INNOVATION March-April 2016

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performance over ‘normal’ buildings, but not in a quantifiable manner. For the next National Building Code, 2020, a committee regarding earthquake design is looking at means to improve and quantify performance of all buildings, using a performance- based design approach. Acceptance of such an approach may be a challenge, due to a possible modest increase in the cost of new buildings—likely less than five percent—to achieve the more resilient designs. Finally, improved public education is important to make the public aware that current code-designed buildings are not ‘earthquake-proof,’ but are designed to generally dissipate earthquake energy by controlled damage (ductility), which results in buildings that are life-safe but may not be occupiable nor useable after the design earthquake. In areas of the world affected by devastating earthquakes, the public is requesting—and in some cases demanding— better earthquake performance for new buildings, as well as an understanding of such performance. New buildings can be designed to be fully functional for a defined earthquake. Designs involving base isolation and supplemental energy dissipation (dampers, replaceable fuses) are proven to achieve such a performance. Furthermore, there are tools for engineers to assess the performance of existing and new buildings, and offer ‘resilience ratings’ readily understood by the public. Such a rating scheme was initiated in the US in late-2015 and could readily be adopted here in BC. John Sherstobitoff, P.Eng., Principal, Seismic & Structures, at Ausenco, Vancouver, has been providing expertise in seismic upgrading in BC for some 26 years. He is currently chair of the Standing Committee on Earthquake Design for the National Building Code of Canada, and chair of subcommittees regarding base isolation, supplementary energy dissipation, and resilience/ performance-based design.

Seismic Upgrading, Performance- based Design and Public Education Three items for improving BC’s resilience and earthquake preparedness are discussed: continued seismic upgrade of high-risk buildings; performance-based design of new buildings; and improved public education regarding building performance, whether new or upgraded. The past 25 years have seen many buildings and a significant amount of infrastructure upgraded in BC—very impressive progress considering no recent history of damaging earthquakes in the region. For example, the Ministry of Education continues its program to upgrade schools using custom, performance-based guidelines to achieve life-safety upgrades of high-risk buildings. A challenge for upgrading public buildings—provincial or municipal—is adequate funding to complete the work in a timely manner. An annual commitment and budget to continually upgrade the highest- risk public buildings in a priority manner, using current performance-based guidelines, is necessary to advance the mitigation. Incentives or mandatory upgrades for high- risk privately owned buildings, such as those recently initiated in San Francisco and Los Angeles, are needed to advance mitigation of this building stock. There is interest and intent worldwide to revise building codes to a performance- based approach that will result in better- performing buildings that will directly contribute to community resilience. For office and residential buildings, current codes achieve ‘life safety’ performance for the design earthquake. However, these buildings may not be occupiable or useable for some time after an earthquake until repairs/replacements are carried out. This is very different from functional use, or continued occupancy, which is necessary for a resilient community. For schools and hospitals, the current codes offer improved

John Sherstobitoff, P.Eng.

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