# Stability and determinacy

1. Sep 1, 2016

1. The problem statement, all variables and given/known data
from the equation r = n+3 , some notes stated n = number of hinges , while some book stated n as number of joints ...Which is true ?

2. Relevant equations

3. The attempt at a solution
taking the example 3.1 , if it's number of joints , then there are 1 hinge (pin) , right ? I dont really understand the notes on the internet ... What does joints in beam mean ?

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Last edited by a moderator: Sep 1, 2016
2. Sep 1, 2016

### phinds

3. Sep 1, 2016

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4. Sep 1, 2016

i checked it an open the uploaded image ...There's no problem . Perhaps you can refresh your browser and try ?
http://imgur.com/a/IDi0d

5. Sep 2, 2016

### PhanthomJay

in this equation for beam determinancy, r is the number of possible force and moment reactions at the external supports, and n is the number of internal hinges (pins, or joints) that sometimes join 2 members together.

In the example, the left support can support forces in 2 directions, and the other support just a vertical force, so r is 3 , and since there are no internal hinges in between supports, n is 0.

These equations tend to cause confusion so don't dwell on them too much.

6. Sep 2, 2016