# How much weight can 1 x 3 11 gauge rectangular steel support before bending?

• oldgit
In summary: The calculations are correct, but the tubing may not be able to support the load.Please ask for a clarification if there is any of this that you don't understand.In summary, Redhoss said that the 1" wide x3" high x6' long piece of rectangular hollow tubing has a wall thickness of 11 gauge, and that the calcs look good. He also said that if the tubing is not a closed section, even if there is a slit with overlap, it will not work as calculated, since it could split open. He said that if it is an extruded closed tubing, the calculation assumptions should be OK.
oldgit
Hi

I wonder if you could help a really thick oldie with a problem, I found this:-

I need to build a set of ramps for my dump trailer. The ramps will be
6' long. I have and want to use 1" x 3" 11 gauge rectangular steel. If
I were to take one 6' piece of this material, stand it on its'
narrowest edge, support it at both ends and place a load at its'
center how much weight will it support before failing. A little
deflection is all right just so it does not permanently bend.*******************************************************************Hello usajohnson, I think I can help you. I searched for properties of
1" x 3" 11 gauge rectangular steel tubing, but that is an odd size. We
will have to calculate the section modulus (excluding corner radius):S = bd^3 - b1d1^3/6db = 1"
d = 3"
b1 = 1 - 2x0.091 = 0.818
d1 = 3 - 2x0.091 = 2.818S = [(1 x 3^3) - (0.818 x 2.818^3)] / (6 x 3) = 0.483 in^3M (maximum bending moment) = [P (point load) x l (length)] / 4Solving for P:P = 4M/lM = s x S
Where:
s (allowable bending stress) = .55 x yield strength of steel
To be conservative we will assume that the steel you have is 30,000 psiM = .55 x 30,000 x 0.483 = 7,969 in-lbP = 4 x 7,969 / 72 in = 442#So, you can say that the tubing will safely support at least 442#. The
tubing you have may actually be as high as 50,000 psi yield strength,
but we don't really know.Please ask for a clarification if there is any of this that you don't understand.Good luck with your project, Redhoss

******************************************************************

and was hoping you could help me understand! I'm trying to calculate for the thickness of steel plate, not box section! If I remove the -b1d1 from S to leave:
S = bd^3/6d
Is that OK? Or am I way off? (Please don't quote 'Integration math', I'm just too thick, never could get the hang of it!)
Any help would be much appreciated

Oldgit

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I am assuming, as Redhoss did, that you have a 1" wide x3" high x6' long piece of rectangular hollow tubing that has a wall thickness of 11 gauge, (or 0.091"). If that is a correct assumption, the calcs look good, although I didn't check the math. Are you saying that this is an incorrect assumption? Or are you worried about local failure of the top wall of the tube under the point load?

Last edited:
If the tubing is not a closed section, even if there is a slit with overlap, it will not work as calculated, since it could split open.
If it is an extruded closed tubing, the calculation assumptions should be OK.

Hi Phanthom J, and Mathmate

Thanks for the reply, I'm afraid that my post has been misunderstood! The stuff in red is a post I found that used maths that was more to my level of understanding, but is for box tube section! I intended to use it to calculate for flat plate and was wondering if the removal of part of the equation ie:-

S = bd^3 - b1d1^3/6d (remove - b1d1^3) to leave

S = bd^3/6d

is the correct interpretation for flat plate, with of course the rest of the equation as is!

I'm trying to calculate the thickness of mild steel plate 12" x 12" x ? for a point load of 20tons. A friend has asked me to build them an olive press and I'd intended to use a 20Ton hydraulic bottle jack to press the olives between two 12" square plates! The olive paste would be in layers between a stack of rigid plastic squares (12" square), in turn between the steel plates! Any distortion of the steel plates is libel to fire the plastic sheets from the press causing injury to my friend, therefore the plates need to be thick enough not to bend under the full load of 20Tons!

I hope you can follow my rambling!

Thanks in advance for any reply's, but please keep the maths simple or my tiny mind my implode!

Oldgit

I am sorry to disappoint you, but anything will bend under a load of 20 tons (or any load). It's a matter of how much deflection that can be tolerated.

## What is the definition of strength of materials?

Strength of materials is a branch of engineering that deals with the study of the behavior of solid objects under various types of stress, such as tension, compression, bending, and torsion.

## What is the purpose of studying strength of materials?

The study of strength of materials is essential for designing and constructing structures that can withstand the forces and stresses they will be subjected to. It helps engineers determine the appropriate materials and dimensions needed for a structure to be safe and durable.

## How are ramps affected by the principles of strength of materials?

Ramps are subject to various types of stress, such as compression and bending, due to the weight of the objects being moved up or down the ramp. The principles of strength of materials are applied to determine the appropriate materials and dimensions for the ramp to support the weight and prevent failure.

## What are some common materials used for ramps and their strengths?

Some common materials used for ramps include wood, concrete, and steel. Wood is relatively strong in compression but can be weak in bending. Concrete has high compressive strength but can be brittle in tension. Steel has high strength in both tension and compression, making it a popular choice for ramps.

## How can the strength of a ramp be tested?

The strength of a ramp can be tested through various methods, such as load testing, strain gauges, and finite element analysis. Load testing involves placing weights on the ramp to determine the maximum weight it can support without failure. Strain gauges measure the amount of stress and strain on the ramp's materials. Finite element analysis uses computer simulations to predict the behavior of the ramp under different loads and conditions.

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