| This huge greenhouse structure in Niagara Falls is the focal point of a pedestrian mall in an 83-acre downtown urban renewal project. Withstanding natural forces was a critical area of concern for the Wintergarden, with problems such as wind pressure, snow loads and variation in temperature. The wind pressure problem was accentuated by the desire to keep parts of the wall open in summer. Computer analysis predicted that the glass curtain wall would move 1.5 inches vertically due to various loadings. To allow for live load, wind load, and thermal effect, DeSimone designed the 100-foot-high latticed steel frame to be laterally supported on 20 reinforced concrete columns, of which 5 (in the highest part of the structure) are 58 feet high. By vertically post-tensioning the columns, lateral deflections were reduced from 4 inches to less than 1 inch. The 4 rows of columns with pin connections support 5 transverse trusses 36 feet on center. The continuous trusses cantilever 14 feet on each end so that no columns had to be placed around the periphery of the greenhouse space to mar its lightness and transparency. 12 longitudinal trusses between the transverse trusses also cantilever at the ends, and are further braced by custom-designed joists. The exterior glass wall was hung from the cantilevered trusses with an expansion joint at the mezzanine level to allow free vertical movement. The vertical mullion support trusses, some as high as 80 feet, were thus hung from the roof trusses. To keep the lower ends from buckling, DeSimone added lateral support by installing trusses at the mezzanine level that formed rigid frames. Special steel details were developed by DeSimone to create jewel-like elegant connections. |
