# Stability and determinacy

## Homework Statement

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 ?

## 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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phinds
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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

PhanthomJay
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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.

• 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.
although there's pin and roller , but there's only 1 member ( not joining 2 members together) , so n = 0 ?

PhanthomJay
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