Building Security:Engineering.pdf
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1、ENGINEERING P A R T 3 CHAPTER 22 PROTECTIVE DESIGN OF STRUCTURES Richard L. Tomasetti, PE Co-Chairman, The Thornton-Tomasetti Group New York, New York John Abruzzo, PE Vice President, LZA Technology The Thornton-Tomasetti Group New York, New York Human history becomes more and more a race between ed
2、uca- tion and catastrophe. H.G. WELLS(1866-1946) English author and historian, Outline of History History is rife with violent incidents directed toward people, buildings, and property. The events of September 11, 2001, and others during the late twentieth century directed toward Americans at home a
3、nd abroad underscored the need for the design and construction community to reach even higher in the quest for advanced engineering techniques to save lives during a terrorist attack or disaster. From benchmark events such as the 1983 attack on the American embassy in Beirut, the 1993 bombing of the
4、 World Trade Center, and the 1995 bombing of the Alfred P. Murrah Federal Building in Oklahoma City, to subsequent attacks on public and private American facilities, embassies and installations overseas, building performance and the ability of a structure to with- stand blast have become two of the
5、more important issues that engineers, architects, and building owners must address. Engineering research after each terrorist event resulted in technological advances and evolving best practices designed to save lives, allow swift and complete building evacuation, and increase life safety. The event
6、s in Oklahoma City prompted an industry-wide examination of progressive col- lapse, reduction of the impact of flying glass, and minimization of damage to neighboring buildings during and after an event or disaster. Much of the testing and evaluation of building systems and construction materials ge
7、nerated after the Oklahoma City bombing was produced for the federal government, initially under the auspices of the U.S. Department of Justice (USDOJ), with the participation of several federal agencies. In June 1995, USDOJ published Vulnerability Assessment of Federal Buildings, assessing the exis
8、ting building inventory at the time. In October 1995, the Interagency Security Committee (ISC) was formed to create long-term design and construction standards for federal building security. The doc- ument, ISC Security Design Criteria for New Federal Office Buildings and Major Modernization Project
9、s, issued in May 2001, was based on the USDOJs earlier findings. 22.3 Although the security design criteria apply to federal facilities, the standards and mitigation strategies are applicable to state, local, and private sector buildings housing government agencies, government contractors, tenants r
10、equiring improved security levels, and owners seeking a greater degree of safety for their tenants and properties. With these standards, building owners, working with design and construction professionals, can develop a comprehensive security plan for a building or site. The security plan: Addresses
11、 risks, threats, design, operations, and technology requirements Identifies low probability, high risk threats to the building, known as abnormal loads Establishes the required structural performance Transparent Security Integrating design, operations, and technology into the security plan is the mo
12、st effective way to achieve transparent security, invisible to the public eye. Sound structural systems and protective design principles are essential elements of maintaining transparent security and enhancing the built environment. Design encompasses planning, programming, design, and construction
13、of physical protective barriers, such as walls, screens, floors, roofs, and standoff or the distance between the target and the blast threat. Operational security includes policies and procedures within a facility or organization. Operations address every aspect of emergency and disaster planning, a
14、nd the role of personnel to ensure the safety of people and property. Technology is an integral part of security planning, and it works best when integrated early in pro- ject development with design and operational policies to achieve operational and capital savings. Selection of appropriate detect
15、ors, sensors, surveillance cameras, and other technology is ulti- mately a decision made by building owners, often based on the advice of security consultants or in-house experts. PROTECTIVE DESIGN OF STRUCTURES Protective design of buildings is accomplished by integrating into the architectural and
16、 engineering building design program various means of mitigating threats, such as biological, chemical, and radi- ological attack, and force protection from blast, fire, ballistic attack, and illegal entry. Protective design of structures deals with the mitigation of force protection threats or abno
17、rmal loads acting on building structural framing and exterior walls. Protection is generally achieved through a combination of standoff, redundancy, and hardening. Standoff, in suburban settings, can be measured in hundreds of feet from public streets. Standoff of 350 feet or more is recommended for
18、 suburban sites, but is impractical in urban settings. However, even a few feet can make a substantial difference in terms of damage to the structure. Therefore, standoff in urban settings is no less critical to protective design of the structure. Redundant systems provide a means of surviving the u
19、nanticipated. Redundant structural systems are necessary for preventing progressive collapse. Hardening and energy absorptive shields can be used to enhance critical structural elements, walls, stairwells, loading docks, and windows where standoff alone is insufficient to reduce the threat to tolera
20、ble levels. While each of these three strategies can be effective as protective measures, project constraints usually demand a combination of these three measures to provide a solution. For instance, in most 22.4ENGINEERING urban environments, it is not practical to even consider a standoff of 350 f
21、eet. In urban centers, stand- off of even 20 feet can have appreciable cost. Therefore, hardening and redundancy need to be incor- porated into the design process to accommodate the effects of abnormal loads. ABNORMAL LOADS Abnormal loads on buildings may be caused by vehicular impact, blast loads f
22、rom accidental or pur- poseful explosions, or local failure due to fire. Once the threat is defined, the structure must perform to a level consistent with established performance criteria, such as preventing structural collapse of part or all of the building. Protection against abnormal loads incurs
23、 cost. To maximize the benefit of protection expense, the first step is determining where protection is needed. This is based on the assets housed in a building and the structural capabilities required for asset protection. For example, if assets are housed within a building in a hardened, undergrou
24、nd space, known as a bunker, they may not be vulnerable to failure of a structural member supporting the b ing entrance canopy. Hardening the entrance canopy to pro the security design goal of asset protection. However,the asset may not be protected if a street level blast destroys a column supporti
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