5.3: Determinacy and Stability of Trusses

The conditions of determinacy, indeterminacy, and instability of trusses can be stated as follows: \[\begin{array}{l}
m+r<2 j \quad \text { structure is statically unstable } \\
m+r=2 j \quad \text { structure is determinate } \\
m+r>2 j \quad \text { structure is indeterminate }
\end{array}\]

where

\(m =\) number of members.

\(r =\) number of support reactions.

\(j =\) number of joints.

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