On Design of Joint Positions for Minimum Mass 3D Frames

An iterative procedure for determining the joint positions and dimensions of cross-sections corresponding to a minimum mass space frame is presented. Stress constraints, displacement constraints and side constraints are taken into account, with the possibility for linking of the design variables, which in addition to the joint positions are the beam dimensions.

The frame is assumed to carry consecutively a number of different systems of loads, including temperature loads and weights. The stressed state analysis includes tension, bending, shear and torsion 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 analytical expressions for the gradients are derived. Illustrative medium scale problems are presented.