CE 201 - Statics

1. CE 201 - Statics Chapter 6 – Lecture 22

2. FRAMES AND MACHINES • Frames And machines are structures composed of pin-connected members. Those members are subjected to more than two forces. • The forces acting at the joints and supports can be determined by applying the three equilibrium equations (Fx=0; Fy=0; Mo=0) to each member. This is done by disasembling the structure and drawing the free-body diagram of each member.

3. Free-Body Diagram • Isolate each part • Include all forces and couple moments acting on each part • Identify knowns and unknowns • Keep the dimensions of of the original structure • Find rectangular components of forces with respect to x and y coordinates • Assume the direction of unknowns or find it by inspection • Identify all two-force members in the structure • Forces common to two members act with equal magnitude but opposite direction.

4. Equations of Equilibrium • By applying equilibrium equations, the unknown forces at the supports and connections can be determined. • As long as the structure lies in the x-y plane, then Fx=0; Fy=0; and Mo=0.

5. Fx=0 Fy=0 Mo=0

6. Fx=0 Fy=0 Mo=0 Fx=0 Fy=0 Mo=0

7. Fx=0 Fy=0 Mo=0 Fx=0 Fy=0 Mo=0 Fx=0 Fy=0 Mo=0