Design the support members AB and CD for the platform lift shown in Figure P5-61. Select a mild steel and choose suitable cross-sectional shapes with no more than a 4 : 1 ratio of moments of inertia between the two principal directions of the cross section. You may choose two different cross sections to make up each arm to reduce weight. The actual structure has four support arms, but the loads shown are for one side of the platform with the two arms shown. The loads shown are under operating conditions. Use a factor of safety of 2 for human safety. In developing the finite element model, remove the platform and replace it with statically equivalent loads at the joints at B and D. Use truss elements or beam elements with low bending stiffness to model the arms from B to D, the intermediate connection E to F, and the hydraulic actuator. The allowable stresses are 0.60Sy in bending and 0.60Sy in tension. Check buckling using either Euler's method or Johnson's method as appropriate. Also check maximum deflections. Any deflection greater than 1/360 of the length of member AB is considered too large.

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-30 30- -72- 32- Dimensions are in inches 30 600 lb 800 lb 600 lb 24 30 45° B.