Tornado Protection Selecting Refuge Areas in Buildings FEMA 431, Second Edition / October 2009 About the Cover The photograph on the cover shows the remains of a central corridor in the Kelly Elementary School, in Moore, Oklahoma. This extensive damage was caused by one of the tornadoes that struck Oklahoma and Kansas on May 3, 1999. The corridor walls, which consisted of lightweight steel frame members with masonry infill topped by clerestory windows, were unable to withstand the extreme loads caused by lateral and uplift wind forces. This type of corridor construction is common and creates special challenges for building administrators and design professionals who must identify refuge areas in schools and other buildings. CONTENTS Foreword... iii Introduction... v Chapter 1: Tornado Profile... 1 Chapter 2: Effects of High Winds... 7 Wind Effects on Buildings... 7 Atmospheric Pressure Changes... 8 Debris Impact... 9 Selecting Refuge Areas... 10 Chapter 3: Case Studies... 11 Xenia Senior High School... 13 St. Augustine Elementary School and Gymnasium... 21 St. Augustine Elementary School Building... 22 St. Augustine Elementary School Gymnasium... 25 Kelly Elementary School... 27 Chapter 4: Selection Procedure... 37 Determine the Required Amount of Refuge Area Space... 38 Review Construction Drawings and Inspect the Building... 39 Assess the Site... 42 Example of Refuge Area Selection Process... General... 46 Required Refuge Area Space... 46 Architectural and Structural Characteristics... 46 Identifying the Best Available Refuge Areas... 52 Verifying the Best Available Refuge Areas... 55 Selecting the Best Available Refuge Areas in Other Types of Buildings..55 Mid-Rise and High-Rise Buildings.... 55 Large Stores and Movie Theaters.... 56 Chapter 5: Conclusions... 57 Information Sources... 61 FOREWORD Tornadoes cause heavy loss of life and property damage throughout much of the United States. Most schools and other public buildings include areas that offer some protection from this danger, and building administrators should know the locations of these areas. This booklet presents case studies of three schools that were struck by tornadoes: Xenia Senior High School in Xenia, Ohio; St. Augustine Elementary School in Kalamazoo, Michigan; and Kelly Elementary School in Moore, Oklahoma, which were struck on April 3, 1974; May 13, 1980; and May 3, 1999, respectively. The resulting damage to these schools was examined by teams of structural engineers, building scientists, engineering and architectural faculties, building administrators, and representatives of the architectural firms that designed the buildings. From these and other examinations, guidance has been developed for selecting the safest areas in existing buildings – areas that may offer protection if a tornado strikes – referred to in this booklet as the best available refuge areas. The guidance presented in this booklet is intended primarily to help building administrators, architects, and engineers select the best available refuge areas in existing schools. Building administrators, architects, and engineers are encouraged to apply this guidance so that the number of injuries and deaths will be minimized if a tornado strikes an occupied school. For the design of safe rooms in schools yet to be constructed, refer to FEMA 361, Design and Construction Guidance for Community Safe Rooms, Second Edition. INTRODUCTION The likelihood that a tornado will strike a building is a matter of probability. Tornado damage to buildings is predictable. Administrators of schools and other public buildings should have a risk analysis performed to determine the likelihood that a tornado will occur and the potential severity of the event. If a building is determined to be at sufficient risk, the safest areas of the building – areas that may offer protection if a tornado strikes – should be identified. This booklet refers to such areas as the best available ref­uge areas. In many buildings, the best available refuge areas are large enough to accommodate the number of people who normally occupy the building. A qualified architect or structural engineer should assess an ex­isting building and identify the best available refuge areas. This booklet presents information that will aid qualified architects and engineers in the identification of the best available refuge areas in existing buildings. Architects and engineers who are designing tornado safe rooms within new buildings may also find this booklet useful, but should refer to Design and Construction Guidance for Community Safe Rooms, Second Edition (FEMA 361) for more detailed information. FEMA 361 includes design criteria, information about the performance of specific construction materials under wind and debris impact loads, and examples of construction plans and costs. The Wind Engineering Research Center at Texas Tech University provided much of the substance of this booklet. Dr. Kishor Mehta of the Center as­sisted in the preparation and review of the material. Invaluable assistance was provided by the architects and engineers of the buildings presented as case studies and by the school administrators. [Begin text box] What Are “Best Available Refuge Areas”? The term best available refuge areas refers to areas in an existing building that have been deemed by a quali­fied architect or engineer to likely offer the greatest safe­ty for building occupants during a tornado. It is important to note that, because these areas were not specifically designed as tornado safe rooms, their occupants may be injured or killed during a tornado. However, people in the best available refuge areas are less likely to be injured or killed than people in other areas of a building. [End text box]