Solving Truss Force Problems: Step-by-Step Guide and Example Calculation

In summary, the conversation discusses a problem involving pins, cables, and forces. The sum of Fx, Fy, and moments must equal zero. The force on point G in the X direction is calculated to be 1661 lb, and the force on point G in the Y direction can be found using the known angle of the element between G and F. The problem can also be solved by isolating an object and making equilibrium statements, potentially leading to an easy solution by hand.
  • #1
xzibition8612
142
0

Homework Statement


See attachment.


Homework Equations



Sum of Fx, Fy, and Moments=0

The Attempt at a Solution



A and B are pins, so there is a x and y component at each of these points. Cable has same tension on either side, 1200. Take the moment at A to be zero: (-1200)(12)+(5/13)(1200)(12)+(-12/13)(1200)(7)+Gx(10).

Gx=1661 lb
1661+Ax=1107, Ax=-553 lb so Ax points to the left.

How do I find Ay and Gy? Then how would I find the force in each member? Thanks.
 

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  • #2
Hi xzibition8612,
All of the points A through G are assumed to be pinned, so all of the straight elements connected to those pinned joints can only be in compression or tension. In other words, the direction of the elements is also the direction of the force, either compression or tension. There can't be any moments applied on any of the pins, just forces in the direction of the elements. So if you found the force on point G in the X direction, then you can easily calculate the force on point G in the Y direction, because the angle that the element that extends between G and F is known from the geometry they give. Just calculate the angle and you find the force on G in the Y direction. The force Gx and Gy should result in the element being in either compression or tension. Does that help?
 
  • #3
As it happens, you CAN solve this problem without getting the reactions first. It all depends on you isolating an object for which equilibrium statements can be made. Your choice of object will determine whether the problem is solved easily by hand. Can you identify, by inspection, any members that may be carrying a zero force?
 

1. What is force in a truss member?

Force in a truss member refers to the amount of external load or weight that is being applied to a specific part of a truss structure. It is a measure of the tension or compression experienced by that particular member.

2. How is force distributed in truss members?

The distribution of force in truss members is determined by the principles of equilibrium. This means that the total force applied to a truss joint is equal to the sum of the forces acting on that joint. The forces are distributed along the members in a manner that ensures the structure remains stable.

3. What factors affect the force in truss members?

The force in truss members is determined by various factors such as the type and magnitude of external load, the geometry and arrangement of the truss structure, and the material properties of the members. Any changes in these factors can affect the distribution and magnitude of force in the truss members.

4. Can force in truss members be calculated?

Yes, the force in truss members can be calculated using the method of joints or the method of sections. These methods involve analyzing the forces acting on the truss structure and using equations of equilibrium to determine the forces in each member. Advanced techniques such as computer-aided analysis can also be used to calculate the force in truss members.

5. How does the force in truss members affect the stability of the structure?

The force in truss members is crucial for maintaining the stability of the structure. If the force in a member exceeds its maximum capacity, it can lead to failure or collapse of the truss. It is important to consider the force distribution and ensure that all members are able to withstand the forces acting upon them to ensure the stability and safety of the truss structure.

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