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Missouri University of Science and Technology Scholars' Mine AISI-Specifications for the Design of Cold-Formed Steel Structural Members Wei-Wen Yu Center for Cold-Formed Steel Structures 01 Jan 1981 Fire Resistance Ratings of Load Bearing Steel Stud Walls with Gypsum Wallboard Protection American Iron and Steel Institute Follow this and additional works at: https://scholarsmine.mst.edu/ccfss-aisi-spec  Part of the Structural Engineering Commons Recommended Citation American Iron and Steel Institute, "Fire Resistance Ratings of Load Bearing Steel Stud Walls with Gypsum Wallboard Protection" (1981). AISI-Specifications for the Design of Cold-Formed Steel Structural Members. 99. https://scholarsmine.mst.edu/ccfss-aisi-spec/99 This Technical Report is brought to you for free and open access by Scholars' Mine. It has been accepted for inclusion in AISI-Specifications for the Design of Cold-Formed Steel Structural Members by an authorized administrator of Scholars' Mine. This work is protected by U. S. Copyright Law. Unauthorized use including reproduction for redistribution requires the permission of the copyright holder. For more information, please contact scholarsmine@mst.edu.                   Fire Resistance Ratings of Load Bearing Steel Stud Walls With Gypsum Wallboard Protection  R E S E A R C H  R E P O R T  R P 8 1 - 1   1 9 8 1  R E V I S I O N  2 0 0 7     American Iron and Steel Institute  research report Fire Resistance Ratings of Load Bearing Steel Stud Walls With Gypsum Wallboard Protection i DISCLAIMER The material contained herein has been developed by researchers based on their research findings and is for general information only.  The information in it should not be used without first securing competent advice with respect to its suitability for any given application.  The publication of the information is not intended as a representation or warranty on the part of the American Iron and Steel Institute, Steel Framing Alliance, or of any other person named herein, that the information is suitable for any general or particular use or of freedom from infringement of any patent or patents.  Anyone making use of the information assumes all liability arising from such use.                                   Copyright 1981 American Iron and Steel Institute Copyright 2002 Steel Framing Alliance Revised Edition Copyright 2007 American Iron and Steel Institute / Steel Framing Alliance ii Fire Resistance Ratings of Load Bearing Steel Stud Walls With Gypsum Wallboard Protection PREFACE This report presents the results of a two-phase study, which included nine full-scale fire tests conducted at Underwriters Laboratory, Inc. (UL), small scale tests at the Research Laboratory of the United States Steel Corp. (USS) to determine the effects of temperature on material properties, and further work by the USS Research Laboratory to develop additional information for refining and substantiating the aforementioned data for temperatures up to approximately 1800 degrees F (982 degrees C). The findings provided some of the back-up data for the fire-resistance ratings given in UL Design No. U425.   Research Team Steel Framing Alliance Fire Resistance Ratings of Load Bearing Steel Stud WallsWith Gypsum Wallboard Protection with or without cavity insulationBuilding Code ProvisionsBuilding codes frequently require load-bearing walls to have a fire-resistance rating that is based on fire testsconducted in accordance with a specification of the American Society of Testing & Materials (ASTM) title ASTME119, Standard Methods of Fire Tests of Building Construction and Materials.In the case of load-bearing walls, this test stipulates that they must: a) withstand fire exposure, under a specifiedloading, without structural collapse, thereby preventing flame passage through the wall, and b) prevent intra-walltransmission of heat that will ignite combustible materials on the unexposed side of the wall for which theindication of failure is defined as a 250 degrees F (139 degrees C) average temperature rise on the unexposedsurface or 325 degrees F (181 degrees C) temperature rise at any one point.  The fire exposure is followed by afire and hose-stream test that is designed to evaluate the wall’s resistance to the passage of the hose streamthrough the wall.Research ProgramThe American Iron and Steel Institute (AISI) sponsored a research program that sought to develop an analyticalmethod that would make it possible to predict the structural behavior of cold-formed sheet-steel studs in load-bearing walls under the conditions set forth in the ASTM E119 Standard Fire Test.  This program called for full-scale fire tests designed to provide data on the effects of insulation, wallboard thickness, and loading on the fire-resistance ratings.The entire study was conducted along two lines:Phase 1 consisted of seven full-scale fire tests conducted at Underwriters Laboratory, Inc. (UL).  Theseinvestigations provided basic data as called for in the program.  While this work was being carried out at UL, theResearch Laboratory of the United States Steel Corp. (USS) was conducting small-scale tests on steel studs, todetermine the effects of temperature on yield strength (Fy), effective cross-sectional strength (Q), and themodules of elasticity (E).Phase II involved further work by the USS Research Laboratory to develop additional information for refiningand substantiating the aforementioned data for temperatures up to approximately 1800 degrees F (982 degreesC).  In addition, during this second Phase, two other full-scale fire tests were run at UL.  These includedincreased instrumentation to measure: a) the wall loading prior to and during the test, B) wall deflection at thepoint of structural failure, and temperature measurements of each steel stud.Construction of Fire-Tested AssembliesThe load-bearing wall assemblies were constructed in two ways – with and without insulation in the concealedspace between cold-formed sheet steel studs spaced 24 inches o.c.  Tests were run on studs faced with 1/2inch or 5/8 inch thick Type X gypsum wallboard in one, two or three layers.  Design of the steel studs followedthe recommendations of the AISI Specification for the Design of Cold-Formed Steel Structural Members, 1968Edition, assuming steel studs were fully braced laterally by the gypsum wallboard.Fire-resistance ratings, construction and material details are given in UL Fire Resistance Directory as DesignNo. U425. (Fig. 1)  The ratings assigned to this Design are based on data from this test program along with datafrom three tests that had been carried out prior to the present work.UL Fire Resistance DirectoryDesign No. U425Interior Walls – Wallboard Protection Both Sides of WallRatingNumber of Layers and Thicknessof Boards in Each LayerPercent ofDesign Load45 min *1 layer, ½  in. thick 1001 hr *1 layer, 5/8 in. thick 1001 ½ hour *2 layers, ½ in. thick 1002 hr *2 layers, 5/8 in. thick or*3 layers, ½ in. thick80100*Ratings applicable to assemblies serving as exterior walls where Classified fireresistive gypsum sheathing  type wallboard is substituted on the exterior face.Exterior Walls – Wallboard Protection on Interior Side of WallRatingNumber of Layers and Thicknessof Boards in Each LayerPercent ofDesign Load45 min 1 layer, 5/8 in. thick 1001 hr 2 layers, ½  in. thick 1001 ½ hour 2 layers, 5/8 in. thick 1002 hr 3 layers, ½ in. thick 1001. Steel Floor and Ceiling Tracks – Top and bottom tracks of wall assemblies shallconsist of steel members, min. No. 20 GSG (0.036 in. thick) galv. steel or No. 20 MSG(0.033 in. thick) primed steel, that provide a sound structural connection between studs,and to adjacent assemblies such as floor, ceiling and/or other walls.  Attached to floorand ceiling assemblies with steel fasteners spaced not greater than 24-in. o.c.2. Steel Studs – Corrosion-protected steel studs, min. 3 ½ in. wide, min. No. 20 GSG(0.036 in. thick) galv. steel or No. 20 MSG (0.033 in. thick) primed steel, cold-formed,shall be designed in accordance with the current edition of the Specification for theDesign of Cold-Formed Steel Structural Members by the American Iron and SteelInstitute.  All design details enhancing the structural integrity of the wall assembly,including the axial design load of the studs, shall be as specified by the steel studdesigner and/or producer, and shall meet the requirements of all applicable local codeagencies.  The max. stud spacing of wall assemblies shall not exceed 24 in.  Studsattached to floor and ceiling tracks with ½ in. long Type S-12 pan head, self-drilling, self-tapping steel screws on both sides of studs.3. Lateral Support Members (Not shown) – Where required for lateral support of studs,support may be provided by means of steel straps, channels or other similar means asspecified in the design of a particular steel stud wall system.4. *Wallboard, Gypsum – Any gypsum wallboard bearing the ULI Classification Markingas to Fire Resistance.  Applied vertically with joints between layers staggered.  Outerlayer of three-layer construction may be applied horizontally.  The thickness and numberof layers and percent of design load for the 45 min, 1 hr, 1 ½ hr and 2 hr ratings are asshown above.  See Wallboard Gypsum (CKNX) Category for names of ClassifiedCompanies.5. Gypsum Sheathing and Exterior Facings – For exterior walls, single layer of ½ in thickexterior regular gypsum sheathing applied vertically and attached to studs and runnertracks with 1 in long Type S-12 bugle head screws spaced 12 in o.c. along studs andtracks.  Exterior facings consisting of aluminum siding, steel siding, brick veneer, orstucco attached to studs over gypsum sheathing and meeting the requirements of thelocal code agencies.  When a min. 3 ¾ in thick brick veneer facing is used, the ExteriorWall Rating is applicable with exposure on either face side.  Brick veneer wall attachedto studs with corrugated metal wall ties attached to each stud with steel screws, not more than each sixth course of brick.6. Fasteners – Screws used to attach wallboards to studs: self-tapping bugle head sheet steel type, spaced 12 in o.c.  Firstlayer Type S-12 by 1 in long; second layer Type S-12 by 1 3/8 in long; third layer Type S-12 by 1 7/8 in long.7. *Batts and Blankets – Placed in stud cavities of all exterior walls.  May or may not be used in interior walls.  Any glass fiberor mineral wool batt material bearing the UL Classification Marking as to Fire Resistance, of a thickness to completely fillstud cavity.  See Batts and Blankets (BZJZ) Category for names of Classified Companies.8. Joint Tape and Compound – Vinyl or casein, dry or premixed joint compound applied in two coats to joints andscrewheads of outer layer.  Perforated paper tape, 2 in wide, embedded in first layer of compound over all joints.*Bearing the UL Classification MarkingFig.1 Details A,B & C. Drawings andaccompanying description of thesethree assemblies are adapted fromDesign No. U425 as given in the ULFire Resistance DirectoryConclusionFigure 2 is a representation of the load-ratio vs. failure-time curves that provided some of the back-up data forthe fire-resistance ratings given in UL Design No. U425.  Here (Fig. 2), the load-ratio (PT/P) is the ratio of thestud failure load at elevated (test) temperature, PT, to that at room temperature, P.  The horizontal line, a load-ratio of 12/23, represents the inverse of the safety factor used in room-temperature design of studs.  Theintersection points, on the horizontal line, made by the failure-time curves, represent the predicted fire-testfailure time if the applied load of 100% of the design load at room temperature.  Thus, dashed lines are used forthe curves above this line because the allowable design loads at room temperature would be exceeded in thisregion.  The vertical scale on the right is the ratio of the allowable fire-test load to the allowable room-temperature load calculated in accordance with the AISI Specification for the Design of Cold-Formed SteelStructural Members, 1968 Edition.In using the fire-resistance ratings assigned to UL Design No. U425 the following should be noted: Loads are expressed as a percentage of the maximum load specified for steel studs by the givenmanufacturer. Steel studs must be designed in conformity with AISI Specification for the Design of Cold-Formed SteelStructural Members (current edition). Insulation in the wall cavity does not affect the assigned fire-resistance rating of interior walls (Fig. 1, DetailA).  UL fire tests demonstrated that a wall assembly, tested without insulation, does not have its structuralintegrity reduced nor are premature hot spots on the unexposed side of the wall produced. Ratings for interior walls are equally applicable to exterior walls (Fig. 1, Detail B).  UL classified fire-resistiveexterior gypsum wallboard sheathing may be substituted for gypsum wallboard on the exterior wall face.Ratings for such exterior walls are applicable for either wall face. If UL classified fire-resistive, water-resistant gypsum wallboard is substituted for the non-water-resistant typeon interior locations, e.g. bathrooms, the assigned rating remains unchanged. For exterior walls having the specified type of brick veneer, the fire-resistance rating applies to either side ofthe wall (Fig. 1, Detail C). Fire-resistive ratings for load-bearing walls can be applied to non-load-bearing walls. Exterior wall facings, if different from those described in the UL Directory, may be acceptable if they aresecured to the steel framing in a manner acceptable to the authority with jurisdiction (Fig. 1, Detail B or C).Figure 2. Curves of the load vs. time relationship for steel stud walls with various gypsum wallboard protections.  Adaptedfrom paper by K.H. Klippstein3References1. “Standard Methods of Fire Tests of Building Construction and Materials,” American Society for Testingand Materials, ASTM E119-79.2. “Specification for the Design of Cold-Formed Steel Structural Members,” American Iron and SteelInstitute, 1968 Edition.3. Klippstein, K.H., “Behavior of Cold-Formed Steel Studs in Fire Tests,” Proceeding, Fifth SpecialtyConference, University of Missouri-Rolla, November 1980.Data, specifications, architectural/engineering information and drawings presented in this publication have beendelineated in accordance with recognized professional principles and practices, and are for general informationonly.  Suggested procedures and products should not, therefore, be used without first securing competentadvice with respect to the suitability for any given application.The publication of material contained herein is not intended as a warranty on the part of the American Iron andSteel Institute-or any person named herein-that these data are suitable for any general or particular use, or offreedom from infringement of any patent or patents.  Any use of these data or suggested practices can only bemade with the understanding that the American Iron and Steel Institute makes no warranty of any kindrespecting such use and the user assumes all liability arising therefrom.This publication was prepared by the Subcommittee on Fire Technology of the Committee onConstruction Codes and Standards1101 17th Street, NW, Suite 1300Washington, DC  20036-4700Copyright 1981 by American Iron and Steel Institute                  Research Report RP-81-1    American Iron and Steel Institute   1140 Connecticut Avenue, NW Suite 705 Washington, DC 20036  www.steel.org       1201 15th Street, NW Suite 320 Washington, DC 20005  www.steelframing.org 

Fire Resistance Ratings of Load Bearing Steel Stud Walls with Gypsum Wallboard Protection

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Fire Resistance Ratings of Load Bearing Steel Stud Walls with Gypsum Wallboard Protection

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