Reaction forces in a pin jointed frame

In summary, the conversation discusses a problem involving finding the angle theta in a frame with calculated angles and a drawn line of forces. The conversation also mentions using a template and plugging in a length to solve the problem.
  • #1
mrtoodles
1
0
This is the question: http://i.imgur.com/Ex2Yx4l.png
I have calculated all the angles in the frame, and have drawn line of forces so that the reaction force at x, reaction force at y, and the 10KN meet up. From then I am stuck, and don't know how to find the angle theta. http://i.imgur.com/gob3Cos.png
 
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  • #2
Hello Toodles, welcome to PF :smile: !

And this is the template:

Homework Statement



Homework Equations



The Attempt at a Solution


(You must have deleted it by accident :smile: -- something that PF rules don't allow !)

What about this Bow's notation hint ? I only see a few red lines, but I don't believe I see any conditions for static equilibrium worked out ?
 
  • #3
mrtoodles said:
dont know how to find the angle theta.
Sometimes it's easier if you plug in a length. What you plug it doesn't matter since it won't affect the angle.
Say the distance between the anchor points, X and Y, is 1.
What is the length of the vertical line up from Y to (let's call it) A?
How long is the line that rises at 30 degrees from A to where it meets the 10kN line at (say) B?
How far is it from A to the vertical line through the load?
How far is it from X to the vertical line through the load?
How high is the topmost point (C) from the baseline?
Etc.
 

1. What are reaction forces in a pin jointed frame?

Reaction forces in a pin jointed frame are the forces that act on the supports or joints of the frame. These forces are equal and opposite to the external forces acting on the frame.

2. How do reaction forces affect the stability of a pin jointed frame?

Reaction forces play a crucial role in maintaining the stability of a pin jointed frame. They counteract the external forces and prevent the frame from collapsing or moving. The magnitude and direction of the reaction forces depend on the external forces and the geometry of the frame.

3. What is the difference between a pinned joint and a fixed joint in terms of reaction forces?

In a pinned joint, there is no moment resistance, so only vertical and horizontal reaction forces are present. In a fixed joint, there is both moment resistance and reaction forces in all three directions (vertical, horizontal, and rotational).

4. How do you calculate reaction forces in a pin jointed frame?

To calculate reaction forces, you need to draw the free body diagram of the frame and apply the equations of equilibrium. The sum of all forces in the x and y directions should be equal to zero, and the sum of all moments at any point should also be equal to zero.

5. Can the reaction forces in a pin jointed frame be negative?

Yes, reaction forces can be negative. Negative reaction forces indicate that the direction of the force is opposite to what was initially assumed. This can happen when the external forces or the dimensions of the frame are changed.

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