Calculating strength of steel square tubing

In summary, based on the provided information, it appears that a triangular design with three pieces and a plate attaching to the next stronger than a square tubing and 3 sided plate. The max load is 1400 lb. The deflection is only 0.00327 in, but stress and buckling must be considered. A competent engineer should be consulted for this type of work.
  • #1
gary d
2
0
Hello,

I'm enrolled in College in the civil engineering program and am looking for guidance with calculating strength of steel square tubing.

We are making a project that has parameters.

1- Must be made of steel
2- 4"x6"x36" is maximum OD of section.
3- 14 lbs is maximum weight
4- the load will be applied at the connection, from the top aimed straight down

We are working on a reasonable budget and I'm working on simple, strong, efficient, designs.
Two of these pieces will be connected to each other, so there will be a connection point.

So far I'm thinking 3x3" square tubing with a wall thickness of 11 gauge at 34" long should do the trick. Looks like 10.6 lbs (according to website lists)

What types of steel should I be considering?
How do I calculate the strength of steel square tubing?
How to I calculate the connection points?
Should I scratch the idea of square tubing and go to a more complex design, like truss design?

Thank you
 
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  • #2
Your description is not enough for me to visualize your problem. Please post a figure.

In general, the word "strength" refers to the maximum load that can be carried. This is going to be determined primarily by
1) the geometry of the structural members;
2) the strength of the connections;
3) the yield strength of the material.

A structure fails when some component either yields or buckles. As a designer, you must consider both possibilities.

Remember that a local failure, such as a connection tear-out, is just as much a failure as collapse due to gross yielding. You can raise yield strengths (up to a point) by using more and more exotic steels, but this is often a question of economics. The structure has to be as strong as it needs to be, not as strong as it can possibly be.
 
  • #3
Thank you for your response.

I think this link should work for the pics

http://s1293.photobucket.com/user/Engineer-man/media/imagejpg1_zps798135ed.jpg.html?sort=3&o=0

http://s1293.photobucket.com/user/Engineer-man/library/?sort=3&page=1
Since the posting I looked into some calculations and basics. Looks like moment of inertia is critical.
Found a calculation that seams on track for my uses. For the triangular design in the photobucket pics,

I used 29500000 modulus of elasticity (E) for carbon steel (seams most common and cheapest,) 1000 lb for (F), (I) moment of inertia, 8.49023, 34 inches long (L), and 2 inches for (Y), which sounds like perpendicular distance to neutral axis... I might have the wrong.

According to an online calculator, I'm looking at .00327 in of deflection. But now to somehow calculate how the joinery will work out...

Is the triangular design with three pieces and a plate attaching to the next stronger then a square tubing and 3 sided plate?
And 1400 lbs will be the most weight loaded.

Thank you
 
  • #4
You said that you did your calcs for 1000 load, but 1400 lb is the max load. Why? Why not use 1400 lb?

You said that the deflection was only 0.00327 in but this is only a part of the picture. What is the stress? What about buckling?

Your wording suggests that you really do not know what you are doing, yet you presume to do structural design. This is dangerous. You really need to involve a competent engineer for this work.
 
  • #5
for reaching out about your project. I am happy to provide some guidance on calculating the strength of steel square tubing.

Firstly, it is important to note that the strength of steel square tubing is determined by its material properties, such as yield strength and ultimate tensile strength, as well as its geometry, such as the wall thickness and cross-sectional area. Therefore, the type of steel you choose will greatly impact the strength of your tubing. Some common types of steel used for structural applications include A36, A500, and A53.

To calculate the strength of steel square tubing, you will need to use equations that take into account the material properties and geometry of the tubing. These equations can be found in engineering handbooks or online resources. It is important to note that these calculations may be simplified for your project, as the load will be applied at the connection point and not distributed along the entire length of the tubing.

Speaking of connection points, it is crucial to design them properly to ensure the overall strength and stability of your structure. This involves considering factors such as the type of connection (welded, bolted, etc.), the size and spacing of the connection points, and the load-bearing capacity of the connection itself. It may be helpful to consult with a structural engineer for guidance on designing the connection points for your project.

As for considering a more complex design, such as a truss, it ultimately depends on your project's specific requirements and budget. Trusses can provide greater strength and load-bearing capacity, but they may also be more expensive and time-consuming to construct. It is important to weigh the pros and cons and choose the design that best fits your project's needs.

I hope this information helps guide you in your project. Remember to always prioritize safety and consult with experts when needed. Good luck!
 

1. How is the strength of steel square tubing calculated?

The strength of steel square tubing is typically calculated using the formula for stress, which is force divided by cross-sectional area. This can be further refined by taking into account factors such as the type of steel and the shape of the tubing.

2. What factors affect the strength of steel square tubing?

The strength of steel square tubing can be affected by several factors, including the type and grade of steel, the thickness of the tubing walls, and the shape and size of the tubing itself. Other factors such as temperature, loading conditions, and manufacturing processes can also have an impact on the strength of the tubing.

3. How can I determine the load capacity of steel square tubing?

The load capacity of steel square tubing can be determined by calculating the maximum allowable stress for the specific type and grade of steel being used, and then applying it to the cross-sectional area of the tubing. This will give you the maximum load that the tubing can handle without experiencing permanent deformation or failure.

4. Is there a standard for the strength of steel square tubing?

Yes, there are various standards and specifications for the strength of steel square tubing, which are set by organizations such as the American Society for Testing and Materials (ASTM) and the American Society of Mechanical Engineers (ASME). These standards ensure that the tubing meets certain criteria for strength, quality, and safety.

5. How does the strength of steel square tubing compare to other types of tubing?

The strength of steel square tubing can vary depending on factors such as the type and grade of steel, as well as the size and shape of the tubing. However, in general, steel square tubing tends to have a higher strength-to-weight ratio than other types of tubing, making it a popular choice for structural applications.

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