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Plane Trusses

Plane Trusses. Plane Truss: Layout. joint[dʒɒɪnt] 节点. objective [əb'dʒektiv] n. 目的；. section ['sekʃən] n. 截面；. Objective - Determination of Internal Forces Definition/Properties Internally Static Determinacy The Method of Joints The Method of Sections.

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Plane Trusses

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  1. Plane Trusses

  2. Plane Truss: Layout joint[dʒɒɪnt]节点 objective [əb'dʒektiv] n. 目的； section ['sekʃən] n. 截面； • Objective - Determination of Internal Forces • Definition/Properties • Internally Static Determinacy • The Method of Joints • The Method of Sections

  3. Bridge Truss Structures: Bridge

  4. Truss Structures: Roof roof [ru:f] n. 屋顶； Commonly Used Roof Trusses

  5. Truss: Definition • Straight Members • Pin-jointed • Loaded at Joints Weights ignored • No-collapsible (rigid) collapsible [kə'læpsəbl] adj. 可折叠的；可变形的

  6. Truss: Rigid or Collapsible • Basic Rigid Form (No-collapsible) • Collapsible Form (Mechanism) Simple Truss

  7. Two-Force Member & Internal Force The Same Internal Force (T/C) at all sections

  8. The Method of Joints Determine the internal forces in all three members.

  9. The Method of Joints: Procedures • Check Static Determinacy: Externally & Internally • Determine the External Reactions (r=3) – FBD of the whole structure; Apply ΣFx=0; ΣFy=0; ΣM=0 • Choose a Start Joint –Only two unknowns/members at the joint; – Apply Σ Fx=0; Σ Fy=0 • Design a Joint Visit Order –Make sure no more than two unknowns need to be found when visiting a particular joint; – Apply Σ Fx=0; Σ Fy=0 • Check the Results by Employing Unused Joints or Equations, if Possible.

  10. The Method of Joints: Example II • Determinate the force in each member of the loaded simple truss. triangle ['traiæŋɡl] n. 三角（形）； All triangles are equilateral

  11. I: Check Static Determinacy 1. r=3, so externally s.d. 2. m=7, j=5; m+r=2j; so internally s.d. II: Find External Reactions

  12. III: Joint Visit Order

  13. IV: Joint Analysis (1)

  14. IV: Joints Analysis (2)

  15. The Method of Joints: Example III • Determinate the force in each member of the loaded simple truss.

  16. The Method of Joints: Example IV • Determinate the force in each member of the loaded simple truss.

  17. The Method of Joints: Example V • Compute the forces in members BC, BE and EF of the loaded truss.

  18. Joints Visit Order

  19. The Method of Sections

  20. Method of sections

  21. The Method of Sections: Example V

  22. Example VI • Compute the force in member DJ.

  23. Advanced Issues • Externally Static Determinacy (Refer to Example IV) • Use of Two or More Moment Equations

  24. Choose a Local Coordinate System coordinate [kəu'ɔ:dinit] n. 坐标； local ['ləukəl] n. 局部； adj. 当地的；局部的；

  25. Advanced Issues: Example VII • Compute all member forces. All inclined members are at 300 or 600.

  26. Local Coordinate Systems

  27. Advanced Issues: Example VII

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