ME221Lecture 331 ME 221 Statics Lecture #33 Section 6.9

ME221Lecture 332 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

ME221Lecture 333 Homework #12 Chapter 8 problems: –1, 2, 4, 8 & 15 Due Monday, December 1

ME221Lecture 334 Quiz #7 Friday, November 21 Analysis of Structures Method of Joints or Method of Sections

ME221Lecture 335 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

ME221Lecture 336 Disassembly Exposes Internal Forces First, reactions of entire structure W A B C D E W A B C D E T AxAx AyAy T AxAx AyAy F BE CyCy CxCx W CyCy CxCx Second, disassemble and solve for internal forces F BE is a two force member

ME221Lecture 337 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  F x = 0;  F y = 0;  M z = 0

ME221Lecture 338 General Procedure Draw FBD for entire structure and solve for reaction forces:  F x = 0;  F y = 0;  M z = 0 Disassemble into component parts –Recognize two force members –Draw FBD and solve for reaction forces - using  F x = 0;  F y = 0;  M z = 0

ME221Lecture 339 Example Problem