How to Calculate Reactions and Forces in a Pin Jointed Frame?

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Discussion Overview

The discussion revolves around calculating reactions and forces in a pin-jointed frame, focusing on static equilibrium in a two-dimensional context. Participants are seeking methods and guidance for solving a specific homework problem involving structural analysis.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Technical explanation

Main Points Raised

  • One participant presents a homework problem involving a pin-jointed frame and expresses uncertainty about calculating reactions and member forces.
  • Another participant inquires about the number of static equilibrium equations applicable to two-dimensional scenarios.
  • Some participants suggest that the equations of static equilibrium include the sum of vertical forces and the sum of horizontal forces.
  • There is a reminder from one participant that the sum of moments must also equal zero, indicating a third equation of equilibrium.
  • A participant mentions having calculated one reaction (VA as 10) but struggles with additional unknowns, indicating a potential issue with the equations set up.
  • Another participant points out that the third equation of equilibrium is being overlooked, suggesting a need for a more comprehensive approach.

Areas of Agreement / Disagreement

Participants generally agree on the necessity of using multiple equations of equilibrium, but there is no consensus on the specific values or methods for solving the problem, as some participants express confusion and differing levels of understanding.

Contextual Notes

Participants have not fully resolved the mathematical steps required to calculate the reactions and forces, and there are indications of missing assumptions or dependencies on specific definitions related to the problem.

warrio1010
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Homework Statement
[PLAIN]http://img847.imageshack.us/img847/1704/pinjointed.png
Calculate the reactions at A and E and the forces in all members.

The attempt at a solution

At a loss regarding the reactions, tried equating vertical and horizontal.
As for the members I guess its just a case of working from the reaction values and using sin and cos but also can't get my head around this.

Any methods/pushes in the right direction much appreciated.
 
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In 2-dimensional work, as this one is, how many equations are there of static equilibrium? And what are they?
 
sum of v=0 and sum of horiz=0
?
 
Don't forget the sum of the moments = 0.
 
I have VA as 10 but can't work out the other two, the equation would suggest that HE-HA+5=0 which leaves two unknowns so I'm stuck with that.
 
You are forgetting about the 3rd equation of equilibrium alluded to in the prior responses.
 

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