ASHRAE AN-04-11-2-2004 Smoke Control and the International Building Code《烟气控制和国际建筑守则》.pdf

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1、AN-04-1 1-2 Smoke Control and the International Building Code John H. Klote, D.Sc., P.E. Fellow ASHRAE ABSTRACT This paper is an overview of the smoke controlprovisions of Section 909 of the 2000 Intemational Building Code (IBC). The IBC allows third-party testing/commissioning and third- party assi

2、stance in review of design aspects. A rational anal- ysis in accordance with well-established engineering princi- ples is specifically required. This analysis must include “suflcient information anddetail” to demonstrate compliance with the code. The code has requirements for the tightness of smoke

3、barriers. Smoke control can be achieved by the pres- surization method, the airflow method, or the exhaust method. The IBC has specijc requirements for the minimum size of a design jire. INTRODUCTION The International Building Code (IBC) was developed by the International Code Council to replace the

4、 three model building codes (BOCA 1999; ICBO 1997; SBCCI 1997). This paper is an overview of the smoke control provisions of Section 909 of the 2000 IBC (ICC 2000), but not all require- ments and exceptions are addressed. For the specific code requirements, readers should see the IBC. For a more det

5、ailed discussion of smoke control with reference to the IBC, see Evans and Klote (2002). For exhaustive information including the fundamental mathematics about the entire topic of smoke management, see Klote and Milke (2002). A coordinated effort among all involved parties is needed to meet the smok

6、e protection provisions of the code. It cannot be overemphasized that the design professionals, including the architect, mechanical engineer, electrical engineer, fire protection engineer, building oficial, and fire chief, as well as all applicable trades, including the fire alarmelectrical Douglas

7、H. Evans, P.E. contractor(s), automatic sprinkler contractor, mechanical contractor, and those responsible for construction of smoke barriers, must work together to accomplish a fully functional smoke control system. Permit applications for architectural, mechanical, and electrical submittals should

8、 not be approved until all aspects of the smoke control system are adequately coordinated. Until applicable fire protection aspects are coor- dinated, renovations and demolition permit applications for existing buildings may also need to be held. It is important to think of fire protection in terms

9、of systems. These systems include the passive barriers (walls and floors) along with the active systems (automatic sprinklers, fire detectiodalarm systems, air-handling equipment, etc.). These systems must work together to achieve a consolidated coordinated approach to fire protection. Section 909 o

10、f the IBC describes both mechanical and passive smoke control systems. Compliance with this section is only required when so directed by other provisions of the code. The purpose of Section 909 is to establish minimum requirements for the design, installation, and acceptance test- ing of smoke contr

11、ol systems that are intended to provide a tenable environment for the evacuation or relocation of occu- pants. Mechanical systems are not mandated. Passive contain- ment may also be used as a viable option to provide a tenable environment for the evacuation or relocation of occupants. The provisions

12、 of Section 909 are not intended for the preser- vation of contents, the timely restoration of operations, or for assistance in fire suppression or overhaul activities. This paper discusses (1) special inspection and test requirements, (2) rational analysis, (3) smoke barrier construction, (4) smoke

13、 control by the pressurization method, John H. Mote is a consulting engineer at Fire and Smoke Consulting, Leesburg, Va. Douglas H. Evans is a fire protection engineer with Clark County Building Department, Las Vegas, Nev. 638 I 02004 ASHRAE. (5) smoke control by the airflow method, (6) smoke contro

14、l by the exhaust method, and (7) determination of a design fire. SPECIAL INSPECTION AND TEST REQUIREMENTS Section 909 was written to allow not only third-party test- ing/commissioning but also assistance in review of design aspects. If the building official feels that departmental staff does not hav

15、e either the time or expertise to adequately review smoke control systems in accordance with Section 909, third- party review may be utilized. Compliance with Section 909 is recognized as one option in meeting the requirements of Section 410.3.7.2 for stage ventilation. Similarly, Section 1008.5.2.1

16、 allows compliance with Section 909 as one option for smoke-protected assembly seating. The other option this section allows is “natural venti- lation.” When the facility is substantially open to the atmo- sphere, natural ventilation can provide protection within the intent of the code. If the facil

17、ity is enclosed, a smoke reservoir calculated in accordance with the exhaust method of Section 909 is necessary to ensure compliance. RATIONAL ANALYSIS A rational analysis in accordance with well-established engineering principles is specifically required. This means that the design must be based on

18、 mathematical calculations using known laws ofphysics. The engineer ofrecord is respon- sible for designing a system that will function properly to fulfill the requirements of Section 909. The desiver is required to include “sufficient information and detail” to demonstrate compliance, as well as gi

19、ve the respective contractors sufficient information to construct the system. When requested by the authority having jurisdiction (AHJ), substantiation of a thorough analysis of the conditions outlined in Section 909.2 must be submitted for review and approval. The analysis needs to address stack ef

20、fect, temperature effect of the fire, wind effect, HVAC systems, climate, and duration of operation. The system must be designed such that the maximum probable normal or reverse stack effect will not adversely interfere with the systems capabilities. In determin- ing the maximum probable stack effec

21、t, altitude, elevation, weather history, and interior temperatures need to be used. Section 909.9 states that buoyancy and expansion caused by the design fire must be analyzed. The system needs be designed such that these effects do not adversely interfere with the systems capabilities. The design n

22、eeds to consider the adverse effects of wind. Wind effect can impact the placement, orientation, and type of fans used. Wind speed is dependent on the height above grade and the surrounding terrain. Therefore, the level of the space, the side of the building, adjacent obstructions (such as build- in

23、gs), and type of equipment need to be considered. The design needs to consider the effects of the heating, ventilating, and air-conditioning (HVAC) systems on both smoke and fire transport. The analysis must include all permutations of systems status. The design must consider the effects of the fire

24、 on the HVAC systems. With respect to climate, the design needs to consider the effects of low temperatures on systems, property, and occu- pants. Air inlets and exhausts must be located so as to prevent snow or ice blockage. All portions ofthe smoke control system must be protected from adverse wea

25、ther conditions, including high and low temperatures, as well as precipitation. This section also requires the designers to consider the potential for adversely impacting internal building systems and egress paths by introducing substantial quantities of unheated outside air. The code requires that

26、all portions of active or passive smoke control systems need to be capable of continued oper- ation after detection of the fire event for not less than 20 minutes. This 20-minute default is based on the weakest link permitted by the code, which is a 20-minute rated door. There are times when 20 minu

27、tes will be inadequate. It is the designers responsibility to determine these instances, along with an appropriate resolution, as a part of the rational analy- sis. In order to meet the requirements of this section, the construction of smoke barriers and all openings in them must be protected for at

28、 least 20 minutes. Opening protectives, as specified in Section 7 14, need not be provided if the airflow or exhaust methods are used in the design and unprotected open- ings are considered fully open. In addition, all portions of an active smoke control system must be capable of continued operation

29、 for at least 20 minutes. These requirements must be included in the analysis by the design professionals. Compliance with these requirements will be documented on the respective plan submittals when requested by the AHJ. Fan locations and their proximity to potential fuel pack- ages must also be co

30、nsidered. If fans are reasonably distant from a sprinkler-protected fire and adequate entrainment can be assured, it should only be necessary to have fans rated somewhat above ambient temperature. The temperatures expected in sprinkler-controlled fires are discussed later. Fans that may be activated

31、 by smoke detection, located in non- sprinkler-protected areas and/or directly above significant fuel loads, should be analyzed by a licensed design professional working within the area of their expertise to determine the maximum expected temperature. ANSUASHRAE Standard 149-2000, Laboratory Methods

32、 of Testing Fans Used to Exhaust Smoke in Smoke Management Systems, can be used as a guide to selecting fans that are expected to function while subjected to elevated temperatures. Solid-state equipment, printed circuit boards, central processing units (CPUs), and other sensitive electronic equip- m

33、ent are highly susceptible to smoke and heat. When such equipment provides smoke control functions/commands, proper protection is necessary. When sensitive electronic equipment is located in rooms separate from the expected room of origin, this equipment may be considered protected ASHRAE Transactio

34、ns: Symposia 639 within the intent of IBC Section 909.12. Mechanical rooms not used as plenums even meet the intent ofthis section. When sensitive electronic equipment is installed within the smoke zone it serves (including mechanical rooms serving as plenums), the designers are expected to provide

35、protection within the intent of IBC Section 909.4.6. This interpretation applies mainly to computer-based technology where the logic must remain functional. In most cases, smoke detectors, addressable modules, and other “end” devices that can be expected to have already fulfilled their function prio

36、r to becoming damaged will not need this additional protection. SMOKE BARRIER CONSTRUCTION Smoke barriers addressed in Section 909.5 must comply with Section 709, and they have to be constructed and sealed to limit leakage areas exclusive of protected openings. In any “solid” material there are actu

37、ally millions of tiny cracks and holes. The concept of the leakage area ratio can be thought of as a way to estimate an equivalent hole size for these millions of tiny cracks and holes. Section 909.5 indicates that the maximum allowable leakage area is to be calculated using the following leakage ar

38、ea ratios: (1) walls at A/A, = 0.00100, (2) exit enclosures at AIA, = 0.00035, (3) all other shafts at A/A, = 0.00150, and (4) floors and roofs at A/AF = 0.00050, where A is the total leakage area, A, is the unit floor or roof area of barrier, and A, is the unit wall area of barrier. These areas hav

39、e units of ft2 (m2). Based on published leakage area data (Klote and Milke 2002; SFPE 2002), these leakage area ratios can be thought of as representing poor quality construction. Because smoke barriers are required to comply with Section 709, they must have a one-hour rating except for 1-3 occupanc

40、ies. Further, they are required to be continuous from outside wall to outside wall and from slab to slab. The layout of smoke control zones in many smoke control systems makes the requirement for barriers that are continuous from exterior wall to exterior wall impractical or impossible. Since the in

41、tent of a smoke control system is to provide a tenable environment for the evacuation or relocation of occupants, it seems unnec- essary to mandate in all cases that smoke barriers be continu- ous from exterior wall to exterior wall. If smoke barriers are properly constructed, smoke can be restricte

42、d to the zone of origin even if the zone is fully contained within the building. Mechanical systems can also be used in “land locked” smoke zones to further ensure that smoke does not migrate into adja- cent zones. Since mechanical systems are not specifically required for compliance with Section 90

43、9, it may be reason- able to take advantage of mechanical systems to justify smoke zones that are “land locked.” If this approach is to be used, it must be discussed with and approved by the AHJ during early conceptual phases of the design. The stipulation in Section 709.4 that smoke barriers must b

44、e continuous from slab to slab, along with the exception, provides guidance when interstitial spaces need to be consid- ered part of a smoke zone, or when they may be considered separate smoke zones. One way to think about it is that smoke compartments may be adjacent either horizontally or verti- c

45、ally. Here again, mechanical systems may be designed to serve these interstitial spaces to help restrict smoke migration into adjacent smoke zones. Openings due to doors, operable windows, and similar gaps are not included in the “equivalent hole” leakage esti- mates. As such, the gaps around doors,

46、 dampers, and other openings must be added to the “equivalent hole size” esti- mated from the formula provided in items 1 through 4 of Section 909.5. In most cases, the area ofthese gaps will be esti- mated using basic math (length times width). Since smoke/ combination dampers required for smoke co

47、ntrol systems are allowed to have some leakage (Class II), there may be times when it will be necessary to include an additional leakage value for a specific damper. With some exceptions, openings in smoke barriers must be protected by automatic-closing devices actuated by the required controls for

48、the mechanical smoke control system, and door openings need to be protected by door assemblies complying with Section 714.2.3. PRESSURIZATION METHOD Section 909.6 states that the primary mechanical means of controlling smoke is by pressure differences across smoke barriers, and maintenance of a tena

49、ble environment is not required in the smoke control zone of fire origin. Section 909.6, in conjunction with Section 909.4.6, spec- ifies that the pressurization method is only intended to contain smoke within the zone of origin for at least 20 minutes. This design approach is not a “purge” system, nor is it intended to provide a tenable environment in the zone of origin. Smaller enclosed spaces with low to moderate ceiling heights will typi- cally use either a mechanical/active pressurization approach or a non-mechanicapassive approach. Mechanical systems will normally use exhaust air t