Designing long-span steel girders by applying displacement control concepts

•A new type of steel girder suitable for covering long spans is proposed.•The shape of the girder is derived through a form-finding procedure.•External prestressed cables act as passive displacement control mechanism. In the present paper a new type of girder, suitable for covering long spans, is introduced. The load resisting mechanism of the system is based on the appropriate shape of the girder which is determined through a form-finding procedure. This optimal geometry is chosen in such a way so that no bending moments appear under external loading. Additional prestressed cables, integrated into the girder, are utilized as a means to limit vertical displacements, thus acting as a passive displacement control mechanism. At the same time, the externally simple supported structural scheme of the girder guarantees that no horizontal reactions are transferred to the columns. An application of this system as the main girder of an open roof structure is used to explain the proposed design method of the girders and to demonstrate the effectiveness of the system in covering long spans.