ME 221 Statics Lecture #33 Section 6.9

1. ME 221 StaticsLecture #33Section 6.9 Lecture 33

2. Homework #11 Chapter 6 problems: • 2, 3, 6 & 7 – Method of Joints • 32, 36, 47 & 53 – Method of Sections • 68 & 75 • Due Friday, November 21 Lecture 33

3. Homework #12 Chapter 8 problems: • 1, 2, 4, 8 & 15 Due Monday, December 1 Lecture 33

4. Quiz #7 Friday, November 21 Analysis of Structures Method of Joints or Method of Sections Lecture 33

5. Frames and Machines • Frames and machines have at least one multi-force member • Frames are designed to support loads • Machines are designed to transmit and modify loads • Just like trusses, frames and machines need to be disassembled to determine member forces • Need to draw a FBD for each member Lecture 33

6. D E C B W A D Cx Cy E Cx FBE Cy W C T T FBE FBE W B A Ax Ax FBE Ay Ay Disassembly Exposes Internal Forces • First, reactions of entire structure • Second, disassemble and solve for internal forces FBE is a two force member Lecture 33

7. Notes on Previous Problem • Without recognizing BE is a two force member the problem, is not tractable. • MUST draw a FBD for entire structure and each disassembled part • Each FBD may have three unknown forces which are found from SFx = 0; SFy = 0; SMz = 0 Lecture 33

8. General Procedure • Draw FBD for entire structure and solve for reaction forces: SFx = 0; SFy = 0; SMz = 0 • Disassemble into component parts • Recognize two force members • Draw FBD and solve for reaction forces - using SFx = 0; SFy = 0; SMz = 0 Lecture 33

9. Example Problem Lecture 33