Denver's totally cast-in-place 312-foot-high Barclay towers is the result of an integrated construction sequence combined with a structural design unusual for a building of its size. Total teamwork on the part of designers and builders was essential to the success of this fast-tracked project designed in 10 weeks, with the 18-month construction period beginning before the design was complete.
While the typical high-rise has interior shear walls and exterior curtain walls, this 32-story concrete tower has no interior shear walls and no curtain walls. The exterior walls are structural as well as architectural. To maximize the amount of valuable interior space, the elevator and stair core of the building were designed only as large as functionally necessary, and not large enough to provide all the lateral stiffness required by the structure. Rather than providing added stiffness still needed with interior shear walls which chop up the interior space, the exterior walls were designed as structural, load-bearing shear walls, thus eliminating any curtain walls. While the construction of these exterior shear walls was comparable in cost to the construction of interior shear walls, eliminating curtain walls saved over 1.1 million dollars.
Architectural as well as structural, the walls were cast with a ribbed exterior surface. The vertical ribs were formed by 1x1-inch rubber strips glued to the inside face of the outside formwork about every 6 inches. The forms were coated with release agent every other floor, giving the building an unintentional striped appearance. This proved acceptable, though, because after construction all the exterior concrete was painted white. The core and exterior shear walls of the building were placed two to three stories ahead of the placing of floor slabs. Neither the building core nor the exterior walls was slipformed; all forms were hoisted by crane from one lift to the next.