OCTOBER 29, 2020

Eastern Time: 2:00PM

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Design of Storm Shelters and Safe Rooms: An Overview

(including Significant Changes Coming in the 2020 edition of the ICC 500 Storm Shelter Standard)

Marc L. Levitan, National Institute of Standards and Technology

This presentation will provide an introduction to the design of hurricane and tornado shelters and safe rooms, along with code and standard requirements for storm shelters. It will focus primarily on wind engineering aspects and design criteria for the full range of extreme windstorm hazards, including wind pressures, windborne missiles, and other debris hazards, followed by highlights of significant changes coming in the new edition of the storm shelter standard to be published late this year.

Design requirements for hurricane and tornado shelters are governed by the ICC 500 Standard for the Design and Construction of Storm Shelters, promulgated by the International Code Council (ICC).  First published in 2008, this standard built upon an earlier industry standard from the National Storm Shelter Association (NSSA) and safe room guidance from the Federal Emergency Management Agency (FEMA).  The wind loading provisions and windborne debris impact criteria of ICC 500 go far beyond the requirements for Risk Category IV facilities provided in the American Society of Civil Engineers ASCE 7 Standard on Minimum Design Loads for Buildings and Other Structures and in the International Building Code.  The ICC 500 standard also addresses associated windstorm hazards such as loads due to atmospheric pressure change in tornadoes, roof loads due to extreme rain and debris, and hydrodynamic loads associated with storm surge and inland flooding. Many thousands of storm shelters and safe rooms have been constructed in the US over the past two decades, including a large number that have been impacted by hurricanes and tornadoes.  To date, there have been no reported failures of storm shelters or safe rooms built to ICC 500 or the similar FEMA P-361 criteria, respectively.

Publication of the next edition of the ICC 500 standard is anticipated by December of 2020.  A number of significant changes have been incorporated in this 3rd edition of the standard.  Key improvements to wind-related provisions include: new load combinations; explicit consideration of impact loads from laydown and falling debris hazards; and a new 10,000-year mean recurrence interval hurricane shelter design wind speed map, with increased speeds in some locations along the Gulf of Mexico coast.

About the speaker:

Marc L. Levitan, Ph.D., is the Lead Research Engineer for the National Windstorm Impact Reduction Program (NWIRP) at the National Institute of Standards and Technology (NIST).  He served as lead investigator for the National Construction Safety Team technical investigation of the 2011 EF-5 tornado in Joplin Missouri and the NIST study of the 2013 EF-5 tornado in Moore Oklahoma.  Dr. Levitan also leads implementation efforts for many of the recommendations resulting from these investigations, in the areas of improved tornado hazard characterization and improved tornado performance of buildings and shelters.

He chairs several tornado-related standards committees, including the Structural Engineering Institute’s task committee developing tornado load provisions for ASCE 7-22, the International Code Council committee developing the 2020 edition of the ICC 500 Storm Shelter standard, and the ASCE/SEI/AMS committee developing a new standard on Wind Speed Estimation in Tornadoes and Other Windstorms (co-chair).

Prior to joining NIST Dr. Levitan was the Charles P. Siess, Jr. Associate Professor of Civil Engineering at Louisiana State University, including 10 years as Director of the LSU Hurricane Center. Earlier in his career, he served as Managing Director of the Wind Engineering Research Field Laboratory at Texas Tech University, where he led design, construction, and operation of an internationally recognized full-scale wind test facility.

Recent recognitions include a U.S. Department of Commerce Gold Medal and a Gears of Government Award for technical innovations to develop new maps of U.S. extreme wind speeds and the National Storm Shelter Association’s Kiesling Award for contributions to the storm shelter industry.