Truss Analysis with Non-Parallel Supports and Point Load: Is My Method Correct?

In summary, the conversation is about a person having trouble solving a truss with supports on the y-axis and a point load in the same direction. They are unsure if their method is correct and ask for confirmation. The expert advises them to indicate whether the members are in compression or tension and mentions that there can be no vertical support reaction at one of the pins. The person thanks the expert and asks if all reaction forces are necessary to calculate internal forces. The expert confirms their results and suggests solving for support reaction forces as a first step to make solving for member forces easier.
  • #1
smrgn92
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Homework Statement



Hi there, I've been having problems with this kind of truss in the attached file. I'm used to resolving forces where the supports are located along the same x-axis, but this time I have the supports on the y-axis and a point load in the same direction. I haven't shown it, but there is a pin joint located at joint A and C. I would like to just simply know if my method is the correct solution.

Homework Equations



See attached file.

The Attempt at a Solution



Firstly I resolved the forces for the reactions at the support in the x direction using the moment of equilibrium equation around joint A. However, I can't seem to find a logical solution for resolving the reactions in the y direction, but upon further analysis I don't think this is entirely necessary, since I'm able to resolve the internal forces without these reaction forces. Have a made a mistake in my analysis?

Thank you forum :)
 

Attachments

  • Internal Forces.pdf
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  • #2
Your results look good, however, please indicate whether the members are in compression or tension, because it is not clear from your calculations. Note also that since members of a pure truss are 2-force members, there can be no vertical support reaction at the pin at C.
 
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  • #3
PhanthomJay said:
Your results look good, however, please indicate whether the members are in compression or tension, because it is not clear from your calculations. Note also that since members of a pure truss are 2-force members, there can be no vertical support reaction at the pin at C.

Thank you, didn't realize there would be no vertical reaction at the pin joint at C, but makes perfect sense. I also indicated tension or compression in the image with arrows on the internal members. I guess another question I had that you answered by confirming my results was that not all reaction forces are necessary to calculate internal forces. :)
 
  • #4
Hmm your arrows look good I guess as long as they are joint forces and not member forces so please indicate (C) for compression in member or (T) for tension in member, to remove all doubt.
Yes you can solve for member forces as you did without first getting that 0 vertical reaction force at C, but generally trusses member forces are more easily solved when you find support reaction forces first, so it's always a good idea to solve for them as a first step.
 

1. What are internal forces in a truss?

Internal forces in a truss are the forces that act on the individual members of the truss structure. These forces include tension, compression, and sometimes shear, and are responsible for keeping the truss stable and able to support external loads.

2. How do internal forces affect the stability of a truss?

The internal forces in a truss play a crucial role in maintaining the stability of the structure. A truss is designed in such a way that the internal forces balance out and cancel each other, resulting in a stable structure that can withstand external loads without collapsing.

3. What causes internal forces in a truss?

Internal forces in a truss are caused by the external loads acting on the structure. These loads can be in the form of weight, pressure, wind, or any other force that is applied to the truss. The internal forces are a result of the truss's members resisting and balancing out these external loads.

4. How do engineers calculate internal forces in a truss?

Engineers use mathematical equations, such as the method of joints and method of sections, to calculate the internal forces in a truss. These methods involve breaking down the truss into smaller sections and analyzing the forces acting on each member to determine the internal forces.

5. Can internal forces cause failure in a truss?

Yes, internal forces can cause failure in a truss if they exceed the strength and capacity of the truss members. This can happen due to overloading, design flaws, or external factors such as extreme weather conditions. It is essential for engineers to carefully calculate and consider the internal forces in a truss during the design process to ensure its stability and safety.

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