advisory notes reinforcing steel

7/28/2019 Advisory Notes Reinforcing Steel

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ADVISORY NOTENUMBER: 008 JANUARY, 1991

REINFORCING STEEL


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ADVISORY NOTEON NOTE NUMBER 008

REINFORCING STEEL JANUARY 1991

C O N T E N T S

PAGE

1 INTRODUCTION 1

2 REINFORCING STEEL 1

3 SPECIFICATIONS 2

4 DEFINITIONS 3

5 SURFACE CHARACTERISTICS 4

6 GRADES 5

7 SIZES AND TOLERANCES 5

8 STEEL MAKING PROCESS 7

9 CHEMICAL COMPOSITION 7

10 WELDING 9

11 REQUIREMENTS FOR

DEFORMATIONS

10

12 MECHANICAL PROPERTIES 10

13 QUALITY CONTROL 16

TABLES1 PREFERRED NOMINAL SIZES 6

2 CROSS-SECTIONAL AREA AND

MASS

6

3 TOLERANCE ON MASS 7

4 CHEMICAL COMPOSITION OF

STEEL

9

5 TENSILE PROPERTIES 14

6 REQUIREMENT FOR DEGREE OF

BENDING AND SIZES OF PINS

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DM NOTE NUMBER 008, JANUARY 1991

ADVISORY NOTE DUBAI MUNICIPALITY

ON NOTE NUMBER 008

REINFORCING STEEL JANUARY 1991

1. INTRODUCTION

Steel is used in two different ways in concrete structures: as reinforcing steel and as

prestressing steel. Reinforcing steel is placed in the forms prior to casting of concrete.

They resist all load stress resultants in co-operation with the surrounding concrete.

Stresses in the reinforcing steel, as in the hardened concrete, are caused only by the loads

on the structure, except for possible parasitic stresses from shrinkage or similar causes.

In contrast, in prestressed-concrete structures large tension forces are applied prior to

letting it act jointly with the concrete in resisting external loads. The prestressing steel is

hence referred as an active reinforcement. The term "active" describes the prestressing

system constantly applying a force to the structural element regardless of the external

loads on that element. In comparison, reinforced concrete is apassive reinforcing

system. The steels for these usages are very different.

ThisADVISORY NOTEdescribes in general terms those essential properties of steel that

form the basis of quality requirements and strength properties necessary to conform with

compliance criteria of modern reinforced concrete design codes. The recommendations

contained in major international standards which are of interest to local practices have

been adopted.

2. REINFORCING STEEL

The most common type of reinforcing steel (as distinct from prestressing steel) is in the

form of bars/wires. These are classified according to methods of production (hot rolled

or cold reduced or cold worked), surface characteristics (plain or deformed), strength

grades (mild steel, or medium-tensile or high- tensile), and weldability.

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3. SPECIFICATIONS

Steel reinforcing bars which are normally used in reinforced concrete construction in the

Emirate comply to the following BS or ASTM specifications.

BS 4449 'Carbon steel bars for the reinforcement of concrete'. This British Standard

specifies requirements for weldable steel bars for the reinforcement of concrete. It covers

plain round steel bars in grade 250 and deformed high yield steel bars in grade 460. The

standard applies equally to hot rolled and cold worked steel bars.

ASTM A 706M 'Low-Alloy steel deformed bars for concrete reinforcement'. This

specification covers low-alloy steel deformed bars for concrete reinforcement intended

for special applications where welding or bending, or both are of importance.

ASTM A 615M 'Deformed and plain Billet-Steel bars for concrete reinforcement'.

Deformed bars complying to this specification are normally used in reinforced concrete

construction in the Emirates.

It is to be noted that the specification does not include weldability as part of the

specification. However, if there is a necessity for welding this material, the specification

shall be supplemented to require a report of material properties necessary to conform to

the provisions of welding procedures.

BS 4482: 'Cold reduced steel wire for the reinforcement of concrete'. This British

Standard specifies requirements for cold reduced plain and deformed steel wire used for

the reinforcement of concrete and for the manufacture of steel fabric. All reinforcing

steels supplied in accordance with this standard are readily weldable.

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4. DEFINITIONS

The following definitions apply.

4.1 Bar: A steel product of plain round or deformed profile, produced by hot rolling.

4.2 Wire: A steel product of any form of cross section produced by cold reduction of

an as-rolled rod.

4.3 Deformed bar or wire: Bar or wire with surface characteristics designed to

increase its bond with concrete, the degree of deformation being as defined in the

relevant standards.

4.4 Rib: A protrusion on the outside of the bar/wire designed to increase its bond with

concrete.

4.5 Longitudinal rib: A uniform continuous protrusion parallel to the axis of the

bar/wire.

4.6 Transverse rib: Any rib on the surface of the bar/wire other than a longitudinal

rib.

4.7 Cold worked deformed bar: A deformed bar which is produced by cold-working

of an as-rolled bar to improve its yield strength property.

4.8 Size (nominal size, d): The diameter of a circle with an area equal to the effective

cross-sectional area of the bar, rod or wire.

4.9 Nominal Density: The value of 0.00785 kg/mm2, per metre run taken for the

purpose of converting a length and cross-sectional area of a wire to its mass.

4.10 Yield point: The stress at the point reached during the test when plastic

deformation occurs without any increase in the force, in material exhibiting a

yield phenomenon.

4.11 Yield stress: The stress measured during the tensile test when the extension is a

specified percentage increase in the gauge length.

4.12 Yield Strength: The yield strength is either the yield point or the yield stress

whichever is lower.

4.13 Characteristic strength: That value of the yield stress below which fall not more

than 5% of the test results.

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4.14 Tensile strength: The stress corresponding to the maximum force sustained during

a tension test of steel product.

4.15 Percentage total elongation at fracture: The total elongation (elastic elongation

plus plastic elongation) of the gauge length at the moment of fracture, expressed

as a percentage of the original gauge length.

4.16 Batch: Any quantity of bars or wires of one size and grade, produced by one

manufacturer or supplier, presented for examination at any one time.

5. SURFACE CHARACTERISTICS

5.1 Deformed Bars

In reinforced concrete a long-time trend is evident toward the use of higher-strength

materials, both steel and concrete. Hot-rolled plain reinforcing bars with 33-ksi (228

MPa) yield points, which were widespread not too long ago, are no longer made. Hot-

rolled deformed steel bars with 410-460 MPa yield by stress, referred to as high-yield

steel bars, are the commonly used reinforcements nowadays.

For most effective reinforcing action, it is essential that steel and concrete deform

together, i.e., that there be a sufficiently strong bond between the two materials. This

bond is provided by the relatively largechemical adhesion which develops at the steel-

concrete interface, and by the natural roughness of the mill scale of hot-rolled

reinforcing bars. But the extent of bond thus developed is found to be inadequate when

high-yield steel bars are used.

To increase the bond with concrete, the surface of the bar is provided with lugs or rib-

shaped protrusions, termed as deformations, in order to provide a high degree of

interlocking of the two materials. Minimum requirements for these deformations

(spacing, projection, etc.) have been developed in lengthy experimental research and are

specified in the standards. Different bar producers use different patterns, all of which

should satisfy these requirements.

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5.2 Plain bars

Plain smooth round bars are produced as hot-rolled possessing a yield point stress of 250

MPa. They can be readily bent, so they are often used where small radius bends are

necessary. The design codes permit the use of plain bars and smooth wire only for spiral

reinforcement either as lateral reinforcement for compression members, for torsion

members, or for confining reinforcement for splices.

5.3 Cold Worked Bars

Cold worked steel bars are recognizable by their twisted configuration of ribs. These

types of bars are more or less obsolete locally and are not recommended; when compared

with hot rolled bars they exhibit inferior bond characteristic. Cold worked steels are

normally readily weldable but they tend to loose strength after heating.

6. GRADES

The specifications mentioned above cover bars of different minimum yield strength

levels: namely, 250 Mpa, 300 MPa, 400 MPa, 460 MPa, and 500 Mpa, designated as

Grades 250, 300, 400, 460, & 500, respectively.

7. SIZES AND TOLERANCES

7.1 Sizes

The range of nominal sizes of bars/wires are given in table 1.The nominal dimensions (

nominal diameter and cross-sectional area) of a deformed bar are equivalent to those of a

plain round bar having the same mass per metre as the deformed bar. In ASTM

specifications, the size of bars are designated by numbers. The designated numbers

approximate the numbers of millimetre.

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TABLE 1 PREFERRED NOMINAL SIZES

Spec Grade Type Nominal Sizes Dia. mm

BS 4449 250 Plain 8, 10, 12, 16

BS 4449 460 Deformed 8, 10, 12, 16, 20, 25, 32, 40

BS 4482 460 Plain/ Deformed 5, 6, 7, 8, 9, 10, 12

ASTM A 706M 400 DeformedNominal

Sizes

Dia. mm

Designation

No

11.3 10

16.0 15

19.5 20

25.2 25

29.9 30

35.7 35

43.7 45

ASTM A 615M 300 Plain / Designation

numbers and

corresponding

diametres400 Deformed are as in

above ASTM A 706M

500

7.2 Cross-Sectional Area and Mass

The cross-sectional area and the mass of the bars/wires shall be calculated on the basis

that these steels have a mass of 0.00785 kg/mm2

per metre run. The values shall be as

given in Table 2.

TABLE 2 CROSS-SECTIONAL AREA AND MASS

Bars/Wires to BS Specifications Bars to ASTM Specifications

Nominal

Size

mm

Cross

Sectional

Area, mm2

Mass per

Metre

Run, Kg

Bar Desig

Nation

No

Diameter

mm

Cross

Section

Area mm2

Mass per

Metre

5 19.6 0.154

6 28.3 0.022

7 38.5 0.302

8 50.3 0.395

9 63.6 0.49910 78.5 0.616 10 11.3 100 0.785

12 113.1 0.888 15 16.0 200 1.570

16 201.1 1.579 20 19.5 300 2.355

20 314.2 2.466 25 25.2 500 3.925

25 490.9 3.854 30 29.9 700 5.495

32 804.2 6.313 35 35.7 1000 7.850

40 1256.6 9.864 45 43.7 1500 11.775

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7.3 Tolerances

British Standards specifies tolerances both for cross-sectional dimension and mass while

ASTM to mass only.

The deviation of any cross-sectional dimension, other than those of ribs, from its nominal

size, shall not exceed 8%. Tolerance on mass shall be as given in Table 3.

TABLE 3. TOLERANCE ON MASS

Specifications Nominal Size mm Tolerance on Mass

Per Metre Run %BS 4449 6 9

8 & 10 6.5

12 & Above 4.5

BS 4482 Under 12 6.5

12 4.5

ASTM A 706 M & All Sizes - 6 and over-mass of any bar be thecause of rejection.

ASTM A 615 M

8. STEEL MAKING PROCESS

The steel is made by refining molten iron in a top-blown basic oxygen converter or by

melting in a basic lined electric furnace. The bars are processed from properly identified

heat moldcast or strand cast steel.

9. CHEMICAL COMPOSITION

The metallurgical phases of steel are ferrite, pearlite and cementite. The presence and

extent of these phases are governed mainly by the carbon content in the steel. Below

about 0.8% carbon, there would be both ferrite and pearlite phases. With increasing

carbon content, from near 0%, the ferrite phase decreases with a corresponding increase

in pearlite phase and at about 0.8% carbon, there would be pearlite phase alone. It has

been established that with the increase of pearlite phase, tensile strength of steel increases

while elongation property i.e ductility reduces. The maximum tensile strength is attained

at about 100 % pearlite phase but the ductility will then be near zero i.e the steel would

be brittle.

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Thus, the mechanical properties of steel are related to the carbon content. To have a steel

of desirable properties the carbon content is to be controlled which is found to lie in a

narrow range of 0.25% to 0.35%.

Alloying elements used in the manufacture of steel modify the phase diagram so that the

point at which the maximum pearlite phase forms is at a different percentage of carbon.

Therefore, an index called 'Carbon equivalent' (CE) has been introduced which converts

the amount of these alloying elements into equivalent percentage of carbon. Elements

commonly used include : Manganese (Mn), Silicon (Si), Copper (Cu), Nickel (Ni),

Chromium (Cr), Molybdenum (Mo), Vanadium (V), Columbium (Co), Titanium (Ti),

and Zirconium (Zi).

Elements, Sulphur(S), Phosphorus(P), Nitrogen are impurities and they have to be kept

low and maximum limits for these are specified in the standards.

Choice and use of alloying elements, combined with carbon, phosphorus, and sulphur to

give the mechanical properties prescribed in the standards is made by the manufacturer.

The heat analysis shall be such as to provide a carbon equivalent value (CEV) not

exceeding the values specified in the Standards. The formulae to be used to calculate

carbon equivalent value are given in the specifications. BS 4449 gives the following

formula, where the individual values are calculated as percentages.

1556

CuNiVMoCrMnCCEV

++

++++=

The chemical composition of the steel based on cast analysis and that of finished bars

representing each heat of steel shall be in accordance with Table 4.

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TABLE 4. CHEMICAL COMPOSITION OF STEEL

Elements, % Maximum CarbonEquivalent

Maximum

Value, %

Specification Grade Cast /

Product

C S P Mn Si

BS 4449 250 Cast 0.250 0.060 0.060 0.42

BS 4449 250 Bar 0.270 0.065 0.065 0.45

BS 4449 460 Cast 0.250 0.050 0.050 0.51

BS 4449 460 Bar 0.270 0.055 0.055 0.54

BS 4482 460 Cast 0.250 0.060 0.060 0.42

ASTM A 706 M 400 Cast 0.300 0.045 0.035 1.50 0.50 0.55

ASTM A 706 M 400 Bar 0.330 0.053 0.043 1.56 0.55

ASTM A 615 M 300

400

500

Cast 0.060

ASTM A 615 M 300

400

500

Bar 0.075

10. WELDING

Reinforcing bars should not be welded without regard to steel weldability and proper

welding procedures. Standards specify requirements for material intended for welding in

terms of carbon equivalent value (CEV) and chemical composition restrictions. Welding

technique is of fundamental importance and welding procedures and consumables

appropriate to the particular grade and quality should be used. The steel chemistry is to

be restricted to a given range to suit a specified procedure. The important consideration is

that the specified welding procedure and steel weldability be compatible. American

Welding Society Standard, AWS D1.4: Structural Welding Code - Reinforcing Steel and

BS 7123 Metal arc welding of Steel for concrete reinforcement, give recommended

welding practices, including pre-heat and interpass temperatures based on the carbon

equivalent value, and the procedure prescribed therein is mandatory. The execution of

welding provisions should be entrusted to appropriately qualified and experiencedpeople

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11. REQUIREMENTS FOR DEFORMATIONS

Deformed bars shall have surface shape as specified in the relevant specifications. Bars

are normally produced to these requirements. When bars do not comply with such

requirements or when in doubt, the performance tests as described in appendix B of BS

4449, shall be conducted by a competent laboratory. The findings of the laboratory shall

be regarded as final.

The principle of the test is to show that deformed bars,for the grade of steel from which

the bars are made, will hold for 2 minutes the specified characteristic strength in a pull-

out test with a free end slip not greater than 0.2mm.

12. MECHANICAL PROPERTIES

Although the tensile strength of the steel bar is regarded as the most important specified

property, it is only one in an array of properties that determine the ability of the steel to

be used effectively and safely under all conditions. The important properties can be

summarised as follows:

Tensile Strength: To impart strength to the reinforced concrete structure.

Tensile Ductility: To provide structural integrity in the presence of cracking.

Bond Performance: To enable the concrete unit to possess tensile properties.

Fatigue Resistance: To enable the structure to endure cyclical loading from causes such

as tide and wave movements, wind and traffic.

Formability: To enable the steel to be bent on small radii with a precise response.

Weldability: To permit joining of bars as splices or in the pre- fabrication of complex

units under non-ideal conditions.

Consistency: To ensure that the above requirements are met with the same response on

every occasion.

The array of properties is met by a combination of chemical composition and rolling mill

practice but there is frequently a tendency for individual requirements to be incompatible.

For example, tensile strength and ductility, as discussed in para 9 above, are inversely

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related and therefore the ability with which high values of both can be achieved

simultaneously is limited.

Further, the work of the reinforcement fabricator which is aimed at providing accurate

cut and bent pieces, improve the above properties but may have a detrimental effect by

damaging the steel. Bad bending operations cause considerable amount of damage to the

ribs of deformed bar which can create premature failure.

NOTE: All bars should be free from defects, e.g. seams, porosity, segregation, non-

metallic inclusions etc., which can be shown to adversely affect the mechanical

properties.

12.1 Condition of Test Specimens

The tensile, bend and rebend tests shall be carried out on straight bars/wires in the

delivery or accelerated aged condition. At the option of the manufacturer or supplier and

in order to simulate natural ageing, test specimens may be subjected to a temperature of

100 degrees celsius for a period of not more than 2 hours.

12.2 Tensile Properties12.2.1 Stress-strain curves.

The two chief numerical characteristics which determine the character of reinforcement

are its yield point (generally identical in tension and in compression) and its modulus of

elasticity E. The latter is practically the same for all reinforcing steels and is taken as E =

200 kN/mm2.

In addition, however, the shape of the stress-strain curve of tensile test of steel, and

particularly of its initial portion, has significant influence on the performance of

reinforced- concrete members.

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Low-carbon steels, typified by the 250 MPa steel tensile test stress-strain curve, show an

elastic portion followed by a "yield plateau," i.e. by a horizontal portion of the curve

where strain continues to increase at constant stress. For such steels the yield point is that

stress at which the yield plateau establishes itself. With further strains the stress begins

to increase again, though at a slower rate, a process which is known as strain- hardening.

The curve flattens out when the tensile strength is reached; it then turns down until

fracture occurs.

Higher-strength carbon steels, such as those with 400 - 500 MPa yield points, either have

a yield plateau of much shorter length or enter strain-hardening immediately without any

continued yielding at constant stress.

While, low-alloy, high-strength reinforcing steels rarely show any yield plateau and

usually enter strain-hardening immediately upon beginning to yield. In such cases the

yield point is defined as the stress at which the total strain under load is 0.45 to 0.55

percent.

Depending upon properties of the steel and manufacturing process, the specifications

prescribe the strain (as shown in Table 5, column 3) for determination of yield strengths

that result in more practical controls on production. But the design Codes (BS 8110:

Structural Use of Concrete and ACI 318: Building Code Requirements for Reinforced

Concrete) define yield strengths somewhat differently from corresponding steel

specifications. These Codes limit the yield strength over 400 MPa to a stress

corresponding to a maximum extension under load strain of 0.35 percent. The purpose is

to provide a basis for standard structural computations in accordance with generally

accepted theoretical equations. The 0.35 strain requirement is not applied to reinforcing

bars having yield strength of 400 MPa or less, because of elasto-plastic stress-strain

behavior of such steel. It should be noted that 0.35 percent strain is the ultimate strain in

concrete assumed in design Codes and for compatibility of strain between steel and

concrete, the yield strength of steel is also set to correspond to this value.

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12.2.2 Requirements of Tensile Properties

The steel, as represented by the test specimens, shall conform to the requirements for

tensile properties-tensile strength, yield stress and elongation-prescribed in Table 5. The

tests on bars/wires to British specifications shall be carried out in accordance with

Appendix C of BS 4449, while bars to ASTM specifications shall be to ASTM A 370

'Methods and Definitions for Mechanical Testing of Steel Products.'

Theyield point or yield stress shall be determined by one of the following methods:

a) The yield point shall be determined by drop of the beam or halt in the

gauge of the testing machine.

b) Where the steel does not have a well-defined yield point, the yield stress

shall be determined at a specified extension under load using an

autographic diagram method or an extensometer. The specified extension

under load i.e. the total strain under load shall be that prescribed in Table

5, appropriate to steel grade and specification.

Theyield strength shall be either the yield point or the yield stress whichever is lower.

TheDuctility i.e. the percentage elongationshall be as prescribed in Table 5. Ductility is

an important parameter in flexural members or columns with significant bending and can

be critical only if the percentage of reinforcing steel is very low so that there is

possibility of steel rupture before concrete crushing. Rupture of longitudinal steel has

generally been precluded in bending members by using steel with ductilities as defined

by standard specifications and by imposing lower limits on steel percentage. Ductility is

obviously important in members subjected to membrane tension. However, it is important

in any inelastic analysis to realize that the "useful" ductility is limited to the strain

corresponding to the greatest stress on the engineering stress-strain curve, which may be

less than half of the ultimate ductility.

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TABLE 5. TENSILE PROPERTIES

Specification Grade Strain

%

Specified Yield

Strength, MPa

Tensile

Strengt,

MPa

Gauge Ductility

Elongation

%

Min Max Min Minimum

BS 4449 250 0.33 250*** 275 5 d* 22BS 4449 460 0.43 460*** 510 5 d 12

BS 4482 460 0.43 460*** 5.65S** 12

ASTM A 706M 400 0.35 400 540 550 200 mm 14For bar Nos. 10,15,2012 For bar Nos. 25,30,35

10 For bar Nos. 45,55

ASTM A 615M 300 0.50 300 500 200 mm 11For bar No. 1012 For bar Nos. 15,20

ASTM A 615M 400 0.50 400 600 200 mm 9 For bar Nos. 10,15,20

8For bar No. 257 For bar Nos.

30,35,45,55

ASTM A 615M 500 0.35 500 700 200 mm 6 For bar Nos. 35,45,5

Note:* d is the nominal size of the test piece.

** S is the original cross-sectional area of the test piece

*** The figures shown for steels to BS specifications under yield strength heading are to be reckoned

ascharacteristic strength values.

12.2.3 Verification of Characteristic Strength (Cv).

Where the characteristic strength, Cv of the material is in doubt/ dispute, the British

Standards prescribe criteria for its verification. The bars/wires in a batch shall be

considered to comply with the specified Cv provided that actual yield stress test results ofspecimens representing the batch satisfy the following conditions.

BS 4449 requires that :

a) no test results in any three tests are less than Cv, alternatively

b) all test results in any ten tests are equal to or greater than 0.93 Cv.

BS 4482 requires that :

a) not more than two test results in any 40 consecutive tests are less than Cv,

and

b) no test results are less than 0.93 Cv.

Note: From the above criterion, it follows that for grade 460 steel, the actual yield

stress can be 0.93 x 460 = 427.8 MPa, say 425 MPa. Even when all the ten test

results are 427.8 MPa, the steel, as per specifications, qualify it to be designated

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as grade 460. But the common practice with the Design Engineers has been to

assume its yield strength to be 425 MPa. It is also to be noted that BS 8110

recommends that design may be based on the appropriate characteristic strength

or a lower value if necessary to reduce the deflection or control cracking.

12.3 Bending Properties

The test methods for evaluating bending properties of the metal shall be as given in

appendix C of BS 4449. The specimens shall be the full section of the bar/wire as

producedand be of sufficient length to ensure free bending. The requirements for degree

of bending and sizes of pins/formers are prescribed in Table 6.

The specimens shall withstand being bent around a pin/former without transverse

cracking on the outside of the bent portion. For the purpose of this test, the presence of

any mill scale is ignored. When rebend testing is specified, the specimens shall be

subjected to the prescribed sequence of operations and that they

show no sign of fracture or irregular bending.

TABLE 6 REQUIREMENT FOR DEGREE OF BENDING AND SIZES OF PINS

Specification Grade Bend Test Angle of Bend PinDiameter

Rebend Test Angle of BendPin Diameter

BS 4449 250 180 2 d* 45 back to 23 2 d

BS 4449 460 180 3 d 45 back to 23 5 d

BS 4482 460 No requirement 45 back to 23 5 d

ASTM A 706M 400

180

180

180

180 3 d for Bar Nos 10,15

4 d for Bar Nos. 20,25



No requirement

ASTM A 615M 300

180

180 3.5 d for Bar Nos. 10,155 d for Bar Nos. 20

ASTM A 615M 400

180

180

90

180 3.5 d for Bar Nos. 10,155 d for Bar Nos. 20,25


9 d for Bar Nos. 45, 55

No requirement

ASTM A 615M 500

90

180 7 d for Bar No. 35

9 d for Bar Nos. 45, 55

No requirement

* d is the nominal diameter of specimen.

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12.4 Fatigue Properties of Deformed Bar

In practice, reinforcing steel has generally not been subject to fatigue failure. The ASTM

specifications do not include restrictions regarding fatigue, but BS 4449 requires that

fatigue properties for each defined bar shape and process route shall be established. The

method of test is described in appendix D. Bars shall be deemed defective or non-

defective depending upon their ability to endure 5 million cycles of stress at the specified

stress range given for the relevant bar size.

13. QUALITY CONTROL

13.1 Marking

In order for bars of various grades and sizes to be easily distinguished, which is necessary

to avoid accidental use of lower-strength or small-size bars than called for in the design,

all deformed bars to ASTM specifications are furnished with rolled-on legible marks on

the surface of the bars at intervals. These identify the producing mill (usually an initial),

the bar size designation, the type of steel (letter W for steels to ASTM A 706 and letter S

for steels to ASTM A 615 specifications), and minimum yield designation. Each

manufacturer shall identify the symbols of his marking system. Plain round bars are

tagged for grade only. BS 4449 requires that deformed bars to have rolled- on mark only

for the origin of manufacturer at intervals not greater than 1.5 m.

New notation letters for type and grade of reinforcement have been introduced in BS

specifications as follows:

R - grade 250 plain reinforcement to BS 4449.

T- grade 460 deformed to BS 4449 or BS 4482.

W - grade 460 plain reinforcement to BS 4482.

Note: The above notations supersedes the notation Y but some design offices still

use the Y notation in the schedules/drawings.

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13.2 Internal Control

The manufacturer shall operate a quality control scheme which shall be available for

inspection by prospective purchaser and inspecting agency. The scope of internal control

to cover cast analysis, testing of specimens and recording keeping of test results, which

shall be maintained for a period of ten years. The rate of testing shall be.

a) For casts up to 50 ton :3 tensile tests, 1 bend test and 1 rebend test;

b) For each 15 ton cast beyond 100 tons additional tests, one of each type.

13.3 Third Party Product Certification Scheme.

The application of quality assurance (QA) scheme is directed towards product

conformity. This is achieved through Quality and Operations Assessment Schedules

which identify to the manufacturer those elements of his operations which will be given

special attention. The schedules lay down the sampling and testing procedures that will

be carried out for both the initial assessment leading to a certificate of approval and

subsequent surveillances carried out in the course of maintenance of the approval.

The Scheme requires strict traceability of material to the parent steel making unit. This

ensures that material is kept under control and that responsibility for performance is

maintained. The steel mills that hold the QA scheme approval are permitted to put the

scheme's identification rolling mark on the bars which, together with a system for

identifying the country of origin and the mill provides a unique form of identification.

Traceability is also applied to all technical documentation in that mill test certificates

carry an embossed QA schemes logo complete with approval number.

13.4 Certificate of Compliance

A certificate shall be issued by the supplier stating the following.

(a) Works producing the reinforcing steel.

(b) Nominal diameter and effective cross-sectional area.

(c) Grade.

(d) Marking system.

(e) Cast number and cast analysis.

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(f) Carbon equivalent value.

(g) Mass of the test unit and standard deviation of the population.

(h) The individual test results of the tensile, bend and rebend tests.

(i) Date of testing.

The certificate shall include the approval number, if any, issued by the Certifying

Authority.

13.5 Testing

Material not covered by a third party product Certification Scheme shall be assessed by

acceptance tests on each batch, even though the manufacturer has issued a Certificate of

Compliance. The testing shall be carried out as deemed necessary (refer clause 13.5.1) at

the Dubai Municipality Laboratory or at any approved laboratory in Dubai.

13.5.1 Extent of Sampling and Testing

For every 50 ton mass of the same steel grade and same nominal diameter from the same

cast, test specimens shall be taken from the different bars/wires for testing as follows:

a) For cross sectional checks and tensile property tests 3 Nos.

b) For verification of characteristic strength, refer clause 12.2.3 10 Nos.

c) For bend test 3 Nos.

d) For re-bend test 3 Nos.

e) For bond test (optional) 6 Nos.

f) For chemical composition analysis and carbon equivalent value

determination (Optional) 3 Nos.

The properties are to be determined in testing the above sampled test specimens for

checking compliance with the specifications. Should the results of the above tests show

that the steel does not meet all the specified requirements, the whole batch is rejected and

removed from the site.

advisory notes reinforcing steel

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