Design Optimization of Connections in Large Radio Telescopes

May 30, 2006
Publication: Optomechanical Technologies for Astronomy, SPIE Proceedings v 6273 p 627313

Abstract: Optimization programs are used routinely in the design of precision structures such as radio telescopes, but design optimization is merely the beginning, rather than the end, of the process. After selecting appropriate member sizes for the optimized solution, careful attention must be paid to the design of the connections to ensure that the effective stiffness of a given member matches that of the optimized design. Given that members rarely span directly to their working points, the effective stiffness of a member is actually a combination of the member cross-section stiffness and the stiffness of the connections at each end. This paper describes the procedure used for the design of a large radio telescope with tubular members and bayonet style connections. Initially, a parametric study was performed to establish gusset plate thicknesses and widths for various tube cross-sections so that the resulting tube/gusset subassembly would match the stiffness of the tubing; the results of this study provided a starting point for designing the connections. Following optimization and member selection for the overall structure, detailed finite element models were constructed for selected connections to assess the effective stiffness of each member framing into these connections. The overall goal was to hold the effective stiffnesses to within a given tolerance. This was accomplished by adjusting plate thicknesses, plate widths, tube-to-plate engagement lengths, and, in a few cases, actually changing the member crosssection to compensate for excessive stiffness or softness at a given connection.