*< "' 'o, i

\

\

NBS TECHNICAL NOTE 7 10" 10

NATL INST OF STAND & TECH

A111D7 E3S311

U.S. DEPARTMENT OF COMMERCE/ National Bureau of Standards
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards 1 was established by an act of Congress March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and technology and facilitate their effective application for public benefit. To this end, the Bureau conducts research and provides: (1) a basis for the Nation's physical measurement system, (2) scientific and

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laMMMXi BXTWtKV

EIBRAJRY

AR 22 »78 BUILDING RESEARCH TRANSLATION

The Behavior of Concrete Structures in Fire

A Method for Prediction by Calculation

Centre Scientifique et Technique du Batiment

Paris, France

Translated by Information Simplified, Inc. P.O. Box 7439

Alexandria, Va. 22307

for the

Center for Building Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D.C. 20234

*«? °^<

U.S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary

Dr. Sidney Harman, Under Secretary

Jordan J. Baruch, Assistant Secretary for Science and Technology

\J, 5 NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

Issued March 1978
National Bureau of Standards Technical Note 710-10

Nat. Bur. Stand. (U.S.), Tech. Note 710-10, 83 pages (Mar. 1978) CODER NBTNAE

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1978

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402

Stock No. 003-003-01896-1 Price $2.40

(Add 25 percent additional for other than U.S. mailing).
Preface

The United States and Frances' Cooperative Program on Building

Technology involves an exchange of personnel and information

between the Center for Building Technology of the National

Bureau of Standards and the Centre Scientifique et Technique

du Batiment (CSTB) . Information contained in this report

was selected for translation and reproduction for sale to

the building community by the Government Printing Office.

The CSTB papers made public through this Technical Note do

not necessarily represent the views of the National Bureau

of Standards on either policy or technical levels. Building

researchers at the National Bureau of Standards consider it a public service to share with -the U. S. building community

these insights into some of the research activities of CSTB.

Center for Building Technology

Institute for Applied Technology

National Bureau of Standards
COMMISSION FOR STUDY OF THE METHOD OF PREDICTING, BY CALCULATION,

THE BEHAVIOR OF CONCRETE STRUCTURES IN FIRE

Coordinator:

Rapporteur:

Secretary:

Members:

Chairman: M. Roger Devars du Mayne, Chairman of the Investment and

Research Council, National Building Federation

M. Michel Adam, Director of Regulations at the Interprofessional Technical Union of the National Federations of

Building and Public Works

M. Andre Coin, Technical Director of the Auxiliary Society of

Business Firms

M. Andre Verzat, Technical Director of the Trade Union Office

for the Masonry and Reinforced Concrete Industries of the

Paris Region

M. Arnault, representing the Industrial Technical Center of

Metal Construction

M, Cabret, representing the Scientific and Technical Center of

Building

M. Brunet, representing L'Europeene d' Enterprises

M. Lopez, representing the Engineering Society for Utilization

of Prestressed Concrete and the Aquitaine Engineering

Office

M. Eliche, representing Research and Engineering Studies, S.A.

MM. Gamot and Marzaux, representing the F. Bouygues firm

MM. Boutin, Lemoine, and Martin, representing SOCOTEC

M. Malaval, representing the Center for Technical Assistance

and Documentation (U.T.I ,B T Po

)

M. Schmol, representing the National Trade Union for Reinforced Concrete and Industrial Technologies

Centre Scientifique et Technique du Batiment [Scientific and Technical

Center for Construction]

A, Avenue du Recteur-Poincare, Paris 16 e

This document cancels and replaces "Recommendations for Predicting, by

Calculation, the Behavior of Concrete Structures in Fire" issued in May

1972 and includes Supplement No. 1 of April 1975.

IV
Introduction

This method gives a means for predicting, bycalculation, the resistance to fire of a reinforced or prestressed element of construction, in accordance

with the directives of 5 January 1959.

It is directly useful in allowing builders to design structures which would with normal likelihood

show the degree of fire resistance required by the

various construction regulations in force. According

to those regulations, only a test furnishes legal

proof of fire resistance.

We would hope that this first step will lead to the

acceptance of calculation of fire resistance as legal proof of satisfactory resistance.
BACKGROUND NOTE BY THE RAPPORTEUR

Rationale

If fire effects are to be introduced into calculations, they must be

given a simple physical definition. This work has already been done by

the editors of the text defining fire test conditions, since they assumed

that a fire could be simulated by a rise in temperature in a standard furnace.

We have adopted this basic hypothesis since it would give us, under

the best possible conditions, the opportunity to compare the results of

calculation of an element and those of the corresponding test, and then to

compare the methods.

The fire study started with a study of the temperature distribution

in an element when it was subjected to a heat flux on a part of its exterior surface. This concept has already been developed by numerous workers,

and we know that the temperature rise follows the Fourier equation which,

for plane problems, can be easily converted to an equation of finite differences. We did this by developing a calculational program on the terminal

both to extract the results that can be used immediately for structures of

simple shapes and also to handle more complex shapes on a case-by-case

basis.

To carry out this calculation successfully it was necessary to know

the "convection + radiation" coefficient of the furnace, which depends on

too many parameters for a precise and usable formulation to be given.

This difficulty was eliminated by giving it a probable expression dependent

on adjusted parameters for finding the average "useful temperature-timedistance" laws that would give the same results as those of tests published

so far.

The temperature distribution being thus defined, we could determine

the first moment at which temperatures of 140 or 180°C are reached on the

face of the element not exposed to the fire and then its thermal insulation in the sense of criterion No. 2.

We then studied the thermal expansion coefficients of materials which

have been published by various authors. Evaluation of the complementary

effects caused by fire thus becomes a problem of strength of materials,

for which we can give solutions whose approximation can be evaluated.

Finally, by using the published results of tests on the weakening of

the various mechanical properties of the materials as a function of temperature (nominal failure stress, elongation, modulus of elasticity, etc.) we can calculate at any instant the breaking moment of a cross-section.

VI
Comparison, for all or part of the structure, of the associated failure

load with the working load allows us to determine the point at which fire

resistance is no longer assured. We were led at this phase of our study

to adopt weighting coefficients for the weak stresses in the concrete and

steel which we assumed in order to find the fire-resistance times given by

published test results.

The Document

We then developed this document according to the above scheme, taking

into account the new orientation of the regulations.

The text portions which discuss resistance to fire are drawn up in the

form of results required and not as means for arriving at them.

This means that all latitude can be left to the engineer in proving

out this text material. It would be unfortunate to restrict opportunities

by too precise requirements, especially since the lack of perspective and

experience could lead us to a poor evaluation of the means.

We decided to draw up an open text that would allow an engineer to

apply, depending on the enthusiasm or interest he wanted to invest, —Simple rules, —Or failure calculations based on the results of given temperatures, —Or temperature and failure calculations, —Or any other method, tests in particular.

Thus our document contains, besides generalities: —Various curves showing the variations in physical and mechanical

properties of concrete and steel materials with temperature —Examination of the different effects of fire —The method of failure calculation which is proposed with the

weighting coefficients adopted —By type of structure (column, wall, slab, beams, hollow bodies) —The simple rules —Temperature results for the most current cases —The adaptation, proposed for the calculation method —The method of calculating temperatures with the approximations and

the list of corresponding instructions.

vi 1
Comments

The reader will find that the validity of the given method is strongly

affected by the reproducibility of the published experimental results, both

with respect to the physical properties of the materials and to the temperature measurements. There are very large dispersions of a type such

that it seems essential to us to continue the studies in these different

areas. This could be done step by step by engineers who would have to

solve a particular problem, or by the manufacturers who would try to find

details of their product properties in order to improve the calculation

justifications involved. This could be done more systematically by re- search laboratories whose collaboration would allow confirmation or improvement of the present method.

Andre Coin

VI IX
TABLE OF CONTENTS

Page

CHAPTER I

Applicability 1

CHAPTER II

Nomenclature 2

CHAPTER III

Changes in the Properties of Materials as a Function of

Temperature 4

3 . 1 Properties of Concrete 4

3.11 Compression 4

3.12 Tension 5

3.13 Expansion 6

3. 14 Modulus of Elasticity 6

3.15 Conductivity 7 3 . 16 Specific Heat 7

3. 2 Properties of Steel 7 3. 21 Concrete Reinforcing of Steel 7 3. 211 Failure Stress in Tension 7 3 . 212 Elastic Limit 8

3 . 213 Elongation at Rupture 9

3.214 Coefficient of Expansion 9

3 . 22 Hard Steels for Prestressing 9

3.221 Strain Limit and Standard Elasticity at 2 Pro Mille 9

3. 222 Elongation at Rupture 10

3 . 223 Expansion 10

CHAPTER IV

Temperature Distribution in Concrete 11

CHAPTER V

Basis for the Justifications and Evaluations of Stresses.... 15

5 .

1

Stresses to Take into Account 15

5.11 Stresses Due to Overall Effects of Expansion 16

5.2 Analysis in Simple or Compound Bending 18

5 .

3

Shattering 21

ix
TABLE OF CONTENTS (cont'd)

Page

CHAPTER VI

General Structural Rules 22

6 .

1

Expansion Joints 22

6.2 Geometric Arrangements 23

6.21 Floors and Beams 23

6 . 22 Loadbearing Elements 25

6

.

3 Arrangement of Reinforcement 26

6.4 Execution Tolerances 27

CHAPTER VII

Construction Rules According to Structure Category 28

7 . 1 Columns 28

7.11 Simple Rules 28

7

.

12 Temperature of Concrete and Steels 29

7.13 Other Columns 31

7 . 2 Stringers 31

7 . 3 Bearing Walls 32

7.31 Simple Rules 32

7 . 32 Temperatures in the Concrete 33

7 . 33 Other Walls 34

7 .

4

Cast Concrete on Continuous Supports 34

7 . 41 Construction Arrangements 34

7.42 Simple Rules for Slabs and Pre-Slabs of Reinforced Concrete.. 35

7.43 Temperature in the Concrete 38

7.44 Other Slabs or Preslabs of Reinforced Concrete—Slabs

and Preslabs of Prestressed Concrete 38

7.5 Main and Secondary Beams, Reinforced Concrete or Prestressed Concrete 39

7.51 Simple Rule 39

7.52 Temperature of the Concrete 43

7 . 53 Other Justifications 45

7 .

6

Slab Floors 46
TABLE OF CONTENTS (cont'd)

Page

7 . 7 Shell-Floors 46

7.71 Simple Rules 46

7 . 72 Temperatures 47

7 . 73 Other Shell Beams 47

7 . 8 Floors of Hollow Ceramic or Concrete 48

7 . 81 Simple Rule 48

7 . 82 Other Justifications 48

CHAPTER VIII

Additional Protection 50

APPENDIX I

Program for Calculating Temperatures 52

References 68

XI

METHOD OF PREDICTING, BY CALCULATION, THE BEHAVIOR

OF CONCRETE STRUCTURES IN FIRE

Chapter I

APPLICABILITY

This document sets forth the justifications or additional analyses

needed to take into account the action of fire in reinforced or prestressed

concrete structures with normal aggregates<>

By extension, it could be applied to structures built with light or special aggregates, provided that one knows the physical and mechanical

properties needed to use it.

Comment:

Structures (elements of construction or whole structures)

should be first dimensioned and analyzed according to the rules of

the trade governing their behavior in relation to other stresses.

The structures are, in other respects, assumed to conform to

all appropriate safety regulations, but the present text discusses only one of the aspects of the more general problem.
Chapter II

NOMENCLATURE

The basic properties of materials are their nominal properties. When

these materials are at a certain temperature 0, the properties have the subscript 0. The properties of concrete depend on its age, which is indicated

by the subscript j(j). The prime indicates compression (and its absence

indicates tension). The presence of a dash over values indicates allowable

values. The following notations are used:

In the cold At a certain

temperature

a

arg

'arg

a

A7

;

eQ

'arg0

'arg0

arg0

~arg0

a6

'boQ

'be

'be

(t)<

Concrete: failure stress in compression

Concrete: failure stress in tension

Steel: elastic limit

Concrete: strain limit

Steel: strain limit

Steel:

Steel:

Steel:

Concrete

failure stress in tension

elongation at rupture

modulus of elasticity

allowable stress in simple

compression

Concrete: allowable compression in bending

compression

Concrete: allowable stress in tension

Steel: allowable stress in tension

Unit extension

The useful distance (u) is the distance from the axis of the steel to a wall subjected to the effect of the fire.

The criteria and requirements are defined by two letters and a number,

which show precisely the nature of the requirement and its duration expressed

in hours. We have, for example,
CF (Coupe-feu = fireproof): 1/2 1 SF (fire-resistive): 1/2 1 PF (Pare-f lammes = flameproof): 1/2 hr

Comment:

or 4 hr

or 4 hr

We recall that a nominal property is the average test value where

the mean square variation is subtracted from the various results.

Fig. 1. Useful

distance, u.

Reinforcing steel is also covered in accordance with the

Regulations for design of reinforced or prestressed concrete in

force.

The directive of the Ministry of the Interior of 5 January

1959 establishes the criteria for determining the degree of fire

resistance of structural elements, the test methods, and the

thermal program (normalized temperature-time curve) showing the

effect of fires. The criteria areCriterion No. 1: mechanical strength

Criterion No. 2: thermal insulation (average heating of 140°C,

maximum of 180°C for the unexposed face)

Criterion No. 3: imperviousness to flames

Criterion No. 4: no emission of flammable gas outside the ex- posed face.

Fire-resistant elements are classified into three categories: —SF, fire-resistive, for which criterion No. 1 only is required.
—PF, flameproof, for which criteria 1, 3, and 4 are required. —CF, fireproof, for which criteria 1, 2, 3, and 4 are required.

In each category the rating is expressed in terms of "degrees" as

a function of the time during which the element has satisfied the

tests defined in the directive.

Chapter III

CHANGES IN THE PROPERTIES OF MATERIALS AS A FUNCTION OF TEMPERATURE

The changes in the mechanical properties of materials as a function of

temperature are defined by polygons whose peaks are shown in the tables

below.

Instead of using these data, we can use experimental results obtained

in laboratories approved for this purpose on materials actually in use. In

this case it will be necessary to request and obtain the agreement of the

Testing Committee for the use of the new figures proposed.

Likewise, future use of the results of new tests by the Testing Committee could lead to publication of additional sheets containing new curves

to be substituted for or to supplement the older ones.

3.1 Properties of Concrete

3.11 Compression

Temperature o°c 250 °C 600 oC 1 000 °c

1 1 0,45

Comment:

The values graphed in Figures 2-8 were taken from test results

published up to this time.
Test results

" cr'je/cri 120

1,00 i £ / '

0,80

0,60

0,45

0,40

o.ao

-^

200 400 600 800 1000 1200 G°C

! Scatter (outer curves are averages of published values)

3.12 Tension

Figure 2

Temperature 0°C 50 °C 600 °C

i 1

Test results

1,20

i cne/cr;

1 OOj

0,80

0,60

40

0,20

i -*• 50 200 400 600 800 1000 1200

e°c

Figuze 3
3.13 Expansion

Al The coefficient of expansion is constant, and is equal to —- : = 10-s per degree Celsius

Test results

'^»e (%)

-<

>

O 200 400 600 800 1000 1200

©°/C

Figure 4

3.14 Modulus of Elasticity

Temperature °C 50 °C 200 °C 400 °C 600 °C

E„

1 1 0,5 0,15 0,05
Test results

1,00

0,30

0,60

0,40

0,20

Figure 5

3.15 Conductivity

Temperature o°c 500 °C 1 000 °c

^kcal/m\h.°C 1,4 0,8 0,5

'kcal/kg. °c

3.16 Specific Heat

At any temperature c,

3.2 Properties of Steel

3.21 Concrete Reinforcing of steel

3.211 Failure Stress in Tension

= 0.22.

Type of steel Temperature

0°C 250 °C 350 oc 500 °C 800 °C

Fe E22 or Fe E2A smooth

CTarK9 round bars for reinforced

°nrs concrete

High adhesion Fe E40 rods, foi

1,00 1,00 0,50

reinforced concrete

1,00 1.00 Welded mesh 1,00 1,00
Comment:

The fact that the values at temperature 9 have the same indexes

as those in the cold does not mean that the mechanical properties

guaranteed in the cold will be the same at temperature 0.

3.212 Elastic Limit

Under any conditions we have:

Temperature o°c 250 °C 750 °C

«.«/ °e 1,00 1,00

Test results

CTae/CTa

700 750

e°c

Figure 6
3.213 Elongation at Rupture

Values are the same as for elongation in the cold.

3.214 Coefficient of Expansion

The coefficient of expansion is constant, with the value:

A] -5 — = 1.5x10 per degree Celsius

Test results

(%

100O 1200

Figure 7

3.22 Hard Steels for Prestressing

3.221. Strain Limit and Standard Elasticity at 2 Pro Mjlle

Temperature (°C) 100 150 500 250

a,0

Stabilized 1,00 1,00 0,20

and

wire-drawn

Sure ° Laminates and 1,00 1,00 0,30

aar6 strands
Test results

j . Corg9/GVg

Figure 8

Key: 1. Laminated steels;

2. Stabilized wire-drawn steels;

3. Strands

3.222 Elongation at Rupture

Values are the same as for rupture in the cold.

3.223 Expansion

The coefficient of expansion is constant and equal to: M 5 -r - 1.5 x 10 per degree Celsius

Comment:

The value adopted is the same as for the Fe E22 or Fe E24 smooth

round bars.

10
Chapter IV

TEMPERATURE DISTRIBUTION IN CONCRETE

The distribution of temperature in concrete is determined directly or by interpolation from experimental results of tests made in approved laboratories.

One knows directly the temperature in the concrete of a structure when

he has available the experimental results for identical geometric arrangements, and provided approval of the testing commission for the results has

been requested and granted.

The temperature in the concrete of a structure is obtained by interpolation when it has been determined analytically according to heat transmission laws. For geometric shapes closest to those proposed, for which

we will have available experimental results that are known and accepted by

the Testing Commission, this method gives values essentially equal to those

obtained during tests.

Thus we proceed as follows:

The curve of temperature increase toward the face exposed to the fire

follows the standard curve,

-

O = 345 log (8£ + 1)

where 6 is the temperature at time t expressed in minutes and Q is the initial temperature.

The temperature toward the face not exposed to the fire is assumed to

remain at temperature .

The temperatures at any point in a structural element in this thermal

state follow the heat laws, the so-called "laws of Fourier."

Comment:

For example, Fig, 9 shows known results for the temperature

reached inside a slab with different increasing values of the useful

distance u (measured from the axis of the steel to the free surface

of the slab exposed to the fire), as a function of the time it has

been subjected to the effects of the fire in a standard furnace.

The curves in Fig. 9 are averages, since the temperature values

depend in part on the thickness of the slabs.

11
400

300

200

;oo11 protected by a 10-cm-thick

lab)

120 160 240

Fig. 9

# CSTB results for an 8.4-cm slab

The curves above are averages, since temperature values depend

partly on the slab thickness.

12
1 1/2 hours

Figure 10. Standard curve for temperature rise.

In the case of floors the face exposed to the fire is the underface; for columns it is the whole surface; and for walls or columns

incorporated in the walls it is the one or two faces exposed, depending on whether or not the wall is the dividing wall of a compartment.

In the case of a two-dimensional problem, the temperature, t,

at the point with the coordinates x and y is given by

8t ~ c P \8xi + Sy2J If this equation is worked out by the finite difference method,

the section is divided into squares with sides Ax=Ay and the time is

divided into intervals

4X

such that

i —1 i i+1

j-l "Gi.t-i

j "^i-u •B« ^i+u

i + i "Stm

4

13
Heat exchange between the structure and the hot and cold surroundings

are found from furnace exchange coefficients normalized for the corresponding

faces.

Comment:

If T is the temperature at the center of a square with side Ax

located in the surroundings and in contact with the interface of the

solid along the square with side Ax marked i, j, and if 9 is the

ambient temperature, we have

•*»+&-"¥)>

h + 2

where h is the overall exchange coefficient of the furnace.

For the side exposed to the fire we can write

. Tm - TPC

h = ac + af — TPC ^

= 40

(

T

"iooo

73

)

3 a+x+^+x3) TPC + 273

X =

Tm + 273

where a is the convection coefficient, 6 kcal/m «hr« C

ot is the radiation coefficient

v

Q is the temperature given by the standard curve

TPC is the temperature of the wall exposed to the fire and thus

the average of the different values

( T

o +T

i -)/2is the length of this wall, and

m is the temperature of the furnace masonry, which is difficult

to estimate, so we set t = Rfi m

M

The function /$ is adjusted to find the results already obtained

for similar structures. We assume that the value 3 = 0.85 is readily

adapted to the results for slabs, walls, and beams and that it is the

value adopted in determining the results given below for these structures. By modifying this value of 3 in particular, we can determine

the temperatures by interpolation.

On the side not exposed to the fire, which remains at temperature

Q Q

, the coefficient h is given by the larger of the two values

8 (TPF — Oo) - 1 0,1 14
where TPF is the average value of the temperature of the unexposed

wall, and thus of (t

o +t. .)/2 along this wall. More sophisticated

programs could, pernaps,

c be conceived which take into account the

heat of vaporization of the water contained in the concrete.

Chapter V

BASIS FOR THE JUSTIFICATIONS AND EVALUATIONS OF STRESSES

The stability of a structure should be guaranteed for a definite time

by the exposure criterion. Thus we have to be sure that the ultimate

stresses over the whole cross-section of a prismatic element are, after this

time, at least equal to the stresses due to the forces which are applied

to it (taking into account the mechanical properties of the materials as a result of the fire).

We therefore are dealing with methods of calculation or analysis in the

final state of resistance, aimed at working out a stability diagram that is

statically permissible, taking into account possibilities of adaptation of

the structure.

Comment:

Use of the method has allowed us to work out, by category of

structure, the simple rules given in Chapter VII.

5,1 Stresses to Take into Account

The reduction elements in every cross-section are calculated by the

usual rules appropriate to the structures by taking into account the possibilities of adaptation and are obtained by considering the following loads

and effects:

If (G) is the stress due to the continuous load,

(P^) is the stress resulting from service loads but not including the

possible increases for dynamic effect

(V) is the stress due to normal climatic effects

(T^) is the stress due to total expansion effects, taking into account

the indications and departures given in Sect. 5. 11, and

(Y) represents instability phenomena expressed, for example, by introduction of imaginary arrows to calculate the columns,

then the total stress is defined symbolically by

15
(S) = (G) + (P

1

) + (V) + (T

x

) + (Y)

We see that in the analysis of a section in the ultimate states, the

hyperstatic effects of the thermal gradient are not to be taken into ac- count because of adaptation phenomena.

Comment:

The difference in temperature between the exposed and unexposed

faces of a frame element leads, for the latter, to a variation in

curvature which most of the time is opposed by the hyperstatic con- nections of this element. As a result, there still are internal

effects which can be calculated.

The analyses of stability at failure are made in the final state

of adaptation, and rotations of the plastic sections thus have the

effect of dissipating the forces mentioned.

The rotations of the sections behaving in plastic fashion are,

however, large and could result, in some cases, in rupture of the steel

reinforcing parts that go through them, which explains the limits

actually imposed on considering continuities in slabs and rough masonry.

(See comment on Sect. 7.44.)

5.11 Stresses Due to Overall Effects of Expansion

Variation in length of each structural element subjected to a fire is,

in general, opposed by surrounding elements, and this results in forces that can be calculated.

The expansion caused by a fire in a reinforced concrete element will be

calculated from the unit coefficient of expansion, — = 10~->, and the

average temperature reached by this element after an exposure time determined by the exposure criterion used for the structure in question.

In the absence of more precise calculations of this temperature, we assume the values

F 1/2 h 1 h 1 1/2 h 2 h 3 h 4 h

1.

Element

expose

au feu

1 face

(plancher)

2.

100 200 300 350 450 500

2 faces

(poteau)

3.

150 300 400 500 600 700

Key: 1 —Element exposed to fire; 2 —(floor); 3 —(column)

16
The distance over which the expansion is to be applied is usually, for

vertical elements, the height of a floor. For horizontal elements this

distance depends on the size of the fire at a given instant, which can be

related to the fire load of the premises and to their partitioning by masonry

(or other incombustible materials) and to any other means for compartmenting

the fire.

Comment:

Indeed, partitioning creates an obstacle to the spread of the

fire, and burning of the fire load during the temperature rise ac- cording to the standard curve results in a maximum duration of the

fire at a particular site. If this length of time corresponds to the

exposure criterion specified, we can assume that the fire occurs

simultaneously throughout a compartment. In the opposite case, this means either that the fire center is displaced in the damage zone by

affecting only a part of this zone at each instant, or that the

fire could not last throughout the whole time corresponding to the

exposure criterion, if it occurs everywhere at once, so that the

average temperature will only be that at the end of the actual time

of the fire.

In the absence of more precise calculations, the following types can be distinguished:

- Linear buildings with a normal partition density and low fire

load, such as dwellings, for which a distance of about 10 m (or a running house width) can be assumed.

- Buildings or premises with few partitions and a high fire load,

such as warehouses, for which the distance will be the smallest distance between compartment partitions, unless special arrangements for

compartmentation of the fire other than the partitions (smoke outlets)

do not permit this distance to be reduced.

- Office buildings, schools, hospitals, warehouses with a small

fire load, parking garages, etc., for which the distance will be that

between the above-mentioned limits, depending on their fire potential,

partition arrangement, and fire compartmentation.

One could, for example, assume only 50% of the smaller of two

distances between joints, or between compartment partitions in linear

cases. This limit could be decreased without going below 25%, and below

10 m in the case of compartments divided off by masonry or concrete

slab partitions extending beyond the false ceilings.

There is thus an advantage in increasing the number of expansion

joints and making them wide enough (based on the probable overall

expansion) without forgetting, however, that the fire protection re- quirements should not lead to planning structures whose design will

be second-rate with respect to linear stresses. Therefore it is

17
sometimes better to not plan for too many joints, even if it means

taking into account the effects of overall expansion in the structure

and their consequences in masonry such as fire walls (e.g. by providing

them with means to resist the consequences of this expansion or sur- rounding them with specially treated joints so as to protect them from

the forces generated). On the other hand, it appears always possible

to make the expansion joints wide enough.

In justification for linear buildings related to the distances between

joints, based on the regulations in force, it is assumed that no account is

taken of the stresses due to the effects of overall expansion.

Comment:

The behavior of linear buildings, as determined during actual

fires, indicates that, when the requirements of the regulations for

reinforced concrete regarding the frequency of expansion joints are satisfied, it is not necessary to take into account the effects of

overall expansion in structural calculations and the arrangement of

structural elements.

The expansion joints of the superstructures should, however, have a minimum width.

Comment:

We assume, for example, 2 cm for 2 hr of exposure to fire, with

a proportional rule applied to the average temperature for exposure

criteria of different duration.

5.2 Analysis in Simple or Compound Bending

The analysis in the ultimate strength state will be made by assuming

conventionally: —For the concrete, a rectangular parabolic diagram characterized by

a maximum stress a'.»/1.5 and by elongations of 2xl0~-^and 3.5 x 10-

^

.

J 9

2%o 3,5%.

Figure 11

18
Comment:

In the absence of precise values, the shortening of 3.5 per

thousand is assumed not to be affected by the temperature.

The symbol a . fl represents the value of the failure stress on day j

of the fire (j being normally greater than 90) at the temperature of the

point located at the barycenter of the compressed zone. —For the steel, an elastoplastic diagram characterized by a /i 15 _ arg 6' ' and by elongations of e and e a arg

*£„

/ _ a. _ o^Jh

[-" ~ Ea - Ea 6J Figure 12

In the case of steel with a flow bearing, we take the smaller of the

two values a „/1.15 or o n in the diagram above,

arg 9 ev To the extent that one uses the real diagram, a . = f(e ), the value

a.8 a of O~ is obtained by assuming a reducing coefficient of 1.15.

For simplification, we assume the following diagrams which correspond

to several frequent cases: —Tension with eccentricity such that the center of pressure lies

between the two layers of steel (equilibrium force N);

*n )N n

A S ^N S

115

CT rq9

1.15

0"org e

h L_... 1

i

1

. J

vn

l

N9

1 1

No 1

N .N»n

Figure 13

19
—Simple bending (equilibrium force M):

Fa = f; = A

1.15

soit y* F

' b

x = j/0,8 £ = 3 510-3 iL±

b C'j9/1,3 x

M « F ( " 1.

)

ovec earn ^ £a ^ Eo 2 Figure 14 —Compression with little or no eccentricity (equilibrium force N):

(7)9/1,5

1

Figure 15

The compressed steel can be taken into account by using the smaller

of the two following stresses:

Either the value a „/1.15

arg or the value which results from the shortening of the concrete

fibers located at the same height

When the justification of the exposure criteria is done by calculation,

we can assume that it is satisfactory if the results obtained do not deviate more than 5% from the required values.

20
5.3 Shattering

The materials used in making concrete, the amounts of each, and the

placement procedures should be selected so that premature shattering of

the concrete will not have adverse effects on the behavior of the structure.

Comment

:

Shattering can result in the elimination of section of concrete

necessary for stability. Shattering may also accelerate heat transmission phenomena.

Observing good practice concerning the mixing of the concrete will

make it possible to achieve this objective for all structures that meet

the simple rules defined later on on the basis of the type of structure.

Comment

:

It should be kept in mind in this regard that a protective mesh

is needed for useful distances of more than 7 cm.

The justification for the arrangement of the forms and the various

reinforcements for them resulting from the application of the simple

rules will be carried out for primary and secondary beams on the assumption

that shattering may expose reinforcement locally, perhaps in a simple cross section.

Besides the analyses called for by the specifications given in Paragraph

5.1 and 5.2, the design engineer should justify the strength of the cross sections by disregarding the stronger reinforcement bars among those placed near the edge. The span in question should be justified by substituting

a factor of 1.05 for the factor 1.15 given in Paragraph 5.2, and this

should be done for the support as well as the span. It is assumed that

this analysis will not be used when beams contain more than 8 rebars at

mid-span and in the case of slabs.

Comment

:

It is assumed that this loss of formwork can affect only the

beams containing more than 8 bars, all of the same type and the same diameter.

One could omit taking into account this shattering when one

of the following conditions is met:

--justification, by tests, of good shattering behavior on the

part of the type of construction planned.

Comment

:

This justification concerns more specifically industrial

products which are offered as prefabricated.

--justification based on observing the rules of concrete

21
preparation in a manner to limit the shattering hazard.

Comment

:

These rules will be worked out during a test program in progress,

--providing additional protection for exposed walls,

--providing a protective grid in areas particularly sensitive

or arranging reinforcement in these zones (frames and longitudinal

bars) in a manner to create a reduced mesh under the conditions set

forth in Paragraph 6.3.

Comment

:

The sensitive zones are, in the case of secondary beams, the

vicinity of the lower bars in the span and the zone of compressed

concrete on the support (in the continuous case).

CHAPTER VI

GENERAL STRUCTURAL RULES

This chapter sets forth a number of rules common to all types of

structures which make it possible to arrange the choice of structural

elements so as to satisfy most easily the required criteria for duration

of resistance to fire.

6.1 Expansion Joints

The reader is referred to Paragraph 5.1.1 and the comments on it,

where these natters have alreadv been examined.

Expansion joints dividing a flameproof or fireproof element should

be studied taking into account the dimensional variations to be considered,

Comment

The object. is to oppose the passage of flames and the omission

of inflammable gases through such joints. The following solutions

may be studied by w^y of example:

--Insert, anchored partly to the skeleton and partly to the

joint

,

--Rabbeted support between two stiffened elements with sponge

material between, (see Figure 16)

22
sponge material

id

black packing

6.2 Geometric Arrangements

6.21. Floors and Beams

In the case of floors and beams, these elements should not, after

being built, exhibit weakened sections.

Comment

:

The three principal causes of weakening are the following:

--first, keying between elements, when it does not extend over

the full thickness of the elements joined nor restores the

monolithic state of the structure by means of reinforcing steel

(especially for the fireproof criterion):

| Not Good

Intermediate

Good

Figure 17

--second, the statically determinate state of the elements,

because continuity on supports enters into the transmission

of forces with the help of the upper reinforcement steel which

is less affected during a fire:

23
Floor

m

LA.

Not

tt

Good

IE 1.x:

Good

Good

Roof

£M

Not Good

^9

c^ Good

Figure 18

Finally, examination of the temperature curves in a cross-section

shows that the parts that are hottest are the projecting angles, and

that the temperature has more effect, the more slender the element.

Thus we would want to avoid ribs that are too slender and walls that

are too thin.

-I r

Not Good Figure 19 Good

One can, however, conceive of structures consisting of elements

which are basically keyed elements, to the extent that they are handled

in a manner to be fireproof.

One can also conceive of isostatic structures where the fireproof

concept is satisfied by the supports and resistance to fire is obtained

by covering the steel or by external protection.

24
On the other hand, when the phenomena of overall expansion predominate, the deformation tendency of the structures seems to be a favorable element.

When it is impossible to avoid grooved supports in a zone that

may be exposed to fire, if there is no additional shielding we have

to protect by reinforcement the angles of the concrete whose spalling

or shattering could result in collapse of the structure, the main

steel reinforcement being placed with the necessary covering.

i

PF

Not good Good

Figure 20

6.22 Loadbearing Elements

As far as loadbearing elements are concerned, their sections will be

designed for the best possible adaptation to the effects of overall ex- pansion.

Comment:

Thus one should see that the largest dimension of the element is

positioned parallel to the smallest dimension of a block between joints

or to that of a fireproof compartment.

At the same time, it is preferable that the longitudinal wind-bracing

elements be concentrated at the center of the blocks between expansion

joints.

Plan view of building

Q I! U I

o f

1 U

D

o

i

: - Q

D D n D I] D Good Not good

Figure 21

25
6.3. Arrangement of Reinforcement

Increasing the covering of the steel is favorable for resistance

to fire.

Comment

:

Since temperatures are always higher in the vicinity of hot

walls and in projecting angles, the calculated reinforcing steel

should be spaced further away from them to balance the forces

(bending and shear force).

Beam Column

Not Good

3

Figure 22

Good

When the useful distance of the first loadbearing bars is more

than 7 cm to the face exposed to the fire, it is necessary to provide

a protective mesh enclosed in 1.5 cm of concrete, the grid spacing of

which is not to exceed 10 cm in one directing, the diameter not being

significant

.

Comment

:

Beyond a certain thickness of covering it has always been found

that during actual fires early shattering of the concrete will rapidly

reduce the effect sought by using the covering.

Remember that too long a useful distance may not be advisable

for the structure to behave well under service stresses.

The slabs and beams should not have reduced reinforcement on the face

exposed to the fire.

Comment

:

It seems desirable, even when they are not justified by design

calculations, to provide systematically for bars in the underface

of the beams or slabs which are anchored in the supports.

26
IX IX

Not Good

3

Good

Figure 23

Reinforcing bars which need not be taken into account in the fireresistance calculations should be placed in the vicinity of the exposed

wa 1 1 s

.

Comment

:

This procedure results in keeping close to the walls rebars

placed in the structural elements for percentage reasons (columns,

shells) and not determined to balance calculated forces. It should

be added that such a rule also offers the advantage that the structure remains properly reinforced for its routine stresses.

6 a 3 ZB

Not Good

2 C r r Good

Figure 24

6.4 Execu t ion tole rances

When the fire-resistance depends mainly on the value of the coverings

selected and the latter are larger than those provided by the rules under

routine stresses, it is necessary:

--On the one hand, to indicate by appropriate detail on the implementation plans the value of these coverings; and

--On the otherhand, to more particularly pay attention to observing

these values in implementation with a tolerance of + 10%.

SK fill
Chapter VII

CONSTRUCTION RULES ACCORDING TO STRUCTURE CATEGORY

7.1 Columns

7.11 Simple Rules

These simple rules concern columns subjected to simple compression, reinforced longitudinally with a percentage of 2% or less, and a slenderness of 50 or less.

The following table gives for F (expressed in hours) fireproof or fireresistive exposure criteria! —The minimum dimension, a , of the side of the column for

cm

a square column

a rectangular column where b = 5a; and —The minimum useful distance, u, from the steel to the face.

F 1/2 1

20

12

12

1 1/2 2

30

16

16

-3

36

20

20

4

acm

Square column

Square column, 1 face

exposed to fire

Column b = 5a

15

10

10

24

14

14

45

26

26

Case of reinforcing

steel with percentage

npne

^cm

Case of reinforcing

steel taken into accoun

in calculation

t 1 2 3 4 6 7

Linear interpolation is used to define, as a function of the fire

resistance time sought, the minimum permissible section of concrete for the

values of the ratio b/a between 1 and 5.

Comment:

For example, for a time of 2 hr, one can select

16 x 18 (or more)

23 x 69 (or more)

30 x 30 (or more)

28
5 b/a

Figure 25

For columns on either side of an expansion joint, when they can be

surrounded by the fire, the minimum section is defined as though the joint

did not exist.

equivalent to

Figure 26

Round columns can be treated according to the rules applicable to square

columns of the same area.

7.12 Temperature of Concrete and Steels

The temperature is estimated by the procedure given in Chapter IV.

Comment:

Application of this method to some current cases has given the

following values:

Table of Average Temperatures of Concrete (and Reinforcing

Steel) in Columns for Distances u to the Free Wall as a Function of Length of Exposure to Fire

u(cm)

Length of exposure to fire

1/2 1-1/2

1.5 410 - 350 600 - 550 700 - 660 770 - 930

3 280 - 240 490 - 430 610 - 540 990 - 620

4.5 120 - 90 340 - 300 480 - 410 580 - 500

The first figure is given for a concrete thickness of 18 cm.

The second is for a concrete thickness of 50 cm.

An average temperature for a concrete thickness between these two

values is obtained by linear interpolation (at a given distance u).

29
The temperatures corresponding to distances intermediate between the

values given in the table are also defined by linear interpolation.

Finally, temperature distribution is not uniform along the edge.

A parabolic variation will be allowed by adding a weighting coefficient

of 1.2 for the temperature at the corners and of 0.9 on the axes of symmetry

of a face to the temperature value in the Table, as shown in Fig. 27.

e from the Table,

0,9 9

1,2 9

Figure 27

Omb,

Figure 28.

Mean temperature in columns surrounded by the fire.

It could be useful to know the temperature at the center of a column. The

following table give some temperature values for certain column sections.

Temperature at the center of columns

1/2

30

1 1 1/2 2

18 x 30 (ou 60 ou 100) ISO 300 400

30 x 30 30 100 140 30 x 60 (ou 100) IS 60 110 48 x 30 IS SO 100 48 x 60 (ou 100) 10

Note: ou = or,

30
7.13. Other Columns

If the rules of Paragraph 7.11 are not applied, the columns are calculated as indicated in Chapter V, using the temperature tables

calculated according to Paragraph 7.12.

Buckling is taken into account using the methods for calculation

in the cold.

Comment

:

Certain of these methods again introduce reduction coefficients

for the stresses. Others introduce additional eccentricities. And

still others make a failure calculation taking into account secondorder effects.

7.2. Stringers

This name is applied to elements subject to tension or in composite

bending with tension when the neutral axis is located outside the 2 layers of steel.

It is assumed that the lengths of time (expressed in hours) of the

exposure criteria (f ireproofness or fire resistance) are satisfied when

the minimum values indicated in the table below are met.

Ia a<b

F 1/2 1 1 1/2 2 2 1/2 3

a (cm) 8 12,5 15 20 24 28

u (cm) 2,5 4,0 5,5 6,5 8,0 9,0

Concrete area a x b (cm2)

equal to or greater than 128 312 450 800 1 150 1 570

31
Resistance can also be justified using the methods set forth in

Chapter V using the temperature distributions given for columns in

Paragraph 7.12.

Nevertheless, when one is concerned with reinforced concrete

stringers where the overlaps are in the zone exposed to fire, the useful

distance values given in the table above should be maintained.

Comment

:

This restriction as to maintaining a minimum useful distance

flows from the uncertainty that adhesion persists. It is logical

to assume that reinforced encircling steel will make this condition

manageable.

7.3. Bearing Walls

This article applies to loadbearing elements in which the larger

dimension is more than 5 times greater than the smaller (b > 5a).

I*

7.31. Simple Rules

These simple rules concern bearing walls in which the slenderness

is equal to 50 or less.

The durations (F, in hours) of the exposure criteria ( fireproofness

and fire resistance) are achieved if the minimum values of a and u in

the table below are maintained.

u(cm)

F 1/2 1

11

1 1/2 2

15

3 4 h

a (cm) 10 13 20 25

Case of reinforcing steel

based on percentage none

Case of reinforcing steel

taken into account in

the calculations

1 2 3 4 6 7

32
7.32. Temperatures in the Concrete

The temperature is estimated according to the provisions of

Chapter IV.

Comment

:

Application of this method to several everyday cases gave the

following values:

Temperature at the useful distance(u)

Depending on the fire-exposure times, the temperatures reached

by the concrete at distance u from the external surface (exposed

to the fire) are those given in the following table:

F 1/2 1

270

405

540

270

405 540

1 1/2

400

520

640

400

520

640

2

500

600 700

475 590

700

3

Fire on

2 sides

u =

. 4,5 cm

3

( 1.8

100

225 340

100 225 340 Fire on 1 side only

u =

( 4,5 cm

il.5

570

680 785

Intermediate values (duration and useful distance) will be obtained

by linear interpolation.

Average temperature of the concrete

The table below gives average temperatures for the concrete

of shells, calculated by the general method, for several cross- sectional dimensions and fire-exposure times.

F 1/2 1

350

140

200

160

10070

1 1/2

480

270

280

220

180 100

2

S70

380

350

278

180

120

3 Fire on 2 sides thick- ness 18 cn or more

Average temperature

Temperature in the

center

170

25

1007550

30

Fire on 1 side only

(average temperature)

( 15 cm a- 20

a -

30

( 4S

440

350

250

165

33
7.33 Other Walls

If the rules of Sect. 7.31 are not applied, the walls are calculated

according to Chapter V using the temperature tables calculated in Sect. 7.32.

Walls whose reinforcement sections have been determined by the methods

applied generally to columns will be analyzed as such.

Other walls, not reinforced or reinforced at percentages not taken into

account in the homogenized section, will be analyzed by taking account of

the phenomena of buckling and without an actual experiment , as is customary for static analyses in the cold.

Comment:

Some methods take into account these phenomena in the form of

undervaluation coefficients of the nominal stress. These will be used

for analyses in fire.

Other methods take into account these phenomena in the form of

additional eccentricities which will be used for analyses in fire.

These walls will, however, have a thickness greater than 8 cm, and

when they must be fireproof, their thicknesses will be at least equal to

those given in Sect. 7.31

7.4 Cast Concrete on Continuous Supports

This section discusses solid slabs or pre-slabs supported on 2, 3, or

4 sides with linear reinforcement of reinforced or prestressed concrete.

7.41 Construction Arrangements

Besides the arrangements already described, the lower face of the slab

exposed to fire should contain a continuous grid of reinforcement using the

lower rebars, a part of which should be anchored to the supports.

Comment:

This rule will be considered satisfied if, in the case of welded

fabric, there is regularly a weld to the supports and if, in the case

of high-adhesion rods, we extend beyond the support alignment (anchoring

it) a section about 1/6 of the span section in the bottom strand:

Either all the rods with l^i or 1/6 of the rods with l^t (l^, is the anchoring length)

34
7.42 Simple Rules for Slabs and Pre-Slabs of Reinforced Concrete

The duration (in hours) of the exposure criteria (f ireproofness and

resistance to fire) are achieved for slabs when the minimum layouts in the

table given below are used.

We note that:

h is the slab thickness (cm),

e is the thickness of the covering and its surfacing (cm),

MQ

is the isostatic moment under the loads and additional loads

according to the indications in Chapter V, and

0^ and M

g are the bending moments balanced by the reinforcing steel on supports with a free length within the span in question, 1„ and 1 .

Comment:

One could take into account, in calculating M and M e

, theoretical

capping added by construction on supports with low continuity to take

into account the moments that are not calculated.

!_M.if"

Figure 29

We use linear interpolation to find u and (1 +l p )/l as a function of

(Mw+Me )/2M .

Time of resistance to

fire

F 1/2 1 1 1/2 2 3 4h

Minimum thickness h + e (cm) 6 7 9 11 15 17,5

Without

rebars on supports

2M

u (cm)

1

1 2 3 4 6 8

With

rebars on supports

M- + M

'>0.B0 2M ^

u (cm)

1

1 0,25

1,5 0,3

2

0,4

2,5 0.53,5

0,55

4,5 0.6

35
Comment:

The minimum thicknesses involved in the degree of fireproofness

depend, probably, on the water content of the concrete. Whenever

possible, therefore, thicknesses greater than those given in the table

should be used.

In the case of slabs which carry load in a single direction, the above

rules concern only the loadbearing rods.

In the case of slabs bearing on three or four sides, the same verification should be made for two bearing layers.

Comment:

It is recalled that bars positioned either to meet a minimum

percentage or a condition of resistance to shattering or for distribution reasons are not subject to the above rules.

Any moment on a support greater than 0.15 times the isostatic moment

of the span concerned could not be taken into account in the application

of the above rules unless the shattering resistance conditions are verified

in the corresponding section.

Comment:

To visualize adaptation, the breaking moment balanced by the steel

must be at least equal to the moment of first cracking of the concrete.

In the case of a rectangular section of width b and total height

hi, the value of the moment of first cracking of the concrete is

Ojbhi 2 /3.6.

In the case of slabs made in two stages and whose lower part has not

been handled by the Avis Technique ["Technical Advice"] procedure with

monitored self-control, the following rules should be applied: — The minimum thicknesses are those of the table above, increased by

2 cm, and — The lower rods of the first stage should form a grid whose openings

do not exceed 10 cm in one direction.

In the case of slabs made in two stages and whose lower part has been

handled by the Avis Technique procedure with monitored self-control, the

rules of the Cahier des Prescriptions Techniques , an appendix of the Avis

Technique , should be followed.

36
Comment

:

These arrangements result from the present state of our knowledge

concerning shattering.

Duration of exposure

to fire F

1/2 1 1 1/2

640 820

400

230

12080

2

700

890

478

300

180

100

3

With any h

" = 3!o u = 4,6

340

225

100

20

840

405

270

14050

20

785 680 870

h Js 9 u = 7,5 A > 12 u = 10,5 h > 15 u = 13,5

400

270

180

Intermediate values of u are obtained by linear interpolation.

Figure 31 gives some values of average concrete temperature as

a function of the duration in hours of exposure of concrete cast

elements to fire.

Average concrete

temperature

600

500

400

Figure 31 300

200

100

8 cm

Duration of exposure

to fire (in hours)

37
7.43 Temperature in the Concrete

The temperatures will be calculated by the method given in Chapter IV.

Comment

:

The application of this method to several current cases has

given:

1

With 8 < h < 40

Figure 30

7.44. Other Slabs or Preslabs of Reinforced Concrete —Slabs and Preslabs

pf Prestressed Concrete

If the preceding rules are not applied, cast elements will be calculated

in accordance with the provisions of Chapter V using temperatures estimated

in accordance with Paragraph 7.43.

Comment

:

In the case of preslabs, the rule of derogation of seams (DTU

Rules for design and calculation of full-slab floors made of prefabricated

concrete preslabs*) is applicable without additional adjustment to

the rules applicable in the cold. The minimum thickness for Criterion

No. 2 on fireproofness is the same as that given in 7.42.

One will make sure thus that the half-sum of the moments on the support

plus that of the span indeed balances the moment induced by the applied

loads, and one will verify the length of the bars in accordance with the

moment curve that results.

No justification for the shear force is required.

38
Comment

:

When the perpendicular forces induced by the effects of expansion

are to be taken into account, justifications in compound bending will

be necessary.

The provisions of Paragraph 7.42 ( and the associated comment), which

are concerned with observing non-fragility conditions, apply equally to

the slabs and preslabs discussed in the present Paragraph 7.44.

Comment

:

Unless one justifies that the hyperstatical ly continuous supports

are well designed so that rotation of plastic hinges permits adaptation,

one will not seek to justify by calculation the arrangement of reinforcing

steel which excessively minimizes the intervention of the span bars.

Hence it would not be necessary to deviate too far in the unfavorable

direction from the limits given in 7.44 for the minimum useful distances

and for the maximum involvement of continuity.

The functional justifications for the plastic hinges, in particular,

should take into account the elongation characteristics beyond

constriction of the reinforcing bars, their adhesion and anchoring in

the concrete, the forms of the support sections, and the percentage

of steel provided.

7.5. Main and Secondary Beams, Reinforced Concrete or Prestressed Concrete

7.51. Simple Rule

The F degrees (expressed in hours) of the exposure criteria (fireproofness and fire resistance) ace achieved for main and secondary beams

if the minimum conditions of the preceeding tables are observed.

* In preparation.

39
Note that:

--e is the thickness of the covering and its finish in cm,

--M is the isostatic moment under the loads and overloads according

to the provisions of Chapter V, —

M

w

and M

g are bending moments balanced by the steel on supports

with free length inside the span considered, lw

and 1 —T is the shear force, once direct transfer has been deducted, and — x is the corresponding shearing stress, and is equal to

T/0.875h.b (b, or bQ if there is a heel)

1

Q^

=£-H ^J4

-' ^

?

OC *ju

Figure 32

Comment:

The heel beams generally encountered are of very variable dimensions

and it is difficult to define simple rules covering all cases.

We find, in particular, that we should justify by calculation

beams for higher degrees than 1.5 hr.

The dimensions of the heels, their height and width, can vary, the

thickness of the web often being the basic criterion. The distribution

of the reinforcing structures may also differ with regard to the number

of layers and the number of rods per layer. Then we have to justify

by calculation;

In the case of slabs made in two stages and whose lower part has not

been made according to the Avis Technique procedure with monitored selfcontrol, the rules for increasing the minimum thickness and reinforcement

grid given in Sect. 7.42 are also applicable.

In the case of slabs made in two stages and whose lower part has been

made according to the Avis Technique with monitored self-control, the provisions of the Cahiers des Prescriptions Techniques appended to the Avis

Technique should be followed.

40
Comment:

These arrangements result from the present state of our knowledge

concerning shattering.

F 1/2 1 11/2 2 3 4h

Minimum

thickness

Entraxe des poutrelles < a 2,5 m 5 6 8 10 14 16.5

(h2 + e) cm

Entraxe des poutrelles > a 2,5 m

(b)

6 7 9 11 15 17,5

Poutres croisees espacees au maximum

de 2,5 m dans chacrue sens (c)4 5 7 9 13 15,5

Mw + Me 2M ~

U

Poutres rectangulaires (".)

b minimal en cm ( e ) Poutres a talon (f ) b minimal en cm ( g )

Jb minimal en cm (h)

h minimal en cm ^ x ) Nombre minimal de lits inferieurs ( j )

/ avec b minimal (k)

. et avec un minimum de barres

I par lit de : (l)

u (cm) )\ avec b superieur a la plus

/ grande des 2 valeurs : 1 metre

f ou 1,5 r^ et.avec 10 barres

\ par lit (m)

1

12

168

5

2

2,5

2

1

16

20

108

2

4

2

2

20

24

12122

5,5

2

3

24

32

14 20

3

6,5

3

4

32

40

1632

3

8.0

4

5

40

50

1850

4

9,0

5

6

Key: (a) and (b) Beam spacing on centers; (c) Crossed beams with maximum

spacing of 2.5 m in each direction; (d) Rectangular beams; (e) Minimum b

in cm; (e) Minimum b in cm; (f) Beams with heel; (g) Minimum b in cm;

(h) Minimum bQ in cm; (i) Minimum h in cm; (j) Minimum number of lower

layers; (k) With minimum b; (l) And with a minimum number of bars per

layer equal to: (m) With b larger than the greater of two values: 1 meter

or 1.5 h^, and with 10 bars per layer.

Comment:

The minimum thicknesses that enter into the degree of f ireproofness

depend probably on the water content of the concrete. Therefore it is

desirable, whenever possible, to use thicknesses greater than those

given in the table.

41
F 1/2 1 1 1/2 2 3 4h

Poutres rectangulaires ( a ) b minimal en cm ( b ) 8 11 14 17 23 29 Poutres a talon ( c ) b minimal en cm (d ) 12 16 20 24 32 40

b minimal en cm ( e ) 8 10 12 14 16 18 h minimal en cm ( f ) 5 8 12 20 32 50

Nombre minimal de lits inferieurs (g)

(h) . avec b minimal

2

2,5

2

2,5

2

3,3

3

4,0

3

5,2

4

6,0

( i ) I et avec un minimum de barres

2 M ^

U,b

\ par lit de : u (cm) J (k) j avec b superieur a la plus

1 grande des 2 valeurs : 1 metre

f ou 1,5 hx et avec 10 barres

2 2 2 3 3 4

' par lit 1 1,5 2 2 3 4, /. + K

1 0.25 0,30 0,4 0,5 0,55 0,60

t ^ ab ou beton precontract classes I (p)

etn (1) neant

( si tout en cadres (m) 1,5 2 2,5 3 3 3.5

Uj (cm) ^6 < t < c^ ( si 40 % au moins en

( etriers ou epingles (n)

at < t ^ Sab11 faut au moins 40 % en

etriers et epingles Co)

(p)

neant

1,5 2 2,5 3 3 3,5

Key: (a) Rectangular beams; (b) Minimum b in cm; (c) Beams with heel;

(d) minimum b in cm; (e) minimum b in cm; (f) Minimum hQ in cm; (g) Minimum

number of lower layers; (h) With minimum b; (i) And with a minimum number

of bars per layer equal to; (k) with b longer than the greater of the 2 values: 1 meter or 1.5 hi, and with 10 bars per layer; (l) Or Class I and II

prestressed concrete; (m) If all are in frames; (n) If at least 40% are

in stirrups and pins; (o) At least 40% must be in stirrups and pins;

(p) Zero.

Linear interpolation will be used to define the values of the terms

b, u, and (lw

+l )/l as a function of intermediate values of the ratio

(Mw+Me )/2M . To calculate u as a function of a heel width (b) intermediate

between the minimum and maximum (1.00 or 1.5 h1

), the same thing is done.

Comment:

When two conditions are required for the same dimension, the most

unfavorable should be met. In particular, the condition of web width,

b

Q

, should be compatible with the condition of useful distance, u, when the flexural bars are placed in cne web.

The rules and comments in Sect. 7.42 which relate to shattering re- sistance conditions also apply to the large and small beams considered in

Sect. 7 .51.

42
Comment:

One could take into account in calculating M and M the theoretical

w e capping added by construction on low-continuity supports to take into

account the non-calculated moments.

When the reinforcement has two bars per layer these should be as near

the center as possible, with the distance between them only that necessary

for good covering (3 cm, e.g., for concrete reinforcing steel and 3-5 cm for

single wires).

Comment:

It is recommended that, —The steel be concentrated toward the center of the beam, not

placing larger-diameter steels in the corners, —The number of layers of steel be increased, —Part of the shear force be balanced by pins or stirrups, and

not just frames near the surface of the concrete be used. —A part of the lower reinforcement be extended on the support.

In the case of joints between small beams or boxes, the simple rules

could be applied on the basis of the sections obtained by assuming that there

is no joint.

Figure 33

7.52 Temperature of the Concrete

The concrete temperature will be calculated by the general method given

in Chapter TV.

Comment:

The use of the general method for particular cases has given the

following results:

Temperatures in the heel of beams as a function of their width

and the length of time exposed to fire.

43
These values were represented solely as a function of the width

of the heel, since the other characteristics—frame, thickness of

the slab, height h—have little effect.

2 The temperatures indicated were given in the axis of 3x3 cm squares into which the section was cut.

Only the right half of the beam was represented, the other being

deduced by symmetry.

1

i

i

»

I

3

3. 3

12

i I

b = 12,18et 24cm

Figure 34. Case of b = 18.

30 tun

60 mn

90 mn

120 mn

12

350 140 370 160 420 230 550 430

600 420 630 470 690 560 780 710

740 610 760 650

810 720

880 820

820 720

840 760 880 810

S40 890

18 *

350 110 30 360 130 50 410 210 140 550 410 360

660 320 200 590 370 260 660 480 390 760 660 610

680 470 360 710 530 430 770 630 550 850 770 730

760 580 490 790 640 560

840 720 670

920 850 820

24 $

350 110 25 5 360 130 50 30

410 210 130 110

550 410 360 350

560 310 160 90 590 360 230 17C

650 470 360 320

760 650 590 570

670 440 280 210

700 500 370 300 750 610 500 460

850 760 705 680

740 540 400 320 7S0 600 480 420

830 700 610 560

910 830 780 760

One can deduce the temperature of the concrete at any point by

linear interpolation from the temperatures shown in the table for

neighboring points.

These temperatures were calculated for the running zone of the rain

and cross beams. Near the supports of the cross beams on the main

44
beams or walls and of the beams on walls or piers, the temperatures

are different because the thermal diffusion is not the same.

In the absence of more precise justification, we assume a decrease

in the temperatures indicated for the running parts at a distance of

2h^ from the support, the reduction coefficient being a maximum of

0.9, as indicated in the figure.

0,9 9(y-3)

Figure 35

Average Concrete Temperatures . An approximate value on the high

side for the average temperature of the concrete will be obtained bycalculating the weighted average relative to the cross-sectional areas

of a slab and a column.

h 2 vzzzz V77A

(x)

doll* , h 2 CyP

poleou

Zh^hj = _ Ta X ^ (a - b) + Ti b (h, + h,) h, (a - b) + b (hx + hj)

Figure 36

1 ,. »

.|

Key: (x) Slab; (y) Column.

For calculating T]_ and T^ we therefore use the results given for

slabs and columns in the earlier sections.

7.53 Other Justifications

Without applying the above rules one could calculate the large and small

beams from information given in Chapter V, using the temperature values

estimated according to Sect. 7.52.

We know that the half-sum of the ultimate moments on the supports added

to the ultimate moment across the span balances the moment created by the

applied loads.

45
Comment:

When the normal forces caused by expansion effects are to be

taken into account, verification in compound bending will be necessary.

One will verify the length of the bars according to the moment curve corresponding to the failure diagram. The diagram of shear force will be

deduced from it. This gives Tq on the support once the direct transfer has

been deducted.

1.

For the shear force we make the two following verifications:

Te T

° "" 0,875 hb (ou b ) [ou = or]

< 2,25 o»

1 |

i [ ^U^n •M

"M M 2

.bp_ 4 Figure 37

cr_-0 corresponds to the temperature 9 measured at the point

characterized by the distances b /4 and h./2, defined in Fig. 37.

2. We verify that the force capable of being resisted by a row of frames,

stirrups, or pins (with a temperature at each bar calculated at a height h, /2, and thus a stress G~

fl /1.15) remains greater than that

found in the cold with service stresses by applying to the latter the

coefficient

1.5 support in the cold

The rules given in Sect. 7.42, which relate to shattering resistance

conditions, also apply to the beams and cross beams indicated in Sect. 7.53.

7.6 Slab Floors

Slab floors will be treated from the standpoint of resistance to fire

like cast elements on continuous supports (Sect. 7.4).

7.7 Shell-Floors

7.71 Simple Rules

The F degrees, expressed in hours, of the exposure criteria (fire proof- ness and resistance to fire) are obtained for shell beams if the following

specifications are met:

46
F (hr) 1/2 1 11/2 2 3 4

Min. thickness (cm) 10 11 13 15 20 25

u for flexural bars

only (.cm,/ 1 1,5 2 3 45 6

7.72 Temperatures

Depending on the case, and especially on the parts of the structure

exposed to the fire, the considerations relative to beams or shells discussed

above are to be applied.

7.73 Other Shell Beams

If we do not apply the above rules, we calculate the shell beams from

the information in' this chapter (VII), using the temperatures estimated

from Sects. 7.3 and 7.5.

These shell beams will, however, be more than 8 cm thick, and when they

must be fireproof, this thickness will be at least equal to that in Sect.

7.71.

Comment:

The difficulty of defining precise rules is due, partly, to the

various possibilities of application of the fire which can, depending

on the case, involve only the anchor, the intermediate part of the shell

beam, the upper part of this beam, or the whole thing. It is also due

to the uncertainties that usually exist with respect to the exact

distribution of forces.

For example, one could —Imagine unloading arches in analyzing the compressive stresses

in the concrete and tensile stresses in the steel, taking the

temperature into account. —Imagine a load transfer which would not use a part of the shell

exposed to the fire, in the case of shell beams on several levels.

Similarly, one could not take into account the action of the wind

in a lintel of a wall with superposed openings for justification with

respect to fire, to the extent that the lintels of the upper and lower

floors may absorb this neglected force.

47
7.8 Floors of Hollow Ceramic or Concrete

7.81 Simple Rule

The F degrees, expressed in hours, of the exposure criteria are obtained by adding a thickness of protective coating, which is a function of

the extent to which the coating remains in place (adhesion or bonding

arrangements).

Comment:

The results of tests on an ordinary plaster coating were used

to prepare a document, DTU No. 25.1, "Travaux d'enduit interieur en platre" [Studies on Interior Plaster Coatings], and for floors thicker

than 14 cm and with a distance between beams of around 0.6 m or less

to show the following values that should be used for this thickness:

F 1/2 1 1-1/2 2

Thickness, cm 1.0 1.3 1.6

These numbers can be used for floors with a cast covering of at

least 4 cm over the hollow part. For durations of more than 1.5 hr the

plaster suggested or special fire-protection plaster is advised since

such plaster gives more consistent results, especially with regard to

adherence.

7.82 Other Justifications

We can design floors, with or without an additional protective coating,

by the methods discussed in Chapter V, the temperatures being determined

from the information in Chapter TV.

Considering the problems posed by maintaining, during a fire, the bonds

between the concrete, the hollow elements, and the protective coating when

there is one, verification of a ceramic or concrete floor with hollow elements can be undertaken only for types of construction for which a similar

model has been the object of a satisfactory study.

Comment:

In the absence of protective coatings, the hollow elements should

be located in such a way as to reduce the width of the joints between

hollow elements and cross beams. Except for special situations, a dimension of 1.5 cm should be considered as the maximum.

The main difficulty is calculation of the temperatures, taking

into account the complexity of the formwork and the juxtaposition of

different materials.

48
It would seem possible, in estimating the part played by the empty

spaces, to substitute for an actual floor some equivalent floors for

determining the temperatures.

For example, we would have: —Floors with hollow elements whose coating thickness on the underface will be less than e s will be made comparable to solid slab

and cross-beam floors. The volume of the hollow filling will be

represented by a thickness distributed equally over the total

height of the soffit and the underface of the slab.

-TOvtA

Figure 38 —In the particular case of hollow elements surrounding the beams,

the actual thickness on the underface of the latter will be used

and the rest of the hollow elements treated as above.

"¥

w2^

Figure 39 —Floors with hollow elements which have on their surface a protective coating of sufficient thickness e are to be considered

as a solid slab whose thickness is equal to the total height of

the floor (using the actual weight to calculate the forces).

Figure 40

49
One will assume for ordinary plaster that the adequate thickness,

e , is 1.0 cm.

s The symbol e' is defined in Chapter VIII.

The simple rules for beams and cross-beams or slabs can be applied

to this associated formwork.

One can also justify the stability of these floors by calculation,

using the methods given in Chapter V.

If the rules for beams and cross-beams are not followed, no justification for the shear force can be* provided.

Chapter VIII

ADDITIONAL PROTECTION

One can obtain the desired fire resistance times by adding material that

is adapted ana suitably bonded to the structure that it is protecting. The

binding means or methods of adhesion should be studied in conclusive tests.

Where this addition of materials does not in itself provide adequate

justification with respect to the exposure criteria, justification is done by

the methods mentioned in Chapter V, the temperature being calculated by the

methods in Chapter IV.

Comment:

The implementation of these protective measures should follow

completely that described in the official reports of these tests.

The chief difficulty is in the calculation of the temperature

because of the juxtaposition of different materials.

To simplify the problem, we can proceed as follows:

We replace a thickness of protective material by a thickness of

concrete which has the same thermal protection properties.

A thickness, e , of material with coefficient X corresponds to a thickness e' of coefficient A in such a way that e' = e/(V/X).

Of course, we have to take into account the special properties of

the material concerned and of the behavior of its bond with the concrete

in order to apply to the coefficient e' a correction factor.

50
Without a more precise justification, we have for the following

materials, the list of which is not limiting, the values

1 cm of lime or cement mortar: 0.67 cm of concrete

1 cm of vermiculite: 2.5 cm of concrete

1 cm of asbestos cement: 2.5 cm of concrete

1 cm of ordinary plaster: 2.5 cm of concrete

We thus obtain an imaginary contour of the structure studied.

To this contour we apply the rules defined above for finding the

value of the temperature of the materials or for observing the simple

rules.

A false ceiling can be taken into account if it has been studied

in an approved laboratory.

If the false ceiling to be used conforms in its arrangement and the

method of attachment to the test conditions, it will be a factor in the fire

resistance time. of the whole and to the extent that the elements which may

be incorporated in it (ducts, lighting fixtures, etc.) have the same characteristics of resistance and insulation.

One could, however take into account a false ceiling only with the

agreement of the chief engineer who thus becomes responsible for ensuring its

maintenance.

51
Appendix I.

PROGRAM FOR CALCULATING TEMPERATURES

One of the programs that can be used is described below.

1.1 Breakdown of the Structural Element

The structural element considered* is enclosed in a rectangular table

of the smallest possible dimensions, observing the following conditions:

The element considered has the hot part below and the cold part above.

The temperatures of the small squares surrounding the element are those of the wall (hot or cold) and are calculated by the program.

The small squares should have the following values:

2 for those of the cold part

1 for those of the hot part

for those of the element considered and for those surrounding

this element

As a result:

1, The number of rows, N, is always equal to N 1+4 where N 1 is

the number of squares equal to the element height

2. The number of columns, N, is equal to

3 for slabs

M 1 + 4 for columns

M 1 + 2 for beams

where M 1 is the largest number of squares across the width of the structural

element.

On the other hand, the presence of the 2 axes of vertical symmetry

makes the temperatures of the first column equal to those of the second and

the temperatures of the last column to those of the next-to-last. They are thus never indicated when the data are entered.

52
Examples

:

[ligne =

ligne N1 »3

ligne Nl « 4

3 Cotefroid CQl£ side Slab

, : epoi S ,eur e = slab thickness

de lo done ^.corfeoox = Nt e/Ax squares = N 1

&x:CO\( Oct correouK ou It pos du eolcul Ax = side of squares or step of

calculation

Cote cnoud Hot side

2,o«»d. S»me.fiever.ico«K £ axes Qf vertical syTnmetry

.Zones de symetrie verticoux Column (surrounded by fire)

2 axes of vertical symmetry

Petite dimension

Ax

no decorreoux

Small dimension

No. of squares

Ax: side of squares

C : dc-mi longueur de lo plus grondt dimension Ml = JL : no de correoux Ax Ml =

G: half-length of largest

( dimension

G/Ax: No. of squares

I. 2 Data Entry

1st line X, c, p, Ax, 3

where X (DAO) is the thermal conductivity of concrete at C,

1.4 kcal/hr in °C

c (C) is the specific heat of concrete, 0.22 kcal/kg °C

P (Rq) is the bulk density of concrete, 2400 kg/m3

Ax (DEL50 is cell side, cm (integer or not)

3 (BETA) is a coefficient involved in the global exchange coefficient

of the oven

53
2nd line L, M, N, ICOD

where L is the number of time intervals at which we want to print out the

results

M is the number of columns in the table

N is the number of rows in the table

ICOD = if we do not want to take out the exact results of

temperatures in the element but their approximate values

= 1 if we want to take out the temperatures calculated at

the center of each cell in a particular zone

3rd line: 1st time requested

4th line: 2nd time requested

L + 2nd line: L-th time requested

Note: The time required is indicated by the computer as a decimal

fraction of an hour (15 min = 0.25, 30 min = 0.5, 1 hr = 1, 1 hr and

30 min = 1.5, etc.)

Next line: Two cases are to be distinguished:

If ICOD = 0, we do not want to print the exact temperatures and we go to the

next line

If ICOD = 1, write Nl, N2, Ml, M2

where Nl and N2 are the numbers in the first and last lines of the table

of results to be printed

Ml and M2 are the first and last columns of the table of result

printed

Next lines:

N lines IN, JD, JF containing each (or Nl +4)

where IN is the number of the line (1 to Nl + 4)

JD and JF are the numbers between the two axes of symmetry of the

first and the last cell of line IN or they take zero values. If there is

no zero in line IN, write IN, 0, 0.

Next lines:

M - 2 lines corresponding to columns located between the two axes of

symmetry

JN, IA

JN is the number of the column from 2 to M - 1

54
IA is the number of the last square of this column JN or the squares with

the value -2

Temperatures a 49 50 51 a 149 150 151 a 249 250 etc. 850 a 949 950 The machine prints

2 axes of vertical symmetry

- 2 oxes desymitri* v erticoux Y1 : i

*

-2 -2 -2 -2 -2 -2 -2 -2 -2 -2 O O

O O O O

i

O O

O O O HI

-1 -1 -1 -1

-1 -1 -1 -1

-J -1 -1 -t

'

-1 -1 -1 -1

-1 -1 -1 -1 -1 -t -1 -1 -1 -1

Bo/2

B/ 2 AX

HT HT»Ni

Ax

C :?

-2 -2 -2 -2 -2 -2 -2 -2 -2 -2

-2 -2 -2 -2 -2

-2 -2 -2 -2 -2

O O O O

O O

O

O

O

-1 -1

-1 -« -1 -)

-1 -1 -1 .1

-1 -1 -' -1

-1 -1 -1 -1

-I

c) Beam

1.3 Printout of Results

d) Beam with heel and rim

For each series of results: —Temperature of the concrete after At(DELT) minutes of fire —AK2 = ; AKK2 = ; DELT =

AKK2 = global coefficient of theoretical exchange permissible in the

calculation taking into account the dimension of the squares

(2xDA/DELX)

AK2 = global coefficient of exchange of the furnace taken into account in

the calculation

If AK2>AKK2: the program calculates with the value of AKK2 and a slight error can be ignored.

> 95

55
TMB is the average temperature of the concrete

TPF is the average temperature of the cold wall

TPC is the average temperature of the hot wall

Output of additional results ultimately requested: temperature at

the center of each square

Output of temperatures of the element considered with the convention

given in the table on the previous page.

When the temperature TPF exceeds 140°C, the machine prints the

corresponding temperature; likewise when TPFM exceeds 180°C

2 . Program

2.1 Definition of Main Variables of the Program

DELX Ax, side of the cell in cm (usually 1, 2, or 3 cm)

TPF avg. temperature of cold wall

TPC avg. temperature of hot wall

DAO Xo > conductivity of material at 0°C

DA X, conductivity of material at t°C

DELT At, temperature deviation

C c, specific heat

RO p, bulk density

BETA 8, coefficient (Tm

= £.TC)

TC 345 log10 (8t + 1) oven temperature

AK1 global coefficient of exchange of furnace on cold side

AK3 global coefficient of exchange of furnace, calculated

AK2 smallest number between AK3 and 2xDA/DELX

AKK2 2xDA/DELX

TPFM maximum temperature of cold wall

TMB average temperature of concrete (arithmetic mean)

56
2.2 List of instructions

EyolJ's»S^EK§SlfliaStf^8S^Z3^*3Tl^

jUOUfe^JQZ«wHfti.T£C(i,301iJQK»tFF^^-,,; ,„.^ 1J „..„.. -.„.—.-— ' • ''.".:"'. r«J

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,

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t. 01A8 ^.6.J3.«a.V*H£.C 6-iao.WS.Lt_ ,. .K-xau-^ ' ^ *^- 'u&&t ^Uss^-a

Li 51 SI —t-^«WRtTE<, S^»*KZ,4KK2vartT^=^'r^^^i^V^-t^^~^^>>4

1. 015Z_ .9, -j^^faaHAmSX^AKZ.-'., F li .CjAKKZ? '..fjt...0,,*9ELT»l,pS»0,/ ). "-J

J.i0158,_..^-,., w.HiVU£Ca,7Z0)ttlCI,J),J»t)i,MZJ^-r^.- _J.il,..,

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4.. Old-., .1100 w LP(J)»107Za52S75 ,

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i-017.Q._ .... IF. p-0. 1*9. 1600.1500, 1700 „ , - v'- ''"Vj j

i.'. oi 7t-J--i7o:i> it-lFC p-o. soisoa, isoft/taoth ; ?-,k-i*^-i-'t«»*'5^^S^^^®^pP^|

't.017Z_i3.GQ. ...IP(J1=»12-G2501952 ... _ . ,. ^ "'"•'^, ^' \^.J^,\-'i

L.017i( 1600 NP»INT(T1(I,J)/100.J ",i^JLi_i. ' ; - '* V'

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L.0L7.6- 1900. !.P»!:.'TCTlCI«v)i!l.aO»)>l " iv, " > ' i' 'v ' ".

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X.017S ...iGW~- lPCul=-ZV7H7ia3>a.?-U*l&777-Z16^__„,.;^-.„^1 , .-^iiC-.^

57
2.2 List of instructions (cont'd)

1 lift- » ,- .*' .'- ' -. -

l.

L.

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2.2 List of instructions (cont'd)

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2.3 Examples

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Key: (a) Concrete temperatures after 30 minutes of fire; (b) Slab 9 cm.

61
(a) Concrete temperatures after

after 61 minutes of fire

**P 'Temperatures du strau amis Jf.MlftUTES "DE FE1

•AK2= >3.AKK2°213.0E,U

THE [> 33i». ~*~ , TPF = 113.

TPC * 721.

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.

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64 minutes (TPFM = 180);

(d) Concrete temperatures

after 90 minutes of fire.

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62
(a) Concrete temperatures after

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(b) Concrete temperatures after

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(b) TEliP Eli/1.TURES OU BETON APRES 151.MIWTE: :rm AK2= Ui,.AKK2 = 171.DELT» 151.

THE = 345. tPf = 279. TPC 8 79.

' TPFH» 279.

256. 256. 256.

302. 3 02. 30.2. 351. 351. 351.

435. 405. 405.

464. 464. 484.

5 2* . 52S. 523.

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63
(a) Concrete temperatures afte«

180 minutes of fire.

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Note: The examples given do not correspond to likely dimensions

for reinforced concrete structures. They are intended to show the use of

the program.

64
2,32 Column

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Key: (a) Concrete temperatures after 31 minutes of fire; (b) Concrete

temperatures after 60 minutes of fire; (c) Column.

65
(a) Concrete temperatures (a)

after 92 minutes of fire.

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(b) Time after which TPF

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(TPF = 147); (c) Time after

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(d) Concrete temperature

after 30 minutes of r ire;

(e) Beam.

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Key: (a) Concrete temperatures after 61 minutes of fire; (b) Concrete

temperatures after 90 minutes of fire.

67
References

Annales de L'Institut Technique du Batiment et des Travaux Publics:

QC/44 of December 1959, "Resistance of Reinforced Concrete to Fire.

Observations after a Fire and Repairs," L. P. Brice and J. Chefdeville.

(In French)

B. B. A. No. Ill of October 1970, "Thermal and Mechanical Properties

of Concrete as a Function of the Temperature," J. Marechal. (In French)

TMC No. 136 of April 1971, "Rules Applicable to Construction of Reinforced Concrete Stacks." (In French)

Safety and Fire Resistance of Concrete Structures - Workshop on Concrete of the AFB on 18 and 19 November 1971," to be published shortly.

(In French)

Ashton, L. A., and Bate S. C. C, "The Fire Resistance of Prestressed Concrete Beams," Proc. Inst. Civil Engineers, vol. 11, Sept. 1960, pp. 15-

38.

ASTM Book of Standards, Part 14, "Methods of Fire Tests of Building Construction and Material" (E 119-61), p. 366 (1964).

Becker, W., "Construction According to Regulations Governing Protection

of Buildings against Fire," Revue VFDB, Cahier 1, 16-th year, 1967.

(In French)

Becker, W., and Stanke, J., "Fire Tests on Prefabricated Reinforced Concrete Supports," 2nd part (publication in the series of texts of the

German Committee on Reinforced Concrete), in preparation. (In French)

Bornemann, P., "The Effect of Protective Layers on the Duration of Fire

Resistance of Reinforced Concrete and Prestressed Concrete Plates,"

Edition du B'itiment, Wiesbaden, 1968. (In French)

British Standard Institution - Council for Code of Practice, "Preliminary

Draft Code of Practice [for] the Structural Use of Concrete."

Cahiers du Centre Scientifique et Technique du Batiment, Tests on Fire

Resistance Made at the C.S.T.B. Experimental Station: 34 series

(In French)

Carlson, C. C, "Fire Resistance of Prestressed Concrete Beams, Study A [:]

Influence of Thickness of Concrete Covering over Prestressing Steel

Strand," Bulletin 147, Research Dept., Portand Cement Association.

Carlson, C. C, Selvaggio, S. L., and Gustaferro, A. H., "Laboratories for

Study and Development of the Portland Cement Association," Skokie,

111., U.S.A., Dept. of Research Bull. 206 [Title in reference list is

in French]

68
Commissie voor Vitroering van Research (Netherlands), "Fire Tests of Prestressed Concrete Beams," CUR Report 13, 54 pp., January 1958.

Coin, A., "Elastic Calculation of a Concrete Beam in a Temperature Field,"

Annales I.T.B.T.P., July-Aug. 1974 (No. 319), Series "Theories et

Methodes de Calcul" No. 169. (In French)

Day, H. F., Jenkinson, E. A., and Smith, A. I., "Effect of Elevated Temperature on High-tensile Steel Wires for Prestressed Concrete," Proc. Inst.

Civil Engineers, vol. 16, pp. 55-70, May 1960.

Gustaferro, A. H., and Carlson, C. C, "An Interpretation of Results of

Fire Tests of Prestressed Concrete Building Components," J. Prestressed

Concrete Institute, Vol. 7, No. 5, October 1962.

Y. Guyon, Prestressed Concrete [Le Beton Precontraint], Eyrolles editeur,

Paris.

Kordina, K. , Basic Data for Projects of Reinforced and Prestressed Concrete Elements with a Definite Duration of Fire Resistance," Reinforced

Concrete Structures, Reports Resulting from Studies and Experience,

by Hubert Rush, Editions W. Ernst et fils, Munich, 1969. (In French)

Kordina, K. , and Bornemann, P., "Fire Behavior of Reinforced Concrete Plates,

Effect of Protective Layers," Berlin, German Committee on Reinforced

Concrete, Cahier 181/1967. (In French)

Kordina, K. , and Meyer-Ottens, C., "Fire Resistance Capacity of Reinforced

and Prestressed Concrete Elements Subjected to Bending Forces,"

L'economie du Batiment, Cahier 617, February 1963. (In French)

Kordina, K. , "Behavior of Reinforced and Prestressed Concrete Elements

When Attacked by Fire," German Committee on Reinforced Concrete,

Cahier 162, 1964. (In French)

Malhotra, H. L., Effect of Temperature on Compressive Strength of Concrete,"

Magazine of Concrete Research, Vol. 8, No. 23, August 1956, pp. 85-94.

Meyer-Ottens, C., "Protection against Fire of Metal, Enclosed, and Coated

Structures," Part I, Sub-floors. Editions de la construction

Metallique, SARL, Cologne, 1968. (In French)

Meyer-Ottens, C., Duration of Fire Resistance of Slabs, Beams, and Supports

of Reinforced or Prestressed Concrete with Statically Determinate

Installation," Report at Congress of the 5th F.I. P. Congress, Paris

196 CCA London 1968. (In French)

Meyer-Ottens, C., "Review and Use of Results of Fire Tests on Construction

of Walls and Floors," publication in series of texts "Reports on Construction Study," in preparation. (In French)

69
Meyer-Ottens, C., and Steinert, J., "Fire Walls, Behavior in Fire and with

Shock," Reports on Study in Construction, Cahier 61, Editions W.

Ernst et Fils, Berlin, 1969. (In French)

DIN Standards (Beuth, S.A.R.L. Berlin 30). Din 4102, sheet 4, "Behavior

of Materials and Elements in Fire. Classification by Definitions,"

Editions 1965 X. (In French)

International Recommendations of the European Concrete Committee, International Federation of Prestressing. (In French)

Seekamp, H., Becker, W., and Struck, W., "Fire Tests on Prefabricated Reinforced Concrete Columns," Berlin, German Committee on Reinforced

Concrete, Cahier 162, 1964. (In French)

Seekamp, H., "Fire Tests with Heavily Reinforced Columns," Berlin, German

Committee on Reinforced Concrete, Cahier 132, 1959. (In French)

Selvaggio, S. L., and Carlson, C. C, "Effect of Stress on Fire Resistance

of Prestressed Concrete," Bulletin 164. Research Dept., Portland

Cement Association.

Selvaggio, S. L., and Carlson, C. C, "Fire Resistance of Prestressed

Concrete Beams. Study B. Influence of Aggregate and Load Intensity,"

Bulletin 171, Research Dept., Portland Cement Association.

Wierig, H. J., "The Behavior of Concrete Parts and Prefabricated Reinforced

Concrete Parts in [Fire]," Deutscher Ausschus fllr Stahlbeton,

vol. 162, Berlin, 1964, Verlag Wilhelm Ernst et Sohn. (In German)

Simon, "Analog Simulation of Live Conduction, Especially in a Plaster Layer

subjected to Dissociation by Gross Heating (Fire)," Revue generale

de thermique, No. 102, June 1970. (In French)

Kordina (K.), Industrial Methods for Increasing Fire Resistance of Large

Structures," Deutscher Beton-Verein, Wiesbaden, 1969. (In German)

Also see Selected Bibliography No. 17, Resistance to Fire and Protection

of Structures in Annales de I'l.T.B.T.P. of December 1970 where will be

found some of the documents cited above as well.

70
iNBS.114ArP.EV. 11-77)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBS TN 710-10

2. Gov't Accession

No.

4. TITLE AND SUBTITLE

BUILDING RESEARCH TRANSLATION

The Behavior of Concrete Structures in Fire

A Method for Prediction by Calculation

7. AUTHOR(S)

S, G. Weber, Translation Editor

3. Recipient's Accession No.

5. Publication Date March 1978

6. Performing Organization Code

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No.

11. Contract/Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP) 13. Type of Report & Period CoveredFinal

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.)

This method provides a means for predicting, by calculation,

the resistance to fire of a reinforced or prestressed concrete

element of construction, in accordance with 1959 French

directives.

The method is useful in allowing builders to design structures

which show the degree of fire resistance required by the

various French construction regulations in force. According

to those regulations, only a test furnishes legal proof of

fire resistance.

French researchers hope this first step will lead to the

acceptance in France of fire resistance calculations as legal

proof of satisfactory resistance.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons)

Calculating concrete fire resistance; codes; concrete fire resistance;

CSTB; fire; fire codes; France; translations.

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serve as a vehicle for final reports of work performed at NBS under the sponsorship of other government agencies.

Voluntary Product Standards—Developed under procedures

published by the Department of Commerce in Part 10, Title 15, of the Code of Federal Regulations. The purpose

of the standards is to establish nationally recognized require- ments for products, and to provide all concerned interests with a basis for common understanding of the characteristics of the products. NBS administers this program as a supple- ment to the activities of the private sector standardizing

organizations.

Consumer Information Series—Practical information, based on NBS research and experience, covering areas of interest to the consumer. Easily understandable language and

illustrations provide useful background knowledge for shopping in today's technological marketplace.

Order above NBS publications from: Superintendent of Documents, Government Printing Office, Washington, D.C.

20402. Order following NBS publications—NBSIR's and FIPS from

the National Technical Information Services, Springfield, Va. 22161.

Federal Information Processing Standards Publications (FIPS PUB)—Publications in this series collectively constitute the Federal Information Processing Standards Register.

Register serves as the official source of information in the Federal Government regarding standards issued by NBS

pursuant to the Federal Property and Administrative Services Act of 1949 as amended, Public Law 89-306 (79 Stat. 1127), and as implemented by Executive Order 11717

(38 FR 12315, dated May 11, 1973) and Part 6 of Title 15 CFR (Code of Federal Regulations).

NBS Interagency Reports (NBSIR)-—A special series of

interim or final reports on work performed by NBS for outside sponsors (both government and non-government).

In general, initial distribution is handled by the sponsor;

public distribution is by the National Technical Information

Services (Springfield, Va. 22161) in paper copy or microfiche form.

BIBLIOGRAPHIC SUBSCRIPTION SERVICES

Hie following current-awareness and literature-survey bibli- ographies are issued periodically by the Bureau:

Cryogenic Data Center Current Awareness Service. A litera- ture survey issued biweekly. Annual subscription: Domestic, $25.00; Foreign, $30.00.

Liquified Natural Gas. A literature survey issued quarterly.

Annual subscription: $20.00.

Superconducting Devices and Materials. A literature survey

issued quarterly. Annual subscription: $30.00. Send subscription orders and remittances for the preceding bibliographic

services to National Bureau of Standards, Cryogenic Data

Center (275.02) Boulder, Colorado 80302.
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