Tower 12, named after the Seattle Seahawks ‘12th Man’, is a 34-story residential tower at 2nd Avenue and Virginia Street in downtown Seattle. Located two blocks from the Pike Place Market, the project is bounded by Cristalla to the north and One Pacific Tower to the west, both of which CKC served as the structural engineer for.
The Tower 12 structure is being constructed of cast-in-place concrete with post-tensioned floor slabs. CKC designed a unique shear wall core to enhance seismic system ductility, improving seismic performance without compromising buildability. Further, outrigger beams off the core eliminated internal columns, which resulted in increased core dead load and improved seismic performance.
Lower level gravity columns utilizes 14,000 psi concrete, which drops in strength at upper levels. This allows standardization of column sizes full height, reducing structural frame cost. Also, high-strength ASTM A706 Grade 80 reinforcing bar was specified in moment frame columns and shear wall boundary elements, which reduces congestion and improves constructability.
The project broke ground in early 2015 and is expected to finish in 2017.