Plane Trusses

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Plane Trusses. Plane Truss: Layout. joint[dnt] . objective [b'dektiv] n. . section ['sekn] n. . Objective - Determination of Internal Forces Definition/Properties Internally Static Determinacy The Method of Joints The Method of Sections. - PowerPoint PPT Presentation

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• Plane Trusses

• Plane Truss: LayoutObjective - Determination of Internal ForcesDefinition/PropertiesInternally Static DeterminacyThe Method of JointsThe Method of Sectionsobjective [b'dektiv] n.

joint[dnt]section ['sekn] n.

• Bridge Truss Structures: Bridge

• Truss Structures: RoofCommonly Used Roof Trussesroof [ru:f] n.

• Truss: Rigid or CollapsibleBasic Rigid Form(No-collapsible)

Collapsible Form(Mechanism)Simple Truss

• Two-Force Member & Internal ForceThe Same Internal Force (T/C) at all sections

• The Method of JointsDetermine the internal forces in all three members.

• The Method of Joints: ProceduresCheck Static Determinacy: Externally & InternallyDetermine the External Reactions (r=3) FBD of the whole structure; Apply Fx=0; Fy=0; M=0Choose a Start JointOnly two unknowns/members at the joint; Apply Fx=0; Fy=0 Design a Joint Visit OrderMake sure no more than two unknowns need to be found when visiting a particular joint; Apply Fx=0; Fy=0Check the Results by Employing Unused Joints or Equations, if Possible.

• The Method of Joints: Example IIDeterminate the force in each member of the loaded simple truss. All triangles are equilateraltriangle ['trail] n.

• II: Find External ReactionsI: Check Static Determinacy1. r=3, so externally s.d.2. m=7, j=5; m+r=2j; so internally s.d.

• III: Joint Visit Order

• IV: Joint Analysis (1)

• IV: Joints Analysis (2)

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

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

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

• Joints Visit Order

• The Method of Sections

• Method of sections

• The Method of Sections: Example V

• Example VICompute the force in member DJ.

• Advanced IssuesExternally Static Determinacy (Refer to Example IV)Use of Two or More Moment Equations

• Choose a Local Coordinate Systemlocal ['lukl] n. adj.

coordinate [ku':dinit] n.

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

• Local Coordinate Systems