58 Introduction to Optimization
Figure 1.27 Scaffolding system.Figure 1.28 Power screw.(h), and screw length(s)as design variables. Consider the following constraints in the
formulation:
1.The screw should be self-locking [1.117].
2.The shear stress in the screw should not exceed the yield strength of the material in
shear. Assume the shear strength in shear (according to distortion energy theory), to
be 0. 577 σy, whereσyis the yield strength of the material.
3.The bearing stress in the threads should not exceed the yield strength of the material,
σy.
4.The critical buckling load of the screw should be less than the applied load,F.1.28 (a)A simply supported beam of hollow rectangular section is to be designed for mini-
mum weight to carry a vertical loadFyand an axial loadPas shown in Fig. 1.29.
The deflection of the beam in theydirection under the self-weight andFyshould