PERSPECTIVE: Tornado Impact Shows Need for Consistent Building Codes Region-Wide

Date Posted: January 25, 2022

Posted In: Discussion, Ideas, Regionalism,

by Tom Finan, Executive Director, Construction Forum

For Marc Levitan, the destruction and death caused by the Dec. 10 tornadoes must have seemed like deja vu all over again, in a bad way.

Levitan is the lead research engineer for the  National Windstorm Impact Reduction Program of the National Institute of Standards and Technology (NIST). In 2005, he was an associate professor of civil engineering at Louisiana State University and director of the LSU Hurricane Center. Levitan was scheduled to attend a meeting on Aug. 30, 2005 to discuss hurricane design standards for New Orleans. On Aug. 29, 2005, Hurricane Katrina hit.

Levitan was also part of the decade-long effort after the Joplin Tornado of 2011 to  measure the intensity of tornados to develop a wind-load standard for tornado-resistant design. Levitan chaired  the ASCE/SEI 7-22 task committee on tornado loads, which developed  Chapter 32 of ASCE/SEI 7-22: “Minimum Design Loads & Associated Criteria for Buildings & Other Structures”. 

That new standard was released nine days before the Dec. 10 tornadoes struck. Once again in Levitan’s career development of a new building wind load standard was overtaken by events. But the tornado work in which he has been involved promises to have a profound impact.

Work began on ASCE Chapter 32/SEI 7-22 in 2014, about the time NIST published a report on its investigation of the Joplin tornado. NIST called for improved measurement and characterization of tornado hazards and new methods for the tornado-resistant design of buildings.

There was a lot of drill-down science conducted following the NIST report.  The researchers, among other efforts, analyzed and filled in gaps in more than 60 years of tornado records, studied how miniature buildings responded to small-scale vortexes in the lab, and performed extensive computer-based structural modeling. And by analyzing damage from Joplin and other tornadoes they were able to back up the performance of their models with real-world data. Then they used their findings to develop tornado hazard maps and methods to help engineers determine what forces their structure would need to stand up against tornados.

Design Standards Based on Science

Tornadoes cause more deaths per year than earthquakes and hurricanes combined, NIST reported.  And storms spawning tornadoes surpass the collective annual insured losses of hurricanes and tropical storms. “But, barring tornado shelters and nuclear power plants, building designs have historically not accounted for tornadoes,” NIST said in a news release last summer. “The extraordinary strength of tornadoes and a common perception that the risk of being struck by one is low have fed into a misconception that addressing tornadoes in building designs would be far too costly.”

That mindset first started to shift in 2011, when a record-breaking tornado season wreaked havoc across the U.S. NIST thoroughly investigated one of the worst events that year, a tornado rated as the most severe on the Enhanced Fujita (EF) Scale — an EF5 — that ripped through Joplin. Among the more than 8,000 buildings damaged in the tornado’s wake were schools, big-box stores, nursing homes, fire stations and a major hospital, which was eventually demolished.

The NIST team, led by Levitan, found that although the most powerful winds laid waste to buildings near the tornado center, more than 70% of the total damage path stemmed from lower wind speeds farther out. And designing for that level of wind is much more economically viable.

“Building codes and standards don’t require design for the worst possible hurricanes and earthquakes. We need to apply that same philosophy to tornadoes and design for the more modest and more common tornado design speeds,” Levitan said. ASCE’s goal is to have its standard incorporated into Chapter 16 of the 2024 International Building Code.

Benefits of a Unified Approach

In an well-researched article on Jan. 23, Steph Kukuljan of the St. Louis Post-Dispatch covered many of the questions that have been raised since Dec. 10. These include everything from the integrity of tilt-up construction, to Amazon’s personnel procedures, to building code requirements.

The problem in applying Dec. 10’s lessons here is that our code requirements — like so many other things in the St. Louis Metropolitan Region — are inconsistent and disconnected.

The benefits of a unified approach, vis-à-vis  tornado-resistant design, are borne out in state law that passed in Illinois in 2015. The law required that all new school structures — which typically have large building footprints and higher human occupancy — incorporate hardened shelter spaces.

The lack of a consistent wind load design code approach region-wide invites code jurisdiction shopping and discourages development. In October of 2021 the St. Louis REALTORS®’ issued a report, “Inconsistent Regulations: Building Codes in St. Louis County” to collectively seek solutions to fragmentation and inconsistency in building codes, inspections, and permitting. The report cited 42 different code versions in effect in St. Louis County, dating from 1995 to 2018. Include the rest of the counties in the region and you have even more incongruity.

On Jan. 14 seven associations signed on and created a new coalition, “Safer, Simpler St. Louis County.” Participants in  the coalition were: Associated General Contractors of Missouri (AGCMO); Missouri Association of Plumbing, Heating Cooling Contractors (MO PHCC); Missouri Growth Association (MGA); Plumbing Industry Council (PIC); St. Louis REALTORS®; Urban Land Institute – St. Louis (ULI-St. Louis); and the U.S. Green Building Council – Missouri Gateway Chapter (USGBC-MGC).

We’ve agreed to get serious about making codes uniform to cut down on confusion, frustration, and waste,” Charles Hinderliter, director of government affairs for the St. Louis REALTORS® said.  “We want to ensure that citizens have equal access to healthy and safe buildings and codes are fundamental to that.”

If we heed the “Safer, Simpler St. Louis County” approach and take it regionwide, the St. Louis Region can send a message to the development community that we are unified in supporting realistic building standards that protect our citizens.