Though its structural designs are often firsts, Magnusson Klemencic Associates has had relatively little difficulty convincing building officials in seismic Seattle that its performance-based skyscraper frames meet the objective of the prescriptive code. Sources credit the engineer and the buildings department for that.
MKA is “certainly a leader” in this area and “Seattle does a very good job managing the process,” says Joe Maffei, a principal with San Francisco-based Rutherford & Chekene, which reviewed Seattle’s two MKA “performance” projects.
|Braced. Skyscraper is first in U.S. with buckling-restrained braces. (Image courtesy of Magnusson Klemencic Associates)|
The most recent review was for the 42-story WaMu Center, nearing completion. The job is an example of a successful process, even for a design called “very much on the leading edge” by local building officials. WaMu’s lateral system joins a ductile core wall, buckling-restrained braces that act as a seismic fuse to stabilize the core, and concrete-filled pipe columns. MKA claims it is the only tall building in North America with BRBs.
For WaMu, MKA early on gave the city a heads up. That is imperative for a smooth approval process, says Jon Siu, principal engineer in Seattle’s Dept. of Planning & Development.
Siu suggests making contact six to nine months prior to applying for a permit. If the process begins during schematic design, structural adjustments can be made before the architecture is set.
Seattle building officials view peer review as a way to improve their plan check process. Peer review for a standard shear-wall-only building, taller than 240 ft, can cost the owner less than $50,000. Review of WaMu cost about $70,000.
It is worthwhile to invest the time and effort to get a really competent peer reviewer, says Siu. And it is “really important” to have confidence in both the design engineer and the reviewer, he adds.
It is also crucial to begin the peer review by negotiating criteria to evaluate the structure. If it is the second time around for the reviewer and the design engineer, the process can take one to six months. If there is a new reviewer or new complexity with the design, it can take nine months, says Siu.
Other advice to building officials: Stay involved in the process, mediate differences when necessary and foster a collaborative effort.
Even before alerting the city buildings department about WaMu, MKA approached its client, architect NBBJ, and built its case for performance design (PD). The architect asked MKA for a comparison of conventional permitting and permitting using PD. That was necessary to compare risks associated with possible plan approval and permitting delays against rewards of a better building, says David Yuan, NBBJ’s project manager.
For both the architect and the developer, the decision to proceed also was based on the relationship with the engineer. “I would not have trusted someone other than MKA,” says Matt Griffin, managing partner of Pine Street Group LLC, which is developing the project with Seneca Real Estate Group, both Seattle. He points to a longtime working relationship with MKA President Ron Klemencic. “The stakes were very high if we were delayed…,” he says. “Ron’s a risk-taker but not a fool.”
Griffin says that PD is not for every project. “I would do it again with a top-notch engineer like MKA on a very complicated high-rise structure, not for a three-story building in suburbia,” he says.