Trussel buckling,question from mechanics of materials

[berdan]

Ok,first of all ,I'm sorry for any further language barrier things,I study in a non-English speaking university,and I might do a mistake in translating some technical terminology.
So,the problem is from mechanics of materials,buckling loads.This subject gives me nightmares as it is,I can barely understand what it is all about.

Homework Statement

http://imageshack.us/photo/my-images/6/krisam.jpg

http://imageshack.us/photo/my-images/6/krisam.jpg

That is the problem basically.Trussel made of 3 beams,two rectangulars,one is round.
First question is what is the minimal force to buckling.
Second is,if we reverse the force (now it acts up instead of down),what is the minimal length of parameter a so that we can use Oiler formula.


My attempt for solution : Non,I don't really know what they want from my life.Mostly,why they don't check if we can use Oiler formula in the first question,and why we have to check in the second?

Thanks in advance.

 

[berdan]

Someone?I'm dying here...

 

[mathmate]

As a starter, I suggest you analyze the structure to find,

step 1: for each member of the truss, calculate maximum force without buckling
- magnitude of the force
- magnitude of the stress
- direction of the force (compression or tension)
- the maximum value of F that will keep the stress of every member below $\rho$y.

step 2: for the compression members,
- calculate the maximum value of F that will not cause Euler buckling.

step 3: if you reverse the force, then the direction of forces and stresses will be reversed.
There will be only one compression member which is longer than the previous case, and it will be relevant to re-calculate the Euler buckling load in terms of F and a.

 

[nvn]

Regarding question 1 (and 2), there are currently infinite solutions. Dimensions a and b are currently not defined; therefore, you can make the truss buckle at any value of applied force F, depending on the values of a and b you choose. Please let me know if I am missing something. Did you omit any information?

 

[DeeNos]

I understand the frustration and difficulty in understanding the concept of trussel buckling and mechanics of materials. I would like to offer some clarification and guidance on how to approach this problem.

Firstly, trussel buckling is a phenomenon in which a structure, such as a truss, collapses due to an applied compressive load. This can be caused by various factors such as material properties, geometric imperfections, and boundary conditions. The minimal force to cause buckling is known as the critical buckling load.

In the first question, you are asked to determine the minimal force needed to cause buckling in the trussel made of 3 beams. This can be calculated using various methods such as Euler's formula or using finite element analysis. It is important to check if Euler's formula is applicable in this case, as it is only valid for certain types of structures and boundary conditions.

In the second question, you are asked to reverse the direction of the applied force and determine the minimal length of parameter a for which Euler's formula can be used. This is because the critical buckling load and length are dependent on the direction of the applied force.

I would suggest reviewing the concepts of trussel buckling and Euler's formula, and also carefully interpreting the given problem before attempting to solve it. If you are still having difficulty, I would recommend seeking help from a professor or tutor who can provide further clarification and guidance. Best of luck in your studies.