First Tornado Safety Building Standard Released
At the beginning of the month, the American Society of Civil Engineers announced the release of its newly updated ASCE/SEI 7-22 with the goal of better protecting infrastructure from tornado damage.
According to ASCE, the Minimum Design Loads and Associated Criteria for Buildings and Other Structures standard is the Society’s most widely used professional standard and a critical tool in a civil engineer’s commitment to protecting the health, safety and welfare of the public.
“ASCE 7 is essential to the profession,” said J.G. (Greg) Soules, Ph.D., P.E., S.E., P.Eng, F.SEI, F.ASCE, Senior Principal Structural Engineer for CB&I and Vice Chair of the ASCE 7-22 Committee. “And it all has to do with the safety of the public. That’s our driving focus.”
Reported to be the first of its kind in the world, the new ASCE standard offers guidance to protect buildings from tornadoes ranking from 0 to 2 on the Enhanced Fujita Scale, which translates to winds ranging from 40 mph at the bottom of EF0 to 157 mph at the top of EF2.
The new standard arrives just weeks after twisters riddled the Midwest, leaving thousands without homes and 77 dead. Research posted by U.S. Tornadoes suggests that approximately 80% of tornadoes in the nation rate between EF0 to EF1 strength, while the tornado that struck Kentucky was reported to rank anywhere between an EF3 and an EF5.
“Tornadoes previously were beyond the probabilities we normally design for,” said Soules, who has been working on the ASCE 7 Committee for 25 years. “But more study was done, and we found that tornadoes were undercounted to the point where they should now be considered.
“We’re not designing tornado shelters with ASCE 7; we’re simply designing for somewhat higher wind loads in certain regions of the country. But it is important to do.”
In superseding the ASCE/SEI 7-16 standard, the new edition also provides up-to-date and coordinated loading provisions for general structural design for all hazards including dead, live, soil, flood, tsunami, snow, rain, atmospheric ice, seismic, wind and fire, as well as how to evaluate load combinations.
The new provisions, the Society reports, are not meant for residential construction, but rather for critical infrastructure such as hospitals and fire stations. In gathering data to provide the update, the committee reportedly drew on new models for more accurate snow load and developed a new multipoint seismic spectrum for certain soft-soil sites.
Due to the infancy of the research, storms ranked EF3 or higher were not included in the newly published guidelines. However, once more research is complete, Don Scott, the chair of the ASCE-7 Wind Load subcommittee, told reporters that more severe storms could be accounted for.
“These are first in the world standards for tornado design, and the research will continue and be able to expand them and clarify them in the future,” Scott said.
According to the new updated standards, new recommendations include making windows impact-resistant, establishing continuous load paths and replacing toenail trusses with steel clips, among others.
“Every six years, hundreds of volunteer professional civil and structural engineers, researchers, building officials, and construction professionals collaborate to update the standard, acknowledging new engineering research, evolving construction techniques, and society’s changing expectations and concerns,” said Ronald Hamburger, P.E., S.E., F.SEI, senior principal with Simpson Gumpertz & Heger Inc. and chair of the ASCE 7-22 Committee.
Additionally, the ASCE 7-22 now requires use of digital data uniquely identified in hazard-specific geodatabases for all environmental hazards. The digital data is available via open access from the ASCE 7 Hazard Tool while a print version is available as a two-volume paperback set or as a PDF.
In 2022, the standard is slated to go up for consideration to be entered into Chapter 16 of the 2024 International Building Code.
Additional Safety Standards
Earlier this year, in June, ASCE released a new manual of practice, reporting that the document will give civil engineers the tools to design, plan and build more resiliently, more consistently.
Specifically, Hazard-Resilient Infrastructure: Analysis and Design, MOP 144, provides guidance and an underlying framework for designing new infrastructure systems with consistency across hazards, systems and sectors.
The new manual is sponsored by the ASCE Infrastructure Resilience Division and was edited by Bilal M. Ayyub, Ph.D., P.E., Dist.M.ASCE. Ayyub is also noted to serve as the director of the Center for Technology and Systems Management of the Department of Civil and Environmental Engineering at the University of Maryland.
Throughout the manual, readers are walked through how to identify and analyze hazards, system failures, the economics of resilience, and technologies for enhancing new and existing infrastructure through probabilistic methods for risk analysis and management of infrastructure projects.
More recently, this month, the Seattle City Councilmembers announced that they were planning to address over 1,100 unreinforced masonry buildings in the city in need of seismic retrofitting, most of which were built before 1945.
At the beginning of December, one of North America’s most active fault lines experienced a slew of more than 40 earthquakes, ranging between magnitudes of 3.5 to 5.8. While the seismic activity was reported to only affect an over 200-mile-long Oregon coast in Newport, the event heightened the level of concern of millions in the region regarding safety and future instances.
Just a few weeks before the onslaught of seismic activity, The Seattle Times noted on Oregon’s efforts to outfit its schools for seismic safety while simultaneously calling out Washington for its vulnerability to potential earthquakes and tsunamis.
Moving forward, Seattle City Councilmembers hope to develop new standards surrounding seismic retrofits, a way to properly identify and categorize the buildings most at risk, coordination across city departments to streamline the process, and eventually, draft legislation that codifies mandatory URM retrofit requirements.
In October, state lawmakers in Oregon passed new legislation outlining fire-safe building codes, in addition to the development and maintenance of a comprehensive statewide map of wildfire risk.
Sponsored by the Committee on Natural Resources and Wildlife Recovery (at the request of Governor Kate Brown), the $200 million wildfire bill mandates the use of fire-resistant materials in new construction.
While the bill aims to better protect property owners from future destruction, it does not come without backlash. This is mostly in part to the legislation having to define a “wildland-urban interface,” where residential areas meet forests and rangelands. Due to these new restrictions, critics from real estate, construction and agricultural industries voiced concerns over whether the bill would increase costs for property owners, homebuilders and farmers and infringe on private property rights.
To mitigate the concerns, opponents of the new building codes have been placed on advisory committees as to better define these new interfaces. Some of members of the committee include Mark Long, CEO of the Oregon Home Builders Association, and Dave Hunnicutt, President of the Oregon Property Owners Association.
While those areas are being outlined, another program—backed with $11 million in funding from the legislation—has already been launched to clear flammable brush from “home ignition zones.”