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Cast-in-Place Structures

Photo by Nic Lehoux
Most of the concrete structural elements at the Vancouver Community Library are exposed.

Vancouver Community Library

Location: Vancouver

Owner/developer: City of Vancouver

Project team: Howard S. Wright, general contractor; Miller Hull Partnership, architect; Kramer Gehlen & Associates, structural engineer; Whitaker Ellis, concrete contractor; CalPortland, ready-mix supplier

The Vancouver Community Library, which opened last summer, is the cornerstone of a planned four-block 600,000-square-foot mixed-use development.

The 80,000-square-foot, five-story building has to carry larger loads than a normal office building. The post-tensioned slabs and roof are supported by two core walls at each end and additional columns.

Most of the structural concrete elements are exposed and required a great deal of care when handling and installing forms.

To ensure proper rebar encapsulation, a pea gravel mix with plasticizers was used in conjunction with external vibration for a smooth finish on the double-skinned medium-density overlay forms. For large parts of most of the floors, the ceilings are the exposed undersides of the post-tensioned slabs, so extra care was taken with the shoring panels to produce a nice finish on the bottom side.

The centerpiece of the library’s nearly 200-foot-long, four-story atrium is a sculptural cast-in-place concrete stairway. It is tied into the post-tensioned decks and into the acid-stained topping slab that make up the landings on the each floor.

The engineers had the contractor keep the shoring under each flight of stairs and landings for 60 days to ensure the stairways wouldn’t twist.

Carefully sized overhangs were incorporated into the design to help control heat gain and glare. The overhang for the top floor is cantilevered concrete, and since all the walls under it were exposed concrete, the contractor could not anchor shoring to them. So the segment was shored from grade using 65-foot-high towers.

In all, the library consumed over 6,000 cubic yards in various mixes.

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