DR. W. GENE CORLEY, P.E., S.E.
ON SECURITY IN FEDERAL BUILDINGS
THE AMERICAN SOCIETY OF CIVIL ENGINEERS
PUBLIC BUILDINGS AND ECONOMIC DEVELOPMENT SUBCOMMITTEE
THE HOUSE COMMITTEE ON TRANSPORTATION & INFRASTRUCTURE
UNITED STATES HOUSE OF REPRESENTATIVES
June 4, 1998
Mr. Chairman and members of the subcommittee:
Good morning. Thank you for the invitation to appear before you today to discuss security in federal buildings.
My name is Dr. W. Gene Corley, P.E, S.E. My career spans more than 35 years as a structural engineer with extensive experience in failure investigations, building codes and reinforced concrete. I began work with the Shelby County, Illinois highway department designing highways and bridges.
I later became a development engineer with the Portland Cement Association where I was directly involved in the development of improved design procedures for structural concrete, concrete pavement, railroads, and structures subjected to fire loads. Today, I am vice president of Construction Technologies Laboratories (CTL), Inc. where I serve as CTL's managing agent for professional and structural engineering and lead structural evaluation projects related to industrial, transportation and parking facilities, bridges and buildings.
In 1995, I was selected by the American Society of Civil Engineers (ASCE) to lead a Building Performance Assessment Team investigating the bombing of the Alfred P. Murrah Federal Building in Oklahoma City, Oklahoma (hereafter referred to as the "Murrah Building").
I appear before you today on behalf of ASCE where I currently serve on several technical committees and on the ASCE Executive Committee of the Technical Council on Forensic Engineering (TCFE). The primary purpose of the TCFE is to develop practices to reduce and mitigate failures by disseminating information on failures and their causes, and also by encouraging research, education, and ethical conduct in forensic engineering practice.
ASCE, founded in 1852, is the oldest national engineering society in the United States. Membership is held by more than 120,000 individual professional engineers, and is divided among engineers in private practice; engineers working for federal, state and local governments; and those employed in research and academia. The Society's major goals are to develop engineers who will improve technology and apply it to further the objectives of society as a whole, to promote the dedication and technical capability of its members, and to advance the profession of civil engineering.
ASCE is pleased to have this opportunity to make recommendations for improving building security. We are extremely interested in working with Congress and government agencies to develop recommendations and guidelines to reduce and mitigate damages caused by catastrophic events such as major blasts, earthquakes, floods, hurricanes, tornados, and other disasters. Most importantly, we want to work with all governmental sectors to get the recommendations into practice to prevent future disasters.
To ensure safer buildings, water systems and other civil engineering works, ASCE develops technical codes and standards that often are adopted by federal, state and local governments. ASCE's national standard for building loads (ASCE 7), for example, is included in the three major U.S. model codes. ASCE's Technical Activities Committee (TAC) Division consists of over 7,000 members who participate on over 500 technical committees. Within TAC, there are 44 active Standards Committees with over 2,000 participants. In addition to individual participation, ASCE's standards program actively reaches out and encourages participation by representatives of affected organizations, thereby extending the potential input into the process beyond the 120,000 ASCE members. These established relationships throughout the civil engineering community ensure that every ASCE standards activity receives a high level of exposure and participation. ASCE is an American National Standards Institute (ANSI) accredited Standards Developing Organization (SDO). As such, our standards development procedures are approved by ANSI and the implementation of those procedures is audited regularly.
I would like to begin by first highlighting some of the key findings released in the 1996 report, "The Oklahoma Bombing: Improving Building Performance Through Multi-Hazard Mitigation" which was published by FEMA and ASCE. This report made specific recommendations concerning the design and construction of new federal buildings and also provided mitigation recommendations for existing federal buildings.
As mentioned earlier, I served as one of the principal investigators on FEMA's Building Performance Assessment Team (BPAT) which was deployed to investigate the damage caused by the malevolent bombing of the Murrah building. The team also included engineers from FEMA, the U.S. Army Corps of Engineers, the General Services Administration and the National Institute of Standards and Technology. FEMA often deploys BPATs to conduct field investigations at disaster sites. Typically, members of a BPAT include representatives of public and private sector entities who are experts in specific technical fields such as structural and civil engineering, building design and construction, and building code development and enforcement.
The purposes of the investigation were to review damage caused by the blast, determine the failure mechanism for the building, and review engineering strategies for reducing such damage to new and existing buildings in the future. Specifically, mechanisms for multi-hazard mitigation, including mitigation of wind and earthquake effects, were considered. Among the strategies evaluated were procedures and details provided in FEMA's 1994 Edition of National Earthquake Hazards Reduction Program Recommended Provisions for Seismic Regulations for New Buildings.
The BPAT visited the area around the Murrah building in Oklahoma City during the period of May 9 through 13, 1995, three weeks after the blast occurred. We were limited in our physical inspections of the site to a distance of 200 feet by the continuing activities of the rescue workers.
While in Oklahoma City, the team conducted investigations by photographic observations, review of construction documents, and collection of samples of structural components. Samples of concrete and reinforcing bars taken from the site were tested to determine physical properties of materials used in the building. The work performed included developing the most probable response of the building to the blast and determining whether new technology can be used to enhance the resistance of buildings to blast, wind, earthquake and other hazards.
One of the key findings from our team's report was that if the 1976 Murrah building had been built using today's seismic building design details, as much as 50 to 80 percent of the structural damage, and presumably the fatalities, could have been prevented. The resulting additional construction costs would not have been millions, but a few thousand dollars.
It is important to understand that the bomb blast to the Murrah building was not devastating by itself -- it just so happened that it was located at a critical point which undermined the whole structure of the building. What we discovered as a result of our investigation was that most of the damage and a vast majority of the fatalities were caused by the progressive collapse of the building.
The Murrah building had what is called an Ordinary Moment Frame design, which is typical of most office buildings not located in earthquake-prone areas. With this design, if a critical element of a building fails, it may start a chain reaction of successive failures that will take down the building. So when the bomb blast destroyed three key columns supporting the Murrah building, the floors progressively collapsed and stacked on top of each other.
Analysis of the Murrah building showed that it would have been impossible to design the building to remain standing with one of its critical columns destroyed by the blast through the use of brute strength alone. However, calculations show that if the additional amounts and locations of reinforcing steel called for in a Special Moment Frame had been used, the Murrah building would have had enough toughness and ductility to prevent about half of the damage. That is, even though the individual columns and slabs would have been damaged, the reinforcing steel would have held many of the building elements in place, keeping large portions of the building erect -- at least sufficiently erect to allow the occupants to escape after the blast.
Special Moment Frames are frequently used in areas of high seismic activity. In this type of construction, ductile detailing, typified by closed-hoop reinforcement to confine columns, continuous bars for continuity, and beam-to-column connections to transfer forces through the joints, provides toughness to resist blast and earthquake forces. Structural members reinforced as Special Moment Frames can provide better resistance to progressive collapse than Ordinary Moment Frames such as used in the Murrah building. Special Moment Frames can provide very large open spaces. Consequently, they are suitable for construction of Federal office buildings.
Special Moment Frames also provide structural systems with much greater ability to dissipate energy than Ordinary Moment Frames, which have limited reserves for dissipating energy from extreme loading such as earthquake and blast.
By using reinforcing details required in seismic building design standards, such as Special Moment Frames or Dual Systems, engineers can build redundancy and "toughness" into the design. Thus, if some supports are damaged by a blast, other supporting mechanisms can still carry most of the load.
Another loss-reduction technique is to prevent a bad situation from getting worse: to prevent progressive collapse. Redundancy is a key design feature for the prevention of progressive collapse. There should be no single critical element whose failure would start a chain reaction of successive failures that would take down a building. Each critical element should have one or more redundant counterparts that can take over the critical load in case the first should fail.
To reduce the risk in any future bombings, the team recommended that the Federal government adopt current seismic building details for new construction where a significant risk exists. Many of the techniques used to upgrade the seismic resistance of buildings also improve a building's ability to resist the extreme loads of a blast and reduce the likelihood of progressive collapse following an explosion. The cost of doing so ranges from 1 to 2 percent of the total cost of a building. This additional cost can be expected to be within the normal differences between high and low construction bids.
While it is not possible to prevent all damage in the immediate area where a blast occurs, steps can be taken to reduce potential damage to existing buildings. Among the strategies considered are rehabilitation or retrofitting of buildings and increasing the distances between the building and sidewalks and street-side parking.
While retrofitting existing federal buildings is more difficult and expensive, there are some practical steps that can help minimize the damage. For instance, additional structural walls can be installed, supplemental supporting frames can be added, and existing columns can be encased in steel and concrete.
I would now like to discuss some of the activities that are currently underway in this area inside of ASCE. Being a professional society composed predominantly of professional engineers, ASCE has a long history of producing and publishing technical documents to advance the art and science of civil engineering. Over 15,000 of our members are actively engaged in producing technical documents primarily through volunteering their time and expertise.
In addition to the report on the Oklahoma City bombing mentioned earlier, ASCE has published two additional books: Blast Effects on Buildings by Mays and Smith published in 1995, and Lessons Learned from the Oklahoma City Bombing by Hinman and Hammond published in 1997.
In 1997, the ASCE Technical Council on Forensic Engineering held its first ever Congress attracting over 400 participants. The resulting proceedings contained numerous papers on the effects of blasts and a panel presentation was held to discuss recommendations for mitigating their effects.
ASCE's largest technical division, the Structural Engineering Institute, created a task committee in 1991 to produce a report describing the state of the practice in structural design for physical security. This document provides both methods guidance and references for structural engineers challenged with a physical security problem. The report contains eight chapters that parallel the steps currently practiced in structural design for physical security.
And finally, this fall, ASCE is organizing a workshop in cooperation with its British counterpart, the Institution of Civil Engineers, for the purpose of exchanging information and knowledge on minimizing the effects of terrorist activities. Topics expected to be addressed include design, construction, and operational techniques.
Currently, no single authoritative document exists to provide definitive guidance to an engineer on mitigating the effects of blasts. Although, the body of knowledge is growing, it is only through the development, adoption, and use of a consensus standard will we be able to achieve a uniform approach to mitigating the effects of blasts.
Practicing engineers, who may not be intimately familiar with designing to mitigate the effects of a blast, need and want a mandatory consensus standard, thereby providing them the assurance that they are meeting their clients' needs.
The major challenge facing all of us is the effective transfer of this knowledge into common practice. We must take steps now to ensure that the existing body of knowledge and the results of future research is readily available for future designers and engineers.
One of the best ways of doing this is through the development of a national consensus standard that can be adopted and used by all practicing engineers. ASCE, as the leader in producing standards for the civil engineering profession, stands ready to assist the federal government in developing this much needed standard.
To move forward in this area, ASCE recommends the following:
1. A national voluntary consensus standard should be developed that could be referenced and used by all government agencies and private sector companies for which mitigating the effects of a blast is a concern.
2. A study should be performed to gather and document the information that is known and available with respect to the effects of blasts on structures. While a good deal of information exists in the private sector, it is believed that a tremendous body of knowledge exists in federal agencies, such as the Department of Defense, that should be documented and shared. In addition, this effort should identify gaps in knowledge thereby allowing the targeting of future research activities.
ASCE appreciates this opportunity to testify. We look forward to discussing our recommendations with you in greater detail. This concludes my testimony. I would be happy to answer any questions.