Material properties

Concrete

In Eurocode 2 the design of reinforced concrete is based on the characteristic cylinder strength rather than cube strength and should be specified according to BS 8500: Concrete - complementary British

Standard to BS EN 206-17 (e.g. for class C28/35 concrete the cylinder strength is 28 MPa, whereas the cube strength is 35 MPa). Typical concrete properties are given in Table 4.

Concrete up to class C90/105 can be designed using Eurocode 2. For classes above C50/60, however, there are additional rules and variations. For this reason, the design of these higher classes is not considered in this publication.

It should be noted that designated concretes (e.g. RC30) still refer to the cube strength.

Reinforcing steel

Eurocode 2 can be used with reinforcement of characteristic strengths ranging from 400 to 600 MPa. The properties of steel reinforcement in the UK for use with Eurocode 2 are given in BS 4449 (2005): Specification for carbon steel bars for the reinforcement of concrete8 and are summarised in Table 5 (on page 4). A characteristic yield strength of 500 MPa has been adopted by the UK reinforcement industry. There are three classes of reinforcement, A, B and C, which provide increasing ductility. Class A is not suitable where redistribution of 20% and above has been assumed in the design. There is no provision for the use of plain bar or mild steel reinforcement, but guidance is given in the background paper to the National Annex9.

Table 3

Selected imposed loads for buildings (from draft UK National Annex to Eurocode 1, Part 1-1)

Category

Example use

qk (kN/m2)

Qk (kN)

A1

All uses within self-contained dwelling units

1.5

2.0

A2

Bedrooms and dormitories

1.5

2.0

A3

Bedrooms in hotels and motels, hospital wards and toilets

2.0

2.0

A5

Balconies in single family dwelling units

2.5

2.0

A7

Balconies in hotels and motels

4.0 min.

2.0 at outer edge

B1

Offices for general use

2.5

2.7

C5

Assembly area without fixed seating, concert halls, bars, places of worship

5.0

3.6

D1/2

Shopping areas

4.0

3.6

E12

General storage

2.4 per m height

7.0

E17

Dense mobile stacking in warehouses

4.8 per m height (min. 15.0)

7.0

F

Gross vehicle weight < 30kN

2.5

Selected concrete properties based on Table 3.1 of Eurocode 2, Part 1-1

Table 4

Selected concrete properties based on Table 3.1 of Eurocode 2, Part 1-1

Symbol

Description

Properties

fck (MPa)

Characteristic cylinder strength

12

16

20

25

30

35

40

45

50

28a

32a

fck,cube (MPa)

Characteristic cube strength

15

20

25

30

37

45

50

55

60

35

40

fctm (MPa)

Mean tensile strength

1.6

1.9

2.2

2.6

2.9

3.2

3.5

3.8

4.1

2.8

3.0

Fcmb (GPa)

Secant modulus of elasticity

27

29

30

31

33

34

35

36

37

32

34

a Concrete class not cited in Table 3.1, Eurocode 2, Part 1-1

b Mean secant modulus of elasticity at 28 days for concrete with quartzite aggregates. For concretes with other aggregates refer to Cl 3.1.3 (2)

The numerical values of the partial factors for the ULS combination can be obtained by referring to Eurocode: Basis of structural design or to Chapter 1.

For members supporting one variable action the ULS combination

1.25 Ck + 1.5 Qk (derived from Exp. (6.10b), Eurocode) can be used provided the permanent actions are not greater than 4.5 times the variable actions (except for storage loads).

Table 3

Selected imposed loads for buildings (from draft UK National Annex to Eurocode 1, Part 1-1)

Table 6

Bending moment and shear co-efficients for beams

Table 7

Exposure classes

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