NBSIR 80-2134

NBS

PUBLICATIONS

R.I.C.

A1110S 0 A A 0 5 3

Fire Performance of Selected

Residential Floor Constructions

Under Room Burnout Conditions

J. B. Fang

Center for Fire Research

National Engineering Laboratory

National Bureau of Standards

U.S. Department of Commerce

Washington, DC 20234

December 1980

Interim Report

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80-2134

1980

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Prepared for: Division of Energy, Building Technology and Standards

Office of Policy Development and Research

m3. Department of Housing and Urban Development

ishington, DC 20410

NBSIR 80-2134

- * r FIRE PERFORMANCE OF SELECTED

RESIDENTIAL FLOOR CONSTRUCTIONS

UNDER ROOM BURNOUT CONDITIONS

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J. B. Fang

Center for Fire Research

National Engineering Laboratory

National Bureau of Standards

U.S. Department of Commerce

Washington, DC 20234

December 1980

Interim Report

Prepared for: Division of Energy, Building Technology and Standards

Office of Policy Development and Research

U.S. Department of Housing and Urban Development

Washington, DC 20410

U.S. DEPARTMENT OF COMMERCE, Philip M. Klutznick, Secretary

Jordan J. Baruch, Assistant Secretary for Productivity, Technology, and Innovation

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director
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TABLE OF CONTENTS

Page

LIST OF TABLES iv

LIST OF FIGURES V

Abstract * . 1

1. INTRODUCTION • 1

2. EXPERIMENTAL DETAILS 3

2.1 Test Room 3

2.2 Wall Materials 3

2.3 Interior Furnishings 3

2.4 Test Assemblies 4 2.5 Structural Loading 9

3. TEST MEASUREMENTS 9

3.1 Temperature 9

3.2 Floor Deflection 10

3.3 Static Pressure at Wall 11

3.4 Heat Flux 11

3.5 Air Velocity at Doorway 11

3.6 Optical Density of Smoke 12

3.7 Gas Concentrations 12

3.8 Data Acquisition 12

4. TEST PROCEDURE 12

4.1 Fire Test 12

4.2 Fire Resistance Criteria 13

5. TEST RESULTS 13

5.1 Room Fire Exposure 13

5.2 Performance of Test Assemblies 16

6. DISCUSSION 18

7. SUMMARY 2 3

8. ACKNOWLEDGEMENTS 23

9. REFERENCES 24

APPENDIX A - Maximum Design Load Calculations

APPENDIX B - Log of Tests Based on Visual Observations

TABLES 1-9

FIGURES 1-26

iii
LIST OF TABLES

Page

Table 1 —• Initial weights of furnishings and wall linings and total

available heat of all combustibles used for fire tests .... 25

Table 2 -- Descriptions of combustible contents 26

Table 3 — Descriptions of test assemblies and loading conditions .... 27

Table 4 — Initial weights and potential heat of combustible materials

in test assemblies 28

Table 5 -- Ambient conditions and fire growth events during the tests . . 29

Table 6 — Summary of various measurements during fully developed stage . 30

Table 7 — Incident heat fluxes measured at various locations 31

Table 8 — Optical density of smoke and gas. concentration of outflowing

gases • . . 32

Table 9 — Summary of the fire resistance period of floor assemblies

in room burnout tests 33

i'

j

IV
LIST OF FIGURES

Page

Figure 1 — Plan View of the Test Room Showing Locations of Furniture

and Wall Linings 34

Figure 2 -- Floor-Ceiling Assembly Construction and Instrumentation

Layout for Test 1 36

Figure 3 — Floor-Ceiling Assembly Construction and Instrumentation

Layout for Test 2 37

Figure 4 — Floor-Ceiling Assembly Construction and Instrumentation

Layout for Test 3 38

Figure 5 — Floor-Ceiling Assembly Construction and Instrumentation

Layout for Test 4 39

Figure 6 — Floor-Ceiling Assembly Construction and Instrumentation

Layout for Test 5. . . 4 0

Figure 7 — Floor Plan Showing Layout of Gypsum Board Ceiling for

Tests 5 to 7 41

Figure 8 — Details of Wood Truss Construction for Test 6 42

Figure 9 -- Floor-Ceiling Assembly Construction and Instrumentation

Layout for Test 6 43

Figure 10 -- Floor-Ceiling Assembly Construction and Instrumentation

Layout for Test 7 44

Figure 11 — Layout of Steel Blocks Distributed Uniformly Over the Top

of Floor Assembly for Test 7 45

Figure 12 -- Plan View of the Test Room Showing Instrumentation Layout. . 47

Figure 13 -- Instrumentation Layout at the Doorway Opening 48

Figure 14 -- Instrumentation Layout-View of West (Back) Wall Showing

Wall Thermocouples and Heat Flux Meters 49

Figure 15 — Instrumentation Layout-View of South Plywood Wall Showing

Wall Thermocouples, Total Heat Flux Meter, and Radiometer. . 50

Figure 16 -- Instrumentation Layout-View of North Plywood Wall Showing

Wall Thermocouples 51

Figure 17 — Comparison of Average Upper Room Gas Temperature for Tests

1 to 4 and Experimentally Derived Fire Exposure Curve. ... 52

Figure 18 -- Comparison of Average Upper Room Gas Temperature for Tests

5 to 7 and Experimentally Derived Fire Exposure Curve. ... 53

Figure 19 -- Floor Deflection Measured at the Center of the Test

Assembly 54

Figure 20 -- Floor Deflections at Center and Quarter Points Along the

Center Joist at Various Times for Test 2 55 — Time Variations of Average Surface Temperatures on the

Unexposed Side of Test Assembly for all Tests Performed. . . 56 v

Figure 21
LIST OF FIGURES (continued)

Page

Figure 22 — Comparison of Surface Temperature of Steel Joist and

Plywood Subfloor for Assemblies With and Without a Protective Ceiling 57

Figure 23 — Relationship Between Floor Deflection and Steel Joist

Temperature at Center of Test Assembly 58

Figure 24 — Relationship Between Floor Deflection and Wood Joist

Temperature at Center of Test Assembly 59

Figure 25 — Time Variation of Average Temperature of Steel Joists at

Various Locations 60

Figure 26 — Relationship Between Floor Deflection and Temperature of

Surrounding Gas and Steel Joist Temperature 61

vi
FIRE PERFORMANCE OF SELECTED RESIDENTIAL FLOOR

CONSTRUCTIONS UNDER ROOM BURNOUT CONDITIONS

Jin Bao Fang

Abstract

A series of seven large-scale room burnout fire

tests was conducted with a set of selected residential

floor-ceiling assemblies to provide data on the performance of the assemblies; these will be compared with

the results in future tests on the same constructions

in a fire endurance furnace. Four wood-frame and

three light gage steel-frame, load-bearing assemblies,

each measuring 3.7 x 3.7 m in size, were exposed from

the underside to a fire environment produced from the

burning of typical furniture and interior finish

materials in a room. The fire resistance periods based

on flame-through of floor assembly and structural failure

of floor joists varied from 10 to 12 minutes for floors

with unprotected wood joists and was 4 minutes or less

for floors with unprotected steel joists. The addition

of a 13 mm thick gypsum board ceiling as a protective

layer increased the fire resistance time of the steel

joisted floor assembly approximately 12 minutes.

Key words: Fire endurance, fire tests, flame through,

floors, furniture, interior finishes, joists, room

fires, steel, wood.

1. INTRODUCTION

The performance of a residential floor-ceiling assembly under fire

exposure conditions is of major importance in the confinement of a fire to

its room of origin. Safe evacuation of building occupants and successful

fire fighting operations are dependent on the structural integrity of the

assembly during the fire.

Wood joist framed floor systems have historically been used above

residential basement rooms in single family dwellings. In recent housing

1
construction techniques, a variety of light-gauge metal joists and preassembled small section wooden trusses have been proposed and used as structural components for floor assemblies. These types of floor framing

are claimed to have advantages over conventional wood joists, e.g., lower

price, ability to carry greater loads, and availability of various specified

lengths. In order to reduce the cost of construction, the floor joists over

basements are often not covered on the underside with a fire protective

ceiling. A building fire may therefore produce a collapse of the unprotected

load-bearing structural elements and spread flames to the next story. Information on the performance of protected and unprotected floojr constructions

when exposed to actual fires is essential in the design of fire-safe buildings.

The fire resistance of structural systems is commonly evaluated under

the fire exposure or elevated temperature conditions specified by the standard

ASTM E119 test method [1], and expressed in terms of the time at which the

structure collapses, passes flame, or has an excessive temperature rise on

the unexposed side. This standard fire exposure curve specified over sixty

years ago represents a limiting curve of burnout tests mostly in masonry

structures and without full recognition of the effects of ventilation (heat

losses through doors and windows) . It does not describe the typical fire

environment likely to result in room fires involving modern furnishings.

However, the majority of regulatory building codes state the fire resistance

requirements of floors in terms of the ASTM E119 test.

The research effort for the current task of the present floor assembly

fire endurance study program sponsored by the Office of Policy Development and

Research within the U.S. Department of Housing and Urban Development (HUD) at

NBS is directed toward providing technical data on the fire performance of

selected loaded floor/ceiling assemblies subject to the specified fire environments developed in earlier work [2]

This report describes the experimental

results of a series of seven full-scale fire resistance tests involving selected

loaded, wood and steel framed residential floors. The fire environments

utilized for these tests were produced from the burning of typical furniture

and interior finish materials in a full-sized room with an open door. Summary

data include the times elapsed to failure of floor joists and to flame-through

of the assembly, the time histories of the floor deflections and the average

unexposed surface temperature, and other parameters reflecting the fire growth

in the room. Structural failure of the floor joists and f lame-through of the

floor assembly were considered principal criteria since they were related

directly to sudden failure of the floor to provide support or safety to the

occupants (residents or fire fighters) . In single-family residential constructions and in other situations where compartmentation is not a design feature,

the time to excessive temperature rise on the unexposed surface of the assembly

2
may not be of major significance. However, in this study, excessive surface

temperature rise on the fire unexposed side of the floor was also considered

as a criterion of fire performance.

2 . EXPERIMENTAL DETAILS

2.1 Test Room

All of the fire resistance tests were performed in a burn room having

a 3.3 x 3.3 m (10.7 x 10.7 ft) floor with 2.3 m (7.4 ft) ceiling height as shown in figure 1. A doorway opening measuring 0.8 m (30 in) wide by 2.0 m

(80 in) was situated in the middle of one of the room walls to serve as the

single source of room ventilation. The basic construction of the burn room

was 0.2 m (8 in) thick standard light weight aggregate-concrete block walls

and a concrete floor. The entire test room was built within an air conditioned, large building to control environmental effects.

2.2 Wall Materials

For each test, the internal walls of the test room were lined with 4-mm

(5/32-in) thick prefinished and printed 3-ply lauan plywood panels. The wall

framing consisted of nominal 25 x 76 mm (1x3 in) wood furring strips spaced

0.4 m (16 in) on center and secured to the concrete block walls with 51 -mm

(2-in) long masonary nails. The plywood panels were applied with long edges

parallel to the frame with interior hardened 25-mm (1-in) long paneling nails,

0.2 m (8 in) on center. The perimeter seams of the paneling walls were

covered with 15.9 x 9.5 mm prefinished wood shoe molding. A summary of the

initial weights of wall materials used for each test is given in table 1.

2.3 Interior Furnishings

The household furniture used for each experiment were those commonly

found in a recreation room and included a sofa, an upholstered chair and

ottoman, an end table, a bookcase, and a coffee table. A description of the

materials, size, and nominal weight of these furniture items is presented in

table 2. Figure 1 shows the floor plan of the typically furnished room

illustrating the layout of wall linings and geometrical arrangement of domestic furniture similar to those used in test 9 of basement room burnout test

series [2]

The loading density of the moveable combustibles used for the

series of fire tests was 23 kg/m2 (4.7 lb/ft 2

) of floor area, which was the

average value for recreation rooms in the basements of single family homes

3
in the Washington, D.C. metropolitan area [3]. In addition to the furnishings,

old record files were added in sufficient quantities to reach the required

fire load density. A total of 4.54 kg paper was placed atop the coffee table,

1.81 kg each on the tops of the ottoman and the end table, and the rest

(approx. 77 kg) on the shelves of the bookcase. An olefin carpet with foam

rubber backing was placed on top of a protective layer of 16-mm (5/8-in)

thick, type X, gypsum wallboard covering the concrete floor.

The initial weights and total available heat of the furnishings and

the wall linings used for all of the fire tests performed are given in table

1. The total fire load density ranged from 35.8 to 38.1 kg/m2 (7.3 to 7.8

lb/ft 2

) with an average of 37.1 kg/m2 (7.6 lb/ft 2) of floor area. An estimate

of total heat available from the burning of the interior furnishings and wall

linings for each test was made using these weight data and the weight percentages of the component materials utilized for constructing the furniture

items based on the information provided in table 2. The heat of combustion

values employed for the available energy calculations were 16.7 MJ/kg for

paper, 18.6 MJ/kg for wood, 46.5 MJ/kg for olefin fabric and carpet, and 26.5

MJ/kg for polyurethane foam. The combustible load had an available energy

density ranging from 724 to 782 MJ/m 2 with a mean of 753 MJ/m2 of floor area.

2.4 Test Assemblies

For each test, a selected floor/ceiling assembly 3.7 m wide by 3.7 m

long (12 x 12 ft) was built over the top of concrete block walls of the burn

room, carried uniformly distributed loads and was subjected to similar fire

conditions. The portion of the assembly exposed to the room fire below was

3.2 x 3.2 m (10.5 x 10.5 ft) finished dimensions. The following types of

floor constructions were tested for their fire resistance in this research

and a description of the structural elements used for the various assemblies

and applied loads are given in table 3.

Assembly 1

The assembly was supported by nominal 51 x 203 mm (2x8 in) wood

joists placed parallel to the wall containing a doorway opening and spaced

0.41 m (16 in) on center as illustrated in figure 2, which shows the construction details and instrumentation layout of the floor system. Each joist

was kiln dried, construction grade no. 2, eastern spruce. The joists were cut

to 3.57 m long and secured to nominal 51 x 203 mm wood rim joists with two

90-mm (3-1/2-in) long 16d common nails at ends of each joist. The rim joists

were toenailed to nominal 51 x 203 mm wood sill plates resting on the tops

4
of concrete block walls using 16d common nails spaced 0.41 m on center. Each

sill plate was positioned with its edge flush with the inner wall surface and

fastened with washers and nuts to 3 anchor bolts embedded in the concrete

which filled the core of top course of blocks in the concrete block wall.

A single layer of 16-mm (5/8-in) thick, underlayment grade Douglas fir

plywood subfloor was laid perpendicular to the joists with end joints staggered 0.81 m (32 in) and secured to the joists with 41 mm (1-5/8 in) long

type S12 screws spaced 0.15 m (6 in) on center at panel edges and 0.31 m

(12 in) bn center at intermediate supports. An olefin carpet with foam

rubber backing measuring 3.67-m long by 3.67-m wide was fixed to the plywood

deck with 16-mm (5/8 in) long carpet tacks spaced 0.20 m on center along its

perimeter

.

Assembly 2

The floor framing used C-shaped, galvanized steel joists, 184 mm

(7-1/4 in) deep with a 45-mm (1-3/4-in) flange, a 14 mm (9/16 in) lip and a 1.26-mm (18 gauge) thickness. The joists were spaced 0.61 m (24 in) on

center beginning with one joist positioned along the centerline of the room

width, except that two end joists had a spacing of 0.41 m from the adjacent

joists to accommodate a 3.25-m span. Figure 3 shows the details of the floor

construction and the arrangement of instrumentation. Each joist was cut

3.57 m (140.5 in) long and secured to nominal 51 x 203 mm (2 x 8 in) wood

rim joist with two 8d 64-mm (2-1/2-in) long common nails driven through steel

end clips. A horizontal galvanized steel strap, 51-mm wide by 1.61-mm (16

gauge) thick, was installed at the mid-span in accordance with structural

design information supplied by the manufacturer for steel joists. The strap

attached to the bottom flange of each hoist and its ends fastened to the concrete block walls. The rim joists were secured to nominal 51 x 203 mm wood

sill plates bolted to the top course of the block walls, with 16d 89-mm

(3-1/2-in) long common nails spaced 0.41 m on center.

The plywood used to form the subfloor was 16 mm (5/8 in) thick,

Douglas fir, supplied in 1 . 22 m by 2 . 44 m (4x8 ft) sheets with long edges

tongue and grooved, and marked APA Group 1 interior with exterior glue in

conformance with U.S. Product Standard, PS 1-74. The plywood was installed

with its long dimensions perpendicular to the joists and its end joints

staggered and fastened to the framing with 48-mm (1-7/8-in) long type S12

screws spaced 0.15 m on center at the panel edges and 0.30 m on center at

the intermediate supports. The 3.67 m by 3.67 m olefin carpet with a foam

rubber backing was secured at its perimeter with 16-mm (5/8-in) long carpet

tacks spaced approximately 0.2 m on center.

5
Assembly 3

The floor system was supported by C-shaped galvanized steel joists,

184 mm (7-1/4 in) deep with a 45-mm (1-3/4-in) flange, and a 1.26-mm (18

gauge) thickness. The joists were spaced 0.81 m (32 in) on centers, and were

fastened to nominal 51 x 203 mm (2 x 8 in) wood rim joists with 8d common

nails driven through steel end clips as shown in figure 4. The rim joists

were secured to nominal 51 x 203 mm wood sill plates anchored to the top of

the concrete block walls of the test room.

A single layer of 19-mm (3/4-in) thick, underlayment grade, tongue and

groove, Douglas fir plywood was installed perpendicular to the joists with

end joists staggered 0.81 m (32 in). The plywood was secured to the joists

with type S12 by 48 mm (1-7/8 in) long screws spaced 0.15 m on center along

the edges and 0.30 m on center along the intermediate joists. A piece of

olefin carpet with foam rubber backing was installed over the plywood deck.

Assembly 4

The test assembly was constructed in a manner similar to Assembly 1,

except that nominal 51 x 203 mm (2 x 8 in) wood joists were spaced 0.61 m

(24 in) on center starting with a floor joist positioned along the horizontal

centerline of the room width, the subfloor was 18 mm (23/32 in) thick, underlayment grade, Douglas fir plywood with long edges tongue and groove, and the

solid 51 x 203 mm bridging of the joists was installed along the mid-span.

The construction details of this floor system is shown in figure 5. The wood

joists used were southern pine, construction grade no. 2, medium grain.

Assembly 5

The assembly consisted mainly of C-shaped galvanized steel joists, 184

mm (7-1/4 in) deep, and 1.26 mm (18 gauge) thick, spaced 0.61 m (24 in) on

center, a 18-mm (23/32-in) thick plywood subfloor, an olefin carpet with foam

rubber backing and a protective layer of 12 . 7-mm (1/2-in) thick gypsum board

ceiling as illustrated in figures 6 and 7. Each joist was 3.57 m (140.5 in)

long and fastened at both ends using 8d common nails driven through galvanized

steel end clips, to nominal 51 x 203 mm (2x8 in) wood rim headers. The rim

headers were secured to sill plates made from the sections of nominal 51 x 203

mm (2x8 in) , construction grade no. 2, southern pine joists and anchored to

the top course of concrete block walls, with 16d nails spaced 0.41 m (16 in)

on center. A horizontal galvanized steel strap 51 mm wide by 1.3 mm (18 gauge)

thick, was installed along the mid-span, in accordance with the structural

design manual furnished by the manufacturer for steel joists.

6
A layer of 18-mm (23/32-in) thick underlayment grade, Douglas fir plywood

subfloor was installed perpendicular to the joists with end joints staggered

0.81 m (32 in) between adjacent rows. The plywood was supplied in 1.22 by

2.44 m (4 x 8 ft) sheet with long edges tongued and grooved and marked APA

group 1, interior with exterior glue. The subfloor was secured perpendicular

to the joists with 48-mm (1-7/8-in) long type S12 screws spaced 0.15 m on

center at the panel edges and 0.30 m on center at the intermediate supports.

All pockets formed by the rim headers, plywood subfloor, and concrete block

walls were filled with 89-mm (3-1/2-in) thick, Rll, kraft paper faced fiber

glass insulation. The plywood deck was covered with olefin carpet with foam

rubber backing.

The ceiling of the assembly was a single layer of 13-mm (1/2-in) thick

regular gypsum board installed with the long dimension perpendicular to the

joists and attached to each joist with type S12 25-mm (I-in) long bugle head

screws spaced at 0.15 m on center along the perimeter of the board and 0.30 m

on center in the field. All joints and exposed screw heads were taped and

covered with joint compound, and the ceiling perimeter seams were finished

with wood trim. The ceiling was painted with two coats of white interior flat

latex paint.

Assembly 6

The structural members used to support the floor-ceiling assembly were

305 mm (12 in) deep by 89 mm (3-1/2 in) wide by 3.56 m (140 in) long wood

trusses with nominal 51 by 102 mm (2x4 in) wood chords and webs. All wood

components had 38 x 90 mm (1-1/2 by 3-1/2 in) cross-section and were kiln

dried, southern pine lumber with construction grade no. 2 for top and bottom

chords and no. 3 for web members. Flat metal connector plates fabricated from

0.11-mm (20 gauge) thick galvanized steel with 8.28-mm (0.326-in) long teeth

were used to secure the web members to the chords. Two plates were applied

with the teeth imbedded in the wood members to both sides of the truss at each

joint. The details of the wood trusses, which were factory built by a structural components and systems producer, are shown in figure 8. The trusses

were spaced 0.61 m (24 in) on center starting with one truss located at the

centerline of the test assembly, except that two end trusses had 0.41 m (16 in)

spacing from the adjoining trusses to adapt to rhe existing span length, and

secured to each nominal 51 x 305 mm (2 x 12 in) wood rim joist with three

76.2-mm (3-in) long lOd common nails. The rim joists were toenailed with

89-mm (3-1/2-in) long 16d common nails spaced 0.41 m on center to nominal 51

x 203 mm (2x8 in) wood sill plates resting on the tops of concrete block

walls. In accordance with recommended practice, a nominal 51 x 152 mm (2 x

6 in) by 3.45-m (136-in) long wood bridging was installed at approximately

7
mid-span and fastened with three 76 mm long lOd nails to the west vertical

web member in the center of each truss.

A single layer of 18-mm (23/32-in) thick, underlayment grade, Douglas

fir plywood with long edges tongued and grooved, was laid perpendicular to

the trusses with end joints staggered 0.81 m with adjacent rows of plywood

and fastened to the trusses using 51-mm long 6d common nails spaced 0.15 m

on center at panel ends and 0.25 m on center at intermediate supports. The

pockets formed by the rim joists, plywood underlayment and the block walls

were filled with 89-mm (3-1/2-in) thick, Rll kraft paper-faced fiber glass

insulation. An olefin carpet with foam rubber backing was installed atop the

plywood subfloor.

The ceiling was 13-mm (1/2-in) thick, regular gypsum wallboard placed

below the trusses with the long dimension at right angles to the framing.

Each piece of gypsum board was attached to the bottom chords of the trusses

with 25-mm (1-in) long S12 bugle head screws spaced at 0.15 m (6 in) on center

along the perimeter of the board and 0.30 m on center in the field. All nail

heads and joints were taped and covered with joint compound, and the ceiling

was painted with two coats of white interior flat latex paint. The intersections between the ceiling and the plywood paneling walls were finished with

wood trim. The construction details of the completed test assembly is shown

in figure 9.

Assembly 7

The floor framing consisted of nominal 51 x 203 mm (2 x 8 in) kiln dried,

construction grade no. 2, southern pine joists spaced at 0.61 m (24 in) on center, with the exception of a 0.41-m (16-in) spacing for the two end joists

apart from the adjacent joists. Each joist was cut to 3.57 m in length and

fastened at its ends to nominal 51 x 203 mm wood rim joist with two 89-mm

(3-1/2-in) long 16d common nails. The rim joists were toenailed to nominal

51 x 203 mm wood sill plates anchored to the top course of the concrete block

walls, with 89 mm long 16d nails spaced 0.41 m on center.

The subfloor was a layer of 18-mm (23/32-in) thick, underlayment grade,

APA group 1, interior with exterior glue, Douglas fir plywood with long edges

tongued and grooved. The plywood subfloor was nailed to the joists with 64-mm

(2-1/2-in) long 8d coated common nails spaced 0.15 m (6 in) on center at end

joints and 0.25 m on center at intermediate supports. Fiber glass insulating

blankets, 89 mm thick, Rll and kraft paper faced, were used to fill the pockets

formed by the rim joists, the plywood subfloor, and the top surfaces of the

block walls. An olefin carpet flooring was secured to the plywood deck at its

8
perimeter with 16-mm (5/8-in) long carpet tacks spaced 0.20 m on center.

The entire floor was protected by a layer of 16-mm (5/8-in) thick, type

X, gypsum wallboard installed with the long dimension perpendicular to the

joists and fastened to the wood framing using 32-mm (1-1/4-in) long type S

bugle head screws spaced 0.15 m on center on the perimeter of the board and

0.30 m o.c. in the field. The ceiling-wall seams were finished with wood

trim and the exposed face of the gypsum board ceiling was painted with two

coats of white interior flat latex paint. Figure 10 illustrates the details

of the floor-ceiling assembly.

The initial weights and the estimated total available heat of the combustible materials used for constructing test assemblies for the series of

fire resistance tests performed are listed in- table 4. A heat of combustion

of 18.6 MJ/kg was employed for wood materials.

2.5 Structural Loading

The floor-ceiling assembly used for each test was loaded, prior to the

fire test, with steel blocks, each measuring 140 x 203 x 152 mm (5-1/2 x 8 x

6 in) high and weighing 22.7 kg (50 lb), to provide an approximation to a uniformly distributed load; this developed maximum allowable deflection or

bending stresses in the floor joists as contemplated by the design for most of

the tests with the exception of tests 1 and 3. A live load of 195 kg/m 2

(40 psf) was applied to the test assemblies for tests 1 and 3 as shown in

table 3, and this loading corresponded to 69 percent and 74 percent of the

respective maximum design loads computed based on maximum permissible deflection of floor joists. The calculation used as the basis for the selection of

the maximum design load for test 7 is presented in Appendix A, and the floor

plan showing the layout of steel blocks distributed over the carpet flooring

of this assembly is given in figure 11.

3 . TEST MEASUREMENTS

3.1 Temperature

The room air temperatures were monitored through bare beaded, 0.51 mm

(0.02 in) diameter (no. 24 B & S gauge), double-cable chrome 1- a lumel thermocouples at 8 stations including seven locations within the test room and one

in the doorway opening. This type of thermocouple was made of two thermocouple cables placed side by side and its measuring junction was formed by

welding the positive wire (chromel) from one cable together with the negative

wire (alumel) from the other one. This procedure was necessary to avoid the

9
problem of the electrical breakdown of the insulation in the individual cables

at temperatures above 800°C. A total of 25 thermocouples were arranged at

various heights in vertical thermocouple "trees" at the seven stations inside

the room as shown in figure 12, and 12 thermocouples positioned in the other

station along the vertical centerline of the doorway illustrated in figure 13.

The air temperatures in the upper part of the room were also measured with

eight commercial metallic-sheathed, mineral-insulated fast-response thermocouples placed 0.61 and 1.22 m below the floor-ceiling assembly at the midpoint and the quarter points of the room length, as shown in figure 12. These

fast-response thermocouples were constructed from chromel-alumel wires with

outside diameter of 1.02 mm (0.04 in) and the measuring junctions contained

within capped 6 . 4 mm (0.25 in) outside diameter stainless steel tubes having

0.9 mm (0.036 in) wall thickness and insulated with magnesium oxide.

The surface temperatures of the plywood paneling and the concrete block

walls were determined at 16 stations with the thermocouple beads attached on the exposed and unexposed surfaces at selected places. One location was at

the front wall for indicating the involvement of combustible linings in fires,

as shown in figure 13; eight were distributed over the back wall in the vicinity of the ignition source on the sofa, shown in figure 14; three stations

each were situated at the left and the right plywood paneling walls, as illustrated in figures 15 and 16.

The temperatures on the unexposed side of the test assembly were

measured using nine bare beaded, 0.51-mm wire diameter, chromel-alumel

thermocouples attached to the top surface of carpet flooring and tightly

covered with ceramic fiber pads, 152 mm square by 13 mm thick. Figures 2 to

6, 9, and 10 show the locations of these thermocouples along with three

additional thermocouples beneath the pads used to measure the temperatures at

the points which appeared to be hottest during the test. Surface temperatures

were also taken with the bare beaded, double-cable thermocouples within the

test assembly. Eight thermocouples were installed in both top and bottom

flanges of each selected floor joist, four on the unexposed surface of plywood

subfloor and one thermocouple placed on the fire exposed face of the ceiling

at the center of the room for the test assemblies with a gypsum board ceiling,

also shown in these figures.

3.2 Floor Deflection

The deflection of the test assembly during the test was measured with

nickel steel cables attached to the midpoint or the quarter points at the top

side of each selected joist, and by means of small pulleys, connected to

10
linear displacement potentiometers mounted on one wall of the test building.

A total of 6 check points for each test structure were employed to provide

the relative movement of the floor surface as shown in figures 2 to 6, 9, and

10 . 3.3

Static Pressure at Wall

The levels of static pressure developed within the fire room were

continuously measured using 64-mm (1/4-in) outside diameter steel pipes

extending through the left wall (south wall) and into the room with their

open ends flush with the exposed surface of the plywood paneling wall. Two

locations used for these pressure measurements included one situated in the

plane 0.3 m from the front block wall at 0.10, 0.30, 0.61, 1.22, 1.70, and

2.13 m below the ceiling and the other one at the mid-width of the paneling

wall, 0.10 m from the ceiling, as shown in figure 12. The exterior ends of

the pipes were connected by copper and polyvinyl chloride tubing to variable

reluctance pressure transducers. Used in combination with carrier demodulators,

these produced an output of 40 mv per Pa pressure change.

3.4

Heat Flux

The total heat fluxes incident at selected locations were determined

using 5 Garaon-foil type, water-cooled heat flux gauges. Two of these gauges

were positioned along the vertical centerline of the back wall flush with the

exposed surface of plywood paneling, one each in the left plywood wall and at

the center of the carpet flooring, facing the ceiling, and one gauge on a stand located 3 m in front of the doorway with its vertically oriented sensing

element viewing the center of the opening, as shown in figures 12, 14 and 15.

The irradiance measurements were made with one Gardon-foil type, wide angle,

water-cooled radiometer with an air stream to eliminate convective heat

transfer, mounted along the centerline of the left plywood wall flush with

its exposed face.

3.5

Air Velocity at Doorway

The horizontal velocities of the air entering and leaving the fire

room through the doorway opening were monitored with 6 bi-directional flow

probes in conjunction with variable reluctance differential pressure transducers and carrier demodulators. These probes were installed normal to the

plane of the opening along its vertical centerline and located at 0.13, 0.48,

0.84, 1.19, 1.55, and 1.91 m from the top of the doorway, as illustrated in

figure 13.

11
3.6 Optical Density of Smoke

Continuous measurements of the optical density of the smoke at various

locations were made by determining the attenuation of a collimated light beam

passing through the effluent gas and impinging on a photodector. The light

sources were auto spot lights energized by a regulated 6-volt D.C. power

supply and the receiver units included photodetectors (PIN3DP) . The two

locations used to monitor smoke concentrations were (1) in the doorway with

5 horizontal measurements at distances of 0.08, 0.30, 0.53, 0.97, and 1.50 m

from the top of the opening, with a 0.76 m long path length along the doorway

width, as shown in figure 13, and (2) outside the room, with the light beam

having a path length of 2.07 m, horizontally underneath the exhaust hood

installed above the door opening.

3.7

Gas Concentrations

The combustion gas venting from the fire room was sampled at four

locations for measuring the concentrations of selected gas species. Three

sampling ports were situated in the doorway at distances of 0.08, 0.38, and

0.76 m down from the doorway top and one in the stack connected to the exhaust

hood. Gas samples withdrawn from the stream of combustion products using

stainless steel tubing, after passing through cold traps and filtering tubes

packed with glass wool, were analyzed for C^, CO ^

and CO levels. Concentrations of CO

2 and CO were measured by means of non-dispersive infrared gas

analyzers and was measured with polarographic type oxygen cells.

3.8

Data Acquisition

L A total of 136 sensors including the thermocouples and various transducers

were automatically read and recorded by a high speed digital data acquisition

system. The data were collected on a magnetic tape at a rate of 8 seconds

per scan during the entire duration of test, and subsequently transferred to

the computer for processing, tabulating, and plotting.

4. TEST PROCEDURE

4.1 Fire Test

For each test, the test assembly was loaded with steel blocks to the

prescribed load density. The application of the uniform load was normally

made within a couple of days prior to the fire test. The ignition source

used for all the experiments was a section of newspaper weighing 400 g and

placed along the central backrest and seat cushions of the sofa supported by

12
a steel frame holder to insure reproducible ignition conditions between

tests. The paper was conditioned to equilibrium with room air controlled at

a dr.y-bulb temperature of 23 + 3°C and a relative humidity of 50 + 5 percent

prior to the test. The fire test was started by remotely igniting the newspaper using an electric heating element and a book of paper matches. Visual

observations and photographic and video tape records were made of the progress of the room fires, the burning characteristics of the assembly, and

flame-through and collapse of the structural elements. The fire was allowed

to burn until the structural failure occurred in the test assembly.

4.2 Fire Resistance Criteria

The structural failure was considered to have occurred under any one of

the following first two conditions:

1(a) The test assembly collapses, no longer sustaining the applied

load

(b) The collapse of test structure can be expected to occur when both

total deflection has attained or surpassed L

2 /800d, and an hourly

deflection rate has equaled or exceeded L

2 /150d, in which L is the

span between supports of structural element, and d is the distance

between the upper and lower extreme fibers of structural component

or assembly [4]

2. Flames or hot gases pass through the test assembly to its unexposed face.

3. The average temperature of the unexposed surface of test structure

increased more than 139°C above its initial temperature or 181°C

at one point.

5. TEST RESULTS

5.1 Room Fire Exposure

Logs of visual observations and records inferred from video tapes taken

through the doorway of the fire room, and at the unexposed surface along the

center joist during the course of the test are given in appendix B. Also,

table 5 presents a summary of experimental results on duration of the test,

initial room air temperature, time to appearance of visible flames on the

newspaper used as the ignition source, time to room flashover based on selfignition of two types of indicator specimens and attainment of a 20 kW/m2

13
heat flux level at the center of the floor, and times elapsed for flames

issuing out of the doorway and for spontaneous ignition of the olefin carpet

floor. In general, all of the tests performed had a similar history of major

events observed during the course of room fire growth. Sustained flaming on

the ignition newspaper in the middle of the sofa was normally observed at

approximately 0.1 to 0.8 min, the sofa was ignited within the next 0.2 to 0.6

min, and the flames from the burning sofa reached the ceiling at 0.6 to 1.3

min after flame appearance.

The time of appearance of visible flames on the newspaper was utilized

as the reference time due to variability of the buildup of flaming on the

newspaper. The rear plywood paneling wall adjacent to the middle of the sofa

became ignited at times ranging from 1.0 to 1.7 min and was immediately followed by vertical flame spreading over the wall surface. As the temperature

increased, the flames traveled across the ceiling and the hot gas layer descended to approximately two-fifths of the room height, and the flashover

indicators and all other combustible materials soon ignited. The flames

blended with heavy smoke passing out of the doorway opening usually occurred

immediately before or just after flashover.

As shown in table 5, the times from the sustained flaming of the newspaper on the couch to the spontaneous ignition of the flashover indicators

varied from approximately 1.5 to 2.5 min with an average of 1.9 min for

newspaper and 1.5 to 2.5 min with a mean of 2.0 min for filter paper. The

time at which the heat flux incident at the center of the floor exceeded

20 kW/m2 was found to range from about 1.4 to 2.4 min with an average time of

1.8 min, which was in agreement with those taken for self-ignition of flashover indicators. The average values of the time elapsed prior to flames

emerging from the doorway and to ignition of the olefin carpet were found to

be 1.7 and 2.1 min, respectively.

Table 6 presents the measured results including the maximum upper room

gas temperature, the maximum rate of heat released within the fire room and

that discharged through the stack, the maximum flow rate of air flowing in

and through the doorway opening, the neutral plane height above the floor

level, and the maximum static pressure developed within the room at the peak

of the fire. The mean temperature of the hot gas in the upper part of the

fire room was obtained by averaging the readings of fast response thermocouples placed at six locations 0.61 m below the ceiling. As shown in the

table, the peak room gas temperature varied from approximately 770°C to

1020°C. Lower temperatures are listed for the first four tests involving

unprotective floor assemblies since the tests had to be terminated before

the fire was fully developed.

14
The total rates of heat released within the fire room were computed from

the oxygen used using the procedure similar to that in earlier work [2]

.

Based on the data for oxygen concentration, gas velocity, and temperature

measurements of the outflowing combustion products in the doorway and in the

smoke stack, the calculated results for the individual room fires during

their fully developed period are summarized in table 6. In test 7, there

appeared to be some difficulties with the gas sampling system for the doorway oxygen and carbon monoxide concentrations, which caused the former to be

high and the latter to be low throughout the test. As shown in the table,

the maximum heat release rate was found to range from approximately 3000 to

4100 kW with an average of 3710 kW based on the data derived from the doorway

measurements, and 5400 to 8500 kW with a mean value of 7480 kW from the stack

measured data. The higher values at the stack in comparison with those at

the doorway were attributed to the additional large quantities of heat evolved

from the burning of the excess pyrolysates with the entrained air underneath

the exhaust hood outside of the fire room.

The peak level of experimentally determined flow rates of air inflow

induced by room fires through the doorway opening varied widely from approximately 0.6 to 0.8 kg/s (average 0.69 kg/s) and exhausting gas outflow ranged

from 1.6 to 1.8 kg/s (average 1.67 kg/s), respectively. The lowest height of

the neutral plane in the doorway was found to be relatively constant with an average value of 0.67 m above the floor level or approximately one-third of

the doorway height. The maximum values of static pressures measured at the

south wall 0.1 m below the ceiling ranged from about 13 to 15 Pa for all test

fires

.

Measured results of the rate of heat transferred to the selected locations in the room walls and the floor and in front of the doorway outside of

the room are summarized in table 7. The average of the highest readings of

two heat flux gauges situated in the west and south plywood walls at a distance of 0.61 m beneath the ceiling is also listed in the table. As shown,

the peak level of total flux acting at the walls varied from approximately

100 to 180 kW/m2 with a mean of 150 kW/m2 for wood-frame floor assemblies and

ranged from 110 to 160 kW/m2 with an average of 130 kW/m2 for steel framed

floors. The higher wall surface fluxes with wood framings were probably due

to thermal emission from the thicker flames at the ceiling in addition to

convective and radiant heating from the upper walls and hot gas layer. Also,

illustrated in the table, the maximum heat flux incident at the center of the

floor was found to vary from about 125 to 160 kW/m 2 with the average value of

140 kW/m2

. The peak rates of heat transferred to a point outside the room

and spaced 3.05 m from the doorway opening from the emerging flames and the

room fire were of the order of 40 kW/m2

. 15
The peak levels of the optical density of the smoke, the CO and C02 gas concentrations, and the lowest oxygen content in the effluent gas measured

separately at the doorway and at the smoke stack are shown in table 8. The

maximum concentrations of smoke and toxic combustion products leaving through

the doorway opening for all the tests were found to have average values of

3.9 OD/m for smoke particulates, 10 percent for CO and 18 percent for C0 2 gas. The lower level of CO observed at the smoke stack than at the doorway

was due primarily to further combustion with oxygen and dilution by entrained

air before it reached the stack sampling probe.

5.2 Performance of Test Assemblies

Assembly 1

Flame penetration which occurred near the joint between two sheets of

plywood subfloor in the southwest corner, located above the right arm of the

sofa, was observed at 10 min: 17 sec. There was a load failure with the falling of steel blocks onto the floor, resulting from structural collapse of the

centrally located wood joist, at 10 min:43 sec. The average surface temperature of the carpet finished flooring increased rapidly to 206°C at 11 min : 7 sec

and the individual temperature readings at 2 locations exceeded 240°C at

10 min:59 sec.

Assembly 2

Failure of the assembly took place at 3 min: 47 sec by the passage of

flames through to the unexposed surface near the center of the assembly. The

deflection of the test floor measured at the center point showed a rapid increase after 3 min: 31 sec and the central joist collapsed at the same time as

f lame-through. The temperature rise on the unexposed surface in the vicinity

of burn-through area reached 163 °C at 3 min: 41 sec.

Assembly 3

Flame penetration near the west quarter point along the center joist

and the west side of the tongue and groove joint between two sheets of plywood underlayment located above the right seat cushion of the sofa was

noticed at 3 min: 58 sec. Structural collapse of the center joist based on the results of deflection measurements occurred at 3 min: 59 sec. One thermocouple positioned on the carpet in the neighborhood of the flame-through

region indicated a steep temperature rise to 239°C at 4 min : 7 sec. The

average temperature rise of the surface thermocouples was less than 45 °C at

the end of the test.

16
Assembly 4

' Deflection measurements at the center of the assembly showed a rapid

increase at 11 min: 52 sec and the centrally located joist fractured with the

falling of steel blocks into the fire room at 12 min. Passage of flames and

hot gases through the assembly to the unexposed surface occurred at

12 min: 2 sec in an area near the center of the assembly on the southeast side

and somewhat away from the thermocouple locations. The average surface temperature on the carpet flooring increased rapidly to 462 °C at 12 min : 8 sec,

and the individual temperature rise of greater than 163 °C occurred almost at

the same instance of flame penetration.

Assembly 5

Failure of the gypsum board ceiling with falling of small fragments of

ceiling materials to the floor was observed at 13 min: 9 sec. Penetration of

flames through the test assembly to the unexposed surface occurred at

15 min: 58 sec. The flame-through region was located near the west quarter

point of the floor joist situated south of the center joist, and at the

juncture of the three sheets of plywood in the southwest direction from the

center of the assembly. The floor sagged more rapidly with a maximum deflection rate of 6.0 mm/s at the time of flame-through, but its joists did not

collapse entirely into the test room due to the support from the horizontal

steel strap along the longitudinal centerline. However, this deflection rate

of the center steel joist exceeded the specific deflection rate of 0.11 mm/s

calculated based on a criterion of structural failure proposed by Ryan and

Robertson [4]. The average temperature rise of the unexposed surface and the

individual temperature measured in the vicinity of the flame-through region

showed a rapid increase up to 163 and 236°C, respectively, at time of flame

passage.

Assembly 6

The protective layer of gypsum board utilized as the ceiling finish for

the assembly failed at 11 min: 51 sec. During construction of the test

assembly, small wood strips 13 x 38 mm in cross section, were nailed to nominal 51 x 305 mm wood rim joists to accommodate 305 mm deep wood trusses. The

joints between these two wood pieces were covered with duct tape on the unexposed side of the test room. The flame penetration at one taped joint located

above the middle of the west block wall occurred at 17 min: 46 sec, which was

7 sec earlier than the passage of flames through the assembly near the center.

The temperature rise of one surface thermocouple positioned on the carpet

17
exceeded 163°C at nearly the same time as the flames passed around the rim

joist. The centrally located joist did not fail until 18 min: 34 sec, due

primarily to the support of the nominal 51 x 152 mm wood bridging fastened at

mid-span, with common nails.

Assembly 7

The gypsum board ceiling began to disintegrate and fell away in random

fragments onto the floor at 23 min : 6 sec. Passage of flames through the

assembly to the unexposed surface was recorded at 35 min: 8 sec. An approximately 0.3-m square opening burned away by the fire was situated between the

center joist and its adjacent joist to north, and at 0.76 m from the front

wall containing the doorway opening. The records of floor deflection measured

at the center of the assembly indicated a significant deflection at 35 min:

sec, and the maximum downward movement at a rate of 8.4 mm/s occurred at

35 min: 18 sec. The maximum values of the average and the individual temperature rises on the unexposed carpet surface at time of test termination were

69 and 108°C, respectively, since thermocouple locations were away from the

burn- through region.

6. DISCUSSION

There are many sources influencing the results of test measurements,

such as the variations of test materials and assemblies, environmental conditions, instruments, and calibration techniques. It is not feasible to

eliminate these variations completely, particularly the non-uniformity of

building materials normally encountered. In order to estimate these uncertainties, a statistical analysis was performed on the experimental data

during the period prior to failure of the assembly for the three fire tests

from the current floor assembly test series which had gypsum board ceilings

and one similar test from the earlier series [2]

The repeatability of

large-scale room fire test used for evaluating the fire performance of these

selected, load-bearing, floor-ceiling assemblies is discussed elsewhere [5]

Time variations of the average gas temperature in the upper part of the

fire room for all the tests conducted are shown in figures 17 and 18 along

with the newly developed fire exposure curve. The derived fire exposure

curve was obtained by approximating the experimental temperature versus time

curve obtained in test 9 from a series of basement room fire tests [2] with

a smooth curve. In this particular test, the 3.2 x 3.2 m burn room was

finished with plywood paneling walls and gypsum board ceiling, and furnished

with a typical loading of 23 kg/m2 of domestic furniture. The newly developed

18
temperature- time curve, which corresponded to an approximate average over the

range of test conditions examined in the test series, was considered to be

more realistic representation of room fires in residential occupancies. The

gas temperatures plotted in the figures were the spatial average value at

various times of gas temperatures measured with 6 fast response thermocouples

located 0.61 m below the underside of test assembly. As shown in the figures,

the temperature levels of the room gases were nearly the same during the fire

growth period, significantly varied after room flashover, and then slightly

scattered. The gas temperatures attained in the fire room with the exposed

wood joist/plywood subfloor as ceiling materials (tests 1 and 4) were considerably lower than those in the rooms lined with gypsum board ceilings (tests

5 to 7) during the fully developed stage. This was due to increased rates of

heat absorbed in maintaining the supply of volatile products from the

pyrolyzing cellulosic materials and to the dilution of the heated air by the

gaseous pyrolysis products which remained unburned in the oxygen-starved

atmosphere. It can be noted that the temperature level of room gases in

test 7 climbed once again toward the end of the test period due to the gradual

and then rapid involvement of the wood joists and plywood subfloor after the

disintegration of the protective gypsum board ceiling. The pyrolysis of the

plywood had a positive effect on the temperature in the room during this time

period because the fire was no longer ventilation-limited and the pyrolysis

products were able to burn in the room.

The performance of the various floor-ceiling assemblies in terms of fire

resistance periods in the room burnout tests are summarized in table 9. The

fire resistance of the test structures is expressed as the time taken from

appearance of sustained flaming of the newspaper on the sofa to (1) passage

of flames through openings or cracks developed in the assembly, (2) structural

collapse, or (3) the attainment of either an average or a maximum individual

temperature on the unexposed surface of 139 or 181°C, respectively, above its

initial temperature, whichever occurs earlier. Also, in the table are the

maximum deflections measured at the center of the individual floor constructions. Structural failure of the floors was recorded when the flocr support

joists collapsed or when the maximum rate of floor deflection exceeded a specific deflection rate of 0.11 mm/ s based on load failure criteria [4]

The times taken to collapse of the floor joists determined on the basis of

visual observations and video tape records were generally in good agreement

with the recorded deflection data.

As illustrated in table 9, failure attributed to penetration of flames

through the test structure or collapse of floor joists varied from approximately 4 min for an unprotected steel joisted floor to 35 min for a floor

19
with a type X gypsum board protective ceiling. In general, the passage of

flames through the assembly usually occurred slightly before structural

failure because the deflection of floor joists with increased temperature

levels developed openings at the plywood floor joints for flames to pass

through. The unprotected floor assemblies consisting mainly of a plywood

subfloor supported by steel joists generally failed within 4 min compared to

10 to 12 min for those with wood framing. This was due to small thickness

and high thermal conductivity of steel members and the rapid reduction in

modulus of. elasticity and yield strength of these structural elements at

elevated temperatures, which caused the larger deflections of the floor joists

and provided increased joint separation and wider gaps for flame-through.

For the fire protective assemblies, the gypsum board ceiling provided a thermal barrier for retarding the heat transmission to the plywood subfloor

and the floor joists. The addition of a protective layer of gypsum board on the ceiling increased the fire resistance period approximately 12 min for

13 mm thick regular board and 23 min for 16-mm, type X gypsum board.

It can be noted that the static loads applied to assemblies 2 and 3 were 100 and 74 percent of the respective maximum permissible design loads as given in table 3. As shown in table 9, the collapse times for these two

steel frame floors under different applied load conditions did not vary

greatly and the difference in time was within 5 percent. While it may be

anticipated that the collapse time will be greater for a floor-ceiling

assembly with lower loads than those with higher loads, this could not be

verified from these limited tests. The floor system used in test 1 involving

wood joists stressed to 69 percent of the maximum allowable value and placed

0.41 m apart had a shorter time to collapse structurally than those employed

in test 4 where the load applied to the assembly developed the full design

stress in the joists spaced at 0.61 m on center. This smaller failure time

might have resulted from a greater reduction in cross-sectional area due to

wood charring as the floor joists were installed parallel to the wall with

the doorway opening and probably received a higher heat flux at the exposed

surfaces. Also shown in the table, the maximum deflection of the floor

assembly for individual tests ranged from approximately 150 to 360 mm. The

small deflections for the assemblies used in tests 4 and 7 were probably due

to the support of a solid wood bridging installed along the longitudinal

centerline.

The time variations of the floor deflections measured at the center of

the test assembly for individual tests are shown in figure 19. As shown,

the steel framed floors (tests 2, 3, and 5) had similar deflection curves

where the deflection became significant only near the time of structural

20
failure of the center joist at which time it rose rapidly. The wood floors

(tests 1, 4, and 7) were slower to deflect than the steel floors and experienced a period of slowly increasing deflection due to gradual loss of the

tensile strength of wood structural elements. The characteristics of the

deflection for the assembly framed with wood trusses with steel fasteners

(test 6) were intermediate to those of the floors supported by steel and

wood joists.

Figure 20 illustrates the floor deflections at the center and the quarter

points along the centrally located joist at various times for test 2. It can

be seen from the figure that the rates of deflections at the center and the

west quarter point increased more rapidly than that at the east quarter point,

although the temperature differences in the room at these locations were less

than 60°C. The temperatures developed in the steel joist at the sections of

both quarter points were found to be approximately the same, but the deflection was substantially different, especially at times of imminent collapse of

the joist. The reason for this wide variation in deflection during the course

of the fire is not known. (Note that the west quarter point was over the

sofa where the exposure might be greater for the first 4 minutes.)

The average surface temperatures on the unexposed side of the floorceiling assembly as a function of time for all the tests performed are shown

in figure 21. These average temperatures were derived from averaging the

readings of 10 thermocouples attached on the carpet surface, including 9

equally spaced thermocouples and one located 1.52 m from the south edge and

0.76 m from the west end of the assembly. As would be expected, the unprotected assemblies (tests 1 to 4) had a faster rise in surface temperature

than the floor systems with a fire protective ceiling (tests 5 to 7). In the

tests conducted, the average temperature increases of greater than 139°C

above the initial temperature on the unexposed surface were not observed

before failure by passage of flames through the assembly. As shown, the

protective ceiling delayed the time of temperature failure by approximately

12 minutes for 13 mm gypsum board and more than 23 minutes for 16 miu type X

gypsum wallboard.

A comparison of the surface temperatures attained at the top and bottom

of the steel joist and that at the top of the plywood subfloor located above

the center of the room for the tests with and without a protective ceiling

(tests 5 and 3) is shown in figure 22. As shown, the temperature in the top

flange of the floor joist was consistently lower than that in its bottom surface. This was due to the fact that there was continuous conduction of heat

away from the top surface to the cooler plywood subfloor, and for the

21
unprotected assembly, the bottom flange received directly more radiant energy

than the top one. As would be expected, the surface temperatures of the subfloor increased at a slower rate because of lower thermal conductivity of

plywood compared to structural steel.

Figure 23 shows a plot illustrating the relationship between the measured

floor deflection at the center of the test assembly and the corresponding

average temperature of the centrally located steel joist at the same instance

for tests 2, 3, and 5. The steel temperature was obtained by averaging the

readings of the two thermocouples attached to the top and bottom of one cross

section along the longitudinal centerline of the test assembly. As shown in

the figure, the deformation of the steel joist became greater as the average

temperature of the structural element increased with fire development. Rapid

deflection of the assembly occurred and the floor joist failed to support the

applied load when the joist reached a temperature level of approximately 650°C

for the unprotected floor assembly and 820°C for the floor with a fire protective ceiling. These steel temperatures were higher than the permissible

temperature of 593 °C for steel structural elements [1] . There was a considerable fall in the steel temperature when the floor deflection was approximately 80 mm in test 5. This was probably due to the decrease in local air

temperatures resulting from the dilution of the heated air surrounding the

joist by the gaseous pyrolysis products from the decomposing plywood subfloor.

A similar plot of floor deflection versus the average of the surface temperatures measured at the top and bottom of the cross-section located at the

middle of the center joist involving wood framed floors for tests 1, 4, and 7 is given in figure 24. As shown, significant deflection was not perceived

until the average exterior temperatures of wood joists attained a temperature

level ranging between 650 and 750°C. The failure of wooden structural elements

was as a result of the reduction in cross sectional area due to charring and

burning during the fires. The charred and burned areas were estimated to

vary from approximately 53 to 75 percent original cross sectional area for

these tests. With the decrease in cross sectional area, the shear and

bending stresses increased and the joist failed when these stresses exceeded

its yield point.

The time variations of the steel temperatures derived from averaging

the values of surface temperatures measured at the top and bottom of the

cross sections situated at various locations are shown in figure 25. It can

be noted that the temperatures developed at two locations in the center joist

increased more rapidly prior to room flashover than those in the other two

neighboring joists due to earlier and direct exposure to the developing fire.

However, this temperature difference attributed to relative locations of floor

joists involved with the fire reduced with time after flashover.

22
The variations in time of the central deflection of the test assembly

and the temperatures of the steel joist and room gas located along the vertical centerline of the test room for test 3 are shown in figure 26. As shown,

the temperatures attained in steel member closely followed the temperature

levels of surrounding gas, which depended upon the fire process. This was

attributed to small thermal inertia because of the relatively high thermal

conductivity and small thickness of steel joists used in the assembly. Also

shown in the figure, the floor deflection increased with an increase in the

joist temperatures.

7 . SUMMARY

Based on the experimental results of 7 room burnout tests to evaluate

the performance of protected and unprotected, load-bearing, wood and steel

framed residential floors subjected to a newly developed fire exposure

condition, the following observations were made:

(1) The unprotected light gauge steel-framed assemblies allowed the

passage of flames and suffered structural collapse in 4 minutes compared to approximately 10 minutes for the exposed wood frame floors.

(2) The use of a 13 mm thick regular or a 16 mm thick type X gypsum

board ceiling increased the endurance time by about 12 min and 23 min,

respectively.

(3) Under fire exposure, wood framed floors deflected at a slower rate

compared to steel-framed floors; their ultimate collapse is ascribed to

gradual reduction in the cross sectional area of floor joists caused by

the charring and burning of wood.

(4) Failure due to passage of flames to the unexposed surface of the

floor structure resulted from the increased deflection of floor joists

with elevated temperatures, which promoted joint separation and developed

openings in the plywood subfloor.

8 . ACKNOWLEDGEMENTS

The author would like to express his gratitude to many members of the

Fire Performance Evaluation Division for their assistance in this study,

especially, Messrs. Thomas Maher and Oscar Owens for constructing the test

rooms and floor assemblies, Mr. Newton Breese for reducing and processing the

experimental data, and Messrs. Sam Steel, Charles Veirtz, William Bailey,

23
Roy Lindauer, Douglas Walton, Billy Lee, and Randy Lawson for assistance in

performing the fire tests.

The author wishes to thank Ward Corporation in Rockville, Maryland, for

providing the wood trusses used in test 6.

This project was supported in part by the U.S. Department of Housing and

Urban Development, under the program management of Mr. James C. McCollom

within the Division of Energy, Building Technology and Standards, Office of

Policy Development and Research.

9 . REFERENCES

[1] "Standard Methods of Fire Tests of Building Construction and Materials,"

ANSI/ASTM E119, 1978 Annual Book of ASTM Standards, Part 18, pp. 763-781,

(American Society for Testing and Materials, Philadelphia, Pa., 1978).

[2] Fang, J. B. and Breese, J. N., Fire Development in Residential Basement

Rooms, NBSIR (in progress) .

Issen, L. A., Single Family Residential Fire and Live Loads Survey,

NBSIR (in progress)

Ryan, J. V. and Robertson, A. F., Proposed Criteria for Defining Load

Failure of Beams, Floors and Roof Constructions During Fire Tests, J. of

Res. NBS , 63C , 121-124 (1959).

Fang, J. B., Repeatability of Large-Scale Room Fire Tests, a paper for

publication (in progress) .

"Design Values for Wood Construction, " National Forest Products

Association, June 1978.

[3]

[4]

[5]

[6]

24
Table

1.

Initial

weights

of

furnishings

and

wall

linings

an<

total

available

heat

of

all

combustibles

used

for

fire

tests

<y rH

dd

U \ o o o o o o o

4- rH Cd >"5 cn rH

H

H

H

H Oh c •H a) x v£> O o Oh m 00

E- cd EC

w 00 >< |

00c

Oh Oh Oh Oh Oh Oh Oh

1C 6C • • • • • • -H A! o o o o o o o 111 o w 2

C/) 1 00 I c 60

•H

d e I •rH “n 00

m CN cn 00 00 00

•H 6 6C • • • • • • • X I cd as o m hO o o O’ o

hO iH pH

XIOO ^5 60 o CN cn CN

m Oh Oh 1 Ec AS Oh o H cn O’ O’

rH s—

PM o- O’ >x hO hO <3-

m

4J

QJ ^~N o rH

H h£> o oo

a, oo • • • • • • • M X o 00 Oh cn o H

cd - u

CN rHH CN CN

H CN

u

(U /—

cn cn o o H

a oo • • • • • • • cd as LD m m o m 00

Pm 00 00 00 Oh 00 00 00 i AS d) /'""N hO CN H cn CN O to oo • j • • • • • • O cd AS rH tH CN CN cn H CN

PQ o ^ O' O’ O’ O’ O’

O

aj ^ 00 Oh Oh CO cn Oh Oh

X tH oo • • • In • • • | d X X rH o o hO H o o w cd w H

iHH

H

HHH

CO 01 0C a) d) /-“N Oh cn 00 Oh o- oo CO d 4-1 i—1 60 • • • • • • • •H 4-1 XI AS o H H o o H H x o cd s~

CN CN CN CN CN CN CN

CO

aH

•Hdu3 3d

Ci £ /-n cn cn cn cn o o oo • • • • • • •H X AS u 4J ^

a) o 4JdM

Cl •H /^“N vO CN 00 CN 00 cn cn

cd oo • • • • • • • X AS cn CN H CH H H H o ^ CN CN CN CN CN CN CN d

4-1 0£ LO• O’

mm CN o o O X cn m O’ o- O’ o

CO

w O’ o* O’ o* o- O’ O’

Test No

H CN cn <r

m hO

25
Table 2. Descriptions of combustible contents

Item Material Size Initial Weight

(kg)

Sofa Grade 1, 100% olefin upholstery 2.15 m wide x 47

fabric, cotton batting side arms, 0.85 m deep x (frame - 24 kg,

foamed polyurethane seat, back 0.81 m high foam - 6.8 kg,

and side cushions, wood frame cover - 6.4 kg

batting, etc. - 9.8 kg)

Upholstered Grade 1, 100% olefin cover 0.79 m W x 23

Chair fabric, urethane foam seat 0.91 m D x (frame - 11.3 kg

cushion, cotton batting, wood 0.93 m H foam - 2.3 kg

frame cover - 1.8 kg

batting, etc. - 7.6 kg)

Ottoman Grade 1, 100% olefin cover 0.61 mW x 7.7

fabric, urethane foam, wood 0.46' mD x (frame - 4.5 kg

frame 0.43 mH foam - 0.9 kg cover - 0.9 kg

batting, etc. - 1.4 kg)

Coffee Laminated veneer top and 1.52 mW x 21 kg

Table sides, finished hardwood 0.51 mD x 0.41 mH

End Laminated veneer top and sides, 0.58 mW x 10.4 kg

Table finished hardwood 0.69 mD x 0.51 mH

Bookcase Wood particle board with 0.76 mW x 42 kg

melamine finished surface 0.36 mD x 1.83 mH

Carpet Olefin pile with rubber foam 3.2 :t 3.2 i 20 kg

cushion backing x9 .mm thick

26
Table 3. Descriptions of test assemblies and loading conditions

• Structural Elements

Test

No.

Floor

Joists*

Plywood

Subfloor**

Thickness mm in

Painted

Gypsum

Board

Ceiling

Thickness mm in

Joist

Spacing m inApplied

kg/mz Loadlb/ft z

Percent

of

Maximum

Allowable

Stress

1 Wood

Joists

15.9 5/8 none none 0.41 16 195 40 69

2 Steel

Joists

15.9 5/8 none none 0.61 24 352 72 100

3 Steel

Joists

19.1 3/4 none none 0.81 32 195 40 74

4 Wood

Joists

18.3 23/32 none none 0.61 24 195 40 100

5 Steel

Joists

18.3 23/32 12.7 1/2 0.61 24 327 67 100

6 Wood

Trusses

18.3 23/32 12.7 1/2 0.61 24 327 67 100

7 Wood

Joists

18.3 23/32 15.9

(Type

X)

5/8

(Type

X)

0.61 24 195 40 100

*Wood Joists, nominal 51 x 203 mm (2 x 8 in)

Steel Joists, 44.5 mm wide x 184.2 mm deep x 1.3 mm thick (1-3/4 x 7-1/4 in x 18 ga)

Super - C Wood Trusses, 88.9 mm wide x 304.8 mm deep (3-1/2 x 12 in), prefabricated with

nominal 51 x 102 mm (2 x 4 in) wood chords and webs

Span of all joists was 3.25 m (10.67 ft)

**An olefin carpet with foam rubber backing was installed over the plywood subfloor.

27
Table 4. Initial weights and potential heat of

combustible materials in test assemblies

Test

Assembly

Initial Weights of the Combustibles kg

Potential

Heat

MJ

Floor

Joists Bridging

Plywood

Subfloor

Olefin

Carpet

Sill

Plates

Rim

Joists

1 113.9 10.9 129.7 25.4 48.7 50.8 7770

2 0 . 0 . 120.2 24.0 41.7 42.2 4910

3 0 . 0 .

. 125.2 25.4 42.6 42.6 5090

4 98.6 9.5 126.6 23.6 56.4 56.4 7560

5 0 . 0 . 106.1 24.0 45.4 49.0 4850

6 203.2

1 8.2

1 126.6 23.1 47.2 92.5 9960

7 95.3 : 9.1 114.3 29.9 54.4 54.4 7480

28
Table

5.

Ambient

conditions

and

fire

growth

events

during

the

tests

i

29
Tabic b. Summary of various measurements during fully developed stage

Test

No .

Maximum

Average

Upper Room

Gas

Temperature

°C

Maximum

Release

kW

Heat

Rate

Maximum Flow Rate

Through Doorway

kg/s

Minimum

Neutral

Maximum

Room

Doorway

Smoke

Stack In Out**

Plane

Height m

Static

Pressure

Pa

1 923 3720 — 0.65 1.60 0.67 13.7

2 779 3620 — 0.70 1.63 0.66 14.4

3 773 2980 8280 0.64 1.56 0.70 13.3

4 894 3790 8460 0.63 1.67 0.64 14.2

5 1012 4110 8470 0.73 1.76 0.68 15.2

6 1019 4030 6860 0.80 1.73 0.66 15.4

7 991 2950* 5350 0.69 1.77 0.70

'Low value is questionable due to some difficulties in the oxygen sampling system.

**The density

be the same

of the combustion products flowing out through the doorway is assumed to as that of dry air in outflow rate calculations.

30
Table 7. Incident heat fluxes measured at various locations

Test

No.

At Walls At Floor

Outside

of Room

Total Radiative

Time

min

Total

Max.

kW/m2 Timemin.

Total

Max.

kW/m2 Timemin.

Max.

kW/m2 Ave.kW/m2 Time

min

Max.

kW/m2

1 11.12 104 98 — — 2.45 164 2.85 44

2 3.78 113 113 — 2.85 163 3.48 38

3 2.05 109 93 — — 3.05 159 3.72 39

4 12.17 130 118 — — 3.17 139 4.37 42

5 12.50 158 122 — — 2.36 128 3.13 39

6 10.17 181 156 11.10 175 2.43 125 2.30 35

7 9.16 I 179

1 160 4.10 167 2.63 133 3.16 38

31
Table 8. Optical density of smoke and gas concentration

of outflowing gases

Test

No

Maximum Optical

Density of Smoke,

OD/m

1 Minimum 0

Concentration,

Vol . %

Maximum Concentration, Vol . % ** CO C02

Doorway

(Avg .

Hood ! Doorway

(Avg.)

Stack Doorway

(Avg .

Stack Doorway

(Avg.)

Stack

1 4.08 2.50

|

, 0.36 7.7X 11.1

! 19.4 10.5

2 4.62 2.79 0.69 i

! 9.56 9.83 17.2 10.9

3 4.34 1.68 0.86 8.90 10.2 0.54 17.1 10.8

4 3.87 2.60 i 0.0

1 9.10 11.8 0 . 66 19.7

• i 11.2

5 3.00 2.89 , 0.22 9.66 10.7 — 11.5

6 3.60 2.28 0.24 1

j 10.5 9.6 0.51

|

i 9.75

7 3.94 2.62 ! 0.73

J

10.7

...

5.91* 0.28

1 8.05

*Low value was due to problems with gas sampling system.

**The maximum concentrations of CO and C09 gases did not occur at the same time.

32
Table 9. Summary of the fire resistance period of

floor assemblies in room burnout tests

Time to Time for

Surface

the Unexposed

to Increase

Maximum

Deflection

Assembly

No.

Flame

Through

min: sec

Structural

Failure

min : sec

Avg . Temp

139 deg C min : sec

1-point Temp.

181 deg C min : sec Time

min : sec

Center

Point mm

1 10:17 10:43 11:02 10:56 10:43 364

2 3:47 3:47 3:50 3:41 3:47 362

3 3:58 3:59 N.R. 4:04 4:07 330

4 12:02 12:00 12:08 12:02 12:00 176

5 15:58 15:58* 15:57 15:55 16:14 328

6 17:53 18:34 N.R. 17:43

. 18:34 325

7 35:08 35:18* N.R. N.R. 35:26 153

* No joist collapse, times refer to excessive deflection rate [4],

N.R. - not reached

33
3200

mm

lulu 0020

34

Figure

1.

Plan

View

of

the

Test

Room

Showing

Locations

of

Furniture

and

Wall

Linings
Key to Figures 2 to 6, and 9 to 10

Symbol Type of Transducers Locations

O Displacement Potentiometer Center and quarter-points of

floor joists

1 Thermocouple On the top of carpet

0 3 Thermocouples

0 1 Thermocouple

(tests 5 to 7)

At the bottom and top of floor

joist, and on the unexposed

surface of plywood subfloor

On the exposed surface of gypsum

board ceiling.

35
EE

LUQt <

toZo

toZ

LU5Q

U

X.

OZ 1

CO

COcouV

CO z<I Q_ocoo

co

36

Figure

2.

Flocr-Ceiling

Assembly

Construction

and

Instrumentation

Layout

for

Test

1.
CO

00

37

Figure

3.

Floor-Ceiling

Assembly

Construction

and

Instrumentation

Layout

for

Test

2.
Section

BB

E

E

o

•H

CJ3 U

u o U 14-1 03G -u O 3

CJ O

*H _3 e c

CD o

03 *H

03 AJ < 03 4J

00 C

g <u *H E

QJ 4—1 CJ 03 •

I G on

S-i M

O 4_i O 3 03 H C 0) fc cfl h

<u

5-i 3

00

•H

aooidans

QOOMAld ..8/?

<

<

c

o

u

a> co

38
E

E

QC<

z “ o o

7> z

Z to 32

Q £

-j u

“i x

< LU

LU

t—o

z

<

Z

<_

Q_

O'o

o

aoouans

QOOMAId ..8/9

)D018

313HDNOD isior

uooid aooM

gpBXPccroTO jUAJUJUi^5Euuw«nu**imijai

—

13d«VD

<

<

c

o

u

0) to

39

Figure

5.

Floor-Ceiling

Assembly

Construction

and

Instrumentation

Layout

for

Test

4.
:

iaa:

iaaa:

iaaa:

\j\

aa

u\

runM. EE

LU

OL

.J

dood

u

M

O

U 4-1 wd -p o d o o

rH hJ < d

4J 00 d d a) •h e

rH

d

•H

u

(U -u u w • 1 d lo U M o u o d to rH d <D

niH Ii <<cou

0) CO

40
WEST

EE

ocO

Z

0221 - 0221 98L H

u

<

tOZ

O

toZ

UJS

o

'O

«n

tN

CM

CO CO

-I 2

UJ

y-O

z

5

l

o

g

to<

UJ

3

O

to

41

Figure

7.

Floor

Plan

Showing

Layout

of

Gypsum

Board

Ceiling

for

Tests

5

to

7.
qx

uT ^ O : 3 CN < CN O n O LU - 2 O o. o z

10 Ot „ m

«/i

T

QC 3 £lO o

to

UJZ0

at

</> UJ

t-<—

a.

Uea

CD£3

CO

**co

CO

UJ

UJ

t-oZ a

UJ-Oz

to<

ta.

UJUX

UJEE

UJ

<*<

COZo

«75 Z

UJQ<

42

Figure

8.

Details

of

Wood

Truss

Construction

for

Test
aoouans

QOOMAld .zz/zi

<

<

c

o

u

0) CO

43

Figure

9.

Floor-Ceiling

Assembly

Construction

and

Instrumentation

Layout

for

Test

6.
I <

<

c

o

u

0) co

I

44

Figure

10.

Floor-Ceiling

Assembly

Construction

and

Instrumentation

Layout

for

Test

7.
WEST

-7Q§ z

°Ou a.UO

CO CNi§

co

— 12 z EE

CN

lO

CO

*= S >>

uj z ^ 9oco y U t- nOU 2 z£

22i *u<KCOuOi COCN

CO<

LU><£

£Kooa

45

figure

11.

Layout

of

Steel

Blocks

Distributed

Uniformly

Over

the

Top

of

Floor

Assembly

for

Test

7.
Key to Figure 12

Symbol

0

£3

S3

O

*

o

Type of Transducers

1 Fast Response Thermocouple

3 Thermocouples

2 Fast Response Thermocouples

7 Thermocouples

1 Thermocouple

1 Total Heat Flux Gauge

3 Gas Sample Ports

6 Static Pressure Probes

1 Static Pressure Probe

1 Total Heat Flux Gauge

Distance Below the Ceiling (m)

0.61

0.30, 0.61, 1.22

0.61, 1.22

0.025, 0.15, 0.30, 0.61,

1.22, 1.70, 2.21

0.61

2.30

0.36, 0.66, 1.04

0.10, 0.30, 0.61,

1.22, 1.70, 2.13

0.10

1.30

46
WEST

HiaON

GL8 Z8Z Z8Z- 018

Hinos

0) 0)

C 4J

cd cn rH c

PH H

QJ3M

•rH

47

EAST

note

:

ALL

DIMENSIONS

ARE

mm
co

co

CO

CO

»o

<

I

o

o

o

a.3

o

u

O

S

OC

* y

COo

oca.>

u

O

CO3

o

a

o

UJ

OC

I

I

»

i

<

<

I

(

( > <

48

NOTE

:

ALL

DIMENSIONS

ARE

mm

V

HORIZONTAL

SMOKE

METER

C?

VERTICAL

SMOKE

METER

Q

INCLINED

SMOKE

METER

Figure

13.

Instrumentation

Layout

at

the

(g)

DOUBLE-WIRE

THERMOCOUPLE

Doorway

Opening

ON

EAST

PLYWOOD

WALL
508

—

*+*

533

*4*

559

*4*

762

4*

787

ees— •9££-*j*-99£ -*|

Q-3

o

u

O

3 -j

£ <

LU Q “ o

co r1 3 Q- O z

Q O

r~r*

LU LU

CO

LUU --J

</) < - "

" £ <i 3 Q iu <

3 </> Z I

o* < '"S U LU ^ z O ozC-o

tt _i 4 >

Q CO < —

2

° 88 “ 31^0 E O'"? ^ E Q Ziu >; ^ loOO £ £

I

E

E

LUec<

toZ

o

COz

UJ5

3

T 1

49

Figure

14.

Instrumentation

Layout-View

of

West

(Back)

Wall

Showing

Wall

Thermocouples

and

Heat

Flux

Meters
610

*+»

991

991»4«

610

iu ' 

EE

LUoc<

toZO

toZ

tu%Q<

LU(—oz

50

Figure

15.

Instrumentation

Layout-View

of

South

Plywood

Wall

Showing

Wall

Thermocouples,

Total

Heat

Flux
51

Figure

16.

Instrumentation

Layout-View

of

North

Plywood

Wall

Showing

Wall

Thermocouples
900

1200

1500

1800

2100

2400

8 8 § o egM n

— o o n 0

o

s

o o

o o

P* 10 o a

o a

u» ^ o o o

o o a m eg «-•

in

CM

z

2

o | (g • H ui

- to

_ a

- io

s <

52

Figure

17.

Comparison

of

Average

Upper

Rooi

Gas

Temperature

for

Tests

1

to

and

Experimentally

Derived

Fire
300

600

900

1200

1500

1800

2100

2400 o a o o

CM

— oaa

Do ao oQ

OOOO oa oa oo oo

UJs eoo o

Od 4-1

t-i CUa. cn a 4-i p cn

cu

<uH

oo

cd

M

m o

<U 4-1 >C <Dp

44 3 O 4->

<D

•rl

T3

a)>

•H

(-1 <u a

cd

4-1 <U 3 >

<uM 6 3

•H C_> U

<u

a) cx n X 3 W COo m xi a « c X

U

O Cd

w

00

CU

V43

00

•H

pH

53
TIME

SEE

300

600

900

1200

1500

1000

2100

2400

o o o a o

o o o a o

I 54

Figure

19.

Floor

Deflection

Measured

at

the

Center

of

the

Test

Assembly
120

ISO

160

210

240

270

o o o o

o o o o QIO m CM

ft* •• Nouoruao

55

Figure

20.

Floor

Deflections

at

Center

and

Quarter

Points

Along

the

Center

Joist

at

Various

Times

for

Test
600

900

1200

1500

1800

2100

2400 ooooooooaoo QinaiOOlflOlflOLDOO

a)u3

4-1u

3

oo

<ubo

pj

<u <

4-1O

COa

o

•r-l 4-1 n) •HM 4-1 0)

n) b! 4J S

> M CO ft

qj a) o

1) ah 44 e s m

•H <1) 4-4 <U H H O fa

<N

(1) U

3

bO

rl

fa

56

ures

on

the

Unexposed

Side

Assembly

for

all

Tests
o

o

o

o

o

CD o

aCD Oa

o

o

to o

o

to o

a

o

m

O

D

DO O

a

Z

5

CO

CM

(Uw

•u

aj

<uI*

cu H

QJ

<J

cd

4-1M

3

CO

4-1O

fio

CO •Hw

ctJ 6o

CJ

CM

CM

<u3

bO

•rl

ptc

57

of

Steel

Joist

and

Plywood

Subfloor

for

Assemblies

With

and

Without

a

Protective

Ceiling
100

200

300

400

500

600

700

BOO

900

1000

m Nouoruaa

58

Figure

23.

Relationship

Between

Floor

Deflection

and

Steel

Joist

Temperature

at

Center

of

Test

Assembly
Q

100

200

300

400

500

600

700

600

900

1000

400i

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

400 o o o o a o

<*» tn N N — m ••• NOLLDTU30

59

Figure

24.

Relationship

Between

Floor

Deflection

and

Wood

Joist

Temperature

at

Center

of

Test

Assembly
TidE

***

SEC

120

150

1

80

210

240

270

o o a a o

§ o> § 8 S s

o

8

Sm* oo

3 030 ••• 3bfUV»3dW3i

<Ub3

cOU

<u %

<4-1 o

co

•H

4-1 cO

•rlM

cO >

co

0) u

>4 O

3 ^4

4-1 CO 03

>4 3

<D O

(X «H 6 H

CU c0 H >

m

CN

<u

»43

bO

•H

&4

60

of

Steel

Joists

at
m ••• Nouojidsa

o o O o o o o o ID O in o in a a

o'*- rr> m CSi (Si •—

•

hO Oo

I

ui$

0 OK ••• 3UrUVU3dfOi

4-1o

3 a) O M

O 3

rH 4-1 PH 03 3 03

a) a, T3 3 B 3

S 03 3

P H

a) 3

03 33 3

3 O

CH 3

•H bO 3

XS 3 3 J-i 03 O •H 3

3 •rl 33 u

o 4-1 3 3

•rl O 3 p4

4-1 3 O 3

03 rH 3 a

r-i 34 p4 s

03 3 3 3

02 n C/3 H

• so

CN 9

033

00

•rl Ph

61

Steel

Joist

APPENDIX A

Maximum Design Load Calculations

The design values [6] for Southern pine, construction grade no. 2, medium

grain, joists with nominal 51 x 203 mm (2 x 8 in) cross section used in test

7 are the following:

allowable bending stress for the extreme fiber, = 8.27 x 10 6 Pa

(1200 psi)

modulus of elasticity, E = 1.1 x 10 10 Pa (1.6 x 10 6 psi)

moment of inertia, I = 1.983 x 10 m

4 (47.635 in 4

) section modulus, S = 2.153 x 10 4 m

2 (13.141 in 2

)

The floor joists under uniform loading were simply supported on a 3.25 m

span and spaced 0.61 m (24 in) on center.

Dead load:

Plywood subfloor (18.3 mm thick)

Wood joists

Gypsum wallboard (15.9 mm thick)

Carpet flooring

Total dead load

(1) Deflection

A limitation of 1/360 of the span length is used as the maximum allowable

total deflection, which is equal to

D = = 0.00903 m (0.35 in)

The uniform load per unit length on the floor joist corresponding

to this maximum deflection, which occurs at the middle of the span

can be obtained as

= 384_ EID = (384) (l.lxlQ 10

) (1.983xl0~ 5

) (0.00903)

5 L

4 (5) ( 3 . 25

)

4

= 1356 (N/m) = 138.3 kg/m (92.8 lb/ft)

and the maximum total allowable load on floor joists with a joist spacing of

0.61 m on center is

9.8 kg/m2

9.8 kg/m2

10.7 kg/m2

1 . 9 kg/m2

32.2 kg/m2 (6.6 lb/ft 2

)
total allowable load = 138.3 x 1/0.61 = 227 kg/m2 (46.5 lb/ft2

)

Therefore, the maximum design load permitted to meet the acceptable

deflection is

live load = total load - dead load

= 227 - 32 = 195 kg/m2

(40 lb/ft 2

)

(2) Bending Moment

The maximum induced moment occurs at the mid-span of the joist and is equal

to the product of the allowable fiber stress in bending and the section

modulus of the joist.

M = Fb

S = (8.27 x 10 6

) (2.153 x 10~ 4

) = 1781 N-m (15770 in-lb)

The allowable load per unit length on a joist can be calculated as

w =

8 M = ( 8 ) (1781)_ _ 1349 (N/m) _ 137>6 kg/m ( 92.3 lb/ft)

IT (3.25)

The total working load expressed in terms of unit area is equal to

total load = 137.6 x = 226 kg/m2 (46.3 lb/ft 2

) U . D 1

and live load allowed for the maximum bending moment is

live load = 226 - 32 = 194 kg/m2 (39.7 lb/ft 2

)

Therefore, the maximum applied load with which the joists are fully

2 stressed to the design value is 195 kg/m (40 psf )

A-2
APPENDIX B

Log of Tests Based on Visual Observations

TEST 1

Time

(min : sec

)

Events

0:10 Smoke rising from the newspaper on the sofa

0:30 Smoke touching ceiling

0:43 Smoke is halfway across ceiling

0:45 Flame appearance on ignition newspaper

0 : 51 Flames extend to 1.4 m above seat cushion of sofa

0:55 Smoke issuing out doorway

1:00 Fire involves center of sofa

1:07 Smoke out doorway to 0.8 m down from the top of doorway

1:12 Flame tip located at 0. 6-1.0 m below the ceiling

1:22 Flames touching the ceiling

1:35 Ignition of carpet

1:36 Smoke halfway down in the room

1:40 Crackling sound in the room

1:50 End cushions split

1:55 Portions of the paneling are igniting

2:02 Small volumes of flames out doorway

2 : 04 Coffee table ignited

2:15 Room flashover occurs (newspaper indicator ignited)

2:17 Filter paper indicator ignited

2:19 Large flames out doorway

2:20 All room contents are burning

2:40 Steady state burning

2:57 Smoke seeping through joist spaces on floor assembly

3:26 Heavy smoking through floor assembly mostly from back

part of room
Time

(min : sec

Events

5:20

7:40

8:35

8:50

11:02

11:34

11:40

11:58

Test 2

Time

(min : sec)

0:04

0:13

0:20

0:24

0:29

0:45

0:50

1:07

1:11

1:18

1:35

1:39

1:45

1:50

1:54

1:59

Smoke is thickening

Crackling in room

Smoke above floor assembly is lightening slightly

Smoke in the room is thickening

Flame through the ceiling

Smoke is darkening

Steel blocks are falling

Test terminated

Events

Light smoke rising from the ignition newspaper

Flames appear on the newspaper

Flames to 0.8 m above seat cushion of the sofa

Center of sofa is burning

Flames to 1.1 m above the central seat cushion

Flames to 1.4 m above sofa seat cushion

Light smoke in top portion of room

Flame spread on sofa center about 0.4 m in width

Flames sporadically touching the ceiling

Flames spreading along ceiling surface

Cushions are smoldering

Flames halfway across the ceiling

Left arm of sofa is smoking

Flames across entire ceiling

Smoke layer halfway down from ceiling

Flames involving about 3/4 of sofa

B-2
Time

(min : sec

)

2 : 02

2:10

2 : 14

2:20

2 : 22

2:25

2:31

2:33

2:35

2:50

3:05

3:25

4:00

4:20

5:10

TEST 3

Time

(min : sec

)

0:05

0:09

0:13

0:20

0:29

0:33

0:43

Events

Flames emerging from doorway opening

Coffee table is smoldering

Coffee table ignited

Heavy smoke layer developed in the room

Flame well out the doorway

Chair is smoldering

Room flashover occurs (newspaper on floor ignited)

Filter paper indicator ignited

Heavy flames out the doorway carpet is ignited

Steady state burning

Smoke is coming through top of floor assembly around

its edges

Vision of the top of floor assembly is obscured almost

completely by smoke

Blocks are falling

Blocks are still falling

Termination of test

Events

Smoke rising from center of ignition newspaper

Flame appearance on the newspaper

Flames on sofa extend to 0.6 m above central seat cushion

of the sofa

Flames to 0.8 m above the seat cushion

Flames to 1.1 m above the seat cushion

Flaming is concentrated on the center of the sofa

Flames are spreading along the top of the sofa and newspaper

B-3
Time

(min : sec

Events

0:47

0:54

1:00

1:10

1:12

1:19

1:35

1:42

1:52

1:59

2:09

2:10

2:15

2:20

2:28

2:30

2:39

2:45

3:00

4:07

4:14

4:32

TEST 4

Time

(min : sec

0:04

0:08

Flames fluctuate between 1.4 to 1.7 m above the seat cushion

Flames covering 1/2 of the center cushion of the sofa

Flames are touching the ceiling

Smoke in room is darkening

Flames are spreading along the top of the sofa

Smoke layer down to 0.6 m below the ceiling

Flames extend halfway across the ceiling

Flames are covering the ceiling

The end cushions of the sofa are splitting

The end cushions ignited

Smoke layer extends halfway down to floor

Flames emerging from doorway

Heavy flames out the doorway

Coffee table ignites

Flashover occurs (newspaper indicater ignited)

Filter paper indicator inflames

Carpet is ignited

Steady state burning

Heavy smoke coming through back of the top of test assembly

Flames penetrate through the floor assembly

Floor assembly collapses

Test terminated

Events

Light white smoke given off from the ignition newspaper

Flames appear behind the newspaper

B-4
Time

(min : sec

Events

0:21 The back of sofa is burning; flames to 0.83 m above

seat cushion

0:45 Flame tip to 1.2 m above seat cushion

0:51 Flames to 1.5 m above the cushion

1:13 Flames to 1.8 m above seat cushion

1:18 The upper part of the room is darkening

1:24 Flames are touching the ceiling

1:29 Smoke layer is filling the upper half of the room

1:50 Flames cover 3/4 of the ceiling area

1:55 End cushions of sofa are splitting

2:01 Flames emerging from the doorway opening

2:07 Entire top of the sofa is burning

2:13 End cushions are burning

2:15 Flames extend 1 m out doorway

2:18 Coffee table is burning

2:22 Newspaper flashover indicator is smoldering

2:25 Heavy smoke down to 0.5 m above the floor

2:26 Room flashover occurs (newspaper indicator ignited)

2:39 Filterpaper indicator ignited spontaneously and carpet

is ignited

2:44 Heavy flames issue out the doorway

2:45 All combustible materials in the room are burning

3: 03 Most of the smoke passing through the floor assembly are

coming from the doorway side

4:14 Smoke above the rear portion of the assembly is thickening

5:15 Top of the room is almost obscured from view by smoke

5:24 Slight increase in smoke density is observed for top of

the room

6:30 Smoke density is decreasing

10:05 Smoke is darkening slightly

11:09 Smoke is getting lighter

B-5
Time

(min : sec)

11:50

12:08

12:10

12:16

TEST 5

Time

(min : sec)

0:03

0:10

0:13

0:20

0:31

0:37

0:40

0:41

0:49

0:52

1:02

1:14

1:20

1:25

1:32

1:35

1:37

1:41

1:45

Events

Smoke density is decreasing

Floor assembly collapses

Flames pass through floor assembly

Test terminated

Events

Light smoke appears from the ignition newspaper

Flame appearance on the newspaper

Flame height 0.8 m above central seat cushion of sofa

Flames to 1.1 m above the seat cushion

Top of central cushion involved in burning

Light smoke is coming out the doorway opening

Flame tip locate at 1.7 m above sofa seat cushion

Flames touch the ceiling occasionally

Flames are touching the ceiling

Black smoke starts to fill the room from the ceiling

Black smoke fills the upper half of the room

Flames begin to turn around the back corner onto the

ceiling

End cushions of sofa are splitting

Flame extends halfway across the ceiling

Flames cover three-fourths of the ceiling area

Black smoke layer is still at halfway down from ceiling

End cushions of sofa are burning

Flames emerging from the doorway opening

Coffee table is burning

B-6
Time

(min : sec

)

1:54

1:55

1:56

2:08

2:10

2:11

2:12

3:40

6:30

8:40

10:45

11:57

13:19

13:54

14:15

15:08

16:08

16:25

TEST 6

Time

(min : sec

)

Events

Room flashover takes place (newspaper indicator ignited)

Filterpaper indicator ignited

Heavy flames coming out the doorway

Chair is burning

Carpet on floor is curling up

Carpet is burning

Steady state burning

Light smoke is coming out from the cracks between the

floor assembly and concrete block walls

Smoke is coming out of test assembly at nearly constant

rate

No appreciable CO reading in the vicinity of test room

Zero CO reading

CO 4 ppm in the area near test room

Small pieces of gypsum board ceiling start falling down

onto the floor

Large pieces of gypsum board drop down

Large fragments of ceiling materials fall down

Wood framing of the sofa collapse

Passage of flames through center of test assembly occurs

Test terminated

Events

0:04

0:06

0:10

0:16

Light smoke rising from the back of the ignition newspaper

Sustained flaming of the newspaper

Flame is spreading across the top of the newspaper

Flames are traveling up the back cushion of the sofa

B-7
Time

(min : sec) Events

0:20 Flames extend to 1.1 m above the sofa seat cushion

0:35 Flames to 1.4 m above seat cushion

0:38 Flames to 1.7 m above seat cushion

0:43 Flames touch ceiling

0 : 53 Flames concentrated on center cushion of sofa

1:02 Smoke in the room is darkening

1:08 Flames extend 1/3 way across the ceiling

1:13 Sofa arms are melting

1:20 End cushions of sofa are burning

1:22 Smoke in the upper part of the room is thickening

1:23 Flames halfway across the ceiling

1:30 Flames emerging from the doorway opening

1:32 Coffee table is burning

1:40 Heavy smoke issuing out the doorway

1:42 The entire sofa is burning

Room flashover occurs (newspaper indicator ignited)

1:43 Filterpaper indicator ignited spontaneously

1:45 Steady state burning

1:49 Carpet is curling up

1:52 Carpet ignited

2 : 25 Light smoke coming through the floor assembly

11:10 South block wall is cracking

11:43 Smoke coming out of cracks in west and south block walls

11:57 Pieces of gypsum board ceiling are falling

12:20 More pieces of ceiling materials drop down

13:35 Test assembly starts deflecting

14:25 Deflection is increasing

15:00 Smoke has obscured the view of weights on floor assembly

15:12 Fragments of wood truss fall and burn on floor

16:25 Smoke is very dense

B-8
Time

(min : sec ) Events

17:03 Crackling sounds in the back of the room

17:52 Flames pass through the rim joist resting on the rear

block wall and the centrally located wood truss collapses

17:59 Flame through the floor assembly in back of room

18:54

TEST 7

Test terminated

Time

(min:sec) Events

0:05 Light smoke rises from the ignition newspaper

0:10 Visible flames appear on the newspaper

0:15 Flame spread across the top of the newspaper

0:22 The back cushion of the sofa is burning

0:25 Flame tip reaches 0.8 m above the seat cushion of sofa

0:35 Flame height 1.1 m above the sofa seat cushion

0:43 Flames to 1.4 m above the seat cushion

0:52 Flame height 1.7 m above the seat cushion

1:02 Flames are touching the ceiling

1:20 Dark smoky layer located above the mid height of room

ceiling

1:27 Ceiling flame extends to one-half way across ceiling

1:30 Seat cushions at both ends of the sofa split open and

expose inner foam

1:37 The entire sofa is involved in burning

1:46 Smoky flames emerge from the doorway

1:47 Coffee and end tables ignited spontaneously

1:51 Room flashover occurs (newspaper indicator ignited)

1:52 Filter paper indicator ignited

2:03 Steady state burning

B-9
Time

(min ; sec) Events

2:08 Carpet is curling up and ignited

3:05 Light smoke is coming out through south block wall near

heat flux-meter location

9:45 Cracks develop in south and west block walls

13:25 Cracking of block walls continues

15:00 Furring strips attached to block walls burn actively

18:45 CO level in the vicinity of test room 9 ppm

19:00 Gypsum board ceiling still intact

19:55 Fire has died down considerably

23:16 Small piece of ceiling material falls off from gypsum

ceiling near doorway

23:43 Flames emerge from doorway once again

24 : 50 Room gas temperature shows a slight increase; the central

portion of gypsum board ceiling falls off

25:30 Another piece of ceiling falls off

26:35 Burning of floor assembly continues and room gas temperature

rises continuously

27:05 Floor is deflecting significantly

28:15 Rapid temperature rise on unexposes surface of test assembly

29:45 Floor deflections are increasing

31:00 Heavy flames come out doorway

34:50 Both deflection and unexposed surface temperature are

rising continuously

35:21 Flames through floor assembly at the location adjacent

to the ceiling above the bookcase

35:26 Test terminated

B-10
NBS-1 1 4 A ( R !. v. a- 7 m

IJ.S. DEFT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR RtPORI NO. NBSIR 80-21342. Gov’t. Accession No.

4. TITLE AND SUBTITLE

Fire Performance of Selected Residential Floor

Constructions Under Room Burnout Conditions

7. All r i iORl S) Jin Bao Fang

r EK! ORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, DC 20234

12. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street, City, sure, ZIP) Division of Energy, Building Technology and Standards

Office of Policy Development and Research

U.S. Department of Housing and Urban Development

Washington, D.C. 20410

3. Recipient’s Accession No.

5, Puhlicdti-vi Date December 1980

6 . Performing Orgam/atin > i> rie

8. Performing C . n i

i

, t ;•

10. Prcject/Task/Work Unit No.

11. Contract/Grant No.

13. Type of Report ;t Period Covererl

Interim

14. Sponsoring Agency Code

IS SUPPLEMENTARY NOTES

I Document describes a computei program; SF-165, FIPS Software Summary, is attached.

16. ABSTRACT (A 2tlO~worJ or less lactual summary of most significant information. If document includes a significant bibliography or

1 1 tier mure survey, mention it here.) A series of seven large-scale room burnout fire tests was conducted with a set of selected residential floor-ceiling assemblies to provide data on the

performance of the assemblies; these will be compared with the results in future

tests on the same constructions in a fire endurance furnace. Four wood-frame and

three light gage steel-frame, load-bearing assemblies, each measuring 3.7 x 3.7 m

in size, were exposed from the underside to a fire environment produced from the

burning of typical furniture and interior finish materials in a room. The fire

resistance periods based on flame-through of floor assembly and structural failure

of floor joists varied from 10 to 12 minutes for floors with unprotected wood

joists and was 4 minutes or less for floors with unprotected steel joists. The

addition of a 12.7 mm thick gypsum board ceiling as a protective layer increased

the fire resistance time of the steel joisted floor assembly approximately 12

minutes.

17. KEY V.TRUS As/.. to twelve entries; a lphabeti i ul order; capitalize only the first letter of the first key word unless a proper mw.t . sepm.i ted hy sent i coions) Fire endurance; fire tests; flame through; floors; furniture; interior finishes;

joists; room fires; steel; wood.

18. AVAILABILITY x Unlimited

I For Official Distribution. Do Not Release to NTIS

Order From Sup. of Doc., U.S. Government Printing Office, Washington, DC

20402, SD Stock No. SN003-003-

" Oidei From National Technical Information Service (NTIS), Springfield, V A. 22161

19. SECURITY CLASS

(THIS REPORT)

UNCLASSIFIED

20. SECURITY CLASS

(THIS PAGE)

UNCLASSIFIED

21. NO. OF

PRINTED PAGES

79

2?. Price

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