ON DESIGN OF JOINT POSITIONS FOR MINIMUM MASS 3D FRAMES

An iterative procedure for determining the joint positions and dimensi ons of cross-sections corresponding to a minimum mass space frame is p resented. Stress constraints, displacement constraints and side constr aints are taken into account, with the possibility for linking of the design variables, which in addition to the joint positions are the bea m dimensions. The frame is assumed to carry consecutively a number of different systems of loads, including temperature loads and weights. T he stressed state analysis includes tension, bending, shear and torsio n of the beam elements. The optimization iteration includes a sequence of quadratic programming problems with the possibility of move-limits . Only ''nearby'' constraints (active strategy) are considered, and an alytical expressions for the gradients are derived. Illustrative mediu m scale problems are presented.