Consulting-Specifying Engineer - September 2008 - (Page 24)

For tall buildings or other facilities that will require full building evacuation to address extreme events, a performancebased engineered approach—during the design phase or a specific analysis of asbuilt conditions—should be used to evaluate the impact of evacuating a large number of people simultaneously on the egress system. Particular concern should be given to notification signals and their effectiveness, assumptions regarding time to begin evacuation, occupant characteristics and assumptions regarding mobility and evacuation time, and physical building features that could restrict or impede occupant flow (choke points, narrow doors or corridors, transition spaces, and other potential flow obstructions). In many cases, it may be necessary for simultaneous full building evacuation to be coordinated and directed by the responding local fire authorities. Protected elevator evacuation Walking down many flights in tall buildings can be difficult for many occupants Protected elevators Elevator use in emergencies has been a topic of research for more than two decades (Klote et al., 1993). This research indicates that elevator use during emergency evacuation is practical and safe, provided that specific enhancements are made to the elevator systems. These enhancements include the following: • Earthquake protection • Emergency power supplies • Emergency communication systems • Smoke and heat protection • Protection against suppression water infiltration • Resistance to the spread of contaminants and gaseous agents • Attention to human factors in management and occupant education/training, among other systems considerations. ASME A17.1 organized two tasks groups, Task Group on Use of Elevators by Firefighters and Task Group on Use of Elevators for Occupant Egress, to review appropriate measures for protected elevators. After conducting a comprehensive analysis, it is expected that these task groups will develop a final set of elevator protection recommendations. If elevators are part of a building evacuation plan, the plan must consider the needs of both exiting occupants and responding emergency workers. Occupants and firefighters must be properly trained in the evacuation plan, and control strategies must be defined and implemented. For instance, the evacuation plan may designate specific elevators to be used by responders only. 80 75 70 Event Floors 65 60 55 Upper Zone Elevators 50 45 Sky Lobby Evacuation Elevators Firefighters Elevators 40 Low Zone Elevators 05 Ground Floor Figure 2 The figure illustrates the use of protected elevators when serving the fire floor and when serving a sky lobby. Source: Arup and may be impossible for some. Elderly, disabled, occupants with medical issues like heart conditions, or those with mobility-impairing injuries may have difficulty negotiating stairs or be incapable of evacuating using stairs. Changes in technology, an aging population, universal design concepts, and the events of Sept. 11 have converged to make elevators a viable option for emergency evacuation. Protected evacuation elevators can now provide a safe and effective alternative to walking down many flights of stairs. In theory, the use of elevators can speed evacuation within tall buildings. This has been proven in real events. For example, reports indicate that 16% of occupants of Tower Two of the World Trade Center escaped through the elevators before the second airplane struck the building (Averill, 2005). There are several strategies for the use of protected evacuation elevators. With appropriate design, it may be possible to allow protected elevators for a large segment of the building population. Alternatively, with good training and stringent controls during emergency evacuations, it may be possible to limit the use of elevators to those who cannot walk down many flights of stairs or those injured during the incident. Another strategy is to allow occupants to descend stairs from the fire floor to a refuge floor (perhaps to a specially designed sky lobby), then choose to use the elevator from that floor or continue down the stairs. These strategies need to be well-defined, engineered, and coordinated by the building personnel and the local fire officials. Special care is necessary to help educate and train occupants in the use of such systems. When employing any of these approaches, elevators must be protected. Appropriate fire and life safety features, appropriate signage and way-finding, and a well-constructed evacuation plan with training are required. As taller buildings are constructed around the world, protected elevators will be become more important. Both the IBC and the Life Safety Code (NFPA 101) allow elevators to serve as one means of egress in towers. The 2006 IBC requires elevators to serve as an accessible means of egress in non-high-rise facilities. The dependence on elevators, along with 24 Consulting-Specifying Engineer • SEPTEMBER 2008 Express Elevators Exit Stairs

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Consulting-Specifying Engineer - September 2008 Contents Viewpoint Letters News M/E�Roundtable Selecting Appropriate Egress Strategies Commissioning On-Site Electrical Systems Mentoring Control Engineers and Technicians Casting Call for Cx Case Study New Products Equipment Lifecycles Advertiser Index Green Space

Consulting-Specifying Engineer - September 2008

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