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SolverHowto

# SolverHowto - Example Problem Description Consider the...

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Example Problem Description Consider the minimum weight design of the four bar truss shown in Figure 1. For the sake of simplicity we assume that members 1 through 3 have the same area A 1 and member 4 has an area A 2 . The constraints are limits on the stresses in the members and on the vertical displacement at the right end of the truss. Under the specified loading the member forces and the vertical displacement δ at the end are found to be We assume the allowable stresses in tension and compression to be 8.74 x 10 -4 E and 4.83 x 10 -4 E, respectively, and limit the displacement to be no greater than 3 x 10 -3 l . The minimum weight design subject to stress and displacement constraints can be formulated in terms of nondimensional design variables Figure 1. Four bar statically determinate truss. . 3 3 6 , 3 2 , 4 , , 5 2 1 4 3 2 1 + = - = = - = = A A E pl p f p f p f p f d . 0 17 . 7 , 0 73 . 5 , 0 3 6 18 3 3 3 , 10 , 10 2 3 1 2 2 1 1 2 1 2 3 2 1 3 1 - = - = - - = + = = = - - x g x g x x g to subject x x OBJ Minimize p E A x p E A x A 1 A 1 A 2 2P P 1 2 3 4 l l 3 l A 1 Member

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