Solving Truss Force Issue: CD & DE Equal to 0?

In summary, the forces in members CD and DE are equal to 0, as stated in the textbook. This is because the structure and loading are symmetric, therefore creating symmetry of forces in these members. This helps to achieve equilibrium at joint d.
  • #1
twj2944
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In the attached problem, I don't understand why members CD and DE are equal to 0. I was under the impression that the combined vertical components of BC and CD should equal 6+downward components of BC and EF, as to counteract the force straight down, but this is not the case.

My questions:

Why are the forces in members CD and DE equal to zero?

If they are equal to 0, what stops the downward force from moving the structure?

Thank you

Note: G and Ay are 6 and 6, not 8 and 6 as shown. I used the right values for my calculations, but for some reason wrote 8 down
 

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  • #2
It's not clear from your post: Who is saying that members CD and DE are equal to 0? Are you talking about the forces in these members?
 
  • #3
Sorry yes - that's what I meant.
 
  • #4
You still haven't answered the main question: who is saying that the forces in members CD and DE are equal to 0?
 
  • #5
The answers in the back of the textbook
 
  • #6
IF THE STRUCTURE AND LOADING ARE BOTH SYMMETRICAL THEN THE EQUILIBRIUM OF JOINT d REQUIRES SYMMETRY OF FORCES IN cd AND de. tHAT IS THE CLUE...
 
  • #7
Hey, you don't have to shout.
 
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1. What is a truss force issue?

A truss force issue is a problem that arises when calculating the forces in a truss structure. It occurs when the sum of the forces in one or more members of the truss is equal to zero.

2. How do I know if CD & DE are equal to 0 in a truss structure?

In order to determine if CD & DE are equal to 0, you will need to draw a free body diagram of the truss and calculate the forces in each member using the method of joints or method of sections. If the sum of the forces in CD & DE is equal to 0, then there is a truss force issue.

3. What causes CD & DE to equal 0 in a truss structure?

There are several possible causes for CD & DE to equal 0 in a truss structure. It could be due to an error in the measurement or calculation of the forces, or it could be caused by external forces acting on the truss, such as wind or earthquakes.

4. How do I solve a truss force issue with CD & DE equal to 0?

The first step to solving a truss force issue is to identify the cause of the problem. If it is due to an error, you will need to recheck your calculations and measurements. If it is caused by external forces, you may need to redesign the truss or add additional supports. If the truss is statically indeterminate, you will need to use additional equations to solve for the unknown forces.

5. Can a truss force issue with CD & DE equal to 0 be dangerous?

In most cases, a truss force issue with CD & DE equal to 0 is not dangerous. However, it is important to address the issue and make any necessary repairs or modifications to ensure the stability and safety of the structure. If left unresolved, it could lead to structural failure and potential danger.

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