Shear Strength of an Erected Pipe

In summary, the conversation discusses the necessary size and type of pipe or tubing needed to withstand given wind speeds for building a "megatree" outdoor Christmas tree. The main pipe will be buried in reinforced concrete and guy-wired, with the lights and star adding about 200 pounds of weight. Suggestions for a 6.10 m mast include a 60.33 mm diameter pipe with a 3.91 mm wall thickness or a 48.26 mm diameter pipe with a 3.68 mm wall thickness. The potential impact of adding lights and the natural frequency of the structure are also mentioned.
  • #1
blackcomb
1
0
Does anyone know how to determine what size/type of pipe/tubing would be necessary to withstand given wind speeds?

Specifically, I'm wanting to build a "megatree", an outdoor Christmas tree made simply by stringing lights from the top to the bottom in a conical shape. I'd like a 20' + tree, but I don't know what size pipe/tube I'd need as the mast.

My initial plan is to bury a 2'-3' pipe in reinforced concrete in the ground to serve as a sleeve for the main pipe (no more than about 1/8" inch play) which would be guy-wired. I want to be able to remove the main pipe after Christmas and cap off the sleeve at ground level.

The lights (and star on top) will add about 200 pounds, spread evenly in all directions around the main pipe, if that makes a difference.

I prefer to use galvanized steel (no PVC). I was considering 1.5", but didn't know if wall thickness would matter in my application. Does anybody have any suggestions on what to go with to ensure winds (short of a hurricane) won't bring it down? Winds in my area will gust from time to time in the 40 mph range. Rare to see 50+ mph sustained winds.
 
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  • #2
For a pipe mast height of 6.10 m above the ground surface, and assuming the guy wires are not pretensioned, I'm currently getting a required steel pipe outside diameter of 60.33 mm, with a wall thickness of 3.91 mm.
 
  • #3
It currently appears a 6.10 m steel pipe having an outside diameter of 48.26 mm and a wall thickness of 3.68 mm might also be adequate.
 
  • #4
Why not tie three of the wires to Earth as guy strands? The forces applied to your tree by the winds will increase as you add lights on multiple strands. Calculation of the withstand rating for the free-standing pipe will not be sufficient for determining its ability to withstand windgusts when lights are attached. I am surprised that the previous answers did not include that factor.
 
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  • #5
re the winds
you'd be looking at "flow induced vibrations" which have scuppered many a structure.
you'll need to figure out the natural frequency of the structure (dont ask me how)
then i think your looking for the strouhal number, you'll get it from the dimensions of the pipe (lenght and diameter),
lol, get someone who's good at fluid mechanincs

on the other hand you could chance your arm
best of luck
 

1. What is shear strength and how is it measured?

Shear strength is a material property that describes its resistance to shearing forces. In the context of an erected pipe, it refers to the ability of the pipe to withstand lateral or sideways forces without bending or breaking. It is typically measured in units of force per unit area, such as pounds per square inch (psi) or newtons per square meter (N/m^2).

2. What factors affect the shear strength of an erected pipe?

There are several factors that can affect the shear strength of an erected pipe, including the type and quality of the material used, the diameter and thickness of the pipe, the welding technique used to join the sections, and the presence of any defects or damage in the pipe.

3. How is the shear strength of an erected pipe calculated?

The shear strength of an erected pipe is calculated by dividing the maximum force that the pipe can withstand before failing by the cross-sectional area of the pipe. This value can be determined through laboratory testing or by using mathematical models and engineering calculations based on the pipe's properties and design.

4. Why is shear strength important for an erected pipe?

Shear strength is important for an erected pipe because it ensures the structural integrity and safety of the pipe. If the shear strength of a pipe is not sufficient, it may fail under the weight of the material being transported, leading to leaks, spills, or even catastrophic failures that can result in property damage and harm to people and the environment.

5. How can the shear strength of an erected pipe be improved?

The shear strength of an erected pipe can be improved by using high-quality materials, maintaining proper welding techniques and procedures, minimizing any defects or damage in the pipe, and designing the pipe with a sufficient safety factor to account for potential external forces and stressors. Regular inspections and maintenance can also help identify and address any issues that may affect the shear strength of the pipe.

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