Technical Investigation

of the May 22, 2011,

Tornado in Joplin, MO

December 10, 2013

NCST Advisory 

Committee Meeting Performance of Buildings, 

Designated Safe Areas and 

Lifelines

Long Phan

Investigation Task Leader

National Institute of Standards and Technology
Investigation Objectives 2 and 3

2. Response of residential, commercial, and critical 

buildings, including performance of designated safe areas

3. Performance of lifelines as it relates to the continuity of 

operations of residential, commercial, and critical 

buildings 

Presentation Outline

• Damage Summary

• Data Collection

• Findings Pertain to Investigation Objectives 2 and 3

– Context

– Building performance

– Performance of shelters/safe rooms/designated refuge areas

– Performance of lifelines

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1. Damage Summary

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Summary of Building-Related Damage, 

Fatalities, and Insured Losses

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Buildings 

Damaged

Residential 7,411 (43% sustained heavy/totaled or demolished classification)

Non–

Residential

553 (1 of 2 major hospitals, 10 public and several parochial 

schools, 28 churches, 2 fire stations, and numerous commercial 

facilities) 

Fatalities

Total 161

All Building–

Related 135 (of 161, or 83.8% of total fatalities)

ResidentialRelated 74 (of 135, or 52.5% of building–related fatalities)

Insured 

Losses

(as of April 

30, 2012)

Residential $0.552 billion

Commercial $1.228 billion
Summary of Damage to Lifelines

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Electricity

Step-down Substations 1 destroyed, 2 

damaged

~ 20,000 customers lost 

electrical power immediately 

after the May 22, 2011 

tornado

Distribution

Poles/Transmission Towers ~ 4,000 damaged

Transformers 1,500 damaged

Transmission/Distribution 

Lines 110 miles downed

Water

Service Lines ~4,000

damaged/leaked

Drastic decrease in water 

pressure and loss of water 

from the two elevated 

Fire storage tanks within 2 hours -Service Lines ~25 broken

Gas

Meters ~ 3,500 damaged

~ 3,500 customers affected

Main ~ 55,000 ft

damaged
2. Data Collection

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Data Collection

• Conducted field surveys of 25 structures and lifeline facilities, 

including institutional, commercial, and residential buildings 

representative of typical construction types, building functions, and 

levels of damage.

• Obtained design and construction information for the surveyed 

buildings, including applicable building codes, and damage/outage 

information from utility companies by working with third parties.

Aerial image © 2011 GeoEye. Building footprint data Pictometry®. Used with permission. Enhancements by NIST.

SJRMC: St. John’s Regional Medical Center
3. Findings

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• National model building codes, standards, and practices seek to achieve 

life safety for the hazards considered in design. Tornado hazards are not 

considered in the design of buildings currently, except for safety–related 

structures in nuclear power plants, storm shelters, and safe rooms.

• There are currently two tornado hazard maps for the contiguous U.S.:

– ANSI/ANS 2.3 (2011) (also NRC/RG 1.76 and DOE 1020), for nuclear–related facilities 

(3 regions, 230 mph maximum wind speed); and 

– ICC 500 (2008) (also FEMA 320 and 361), for shelters and safe rooms (4 regions, 250 

mph maximum wind speed).

• Current building codes and standards prohibit the use of aggregate roof 

surfacing materials or ballast for hurricane–prone regions, but allow their 

use elsewhere based on mean roof height and exposure category.

For the City of Joplin, the building code at the time allowed aggregate 

roof ballast for buildings with a mean roof height of ≤ 110 ft. 

Findings – Context 

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• In the State of Missouri, adoption and enforcement of building codes are 

at the local government level. The City of Joplin’s building department 

has a long history of code adoptions, and typically has adopted the latest 

national model building codes shortly after they have been issued.

• Like most other municipalities in tornado–prone areas and the 

contemporaneous model building codes, the City of Joplin did not 

mandate the construction of shelters or safe rooms in residential or non–

residential facilities.

Additionally, the City did not own or operate any public storm shelters. 

The lack of public shelters and requirements for safe rooms meant that 

many residents, particularly those who were living in multi–family 

residential buildings or older nursing homes, did not have access to such 

sheltering options during this tornado.

Findings – Context (con’d)

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• F8: Buildings are not designed to withstand tornado 

hazards (extreme wind speeds and wind-borne debris). 

Most buildings in the damaged area of Joplin were 

subjected to wind speeds close to or above the nontornadic wind design requirements of applicable building 

codes.

• F9: Regardless of construction type, buildings were not 

able to provide life–safety protection. Of the 161 fatalities, 

135, or 83.8 percent, were related to building failure 

(slightly more than half in residential buildings, the rest in 

non-residential buildings).

Findings – Building Performance

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Findings – Building Performance

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• F10: Engineered buildings that:

− Had redundant lateral load 

capacity or that did not depend on 

roof bracing (steel and concrete 

moment frames) withstood the 

tornado without collapse.

− Had reinforced concrete or 

composite concrete-steel roof also 

withstood the tornado without 

collapse. 

− Relied on bracing from a less 

robust roof system (such as box–

type system (BTS) buildings with 

light steel roof decks) were prone 

to structural collapse.
• F11: Collapses of BTS buildings typically began with failure of the roof 

system due to wind uplift (failure of roof deck–to–joist or joist–to–wall

connections), which led to the loss of lateral bracing for perimeter walls, 

causing them to collapse by rotation at the base due to lateral load. 

Findings – Building Performance (cont)

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Collapsed tilt-up panels

Metal roof decks missing Available design information Collapsed roof trusses

showed that the roof 

connections of these buildings 

were adequate for code–level 

design wind pressures, making 

it unlikely that these buildings 

could have failed in wind 

speeds under 115–120 mph, 

which are the current code–

level design wind speeds. 
Findings – Building Performance (cont)

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• F12: BTS buildings that sustained structural collapse had two 

common design features:

− Light–gauge metal roof systems, and

− Friction–only wall–to–footing connections (currently accepted 

practice for areas with low or no seismic risk).

• F13: Pre–engineered metal buildings (PEMB) sustained 

significant damage to envelopes, but no collapses of primary 

rigid steel frame.
• F14: Failures of residential wood–frame buildings predominantly 

involved failure of the connections between structural components 

(roof from walls and walls from foundation). This indicates lack of 

robustness in the connections and in the continuity of the vertical load 

path from roof to foundation.

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Findings – Building Performance (cont)

• F15: Better structural 

performance in one of the NIST–

surveyed multi–family residential 

buildings can be attributed to use 

of robust hurricane connectors, 

typically only required for 

residential wood–frame buildings 

in hurricane–prone regions.

© 2011 GeoEye. Used with permission. Enhancements by NIST.
• F16: All NIST–surveyed engineered 

buildings that did not collapse, as well 

as engineered buildings that 

collapsed, sustained significant 

damage to the envelopes and interiors 

due to the combination of wind 

pressure, impacts by wind–borne 

debris, and water intrusion.

• F17: The failure of building envelopes 

at SJRMC, which led to loss of 

protection and subsequent extensive 

damage to building interiors, was the 

primary cause for the complete loss of 

functionality of this critical facility 

despite the robust structural system 

that withstood the tornado without 

structural collapse. 16

Findings – Building Performance (cont)

© 2011 Malcolm Carter. Used with permission.
• F18: The majority of the impact–resistant 

windows on the fifth floor (Behavioral 

Health Unit) of the West Tower of SJRMC 

remained intact, whereas most regular 

dual–pane insulated windows at SJRMC 

were broken when exposed to the same 

tornado hazards. 

• F19: While there was no direct evidence 

that roof aggregate contributed to any 

injuries or fatalities in Joplin, there was 

evidence that roof aggregates contributed 

to envelope damage in SJRMC buildings 

and surrounding structures, thus adding to 

the tornado debris hazard and the 

potential for injuries or fatalities.

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Findings – Building Performance (cont)

Intact windows on the fifth floor (Behavioral Health Unit)
• F20: Joplin residents had limited access to underground or tornado–

resistant shelters. There were no community shelters or safe rooms 

in the City of Joplin or Jasper County at the time. About 82 percent of 

the homes in Joplin did not have basements. Only a few non–

residential buildings had underground locations (e.g., basements). 

• F21: Most high–occupancy commercial and critical facilities surveyed 

by NIST had designated refuge areas for tornadoes. However, many 

of these areas suffered severe damage and yielded no positive 

outcomes with respect to loss of life. The locations of these areas 

were not always based solely on structural considerations.

There are currently no standards, requirements, or guidelines for 

designating refuge areas in commercial or critical buildings 

Findings – Performance of 

Shelters/Safe Rooms/Designated 

Refuge Areas

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• F22: Currently there are optional 

model code provisions for the design 

of specially purposed shelters, but 

such shelters are not required.

• F23: Based on a few instances 

observed in this tornado, in–home 

shelters did perform well and provided 

life–safety protection to the home 

occupants. NIST found no statistics 

on how many of the 7,411 damaged 

residential structures had in–home 

tornado shelters.

Findings – Performance of 

Shelters/Safe Rooms/Designated 

Refuge Areas (cont)

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Aerial image © 2011GeoEye. Used with 

permission. Enhancements by NIST.

Source: FEMA MAT.

Source: FEMA MAT.
• F24: All utilities (water, gas, power) were lost in the areas damaged by 

the Joplin tornado. The utility providers restored service to critical 

buildings (SJRMC, water treatment plant) within 24 hours.

• F25: The failure of building envelopes at NIST–surveyed critical 

facilities, and resultant severe damage to their interior and internal utility 

distribution systems, was the primary cause of the facilities’ complete 

loss of functionality despite restoration of utility services within 24 

hours. 

• F26: In critical facilities constructed in Joplin prior to 1998, the design 

wind speed for high–occupancy buildings was higher than that specified 

for buildings housing the facilities’ backup power generators.

Findings – Performance of Lifelines 

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