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What is this "1" in this stiffness matrix?

http://www.annualreviews.org/article/suppl/10.1146/annurev.earth.35.031306.140104?file=ea.35.rayfield.pdf

$$K_e= \frac{E^e A^e 1}{L^e} \begin{bmatrix}1&-1\\1&-1\end{bmatrix}$$

eq. 6, p. 2.

Typo or some kind of indicator perhaps? I don't see it significant, because even without it, it expresses the system of eqs 3 and 4.

mavavilj
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1 Answers1

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I think so yes, the $E^eA^e1=E^eA^e$. But, I found another mistake. The matrix should be \begin{bmatrix} 1 &-1\\ -1 & 1 \end{bmatrix} Your $2^{\mathrm{nd}}$ equation has $-1$ with $u_1$.

Abhinav Jha
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  • I thought this was a matter of convention, since if one considers the total force, i.e. F1+F2, then one can reorder the terms. – mavavilj Aug 20 '20 at 06:59