What size square mild steel pipe will support load

In summary, the conversation discusses the minimum size square steel pipe needed to bear a load of 500 lbs. The proposed pipe is mild steel, 2.5 inches square, 12 feet long, and 1/8 inch wall thickness. The calculation for the yield factor of safety and allowable bending stress is also mentioned. The conversation also touches on the need for additional supports to prevent overstressing and potential dangers during the lifting process.
  • #1
hemeoncdoc
3
0
Can anyone please help me with a question re the minimum size square steel pipe needed to bear a load. I loved physics but never took mechanical engineering. I am rigging a winch to one end of a pipe to lift a static load (holding up a gangway temporarily to repair). The gangway weighs around 500 lbs., and will be supported in the middle (essentially all of the weight). The proposed pipe is mild steel, 2.5 inch square, 12 feet long, 1/8 inch wall thickness, and connected at the other end and in the middle to supports. In essence, would the pipe bend if holding that load at 6 feet out from the support? What size pipe would bear the load? Thanks!
 
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  • #2
So far, it sounds like you have a simply-supported beam or second class lever. If the yield factor of safety is 2.0, and if the allowable bending stress of your square tube material is Sb = 157.5 MPa, and if your load is statically applied, then your beam stress level would be R = sigma/Sb = (151.9 MPa)/(157.5 MPa) = 96.4 %. For a given value of Sb, you want to ensure R does not exceed 100 %.
 
  • #3
Sorry for my ignorance... but does that mean that the square pipe in question will support the load? Thanks
 
  • #4
R > 100 % indicates a component is overstressed. Notice the value of R in post 2, which is for the proposed beam size described in post 1.

After lifting, support (prop) the load with additional, stable supports, before getting human body parts underneath the load.

How do you propose to attach the midspan load to the beam such that the load is not concentrated on a fine line across the beam, and also does not slip longitudinally along the beam if (when) the lever angle is steep?
 
  • #5
Thanks for the follow-up.
 

1. How do I determine the appropriate size of square mild steel pipe for my load?

The size of the square mild steel pipe needed to support a load depends on several factors, including the weight of the load, the distance between supports, and the type of loading (e.g. static or dynamic). A structural engineer or a load-bearing capacity calculator can help determine the appropriate size.

2. What is the maximum load that a square mild steel pipe can support?

The maximum load that a square mild steel pipe can support depends on its size, length, and the material properties of the steel. The American Society for Testing and Materials (ASTM) has standards for different grades of steel and their respective load-bearing capacities.

3. Can a square mild steel pipe support both tensile and compressive loads?

Yes, a square mild steel pipe can support both tensile (pulling) and compressive (pushing) loads. However, the amount of load it can support in each direction may differ due to factors such as the pipe's shape and orientation.

4. What are the advantages of using a square mild steel pipe for load-bearing purposes?

One advantage of using a square mild steel pipe for load-bearing purposes is its high strength-to-weight ratio. It is also readily available, cost-effective, and has good corrosion resistance. Additionally, its square shape allows for easy connections and installation.

5. How does the thickness of a square mild steel pipe affect its load-bearing capacity?

The thickness of a square mild steel pipe directly affects its load-bearing capacity. Thicker pipes can support more load than thinner ones, as they have a larger cross-sectional area and can resist bending and buckling more effectively. However, a thicker pipe may also be heavier and more expensive.

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