1、NFPA 251 Standard Methods of Tests of Fire Resistance of Building Construction and Materials 2006 Edition NFPA, 1 Batterymarch Park, Quincy, MA 02169-7471 An International Codes and Standards Organization IMPORTANT NOTICES AND DISCLAIMERS CONCERNING NFPA DOCUMENTSNOTICE AND DISCLAIMER OF LIABILITY C
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21、 headquarters, addressed to the attention of the Secretary, Standards Council, NFPA,1 Batterymarch Park, P.O. Box 9101, Quincy, MA 02269-9101.For more information about NFPA, visit the NFPA website at www.nfpa.org.Copyright 2005, National Fire Protection Association, All Rights ReservedNFPA 251Stand
22、ard Methods of Tests ofFire Resistance of Building Construction and Materials2006 EditionThis edition of NFPA 251, Standard Methods of Tests of Fire Resistance of Building Constructionand Materials, was prepared by the Technical Committee on Fire Tests and acted on by NFPAat its June Association Tec
23、hnical Meeting held June 610, 2005, in Las Vegas, NV. It was issuedby the Standards Council on July 29, 2005, with an effective date of August 18, 2005, andsupersedes all previous editions.This edition of NFPA 251 was approved as an American National Standard on August 18,2005.Origin and Development
24、 of NFPA 251NFPA 251 originated in the recommendations of the International Fire Prevention Con-gress in London in 1903. It was presented to the NFPA by the Committee on Fire-ResistiveConstruction in 1914. It was adopted officially in a revised form in 1918. Successive editionswere published in 1926
25、, 1934, 1941, 1955, 1958, 1959, 1960, 1961, 1963, 1969, 1979, 1985, and1990. It was overseen, in succession, by the Technical Committee on Fire-Resistive Construc-tion, the Technical Committee on Building Construction, and, for the last three editions, bythe Technical Committee on Fire Tests.The 199
26、5 edition of this document was a reconfirmation of the earlier edition with only afew items being addressed. Substantial investigation and record research was done on thetopic of the hose stream application on test specimens. The findings of the committee did notsupport modification of the provision
27、 that permits a test assembly to be tested for one-half thetime required for an hourly rating and then to be tested by a hose stream.The committee also modified the title of this document in response to the research doneto convey a truer sense of the standards proper application.The 1999 edition was
28、 a reconfirmation of the 1995 edition with minor editorial modifications.The 2006 edition includes a complete editorial rewrite for compliance with the Manual ofStyle for NFPA Technical Committee Documents. The title of the document was revised to moreaccurately reflect the subject matter, and furth
29、er organizational and editorial changes weremade to improve the application of the test method. Technical changes include the additionof definitions of fire resistance and fire resistance rating and modifications to the hose stream testrequirements.2511Technical Committee on Fire TestsWilliam E. Fit
30、ch, ChairOmega Point Laboratories Inc., TX RTJesse J. Beitel, Hughes Associates, Inc., MD SEApril L. Berkol, Starwood Hotels and Resorts Worldwide,Inc., NY URep. American Hotel and Lodging AssociationRobert G. Bill, Jr., FM Global, MA IJohn A. Blair, The DuPont Company, DE MRep. Society of the Plast
31、ics Industry, Inc.Gordon H. Damant, Inter-City Testing and ConsultingCorp. of California, CA SEThomas W. Fritz, Armstrong World Industries, Inc., PA MPravinray D. Gandhi, Underwriters Laboratories Inc., ILRTJames R. Griffith, Southwest Research Institute, TX RTGordon E. Hartzell, Hartzell Consulting
32、, Inc., TX SEMarcelo M. Hirschler, GBH International, CA SEAlfred J. Hogan, Reedy Creek Improvement District, FL ERep. International Fire Marshals AssociationWilliam E. Koffel, Koffel Associates, Inc., MD SEJames R. Lawson, U.S. National Institute of Standardsand Technology, MD RTRodney A. McPhee, C
33、anadian Wood Council, Canada MFrederick W. Mowrer, University of Maryland, MD SEDavid T. Sheppard, U.S. Department of Justice, MD RTKuma Sumathipala, American Forest others use a systemof hydraulic rams for floor and roof assemblies. Where a uni-formly distributed load is simulated by point-loading
34、(severalsmall-area loads), it is recommended that the load at any sucharea not exceed 25 percent of the total load and that the indi-vidual load have a width at least equal to the depth of the floor.Wall furnaces generally are equipped with hydraulic rams.G.8.3 This standard requires that load-beari
35、ng walls and parti-tions sustain the applied test load during the fire endurance andhose stream tests. A former provision that required load-bearingwalls and partitions to sustain twice the specified superimposedtest load after cooling but within 72 hours of the test period hasbeen deleted from the
36、method as being unrealistic. Nonbearingwalls and partitions are not loaded during the test but are re-strained on all sides. This restraint could impose more stress thana load on top. The ASTM Committee E-5 has reviewed the load-ing procedures for framed walls and partitions several times. Itwas the
37、 committees unanimous decision that such a wall betested either with calculated maximum design load or with a loadexpected to occur in practice. The method used to compute thedesign loads should be reported.G.8.4 Some important stresses, such as those caused by creepand shrinkage in the wall itself
38、and its supporting frame, arepresent, and the designer should recognize these stresses in theanalysis. The ASTM Committee E-5 has investigated the possibil-ity of openings occurring in joints at the corners of non-load-bearing enclosures due to differential movement. While the pos-sibility exists th
39、at this will occur, the committee has not found itfeasible to amend the test based on available data.G.8.5 Double walls pose a unique problem for load application.Which wall should be loaded? Should both walls be loaded simul-taneously? The ASTM Committee E-5 has devoted considerabletime to debating
40、 this problem and recommends that the deci-sion be made by the user after an analysis of the loading condi-tions anticipated in service both before and after a fire. Suchloading conditions are to be reported.G.9 Integrity. All walls and partitions that qualify for a fireendurance classification of 1
41、 hour or more are required to besubjected to the cooling impact and erosion effects of a streamof water from a 212 in. (63.5 mm) hose discharging through astandard play pipe equipped with a 118 in. (28.6 mm) tip un-der specified pressures. In this hose stream test, the ability ofthe construction to
42、resist disintegration under adverse condi-tions is examined. The requirement for a hose stream test wasremoved from the test procedure for columns and floor orroof assemblies because of impracticality and the possibility ofexcessive damage to the furnace.G.10 Conditions of Tests.G.10.1 Columns gener
43、ally are tested with all four sides ex-posed to the test fire. However, it is possible to test a columnwith three sides exposed (with the fourth side against a wall).This standard requires that specimens be tested under condi-tions contemplated in the design. The former general practiceof testing co
44、lumns with pin connection at the top and bottomto simulate the most critical condition is no longer a criterion.G.10.2 Columns are required to sustain successfully the designload during the test period. This standard also permits columnsto be loaded up to 134 times the design load prior to the fire
45、test,if desired by the submitter. Such loading, however, should not beconstrued as having had a deleterious effect on the fire endur-ance test performance. Instead of loading, steel columns, whoseprotective covering does not carry a load, can be assigned a fireresistance classification on the basis
46、of the temperature of thesteel only. With such columns, the protective cover should berestrained against longitudinal expansion. Wood columns aretested for load-carrying ability only.G.10.3 Test results have established that variations of re-straint conditions can influence the time of fire resistan
47、ce fora structure or a structural element considerably. Restraintsgenerally are beneficial to fire resistance; however, there areconditions under which restraint can have a detrimental effecton the performance of a specimen during a fire resistancetest.34, 35 The users of test results are advised to
48、 study thereference documents as well as Annex E and Table E.1.5.G.10.4 An unrestrained fire resistance rating for a steel beam ora reinforced concrete beam used as part of an assembly tested inrestrained condition can be assessed from the temperaturerecords obtained for the steel or the reinforcing
49、 steel, respec-tively (see Chapter 13). It is also possible to evaluate the protectivecover of steel beams by measuring the temperature of the steelthat is protected (see Chapter 14). The fire resistance rating deter-mined under the provisions of Chapter 13 is applicable only tobeams used with a floor or roof construction that has a compa-rable or greater capacity for heat dissipation from the beam thanthe floor or roof with which the beam is tested.G.11 Other Observations.G.11.1 No limitation is imposed on the deformation of thespecimen during or
