Stability Design of the Bow String Trusses of the Virginia Beach Convention Center

Exemplifying the integration of architectural and structural form, the Virginia Beach Convention Center is defined by a striking 80’ (24 m) tall glass curtain wall at the entry to the Prefunction Hall. The window wall is inclined and subtly curved along its height to suggest the billowed profile of a ship’s sail in wind, and is supported by vertically spanning, lens shaped bow-string trusses which act as cablestayed masts. The bow string trusses consist of an 8” (200 mm) diameter double extra strong pipe compression chord flanked on each side by 1 5/8” (40 mm) stressed steel cables acting as tension ties. The compression chord is extremely slender when considering its height between its pin-ended support points. This central spine relies upon the adjacent cables in tension to maintain its stability. Under lateral loads, the bow string truss central spine develops destabilizing axial compression while the cable tie develops stabilizing axial tension. Essentially, the individual bow string trusses are self-stabilizing mechanisms; the compression chord’s tendency to buckle is resisted by the cable’s tensile stabilization forces. Rigid cruciform arms act to link these balancing mechanisms, and therefore serve as brace points along the height of the compression spine. The system maintains a visual ‘lightness’ as its stability does not rely upon direct member connectivity between compression chords. This paper describes the design of the bow string truss system supporting the curtain wall, with emphasis on the stability design of the individual trusses and of the overall system. Analytical methods which account for the geometrically nonlinear load-deformation relationship of the structure are described, as well as the means by which to account for the variation in stiffness of the compression chord as a function of stress level.