Example 3: Draw the free-body diagram of member ABC.
Draw FBD of ABC: Member ABC is supported by a smooth pin at A, and is connected to member BD by a pin connection at B. We have to be careful here. Although BD may appear to be a two-force member, a closer examination indicates that it is NOT. This is due to the fact that there is a couple moment acting on member BD. Therefore, it is no longer a two-force member. So in this case, we do not know the direction of force at point B, and we have to show it in terms of its two components. Now we can proceed to draw the FBD of ABC as shown below.