• KevCah
In summary, the critical buckling load of a pinned-ended strut is the knee in the load-displacement curve. It can only be determined by eye if some other information is not provided.

#### KevCah

Hi guys,

I was wondering could I get some help with determining the experimental critical buckling load of a pinned ended strut. I am hoping to compare predicted values from Euler buckling and Perry Robertson to experimental values. I have carried out a experiment where by I applied a axial load to the strut and recorded both the horizontal and vertical displacement. From this data can I apply a formula to give me the critical buckling load? Or is the critical buckling load simply the highest value recorded in the experiment?

Thanks for any help!

Assuming that your strut was initially straight (so that it would actually buckle rather than simply bend), then make a plot of load as a function of axial displacement. You should see a pronounced "knee" in the curve. That is the buckling load. It is not the highest load recorded because most post-buckled columns continue to support the load and the load rises slowly.

There is no clearly defined "knee" in some of my samples. Is there anymore accurate way to determine the "knee" rather then doing it by eye? I am just trying to keep my experimental errors to a minimum.

KevCah said:

There is no clearly defined "knee" in some of my samples. Is there anymore accurate way to determine the "knee" rather then doing it by eye? I am just trying to keep my experimental errors to a minimum.

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If you look at the test results for Sample 1, I would say the 'knee' is clearly defined when the test load is approx. 350-360 Newtons. Where the applied load is relatively constant, the test piece undergoes a measurable change in deflection, which suggests that some sort of inelastic behavior is occurring. The other two samples do not appear to exhibit the same behavior.

Of course, a lot of information about the test pieces and the test set up have not been disclosed.

What is the material and what is your geometry (length, width, etc. for the test specimens)?
Did your experiments result in a permanent set, or were they fully elastic? (Buckling is an elastic phenomenon; plastic deformation puts an end to all questions of buckling.)

I don't think we can help you very much without this data.

## 1. What is Experimental Critical Buckling Load?

Experimental Critical Buckling Load is a measure of the maximum compressive load that a column or structural member can withstand before buckling occurs. It is an important parameter in structural engineering and is used to determine the stability and safety of a structure.

## 2. How is Experimental Critical Buckling Load determined?

Experimental Critical Buckling Load is determined through physical testing of a structural member under increasing compressive loads. The load at which buckling occurs is recorded and used to calculate the critical buckling load.

## 3. What factors affect Experimental Critical Buckling Load?

Experimental Critical Buckling Load can be affected by various factors such as the material properties of the structural member, its dimensions, and the type of loading. Other factors such as imperfections in the member or the presence of external forces can also influence the critical buckling load.

## 4. How is Experimental Critical Buckling Load used in structural design?

Experimental Critical Buckling Load is used in structural design to ensure that a structure can safely withstand the expected compressive loads. It is compared to the calculated critical buckling load to determine if the structure is stable and to make any necessary adjustments in the design.

## 5. Can Experimental Critical Buckling Load be accurately predicted?

Experimental Critical Buckling Load can be predicted with a certain level of accuracy through mathematical models and simulations. However, the results may vary depending on the complexity of the structure and the accuracy of the input parameters. Physical testing is still necessary to verify the predicted values.