Mitigation Assessment Team Report: Midwest Tornadoes of May 3, 1999
(FEMA 342)

On the evening of May 3, 1999, an outbreak of tornadoes tore through parts of Oklahoma and Kansas, in areas that are considered part of "Tornado Alley", leveling entire neighborhoods and killing 49 people. The storms that spawned the tornadoes moved slowly, contributing to the development and redevelopment of individual tornadoes over an extended period of time.

On May 10, the Federal Emergency Management Agency's Mitgation Directorate deployed a MAT to Oklahoma and Kansas to assess damage caused by the tornadoes. This report presents the MAT's observations, conclusions, and recommendations, which are intended to help communities, businesses, and individuals reduce future injuries and the loss of life and property resulting from tornadoes and other high-wind events

Cover (452 KByte PDF Document)

 

Table of Contents (57 KByte PDF Document)

• List of Figures and Tables
• List of Acronyms

Executive Summary (618 KByte PDF Document)

 

1 Introduction (898 KByte PDF Document)

• 1.1 Purpose
• 1.2 Team Composition
• 1.3 Methodology
• 1.4 Presentation of Findings

2 Background on Tornadoes and History of the Storm
(702 KByte PDF Document)

• 2.1 The Fujita Scale and Tornado Probability
• 2.2 Tornadoes and Associated Damage
• 2.3 Background of the Event

3 General Assessment and Characterization of Damage
(1,301 KByte PDF Document)

• 3.1 Property Protection
• 3.1.1 Overview of Buildings Evaluated
• 3.1.1.1 Residential Buildings
• 3.1.1.2 Non-Residential Buildings
• 3.1.2 Continuous Load Path and Wind Loads
• 3.2 Windborne Debris
• 3.2.1 Missile Types and Sizes
• 3.2.2 Windborne Missile Quantity
• 3.3 Personal Protection and Sheltering
• 3.4 Local, State, and Federal Regulation
• 3.4.1 Oklahoma
• 3.4.2 Kansas

4 Observations on Residential Property Protection (1,888 KByte PDF Document)

• 4.1 Single Family Conventional Construction
• 4.1.1 Load Paths
• 4.1.2 Roof and Wall Sheathing
• 4.1.3 Structural Connections
• 4.1.4 Increased Load
• 4.1.5 Roof Coverings
• 4.1.6 Exterior Wall Coverings
• 4.1.7 Garage Doors
• 4.1.8 Windows and Doors
• 4.1.9 Masonry Veneer
• 4.1.10 Masonry Chimneys
• 4.2 Multi-Family Construction
• 4.3 Manufactured Housing

5 Observations on Non-Residential Property Protection (871 KByte PDF Document)

• 5.1 Continuous Load Path
• 5.1.1 Tilt-Up Precast Concrete Walls with Steel Joists
• 5.1.2 Load Bearing Masonry with Steel Joists
• 5.1.3 Steel Frame with Masonry Infill Walls
• 5.1.4 Light Steel Frame Buildings
• 5.1.5 Laminated Wood Arches with Wood Frame Roof
• 5.1.6 Masonry Walls with Pre-Cast Hollow Core Floors
• 5.2 Increased Load
• 5.2.1 Tilt-Up Precast Concrete Walls with Steel Joists
• 5.2.2 Load Bearing Masonry with Steel Joists
• 5.2.3 Masonry Walls with Pre-Cast Hollow Core Floors
• 5.3 Non-Residential Roof and Wall Coverings
• 5.3.1 Roof Coverings
• 5.3.2 Wall Coverings
• 5.3.3 Laminated Glass
• 5.3.4 Garage Doors, Exterior Doors and Windows

6 Observations on Personal Protection and Sheltering (981 KByte PDF Document)

• 6.1 Shelters
• 6.1.1 Types of Shelters
• 6.1.2 Use of Shelters
• 6.1.3 Maintenance and Design Issues of Shelters
• 6.1.4 Shelter Accessibility
• 6.1.5 Shelter Ventilation
• 6.1.6 Shelter Location
• 6.2 Other Places of Refuge
• 6.2.1 Refuge in Residences
• 6.2.1.1 General Observations
• 6.2.1.2 Case Study of Residential Core Remnants
• 6.2.2 Refuge in Non-Residential Buildings

7 Conclusions (783 KByte PDF Document)

• 7.1 Residential Property Protection
• 7.1.1 Single- and Multi-Family Homes
• 7.1.1.1 Load Path and Structural Systems
• 7.1.1.2 Increased Load Caused by Breach of Envelope
• 7.1.1.3 Roof and Wall Coverings
• 7.1.1.4 Masonry Veneer
• 7.1.2 Manufactured Housing
• 7.1.2.1 Foundations
• 7.1.2.2 Anchors
• 7.1.2.3 Strapping
• 7.1.2.4 Superstructure
• 7.2 Non-Residential Property Protection
• 7.2.1 Load Path
• 7.2.2 Increased Load Caused by Breach of Envelope
• 7.3 Personal Protection and Sheltering
• 7.3.1 Residential Shelters
• 7.3.2 Group Shelters
• 7.3.3 Community Shelters
• 7.3.4 Other Places of Refuge

8 Recommendations (610 KByte PDF Document)

• 8.1 General Recommendations
• 8.2 Property Protection
• 8.2.1 Residential and Non-Residential Buildings
• 8.2.2 Codes and Regulations, Adoption and Enforcement
• 8.2.3 Voluntary Actions
• 8.3 Personal Protection
• 8.3.1 Residential Sheltering
• 8.3.2 Group and Community Sheltering
• 8.3.3 Places of Refuge

9 References (24 KByte PDF Document)

Appendixes

Appendix A Members of the Building Performance Assessment Team (33 KByte PDF Document)

Appendix B Acknowledgements (26 KByte PDF Document)

Appendix C Taking Shelter from the Storm Brochure (207 KByte PDF Document)

Appendix D National Performance Criteria for Tornado Shelters (141 KByte PDF Document)

Appendix E List of Websites (24 KByte PDF Document)

 

You may obtain a printed copy of this publication by contacting FEMA's Distribution Center at 1-800-480-2520, and requesting publication number FEMA 342.