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Structure Analysis I

Structure Analysis I. Lecture 5. Trusses. Trusses in Building. Trusses Types for Building. Truss Bridge. Truss Bridge Types. Classification of coplanar Truss. Simple Truss. Compound Truss. Complex Truss. Determinacy. For plane truss If b+r = 2j statically determinate

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Structure Analysis I

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  1. Structure Analysis I

  2. Lecture 5 Trusses

  3. Trusses in Building

  4. Trusses Types for Building

  5. Truss Bridge

  6. Truss Bridge Types

  7. Classification of coplanar Truss Simple Truss

  8. Compound Truss

  9. Complex Truss

  10. Determinacy For plane truss If b+r = 2j statically determinate If b+r > 2j statically indeterminate Where b = number of bars r = number of external support reaction j = number of joints

  11. Stability For plane truss If b+r < 2j unstable The truss can be statically determinate or indeterminate (b+r >=2j) but unstable in the following cases: External Stability: truss is externally unstable if all of its reactions are concurrent or parallel

  12. Internal stability: Internally stable Internally unstable Internally unstable

  13. Classify each of the truss as stable , unstable, statically determinate or indeterminate.

  14. The Method of Joints STEPS FOR ANALYSIS 1. If the support reactions are not given, draw a FBD of the entire truss and determine all the support reactions using the equations of equilibrium. 2. Draw the free-body diagramof a joint with one or two unknowns.Assume that all unknown member forces act in tension (pulling the pin) unless you can determine by inspection that the forces are compression loads. 3. Apply the scalar equations of equilibrium,  FX = 0 and FY = 0, to determine the unknown(s). If the answer is positive, then the assumed direction (tension)is correct, otherwise it is in the opposite direction (compression). 4. Repeat steps 2 and 3 at each joint in succession until all the required forces are determined.

  15. The Method of Joints

  16. Example 1 Solve the following truss

  17. Group Work Determine the force in each member

  18. Zero Force Member 1- If a joint has only two non-colinear members and there is no external load or support reaction at that joint, then those two members are zero-force members

  19. Zero Force Member 2- If three members form a truss joint for which two of the members are collinear and there is no external load or reaction at that joint, then the third non-collinear member is a zero force member.

  20. Example 2 Find Zero force member of the following truss

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