When a structural challenge on a difficult project presents itself and conventional solutions seem inadequate, the design ingenuity in the precast concrete industry responds by creating innovative new systems. This scenario is exemplified in the case of an owner of a proposed mid-rise condominium tower in downtown Minneapolis, Minn., who wanted column-free parking levels to accommodate sufficient vehicle space for planned condominium units. But were column-free parking levels even possible? This article presents the results of the entrepreneurial work of an innovative structural engineer in the precast concrete industry and the conception of the new Prestressed Open Space Truss (POST) system, a solution wherein precast concrete trusses span between exterior columns to produce column-free interiors for owners and residents. The Bookmen Stacks condominium project in Minneapolis was the first application of the new ER-POST, and this article discusses this project as well as a subsequent application of the new truss design in the Cobalt condominiums, also in Minneapolis.
