ME 221 Statics Lecture #30 Sections 6.6 – 6.7 & Exam 3 Review ME221 Lecture #30 1 Homework #10 Chapter 7 problems: – 5, 8, 19, 21, 24, 26 & 35 • Due Today ME221 Lecture #30 2 Homework #11 Chapter 6 problems: – 2, 3, 6 & 7 – Method of Joints – 32, 36, 47 & 53 – Method of Sections – 6.47: E-G should be 0.2m • Due Friday, November 22 ME221 Lecture #30 3 Exam #3 Friday, November 15 Details Later ME221 Lecture #30 4 Trusses Composed of slender straight pieces connected together by frictionless pins where all the loads (no moments) are applied. Each member will act as a two-force member (either in tension or compression). All the forces acting on a truss member are axial. ME221 Lecture #30 5 Analysis of Trusses Using the Method of Joints PBy PBx B We need to solve for: (1) - Internal forces FAB, FAC, and FCA (2) - Reactions Ax, Ay and Cy PAY PAx Ax a A Ay ME221 Lecture #30 PCy b PCx C C y 6 Using Matrix Notation 1 0 1 FAB cos a F sin a 0 0 0 AC cos b 0 FBC cos a 0 = sin a 0 sin b 0 A x 1 cos b 0 Ay 0 0 0 sin b 0 C y Using manual calculations Look for joints with 2 unknowns ME221 Lecture #30 -1 0 0 1 0 0 0 0 0 0 0 0 1 PAx P Ay PBx P By PCx PCy 7 Example 6 kN A B 3 kN 0.9 m C D E 1.2 m ME221 1.2 m Lecture #30 8 6 kN A 4 B 4 9 5 15 3 kN C 16 15 16 9 5 4 4 E D ME221 Lecture #30 9 Method of Sectioning If the question is to find internal forces in selected members of the truss, then one can alternatively use the method of sectioning. Example: Determine the force in members FG and FH 12 kN A C 12 kN E G I 1.8 m B ME221 D F Lecture #30 4 @ 2.4 m=9.6 m H J 10 12 kN A C 12 kN E G I FGE B D 1.8 m FGF FHF F 12 kN A C H J 12 kN E G FEG I FFG B D Fx ME221 0 Fy F FEH 1.8 m H M Anypo int 0 0Lecture #30 J 11 Exam #3 Chapter 9: Moments of Inertia – – – – – – ME221 Second Moment of Area; Ixx & Iyy Polar Moments; J0z Parallel Axis Theorem Composite Areas Principal Second Moments; Ixy Mohr’s Circle Lecture #30 12 Exam #3 Chapter 5: Equilibrium of Rigid Bodies – – – – – ME221 Equilibrium Equations Supports Free Body Diagrams Two-Force Members 3D Equilibrium Lecture #30 13 Exam #3 Chapter 7: Internal Forces in Structures – – – – ME221 Internal Forces Shear Forces Bending Moments Shear & Bending in Beams Lecture #30 14