Chapter 1, Problem 24E

The 2D truss shown in the figure is assembled to build the global matrix equation. Before applying boundary conditions, the dimension of the global stiffness matrix is $8\times 8$. Write (row, column) indices of locations corresponding to nonzero DOFs of the stiffness matrix, such as $\left(1,1\right)$, $\left(1,2\right)$, and so forth. The order of global DOFs is $\left\{Q\right\}={\left\{u_1,v_1,u_2,v_2,u_3,v_3,u_4,v_4\right\}}^T$. Since the stiffness matrix is symmetric, only write its upper-right portion.