In Plain View

by Robin Wendler, Struct. Engr. and Managing Prin.; ZFA Struct. Engrs., Santa Rosa, CA,

Serial Information: Civil Engineering—ASCE, 2000, Vol. 70, Issue 12, Pg. A10-A16

Document Type: Feature article


(Available only in Special Structural Issue) A structural engineer's work is typically hidden beneath layers of concrete and plaster, but the Pittsburgh Civic Center in the eastern part of California's Bay Area exhibits its skeleton and circulatory system for all to see. The three-story, 70,000 sq ft (6,503 m²) civic center features a unique glass and steel design. The vaulted main roof over the third floor, designed to reflect local steel mill architecture, rises 25 ft (8 m) to the ridge, with steel gable trusses spanning 43 ft (13 m) and a continuous clerestory over the ridge. The entire building gently curves in semicircular fashion around the center lobby, with a plan radius of about 300 ft (91 m) and an arc of more than 90 degrees. Each floor steps back from the inside curve of the floor below and aligns on the outside curve. These stepped areas are used to create light wells and exterior roof decks and walkways. On the inside curve, the lobby is open to the roof of the third floor and has stepping glass roof and walls leading from the one-story entry height to the 56 ft (17 m) tall ridge. On the outside curve, each floor has a cantilevered exterior walkway deck. In addition, the building ends are stepped back at each floor, providing additional roof deck area and space for mechanical ductwork. Fire protection of the exposed steel was a concern, especially in the city council chambers assembly room on the third floor, where large groups of people are expected to gather. To accommodate both safety and aesthetics, intumescent paint (a thin, fire-resistive coating) was used in lieu of the unsightly fireproofing spray that would traditionally be hidden by walls.

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