Now comes the fun bit. We will now look at the actual forces acting within each truss member using a technique called the method of joints.
This method works by first considering each joint in the truss structure. We isolate the joint by drawing its FBD, and replace all truss members connected to the joint by the forces that they exert on the joint. The magnitude of the forces is then determined by applying the equations of equilibrium ([ΣF_{x} = 0] and [ΣF_{y} = 0]) on each joint.
A common confusion that students face is determining whether each member is in tension or compression. There are many ways to go about doing this, but the trick is to stick to only one method consistently.
The way I would recommend is to treat compression as a pushing force and tension as a pulling force:
Now comes the fun bit. We will now look at the actual forces acting within each truss member using a technique called the method of joints.
This method works by first considering each joint in the truss structure. We isolate the joint by drawing its FBD, and replace all truss members connected to the joint by the forces that they exert on the joint. The magnitude of the forces is then determined by applying the equations of equilibrium ([ΣF_{x} = 0] and [ΣF_{y} = 0]) on each joint.
A common confusion that students face is determining whether each member is in tension or compression. There are many ways to go about doing this, but the trick is to stick to only one method consistently.
The way I would recommend is to treat compression as a pushing force and tension as a pulling force: