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
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: DefinitionStraight Members Pin-jointedLoaded at JointsWeights ignoredNo-collapsible (rigid)collapsible [k'lpsbl]adj.
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.