SUPPLEMENT 7 The Application of Performance- Based Design Concepts for Fire and Life Safety Milosh Puchovsky, P.E. James Quiter, P.E. Editor’s Note: This supplement provides a brief overview regarding the application of performance-based design approaches for fire and life safety. Specific examples regarding egress, occupant loading, structural fire protection, smoke management, and sprinkler protection are addressed. Milosh Puchovsky, P.E., is a principal fire protection engineer with NFPA, where he oversees NFPA’s projects on Performance-Based Codes and Fire Risk. He also serves as staff liaison to a number of technical committee projects, including those responsible for NFPA’s Building Construction and Safety Code and Life Safety Code. Milosh also oversees NFPA’s High-Rise Building Safety Advisory Committee. Jim Quiter, P.E., is a principal of Arup and the leader of Arup Consulting in the United States. He is also chair of the Safety to Life Technical Correlating Committee and a member of the NFPA 5000௡ Technical Correlating Committee, as well as Chair of the NFPA High- Rise Building Safety Advisory Committee. Jim is a registered professional engineer in several states. The application of performance-based design con- Over the past several years, a more formalized cepts has been permitted by various codes and stan- approach to the equivalency concept has been devel- dards through equivalency or alternative means of oped. This approach is often referred to as perfor- protection provisions. Initially, the overall concept mance-based design. Both the Society of Fire was to allow for the use of alternative approaches or Protection Engineers (SFPE) and NFPA have devel- technologies in meeting the intent of the code. As oped guidance documents in this regard.1,2 As noted such, equivalency concepts were pursued where the in Chapters 4 and 5 of the Life Safety Code, perfor- code did not specifically address a given situation, or mance-based design is now specifically addressed where priority was given to a design concept that and permitted by NFPA 101 as well as NFPA 5000௡, called for a building arrangement or feature that was Building Construction and Safety Code௡.3 not in strict compliance with the prescriptive provi- The application of performance-based design for sions of the code. While the equivalency approach fire safety should include a risk analysis to identify has been implemented for decades, no guidance or the types of fires to be considered. This is an im- established approach existed that would aid the de- portant step, as the threat to occupants by fire needs signer or the enforcing authority in making appro- to be identified and quantified if an appropriate fire priate decisions about the equivalent means of safety solution is to be developed. Traditional build- protection. ing regulations do not identify the fire hazard against 1207 1208 Supplement 7 • The Application of Performance-Based Design Concepts for Fire and Life Safety which the standard protects. In most cases, building floor is 795 ft (242 m) above grade. In accordance with regulations prescribe a solution to some unidentified applicable regulations, some floors of the structure or vague fire situation. could include an occupant load in excess of 500 peo- Performance-based design provides a more flexi- ple. Strict adherence to the Life Safety Code requires ble approach, allowing greater design freedom while three remote exit stairs leading from the top of the specifically addressing fire and life safety concerns of tower to the base of the building. The physical area a specific building project. When properly applied, it of the supporting structure is not large enough to provides a more informed approach so that life safety provide remotely located stairs in accordance with risks can be more carefully addressed. Performance- the Code, and the height of the building makes the based design also typically involves the use of com- use of stairs as a means of egress somewhat impracti- puter fire models or other fire engineering calculation cal. An alternative approach based on performance- methodologies, such as timed egress studies, to help based design concepts was necessary to develop a assess if the proposed fire safety solutions meet the workable egress strategy. fire safety goals under the conditions specified. Although performance-based design can be ap- Exit Program plied to any building project, it is most effective for The primary evacuation method for this building is complex and unusual structures, particularly those the use of typical exit stairs for the occupied floors, that do not fit well within the guidelines of prescrip- discharging to areas of refuge on the lowest two floors tive building regulations. Examples include conven- of the pod. In other words, from floors 3 through 10 tion centers, shopping malls, airport terminals, of the pod, three sets of exit stairs are provided, each transportation centers, and buildings with unen- enclosed in 2-hour fire-resistant construction, just as closed vertical openings, all of which pose challenges would be found in most other buildings. However, with regard to egress, spread of fire and smoke, and these stairs discharge to an area of refuge at the low- detection and suppression. Museums and historic est two levels of the pod, which is still 750 ft (230 m) structures also benefit from performance-based de- above grade. These two areas of refuge are used for sign because the designers of these buildings must no other purpose, and consist entirely of non- balance aesthetics and historic preservation with fire combustible construction. Rather than rely on me- safety concerns, and building regulations do not usu- chanical systems to maintain the areas of refuge free ally address property protection or historic preserva- of smoke in the event of a fire, the two floors are tion. For similar reasons, industrial facilities with open to the surrounding exterior environment so that hazardous or sensitive processes and contents also natural ventilation occurs. Since the two areas are benefit from performance-based design. below the occupied levels, it is unlikely that a fire in an occupied level would spread to the areas of refuge. EGRESS FROM AN OBSERVATION TOWER Additionally, all the floors including the areas of ref- uge are provided with sprinkler, standpipe, and In developing the fire and life safety program for a alarm systems, further reducing the likelihood of building such as an observation tower with a large downward fire spread. (Detectors are located on all population and amusement rides, numerous issues floors other than the open refuge floors.) need to be addressed. The tower rises over 900 ft (274 From the area of refuge, a single stair leads down m) above grade, with eight occupied levels and two through the shaft of the tower to grade. The primary amusement rides in the ‘‘pod’’ or upper portion of evacuation route from the area of refuge involves the the tower. At the base of the tower is a casino building. elevators. These elevators have two levels and travel Occupied floors of the pod include two levels of ob- at a speed of up to 1,800 ft/min. They can discharge servation deck, a restaurant, a meeting room level, either within the main casino or at two specially de- wedding chapels, and a bar level. The top level func- signed discharge levels at the roof of the base build- tions as an amusement level, containing a roller ing. These discharge levels are enclosed in 2-hour coaster and ‘‘space shot’’ ride. Exhibit S7.1 illustrates fire-resistant construction from the roof to grade and level 6 of the pod, which functions primarily as a are separated from all other areas by 2-hour fire- restaurant. Exhibit S7.2 illustrates level 8 of the pod, resistant construction. which functions as the lower observation level. Ex- hibit S7.3 illustrates level 1 of the pod, which serves Special Elevator Shaft Protection as one of two refuge areas. The most obvious concern is providing for emer- To increase the reliability of the elevators and the gency egress, considering that the lowest occupied safety of the elevator car occupants, special protection 2006 Life Safety Code Handbook Egress from an Observation Tower 1209 Exhibit S7.1 Observation tower, pod level 6. has been provided. The tower design was undertaken 3. Elevator lobbies are on a separate smoke control during the same time period in which the National zone to maintain pressurization with relation to Institute of Standards and Technology (NIST) was adjacent spaces. Therefore, smoke in an adjoining initiating studies on the use of elevators for building area will not spread into an elevator lobby. evacuation. Many of the recommendations developed 4. Openings into the elevators are slightly raised by NIST have been incorporated as design concepts from the remainder of the floor, preventing water for the tower. The concepts include the following: flow on a floor level from spilling into the elevator hoistway. 1. Elevators open into 2-hour fire-resistance-rated el- 5. Because the areas of refuge are at the two lowest evator lobbies on all floors, at both the top and the floor levels of the pod, the elevators will not need bottom of the building. to travel past a fire floor. Elevators will travel only 2. There are four elevators that travel through the between the areas of refuge and the base building. shaft from the base to the top. Two independent Areas of refuge for disabled persons are provided elevator machine rooms serve these elevators. The within the enclosed pressurized stairwells at each elevator machine rooms are separated by 2-hour level. fire-resistant construction and have a 4-in. curb 6. Elevator shafts are vented to the outside at the installed between them so that water flow in one top, and the vents are separate from the machine machine room will not affect the other.