How Are These Members in Compression and Tension

In summary, the problem is to determine the forces in each member of a truss and determine if they are in tension or compression. The horizontal component of force CB is acting towards the left, indicating that member CB is in tension, while the vertical component of force CB is facing upwards, causing member CA to be in compression. However, the book states the opposite, with member CA in tension and BC in compression. The key is to understand that the force in question is the one the member is applying at the joint, not the force acting on the member. Therefore, member CB is in compression and member CA is in tension.
  • #1
wahaj
156
2

Homework Statement


I'm supposed to find the forces in each member and then determine whether they are in tension or compression. I got the magnitudes right but it seems my directions are wrong according to the book but I am confident that I did the question right. The diagram is part of a larger truss connected at point A and B so point A and B only have he forces shown in the free body diagram.

Homework Equations



Statical equilibrium equations

The Attempt at a Solution



Since the 600N external force is acting towards the right, then the horizontal component of force CB will act towards the left to balance everything out. This will result in the force CB facing towards point C. This means that member CB is in tension. Now since the vertical component of force CB is facing upwards force CA will act downwards to balance everything out which would result in member CA being in compression. But the book says that it is CA which is in tension and BC which is in compression. So who is right? Me or the book?
 

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  • #2
wahaj said:
the horizontal component of force CB will act towards the left to balance everything out. This will result in the force CB facing towards point C. This means that member CB is in tension.
No, that's backwards. The force in question is the force the member CB is applying at point C. If that force is towards C then it means the member C is under compression.
As you know, action and reaction are equal and opposite. If the force from CB on the joint C is acting from B towards C then the force from the joint C on member CB is acting from C towards B.
 

Related to How Are These Members in Compression and Tension

1. What is compression and tension in regards to structural design?

Compression and tension are two types of forces that act on a structure. Compression is a force that pushes the particles of a material together, while tension is a force that pulls them apart. In structural design, these forces are important to consider because they determine how a structure will behave under different loads.

2. How can we tell which members are under compression and tension?

The members in compression are those that are being pushed together by a force, while the members in tension are those that are being pulled apart. A visual inspection of the structure can often reveal which members are under compression and which are under tension. Additionally, engineers can use mathematical calculations and computer simulations to determine the forces acting on each member.

3. What factors contribute to a member being in compression or tension?

The main factors that contribute to a member being in compression or tension are the load applied to the structure, the material properties of the member, and the design of the structure. The magnitude and direction of the load determine the type of force acting on the member, while the material properties and design determine how the member will respond to that force.

4. What happens when a member experiences both compression and tension?

In some cases, a member may experience both compression and tension at different points along its length. This is known as a combined loading condition. When this happens, the member will behave differently depending on the location of the forces. Engineers must carefully consider these different loading conditions in order to design a structure that can withstand all types of forces.

5. How do engineers account for compression and tension in structural design?

Engineers use various design techniques and calculations to determine the amount of compression and tension that a structure and its members can withstand. This includes considering the type and magnitude of the loads, the material properties of the members, and the overall design of the structure. Additionally, engineers may use reinforcement or support structures to help distribute forces and prevent failure in areas experiencing high levels of compression or tension.

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