Linkage-based movable bridges: Design methodology and three novel forms

Linkages have been widely used in machines and deployable structures, but these mechanisms have rarely been employed in the design of movable bridges. This paper explores the use of linkages both to actuate the kinematic motion and to serve as structural elements of movable bridges. First, the design methodology for these forms is presented which includes (1) physical shape-finding to develop a conceptual design, (2) generation of a parametric model and kinematic equations, and (3) multi-objective structural optimization for minimum self-weight and minimum force for operation. This optimization procedure includes shape optimization to determine the lengths and relative angles of members and sizing optimization to design the section profiles of members to meet the specifications of current American bridge design code. Heuristic algorithms, including descent local search and multi-objective simulated annealing, are employed. Three novel linkage-based forms, featuring 38 m movable spans, that were designed using this methodology are presented. This research suggests the beginning of an investigation into alternative forms for movable bridges using linkages.