On a Quest to Improve Concrete Construction in Seismic Zones
ENR 9/26-10/3/16 p. 30
Earthquake engineer pioneered the use of high-strength steel fiber as a much-needed rebar decongestant in shear-wall link beams.
If he hadn’t taken a job in a Seattle design office after college, seismic structural engineer Cary Kopczynski would have gone into construction, like his father.
Growing up in Spokane, Wash., the 65-year-old engineer spent summers in high school and college working as a laborer. “It gave me a good appreciation of what happens in the field,” says Kopczynski, senior principal and CEO of the 30-year-old Bellevue, Wash., firm that bears his name.
To this day, Kopczynski dons a virtual hardhat when designing a structure. “I always begin by thinking of available materials and equipment and the builder’s needs,” he says.
The focus on constructibility, backed up by a willingness to take calculated risks, is improving concrete construction in the earthquake-prone Northwest. Most recently, Kopczynski pioneered the use of steel-fiber-reinforced concrete (SFRC) link beams—headers that connect shear-wall elements—to reduce reinforcing-steel congestion. Batch-plant-mixed SFRC slashes link-beam rebar by about 40%, eliminates difficult diagonal bars and reduces the sizes of remaining bars.
On the two 450-ft-tall towers of the Lincoln Square Expansion in Bellevue, SFRC link beams are credited with maintaining the schedule. “Cary’s work is changing the way we build concrete structures,” says Brian Caudle, assistant superintendent for GLY Construction, LSE’s general contractor.
SFRC link beams are not yet in the code. Consequently, for the four towers in the Seattle area with SFRC link beams, Cary Kopczynski & Co. had to do performance-based seismic design to get a nod from building officials. “Working with the design community, code officials, universities and building owners, Cary’s team led the charge to introduce SFRC into mainstream construction in our market,” says Caudle.
SFRC is not the engineer’s first rebar decongestant. About a decade ago, he pioneered use of high-strength rebar—100 ksi, instead of 60 ksi—as seismic confinement in columns in a 31-story residential tower in Seattle. The rebar sped construction of the column-beam connection by 25%.
Kopczynski is still working toward making structural SFRC routine. Toward that end, he recently helped to get funding, mostly from the Charles Pankow Foundation, for link-beam tests on different fiber doses from different suppliers. The tests will help to create a performance specification, he says.
“Cary was the first practicing engineer who believed in these ideas,” says Gustavo J. Parra-Montesinos, an engineering professor at the University of Wisconsin and lead investigator for the Pankow research. “He was willing to take the risk to implement [earlier] research into a high-rise structure.”
Beyond link beams, Kopczynski wants to see SFRC shear walls. He is also pushing ever-higher-strength concrete and high-strength welded-wire reinforcement. “Concrete’s potential is enormous,” he says.