would be appropriate to use compensator connection ports to restrict horizontal displacement and rotation, in order to simulate the boundary conditions more effectively. I’m just throwing out an idea to encourage everyone to share their opinions.

I guess a eccentric load refers to one generated by gravity, with a vertical direction； And models like mine also have the issue of torque generated by wind load horizontal forces ； Furthermore, since the structural shapes are different, the methods for calculating wind vibration coefficients may also vary; towers and steel chimneys are both straight. The design is simpler compared to models like mine.

The wind vibration coefficient cannot be taken into account; even for the wind load coefficient of the structure, there is no value corresponding to this shape. Therefore, only estimation is possible. One can consider the wind-facing area on the sides, calculate the magnitude of the wind load force, and then convert it into a vertical force by considering its direction and application height. As for wind vibrations or even higher-order wind vibrations, they are methods that are not taken into account in engineering. Overall, I think stress analysis can be carried out using either ANSYS or Midas for structural analysis; it just takes time. Roughly speaking, I believe the conversion method I mentioned can at least be used to determine the stiffness of vertical pipelines. If you want a detailed calculation or analysis, go with simulation.

If wind-induced vibrations are not taken into account, there is basically no difficulty, but it is clearly risky to ignore them; the wind-induced vibration coefficient is greater than 1, and this coefficient varies depending on the location. Indeed, there are currently no standards that address such issues. I have a headache; some people say that simulating it using fluid dynamics software is too complicated.

It is quite troublesome to calculate this force in detail without taking wind-induced vibrations into account. First of all, it’s not possible to determine the shape coefficient for wind loads; the shape coefficients for wind loads on towers and chimneys are specified in GB50009, and it’s certainly impossible to comply with those requirements. All that can be done is to carry out an approximate estimation for the project. As for earthquakes, it’s even more impossible to predict accurately; whether their own periods can be simulated using a multi-body model is itself a question. So the method I mentioned is merely a relatively conservative approach that can be considered in engineering terms for calculations; it’s practically impossible to get accurate results using it. So considering wind vibration again would be even more troublesome; it’s basically impossible to carry out calculations using current methods, though conducting more simulations and analyses does present some possibility.