Truss Method of Joints: Solving Unequal Member Forces

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SUMMARY

The discussion focuses on the application of the Truss Method of Joints for analyzing a truss structure lacking diagonal bracing. It concludes that without diagonals, the structure experiences bending and shear stresses, making the method of joints inapplicable. The user is advised that the asymmetrical nature of the truss will result in non-mirror image forces, and frame analysis is recommended due to the presence of moment-carrying joints.

PREREQUISITES
  • Understanding of the Truss Method of Joints
  • Knowledge of structural analysis principles
  • Familiarity with axial loads and their effects on truss members
  • Concept of moment-carrying joints in frame structures
NEXT STEPS
  • Study the effects of diagonal bracing on truss stability
  • Learn about frame analysis techniques for structures with moment-carrying joints
  • Explore the differences between axial loads and bending/shear stresses in trusses
  • Investigate software tools for structural analysis, such as SAP2000 or RISA-3D
USEFUL FOR

Structural engineers, civil engineering students, and professionals involved in truss design and analysis will benefit from this discussion.

gmreit
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Homework Statement


The load is known. Just 2 reactions needed to describe all external forces.

Homework Equations


method of joings

The Attempt at a Solution


I'm working on a pretty simple truss for work and want to check some of the elements for buckling. The strange thing is I am not getting equivalent member forces for each side of the truss. Without any additional diagonal bracing in the middle I thought it will be a pretty straight forward case. Not sure what I am missing because I figured Fmn = Fah and Fbc = Ff but I am not getting that.
 

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Firstly, you don't have a truss, because you are missing the diagonals. As a result, you will have bending and shear stresses in the top and bottom chords, so you cannot use the method of joints which pertains to truss members with axial loads only.
Secondly, if you added those diagonals, you could solve for the member forces, but the truss is not symmetrical the way you have drawn it, so you shouldn't expect mirror image forces.
 
I do see what you are saying. Frame analysis would probably be a better fit I believe since joint A, B,C, D, E, F, G, AND N are pin joints but H thru M are moment carrying joints.
 

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