Bellevue engineering firm Cary Kopczynski & Company has received an award from the Post-Tensioning Institute for work on the Cosmopolitan in Seattle.

The Cosmopolitan tower boasts a wide-open design thanks to post-tensioning. A concrete shear wall core, wrapped by a 6-foot-wide thickened drop-head slab on three sides, allows 8-inch-thick post-tensioned slabs to span almost 40 feet from the core to the building’s perimeter, eliminating interior columns.

High-strength concrete eliminated the need for ductile frames while also minimizing wall size and maximizing views. Mechanical ductwork, water supply lines and most building utilities were run through the post-tensioned slabs, allowing for open ceilings in the residential units.

Other project team members include Mithun (architects), Morteson (contractor) and Central Steel (post-tensioning supplier).

Kopczynski’s award came in the Residential Buildings category.ww