How do I determine the support reactions in a method of joints truss?

In summary, the conversation is about determining support reactions in a truss structure. The person is having trouble understanding how to determine the reactions and has read all available text but is still stuck. They have attempted to solve the problem using the three laws of equilibrium, but are unsure of where the reactions are and how to find them. A helpful website is suggested, which uses Newton's 2nd law and torque equations to solve for the unknowns.
  • #1
mikel lowery
2
0
Hi, I am really stuck here. My problem is with determining the support reactions. I understand that this needs to be done first before working on each truss member. But I don't understand how to determine them. I have read and re-read all my available text and still stuck.

The question I can't solve, " Determine the force in each member" of the attached. Each joint are pin joints.

Can some one please walk me through this?

Regards

Mikel

<- Edit ->

I have tried to solve rather than just ask, I'm aware that the 3 laws of equilibrium apply for the reactions, sum of x =0, sum of y= 0 and sum of Mc = 0. I just don't understand 1. Where the reactions are and 2. how to determine them?
 

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  • #2
You picture hasn't been approved yet, but if this is a static equilibrium question, it sounds like a pretty classic problem. You can't solve it with just the sum of x and y forces because you have too many unknowns. But the torques also are balanced. So you can get a second system of equations and solve for the unknowns.
 
  • #3
merryjman,
Thank you for your reply. I think I understand the theory, I am just unsure of how to put together. How do I determine where the reactions are and find them?
Regards
 
  • #4
Still can't view the picture, but I think this website will be helpful: http://physics.uwstout.edu/Statstr/Strength/StatII/stat22.htm

If your situation is similar to that, then you use Newton's 2nd to figure out where the reaction forces are, and the torque equations to eliminate some of your unknowns in the force equations. In the example on the website, there is a reaction force at the pin joint, for example.
 
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1. What is the method of joints in truss analysis?

The method of joints is a technique used in structural engineering to analyze the internal forces in a truss. It involves breaking down the truss into smaller sections and using the equilibrium equations to determine the forces at each joint.

2. How do I determine the reactions at the supports using the method of joints?

The first step in using the method of joints is to isolate the truss and draw a free body diagram. Then, apply the equilibrium equations to determine the reactions at the supports. These reactions will serve as the starting point for analyzing the internal forces in the truss.

3. Can the method of joints be used for all types of trusses?

Yes, the method of joints can be used for any type of truss, including simple, compound, and complex trusses. The only requirement is that the truss must be in static equilibrium.

4. Are there any limitations to the method of joints?

The method of joints assumes that all members of the truss are connected by pins at the joints and that the members are only subjected to axial forces. This means that it cannot be used for trusses with members that are not connected by pins or for trusses with members that are subjected to bending moments.

5. Is the method of joints the most efficient way to analyze a truss?

The method of joints is a simple and straightforward approach to analyzing trusses. However, for more complex trusses, other methods such as the method of sections or the method of virtual work may be more efficient. It is important to choose the appropriate method based on the specific truss being analyzed.

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