Finding real force in trusses

In summary: The 10kN force is trying to rotate ABF in a clockwise direction. To counter that, point E must exert a reaction force that points to the left and to the right with a magnitude of 15kN each.In summary, the conversation discusses the difficulty in finding the other real force in a truss system given the applied forces at point F and E. The author suggests using a free body diagram to analyze the forces and explains how the reaction force at point E can be determined.
  • #1
fonseh
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Homework Statement


It's given that the applied force is 10kN at F and 25kN at E . I have trouble of finding the other real force in the member of the trusses .

Homework Equations

The Attempt at a Solution


So , i start by drawing the FBD at F . I have 10kN point downwards , so the reaction is 10kN upwards , so it's in equilibrium . But , i really have no idea how the author get the reaction 15kN ( in tension) pointing to the left and to the right . Can someone explain about it ? ( i have draw the FBD at E inside the second diagram)
 

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  • #2
fonseh said:

Homework Statement


It's given that the applied force is 10kN at F and 25kN at E . I have trouble of finding the other real force in the member of the trusses .

Homework Equations

The Attempt at a Solution


So , i start by drawing the FBD at F . I have 10kN point downwards , so the reaction is 10kN upwards , so it's in equilibrium . But , i really have no idea how the author get the reaction 15kN ( in tension) pointing to the left and to the right . Can someone explain about it ? ( i have draw the FBD at E inside the second diagram)
Consider the triangle ABF as a rigid body in its own right. Take moments about B.
 
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1. How do you determine the real force in trusses?

In order to find the real force in trusses, you need to use the method of joints or method of sections. Both methods involve analyzing the forces acting on each joint or section of the truss and solving for the unknown forces using equations of equilibrium.

2. What are the different types of forces present in trusses?

The types of forces present in trusses include tension, compression, and shear. Tension forces occur when the truss is being pulled apart, compression forces occur when the truss is being pushed together, and shear forces occur when the truss is being pushed or pulled in different directions.

3. How do external loads affect the real force in trusses?

External loads, such as weight or forces acting on the truss, can affect the real force in trusses. These external loads create internal forces within the truss, which must be accounted for when determining the real force in each member of the truss.

4. What are the assumptions made when finding real force in trusses?

When analyzing trusses, it is assumed that the members are connected by frictionless pins, the joints are perfectly rigid, and the loads are applied only at the joints. These assumptions allow for a simplified analysis of the truss and help to determine the real forces within the truss.

5. Can the method of joints and method of sections be used interchangeably to find real force in trusses?

Yes, both methods can be used to determine the real force in trusses. The method of joints is typically used for trusses with a small number of members, while the method of sections is more commonly used for trusses with a larger number of members. However, the same principles and equations are used in both methods.

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