Forces in Truss Members (Statics)

In summary: L to A and 1.5KN on D.Thank you for your help guys. I'll work on it again today and see if this different train of thought will get me through it. :)
  • #1
cpmustang07
3
0

Homework Statement



See attachment.
Edit: Point A is a pinned connection (has a reactionary force in X and Y direction). Point B is a roller connection (only has reactionary force in Y direction)

Homework Equations



Sum Fx=0
Sum Fy=0
Sum of Moments=0


The Attempt at a Solution




Find reaction forces at point A and D. Normally this wouldn't be an issue. I'd just find the reaction force of D by solving for the moment around point A. Then find A by knowing that the sum of forces in Y direction is 0. However, dimensions are not given in the problem. I have the answers, but I do not see how to get to them.

After finding reaction forces, isolate each joint and begin with joint with no more than two unknowns. Proceed until all forces are found.
 

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  • #2
These are all equilateral triangles...each horizontal member has the same length, L. What would be the perp. distance from the applied load to A?
 
  • #3
PhanthomJay said:
These are all equilateral triangles...each horizontal member has the same length, L. What would be the perp. distance from the applied load to A?

3*cos(60)*L, correct?
 
  • #4
cpmustang07 said:
3*cos(60)*L, correct?
Interesting way to say 1.5L, which is correct.
 
  • #5
SammyS said:
Interesting way to say 1.5L, which is correct.

No...
 
  • #6
Phrak said:
No...
Why not?? If the length of each horizontal member is L, the perpendicular distance from the line of action of the applied load to A is 1.5 L.
 
  • #7
PhanthomJay said:
Why not?? If the length of each horizontal member is L, the perpendicular distance from the line of action of the applied load to A is 1.5 L.

right. 1.5L to A and 1.5KN on D.
 
  • #8
Thank you for your help guys. I'll work on it again today and see if this different train of thought will get me through it. :)

I got it guys. Thank you. Apparently I'm really slow. ;)
 
Last edited:

What is a truss and how does it work?

A truss is a structure made up of interconnected beams or bars that are designed to withstand external forces. It works by distributing the applied forces evenly across its members, resulting in a stable and rigid structure.

What are the different types of forces that act on truss members?

The main types of forces that act on truss members are tension, compression, and shear. Tension forces pull on the members, compression forces push on them, and shear forces are parallel to the surface of the member.

How do you determine the internal forces in truss members?

To determine the internal forces in truss members, you can use the method of joints or the method of sections. The method of joints involves analyzing the forces at each joint in the truss, while the method of sections involves cutting the truss into smaller sections and analyzing the forces acting on each section.

What is the difference between a statically determinate and statically indeterminate truss?

A statically determinate truss is one in which the internal forces can be determined using the equations of static equilibrium. A statically indeterminate truss, on the other hand, has more unknown forces than the number of equations available to solve for them. In this case, additional information or assumptions are needed to solve for the internal forces.

How do you ensure the stability of a truss?

To ensure the stability of a truss, the forces acting on it must be in equilibrium. This means that the sum of all the forces in the horizontal and vertical directions must be equal to zero, and the sum of the moments around any point must also be equal to zero. Additionally, the truss must be able to resist deformation or movement under the applied forces.

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