Leadership in Engineering
Performance-Based Seismic Design
Performance-based seismic design (PBSD) of high-rise buildings is a new methodology recently pioneered by MKA that is transforming the structural design of tall buildings in regions of high seismicity. Simply put, PBSD uses advanced design methods that meet the intent and performance objectives of the Building Code without relying on Code-prescriptive design provisions. Performance-based design itself is not new, but MKA’s application to high-rise buildings is cutting edge. To date, the firm has designed 67 PBSD structures--multiples more than any other engineer in the world. The two towers of One Rincon Hill in San Francisco (shown above) were both designed by MKA using PBSD methodology.
MKA’s PBSD approach eliminates the need for a backup perimeter moment frame traditionally required by Code for buildings over 240 feet tall. The frame limits views, prohibits balconies, disrupts space planning, and increases cost (examples above, left and middle). MKA’s PBSD system (example above, right), reduces construction challenges, increases space planning and architectural freedom, and provides a more efficient and reliable building.
Structural design criteria developed by MKA served as the basis for portions of the PBSD guidelines developed by the Pacific Earthquake Engineering Research Center (PEER), the City of San Francisco Administrative Bulletin AB-083 on tall building design, and the Los Angeles Tall Buildings Structural Design Council.
Using PBSD methodology, MKA engineers carefully analyze the modeled building performance then specify elements of strength and stiffness exactly where they are needed and eliminate them where they are not, to more precisely allocate load-resisting structural elements.
Through application of powerfully sophisticated nonlinear time history analysis—practical only recently due to advancements in computer systems and programs—MKA engineers can more reliably and directly predict building response during a maximum ground shaking event. The structure’s design is then “tuned” and optimized to respond in the most efficient way possible.
In addition to analytic advancements, MKA led the development of improved construction details through laboratory testing of full-scale building subassemblies, including floor-slab connection details (pictured, top right) and more constructable concrete coupling beams. This has enhanced the industry’s understanding of building element response under varying earthquake demand levels.
