I came across a very interesting document the other day, called the Tall Building Safety Strategy.
This report is part of a larger project, called Tall Buildings in San Francisco:
The San Francisco Tall Buildings Study is the first study in the nation to look at the impact of earthquakes on a large group of buildings higher than 240 feet. The resulting report will characterize the issues and available information; propose regulatory and procedural recommendations where appropriate; and identify areas where future studies would be helpful.
The San Francisco Office of Resilience and Capital Planning under City Administrator Naomi Kelly is working with the Applied Technology Council (ATC) to conduct the Study. ATC is a non-profit organization with a mission to develop and promote state-of-the-art, user-friendly engineering resources and applications for use in hazard mitigation. A panel including the City Administrator, Department of Building Inspection, Department of Emergency Management, and the San Francisco Public Utilities Commission is overseeing the various work products. In addition, a broad group of tall building stakeholders and experts will meet several times during the study to provide additional feedback and review.
This is kind of new ground. As the report observes, there are a lot of topics here that haven't received much discussion.
Partly this is because the West Coast is different. New York City doesn't have earthquakes. Nor does Chicago, or Atlanta, or Houston, etc.
And, until very recently, people on the West Coast chose to spread out, rather then to increase urban density. Even in my childhood, when we moved to Los Angeles in 1970, the L.A. City Hall had until very recently been the tallest building on the West Coast.
But it's all different now. Urban density is racing upward, as people on the West Coast finally have come to understand the downsides of urban sprawl. From San Diego and Los Angeles, to San Jose and San Francisco, and all the way to Seattle and Vancouver, the West Coast's modern urban centers are being built much more along the lines of Manhattan, with extremely dense urban cores and an anticipation that these cores will not be just places of work, to which people commute to and from the suburbs, but centers of urban living.
And so the Tall Buildings Safety Strategy report poses some extremely challenging questions, for example:
Studies conducted in this project estimate that for a tall building designed to current standards, it might take two to six months to mobilize for and repair damage from a major earthquake, depending on the building location, geologic conditions, and the structural and foundation systems. Long downtimes in tall buildings can have disproportionate harmful effects on residents and businesses in San Francisco. By the City’s tentative recovery goals, even three months of downtime is unacceptably long for major employers and other recovery-critical uses.
The San Francisco Fire Department (SFFD) and the Department of Emergency Management (DEM) should coordinate a study to evaluate the adequacy of automatic fire suppression and occupant evacuation systems in tall buildings for conditions following a significant earthquake. The study should be coordinated with other City departments and within the broader context of the San Francisco Emergency Response Plan to evaluate whether (1) the in-building secondary water supply for automatic fire suppression in tall buildings is sufficient to inhibit fire spread and allow safe evacuation, and (2) the building code provisions that rely on elevators for evacuation during a fire emergency will be effective following an earthquake.
Cordons or barricades are often needed to protect the areas around a damaged building. The cordoned area is generally based on the perceived level of damage and the risks posed by potential aftershocks, wind loading, time-dependent creep effects, or other factors. While cordons may be required around buildings of any height, the disruptive implications of current generic guidance for cordon distance increase dramatically with building height, potentially leading to unnecessary closure of neighboring buildings and infrastructure.
As described in the project report, the 240-foot height criterion for the initial database was somewhat arbitrary. To the extent that the San Francisco Building Code imposes elevator, fire safety, and other requirements on high-rise buildings defined as those taller than 75 feet, it would be useful to expand the database to include at least all buildings above this height.
Yes, yes, yes, and yes.
This is really complicated stuff, and it isn't going to be easy to address.
It's really fascinating to see that the City of San Francisco is targeting these problems head-on, or at least openly admitting that they exist.
Hopefully other major West Coast cities are doing the same thing, or are at least closely following this work in order to benefit from it and incorporate it into their own plans.
One day, there will be a mag-8 earthquake somewhere on the populated region of the West Coast; perhaps it will even happen during my lifetime.
I sure hope we are prepared, taking the proper time during these (relatively) easy times to prepare for what will, someday, happen.
As the ant said to the grasshopper...