Help with a statics problem finding free members and two force members

  • #1
Zulliz
3
0
Homework Statement
So ive gotten the problem i have to solve, and for some reason this 2-member forces and dividing the frame into members simply does not click with my brain, it should be so simple, yet i cannot get it right.

Ive attatched a picture of the problem as well as my intended equation for moment around point A, can you guys tell me if im on the right track?

And even better can you help me find the forces applied in A, B, C and D? Im completely stuck, for some reason my brain cannot comprehend this 2 force member stuff and i dont know why…
Relevant Equations
SUMof moments in clockwise direction around A = 0
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  • #2
Welcome, @Zulliz !

Your first attempt seems to be correct, but representing the vector F at D would be better.

The horizontal 2F keeps pressure on point C, and the 2-member acts like one solid part.
 
  • #3
Lnewqban said:
Welcome, @Zulliz !

Your first attempt seems to be correct, but representing the vector F at D would be better.

The horizontal 2F keeps pressure on point C, and the 2-member acts like one solid part.
But how would i go about it then? Can you elaborate? As I tried to explain my brain is simply shutting down on the two-force members and im having such a hard time understanding how to do them unfortunately.

Would i do sum of moments around B to find the force F pressing up at point C using the 2F x a - 2a x C?
 
Last edited:
  • #4
Zulliz said:
But how would i go about it then? Can you elaborate? As I tried to explain my brain is simply shutting down on the two-force members and im having such a hard time understanding how to do them unfortunately.
If the problem requires you to analyze each part separately, do a free body diagram of each.
Represent the external given forces first.
Then, represent all the reactions (forces and torques) that the part would need to have acting on it in order to remain in static equilibrium (not moving).

Zulliz said:
Would i do sum of moments around B to find the force F pressing up at point C using the 2F x a - 2a x C?
You will need to calculate the magnitude of the force acting at D first, since that moment matters.
 
  • Like
Likes Zulliz
  • #5
Lnewqban said:
If the problem requires you to analyze each part separately, do a free body diagram of each.
Represent the external given forces first.
Then, represent all the reactions (forces and torques) that the part would need to have acting on it in order to remain in static equilibrium (not moving).


You will need to calculate the magnitude of the force acting at D first, since that moment matters.
So something like this?
 

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FAQ: Help with a statics problem finding free members and two force members

What are free members in statics?

Free members in statics are structural elements that are not subjected to any external constraints or supports, allowing them to move freely in space. These members can experience forces but are not fixed or restrained at their ends, making them essential in analyzing the overall behavior of a structure.

How do you identify two-force members?

Two-force members are structural elements that are subjected to forces at only two points, typically their ends. To identify them, look for members that connect two joints without any external loads applied along their length. The forces acting on these members must be equal in magnitude, opposite in direction, and collinear.

What is the significance of finding free and two-force members in a structure?

Identifying free and two-force members is crucial for simplifying the analysis of a structure. Free members can be ignored in equilibrium equations, while two-force members can be analyzed using simple force balance equations. This helps in reducing the complexity of the problem and allows for more efficient calculations.

How can free and two-force members affect the stability of a structure?

Free and two-force members can influence the stability of a structure by affecting how loads are distributed and transferred. If two-force members are not properly aligned or if free members are not adequately supported, it can lead to structural failure or excessive deformation. Proper identification and analysis ensure that the structure remains stable under applied loads.

What are some common mistakes when analyzing free and two-force members?

Common mistakes include misidentifying members as free or two-force when they are not, overlooking external loads that may affect these members, and failing to apply the correct equilibrium equations. Additionally, assuming that all members can be treated as two-force members without considering their actual loading conditions can lead to incorrect conclusions in the analysis.

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